Implications of Habitat Loss on Seed Predation and Early Recruitment of a Keystone Palm in Anthropogenic Landscapes in the Brazilian Atlantic Rainforest.

PubMed

Soares, Leiza Aparecida S S; Faria, Deborah; Vélez-Garcia, Felipe; Vieira, Emerson M; Talora, Daniela C; Cazetta, Eliana

2015-01-01

Habitat loss is the main driver of the loss of global biodiversity. Knowledge on this subject, however, is highly concentrated on species richness and composition patterns, with little discussion on the consequences of habitat loss for ecological interactions. Therefore, a systemic approach is necessary to maximize the success of conservation efforts by providing more realistic information about the effects of anthropogenic disturbances on natural environmental processes. We investigated the implications of habitat loss for the early recruitment of Euterpe edulis Martius, a keystone palm in the Brazilian Atlantic Forest, in nine sampling sites located in landscapes with different percentages of forest cover (9%-83%). We conducted a paired experiment using E. Edulis seeds set up in experimental stations composed of a vertebrate exclosure versus an open treatment. We used ANCOVA models with treatments as factors to assess the influence of habitat loss on the number of germinated seeds, predation by vertebrates and invertebrates, infestation by fungi, and number of seedlings established. Habitat loss did not affect the probability of transition from a dispersed to a germinated seed. However, when seeds were protected from vertebrate removal, seedling recruitment showed a positive relationship with the amount of forest cover. Seed infestation by fungi was not significant, and seed predation was the main factor limiting seed recruitment. The loss of forest cover antagonistically affected the patterns of seed predation by vertebrates and invertebrates; predation by invertebrates was higher in less forested areas, and predation by vertebrates was higher in forested areas. When seeds were exposed to the action of all biotic mortality factors, the number of recruited seedlings was very low and unrelated to habitat loss. This result indicates that the opposite effects of seed predation by vertebrates and invertebrates mask a differential response of E. edulis recruitment to habitat loss.

Implications of Habitat Loss on Seed Predation and Early Recruitment of a Keystone Palm in Anthropogenic Landscapes in the Brazilian Atlantic Rainforest

PubMed Central

Soares, Leiza Aparecida S. S.; Faria, Deborah; Vélez-Garcia, Felipe; Vieira, Emerson M.; Talora, Daniela C.; Cazetta, Eliana

2015-01-01

Habitat loss is the main driver of the loss of global biodiversity. Knowledge on this subject, however, is highly concentrated on species richness and composition patterns, with little discussion on the consequences of habitat loss for ecological interactions. Therefore, a systemic approach is necessary to maximize the success of conservation efforts by providing more realistic information about the effects of anthropogenic disturbances on natural environmental processes. We investigated the implications of habitat loss for the early recruitment of Euterpe edulis Martius, a keystone palm in the Brazilian Atlantic Forest, in nine sampling sites located in landscapes with different percentages of forest cover (9%-83%). We conducted a paired experiment using E. Edulis seeds set up in experimental stations composed of a vertebrate exclosure versus an open treatment. We used ANCOVA models with treatments as factors to assess the influence of habitat loss on the number of germinated seeds, predation by vertebrates and invertebrates, infestation by fungi, and number of seedlings established. Habitat loss did not affect the probability of transition from a dispersed to a germinated seed. However, when seeds were protected from vertebrate removal, seedling recruitment showed a positive relationship with the amount of forest cover. Seed infestation by fungi was not significant, and seed predation was the main factor limiting seed recruitment. The loss of forest cover antagonistically affected the patterns of seed predation by vertebrates and invertebrates; predation by invertebrates was higher in less forested areas, and predation by vertebrates was higher in forested areas. When seeds were exposed to the action of all biotic mortality factors, the number of recruited seedlings was very low and unrelated to habitat loss. This result indicates that the opposite effects of seed predation by vertebrates and invertebrates mask a differential response of E. edulis recruitment to habitat loss. PMID:26186339

Seed size and provenance mediate the joint effects of disturbance and seed predation on community assembly

Treesearch

John L. Maron; Dean E. Pearson; Teal Potter; Yvette K. Ortega

2012-01-01

Local plant community assembly is influenced by a series of filters that affect the recruitment and establishment of species. These filters include regional factors that limit seeds of any given species from reaching a local site as well as local interactions such as post-dispersal seed predation and disturbance, which dictate what species actually establish. How these...

Tree-to-tree variation in seed size and its consequences for seed dispersal versus predation by rodents.

PubMed

Wang, Bo; Ives, Anthony R

2017-03-01

Individual variation in seed size and seed production is high in many plant species. How does this variation affect seed-dispersing animals and, in turn, the fitness of individual plants? In this study, we first surveyed intraspecific variation in seed mass and production in a population of a Chinese white pine, Pinus armandii. For 134 target trees investigated in 2012, there was very high variation in seed size, with mean seed mass varying among trees almost tenfold, from 0.038 to 0.361 g. Furthermore, 30 of the 134 trees produced seeds 2 years later, and for these individuals there was a correlation in seed mass of 0.59 between years, implying consistent differences among individuals. For a subset of 67 trees, we monitored the foraging preferences of scatter-hoarding rodents on a total of 15,301 seeds: 8380 were ignored, 3184 were eaten in situ, 2651 were eaten after being cached, and 395 were successfully dispersed (cached and left intact). At the scale of individual seeds, seed mass affected almost every decision that rodents made to eat, remove, and cache individual seeds. At the level of individual trees, larger seeds had increased probabilities of both predation and successful dispersal: the effects of mean seed size on costs (predation) and benefits (caching) balanced out. Thus, despite seed size affecting rodent decisions, variation among trees in dispersal success associated with mean seed size was small once seeds were harvested. This might explain, at least in part, the maintenance of high variation in mean seed mass among tree individuals.

Granivory of invasive, naturalized, and native plants in communities differentially susceptible to invasion.

PubMed

Connolly, B M; Pearson, D E; Mack, R N

2014-07-01

Seed predation is an important biotic filter that can influence abundance and spatial distributions of native species through differential effects on recruitment. This filter may also influence the relative abundance of nonnative plants within habitats and the communities' susceptibility to invasion via differences in granivore identity, abundance, and food preference. We evaluated the effect of postdispersal seed predators on the establishment of invasive, naturalized, and native species within and between adjacent forest and steppe communities of eastern Washington, USA that differ in severity of plant invasion. Seed removal from trays placed within guild-specific exclosures revealed that small mammals were the dominant seed predators in both forest and steppe. Seeds of invasive species (Bromus tectorum, Cirsium arvense) were removed significantly less than the seeds of native (Pseudoroegneria spicata, Balsamorhiza sagittata) and naturalized (Secale cereale, Centaurea cyanus) species. Seed predation limited seedling emergence and establishment in both communities in the absence of competition in a pattern reflecting natural plant abundance: S. cereale was most suppressed, B. tectorum was least suppressed, and P. spicata was suppressed at an intermediate level. Furthermore, seed predation reduced the residual seed bank for all species. Seed mass correlated with seed removal rates in the forest and their subsequent effects on plant recruitment; larger seeds were removed at higher rates than smaller seeds. Our vegetation surveys indicate higher densities and canopy cover of nonnative species occur in the steppe compared with the forest understory, suggesting the steppe may be more susceptible to invasion. Seed predation alone, however, did not result in significant differences in establishment for any species between these communities, presumably due to similar total small-mammal abundance between communities. Consequently, preferential seed predation by small mammals predicts plant establishment for our test species within these communities but not between them. Accumulating evidence suggests that seed predation can be an important biotic filter affecting plant establishment via differences in consumer preferences and abundance with important ramifications for plant invasions and in situ community assembly.

Effects of rodent species, seed species, and predator cues on seed fate

NASA Astrophysics Data System (ADS)

Sivy, Kelly J.; Ostoja, Steven M.; Schupp, Eugene W.; Durham, Susan

2011-07-01

Seed selection, removal and subsequent management by granivorous animals is thought to be a complex interaction of factors including qualities of the seeds themselves (e.g., seed size, nutritional quality) and features of the local habitat (e.g. perceived predator risk). At the same time, differential seed selection and dispersal is thought to have profound effects on seed fate and potentially vegetation dynamics. In a feeding arena, we tested whether rodent species, seed species, and indirect and direct predation cues influence seed selection and handling behaviors (e.g., scatter hoarding versus larder hoarding) of two heteromyid rodents, Ord's kangaroo rat ( Dipodomys ordii) and the Great Basin pocket mouse ( Perognathus parvus). The indirect cue was shrub cover, a feature of the environment. Direct cues, presented individually, were (1) control, (2) coyote ( Canis latrans) vocalization, (3) coyote scent, (4) red fox ( Vulpes vulpes) scent, or (5) short-eared owl ( Asio flammeus) vocalization. We offered seeds of three sizes: two native grasses, Indian ricegrass ( Achnatherum hymenoides) and bluebunch wheatgrass ( Pseudoroegneria spicata), and the non-native cereal rye ( Secale cereale), each in separate trays. Kangaroo rats preferentially harvested Indian ricegrass while pocket mice predominately harvested Indian ricegrass and cereal rye. Pocket mice were more likely to scatter hoard preferred seeds, whereas kangaroo rats mostly consumed and/or larder hoarded preferred seeds. No predator cue significantly affected seed preferences. However, both species altered seed handling behavior in response to direct predation cues by leaving more seeds available in the seed pool, though they responded to different predator cues. If these results translate to natural dynamics on the landscape, the two rodents are expected to have different impacts on seed survival and plant recruitment via their different seed selection and seed handling behaviors.

Effects of rodent species, seed species, and predator cues on seed fate

USGS Publications Warehouse

Sivy, Kelly J.; Ostoja, Steven M.; Schupp, Eugene W.; Durham, Susan

2011-01-01

Seed selection, removal and subsequent management by granivorous animals is thought to be a complex interaction of factors including qualities of the seeds themselves (e.g., seed size, nutritional quality) and features of the local habitat (e.g. perceived predator risk). At the same time, differential seed selection and dispersal is thought to have profound effects on seed fate and potentially vegetation dynamics. In a feeding arena, we tested whether rodent species, seed species, and indirect and direct predation cues influence seed selection and handling behaviors (e.g., scatter hoarding versus larder hoarding) of two heteromyid rodents, Ord's kangaroo rat (Dipodomys ordii) and the Great Basin pocket mouse (Perognathus parvus). The indirect cue was shrub cover, a feature of the environment. Direct cues, presented individually, were (1) control, (2) coyote (Canis latrans) vocalization, (3) coyote scent, (4) red fox (Vulpes vulpes) scent, or (5) short-eared owl (Asio flammeus) vocalization. We offered seeds of three sizes: two native grasses, Indian ricegrass (Achnatherum hymenoides) and bluebunch wheatgrass (Pseudoroegneria spicata), and the non-native cereal rye (Secale cereale), each in separate trays. Kangaroo rats preferentially harvested Indian ricegrass while pocket mice predominately harvested Indian ricegrass and cereal rye. Pocket mice were more likely to scatter hoard preferred seeds, whereas kangaroo rats mostly consumed and/or larder hoarded preferred seeds. No predator cue significantly affected seed preferences. However, both species altered seed handling behavior in response to direct predation cues by leaving more seeds available in the seed pool, though they responded to different predator cues. If these results translate to natural dynamics on the landscape, the two rodents are expected to have different impacts on seed survival and plant recruitment via their different seed selection and seed handling behaviors.

Hypercarnivorous apex predator could provide ecosystem services by dispersing seeds

PubMed Central

Sarasola, José Hernán; Zanón-Martínez, Juan Ignacio; Costán, Andrea Silvina; Ripple, William J.

2016-01-01

Large “hypercarnivorous” felids are recognized for their role as apex predators and hence as key elements in food webs and ecosystem functioning through competition and depredation. Here we show that cougars (Puma concolor), one of the largest and the most widely ranging apex felid predators with a strictly carnivorous diet, could also be effective secondary long distance seed dispersers, potentially establishing direct and non-herbivore mediated interactions with plant species at the bottom of the food web. Cougars accidently ingest and disseminate large amounts of seeds (31,678 seeds in 123 scats) of plant species initially consumed by their main prey, the Eared Dove Zenaida auriculata. The germination potential of seeds for the three plant species most abundantly found in cougar scats (19,570 seeds) was not significantly different from that observed in seeds obtained from dove gizzards, indicating that seed passage through cougar guts did not affect seed germination. Considering the estimated cougar density in our study area, dispersal of seeds by cougars could allow a mean, annual seed spread of ~5,000 seeds per km2. Our results demonstrate that strictly carnivorous, felid predators could have broad and overlooked ecological functions related to ecosystem structuring and functioning. PMID:26791932

Hypercarnivorous apex predator could provide ecosystem services by dispersing seeds.

PubMed

Sarasola, José Hernán; Zanón-Martínez, Juan Ignacio; Costán, Andrea Silvina; Ripple, William J

2016-01-21

Large "hypercarnivorous" felids are recognized for their role as apex predators and hence as key elements in food webs and ecosystem functioning through competition and depredation. Here we show that cougars (Puma concolor), one of the largest and the most widely ranging apex felid predators with a strictly carnivorous diet, could also be effective secondary long distance seed dispersers, potentially establishing direct and non-herbivore mediated interactions with plant species at the bottom of the food web. Cougars accidently ingest and disseminate large amounts of seeds (31,678 seeds in 123 scats) of plant species initially consumed by their main prey, the Eared Dove Zenaida auriculata. The germination potential of seeds for the three plant species most abundantly found in cougar scats (19,570 seeds) was not significantly different from that observed in seeds obtained from dove gizzards, indicating that seed passage through cougar guts did not affect seed germination. Considering the estimated cougar density in our study area, dispersal of seeds by cougars could allow a mean, annual seed spread of ~5,000 seeds per km(2). Our results demonstrate that strictly carnivorous, felid predators could have broad and overlooked ecological functions related to ecosystem structuring and functioning.

Pollination and seed dispersal are the most threatened processes of plant regeneration

NASA Astrophysics Data System (ADS)

Neuschulz, Eike Lena; Mueller, Thomas; Schleuning, Matthias; Böhning-Gaese, Katrin

2016-07-01

Plant regeneration is essential for maintaining forest biodiversity and ecosystem functioning, which are globally threatened by human disturbance. Here we present the first integrative meta-analysis on how forest disturbance affects multiple ecological processes of plant regeneration including pollination, seed dispersal, seed predation, recruitment and herbivory. We analysed 408 pairwise comparisons of these processes between near-natural and disturbed forests. Human impacts overall reduced plant regeneration. Importantly, only processes early in the regeneration cycle that often depend on plant-animal interactions, i.e. pollination and seed dispersal, were negatively affected. Later processes, i.e. seed predation, recruitment and herbivory, showed overall no significant response to human disturbance. Conserving pollination and seed dispersal, including the animals that provide these services to plants, should become a priority in forest conservation efforts globally.

Seed traits and taxonomic relationships determine the occurrence of mutualisms versus seed predation in a tropical forest rodent and seed dispersal system.

PubMed

Wang, Zhenyu; Cao, Lin; Zhang, Zhibin

2014-06-01

Although many studies have been carried out on plant-animal mutualistic assemblages, the roles of functional traits and taxonomy in determining both whether interactions involve mutualisms or predation and the structure of such assemblages are unclear. We used semi-natural enclosures to quantitatively assess the interaction strengths between seeds of 8 sympatric tree species and 4 rodent species in a tropical forest in Xishuangbanna, Yunnan, Southwest China. We found 2 clusters of species in the seed-rodent network represented by 2 genera in the Fagaceae (Castanopsis, Lithocarpus). Compared to seeds of 3 Castanopsis species, seeds with heavy weight, hard coat or caloric content (including 3 Lithocarpus species) were eaten less and more frequently hoarded by rodents. In turn, hoarded seeds showed less predation and more mutualism with rodents. Our results suggest that seed traits significantly affected the hoarding behavior of rodents, and, consequently, the occurrence of mutualisms and predation as well as assemblage structure in the plant-animal seed dispersal system. Taxonomically-related species with similar seed traits as functional groups belong to the same substructures in the assemblage. Our results indicate that both seed traits and taxonomic relationships may simplify thinking about seed dispersal systems by helping to elucidate whether interactions are likely to be dominated by predation or mutualism. © 2013 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and Wiley Publishing Asia Pty Ltd.

Imidacloprid seed treatments affect individual ant behavior and community structure but not egg predation, pest abundance or soybean yield.

PubMed

Penn, Hannah J; Dale, Andrew M

2017-08-01

Neonicotinoid seed treatments are under scrutiny because of their variable efficacy against crop pests and for their potential negative impacts on non-target organisms. Ants provide important biocontrol services in agroecosystems and can be indicators of ecosystem health. This study tested for effects of exposure to imidacloprid plus fungicide or fungicide-treated seeds on individual ant survival, locomotion and foraging capabilities and on field ant community structure, pest abundance, ant predation and yield. Cohorts of ants exposed to either type of treated seed had impaired locomotion and a higher incidence of morbidity and mortality but no loss of foraging capacity. In the field, we saw no difference in ant species richness, regardless of seed treatment. Blocks with imidacloprid did have higher species evenness and diversity, probably owing to variable effects of the insecticide on different ant species, particularly Tetramorium caespitum. Ant predation on sentinel eggs, pest abundance and soybean growth and yield were similar in the two treatments. Both seed treatments had lethal and sublethal effects on ant individuals, and the influence of imidacloprid seed coating in the field was manifested in altered ant community composition. Those effects, however, were not strong enough to affect egg predation, pest abundance or soybean yield in field blocks. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Impacts of logging on density-dependent predation of dipterocarp seeds in a South East Asian rainforest.

PubMed

Bagchi, Robert; Philipson, Christopher D; Slade, Eleanor M; Hector, Andy; Phillips, Sam; Villanueva, Jerome F; Lewis, Owen T; Lyal, Christopher H C; Nilus, Reuben; Madran, Adzley; Scholes, Julie D; Press, Malcolm C

2011-11-27

Much of the forest remaining in South East Asia has been selectively logged. The processes promoting species coexistence may be the key to the recovery and maintenance of diversity in these forests. One such process is the Janzen-Connell mechanism, where specialized natural enemies such as seed predators maintain diversity by inhibiting regeneration near conspecifics. In Neotropical forests, anthropogenic disturbance can disrupt the Janzen-Connell mechanism, but similar data are unavailable for South East Asia. We investigated the effects of conspecific density (two spatial scales) and distance from fruiting trees on seed and seedling survival of the canopy tree Parashorea malaanonan in unlogged and logged forests in Sabah, Malaysia. The production of mature seeds was higher in unlogged forest, perhaps because high adult densities facilitate pollination or satiate pre-dispersal predators. In both forest types, post-dispersal survival was reduced by small-scale (1 m(2)) conspecific density, but not by proximity to the nearest fruiting tree. Large-scale conspecific density (seeds per fruiting tree) reduced predation, probably by satiating predators. Higher seed production in unlogged forest, in combination with slightly higher survival, meant that recruitment was almost entirely limited to unlogged forest. Thus, while logging might not affect the Janzen-Connell mechanism at this site, it may influence the recruitment of particular species.

Effects of seed density and proximity to refuge habitat on seed predation rates for a rare and a common Lupinus species.

PubMed

Pardini, Eleanor A; Patten, Melissa V; Knight, Tiffany M

2017-03-01

Biotic interactions such as seed predation can play a role in explaining patterns of abundance among plant species. The effect of seed predation will depend on how the strength of predation differs across species and environments, and on the degree to which seed loss at one life-cycle phase increases fitness at another phase. Few studies have simultaneously quantified predispersal and postdispersal predation in co-occurring rare and common congeners, despite the value of estimating both for understanding causes of rarity. We quantified predispersal seed predation on the rare, herbaceous species Lupinus tidestromii (Fabaceae) and its common, shrubby congener L. chamissonis across multiple years in the same community. We experimentally measured postdispersal seed predation at two seed densities and locations near or far from an exotic grass housing high densities of deer mice ( Peromyscus maniculatus ), their primary, native seed predator. The common L. chamissonis had the lowest predispersal seed predation of the two lupine species, potentially because of its height: its high racemes received less predation than those low to the ground. By contrast, the same species experienced higher postdispersal seed predation, and at predators traveled long distances away from refuge habitat to consume their seeds. Across both plant species, mice preferentially predated high-density seed sources. Our results show differences in the magnitude and direction of seed predation between the species across different life-cycle phases. We demonstrated possible roles of proximity to refuge habitat, seed density, and seed size in these patterns. Congeneric comparisons would benefit from a comprehensive framework that considers seed predation across different life-cycle phases and the environmental context of predation. © 2017 Botanical Society of America.

Past agricultural land use and present-day fire regimes can interact to determine the nature of seed predation.

PubMed

Stuhler, John D; Orrock, John L

2016-06-01

Historical agriculture and present-day fire regimes can have significant effects on contemporary ecosystems. Although past agricultural land use can lead to long-term changes in plant communities, it remains unclear whether these persistent land-use legacies alter plant-consumer interactions, such as seed predation, and whether contemporary disturbance (e.g., fire) alters the effects of historical agriculture on these interactions. We conducted a study at 27 sites distributed across 80,300 ha in post-agricultural and non-agricultural longleaf pine woodlands with different degrees of fire frequency to test the hypothesis that past and present-day disturbances that alter plant communities can subsequently alter seed predation. We quantified seed removal by arthropods and rodents for Tephrosia virginiana and Vernonia angustifolia, species of conservation interest. We found that the effects of land-use history and fire frequency on seed removal were contingent on granivore guild and microhabitat characteristics. Tephrosia virginiana removal was greater in low fire frequency sites, due to greater seed removal by rodents. Although overall removal of V. angustifolia did not differ among habitats, rodents removed more seeds than arthropods at post-agricultural sites and non-agricultural sites with low fire frequencies, but not at non-agricultural sites with high fire frequencies. Land-use history and fire frequency also affected the relationship between microhabitat characteristics and removal of V. angustifolia. Our results suggest that historical agriculture and present-day fire regimes may alter seed predation by shifting the impact of rodent and arthropod seed predators among habitats, with potential consequences for the establishment of rare plant species consumed by one or both predators.

Effects of pollen load, parasitoids and the environment on pre-dispersal seed predation in the cleistogamous Ruellia nudiflora.

PubMed

Munguía-Rosas, Miguel A; Abdala-Roberts, Luis; Parra-Tabla, Víctor

2013-11-01

Few studies have simultaneously addressed the effects of biotic and abiotic factors on pre-dispersal seed predation (PSP). Plant-seed predator interactions may be influenced by natural enemies and pollinators (the latter through changes in fruit or seed traits), and the activity of pre-dispersal seed predators and their natural enemies may both be affected by the abiotic environment. Additionally, in the case of cleistogamous plants with fruit dimorphism, PSP may be biased towards larger and more seeded chasmogamous (CH) fruits [relative to the smaller cleistogamous (CL) fruits], and the effects of biotic and abiotic factors may be contingent upon this fruit dimorphism. We studied PSP in the cleistogamous Ruellia nudiflora using a split-plot experimental design and asked the following: (1) is PSP biased towards CH fruits and is there an effect of pollen load on PSP? (2) Do parasitoids influence PSP and is their effect influenced by pollen load or fruit type? And (3) do light and water availability modify PSP and parasitoid effects? PSP was higher for CH relative to CL fruits, and under low water availability it was lower for pollen-supplemented CH fruits relative to open-pollinated CH fruits. Parasitoids were not influenced by abiotic conditions, but their negative effect on PSP was stronger for pollen-supplemented CH fruits. Overall, we show that fruit dimorphism, abiotic factors and natural enemies affect PSP, and that these effects can be non-additive.

Insect Seed Predators in Erythrina falcata (Fabaceae): Identification of Predatory Species and Ecological Consequences of Asynchronous Flowering.

PubMed

Pereira, C M; Moura, M O; Da-Silva, P R

2014-06-01

Seed predation by insects exerts negative effects on plant reproduction by limiting the supply of seeds and preventing germination. Seed predators of the family Fabaceae are usually generalists, which increases the rate of predation. One strategy to minimize seed predation, developed by plants from temperate regions, is "escape in time," i.e., flowering before or after the peak of predation. For tropical species, few studies have investigated the strategies used by plants to minimize seed predation. Here, using Erythrina falcata, a tropical species of Fabaceae, we test three main hypotheses: (i) escape in time is a mechanism used by E. falcata to minimize seed predation, (ii) the predators of E. falcata seeds are generalists, and (iii) the biometric variables of the pods can influence seed predation. In order to test these hypotheses, we determined the flowering time of E. falcata, rate of seed predation, the predators insects, and biometric variables of the pods. The analyzed trees were grouped into three classes: "early," "peak," and "late" flowering. The average seed predation rates on trees in the early and late classes were 65% and 50%, respectively, and in the peak class, 80%; thus, our first hypothesis can be accepted. Three species of Lepidoptera and two of Coleoptera were found preying on E. falcata seeds. These species were observed to be generalist predators; thus, our second hypothesis can be accepted. The biometric variables of the pods cannot influence seed predation rate. The ecological consequences of asynchronous flowering on plants and insects are discussed.

Impacts of logging on density-dependent predation of dipterocarp seeds in a South East Asian rainforest

PubMed Central

Bagchi, Robert; Philipson, Christopher D.; Slade, Eleanor M.; Hector, Andy; Phillips, Sam; Villanueva, Jerome F.; Lewis, Owen T.; Lyal, Christopher H. C.; Nilus, Reuben; Madran, Adzley; Scholes, Julie D.; Press, Malcolm C.

2011-01-01

Much of the forest remaining in South East Asia has been selectively logged. The processes promoting species coexistence may be the key to the recovery and maintenance of diversity in these forests. One such process is the Janzen–Connell mechanism, where specialized natural enemies such as seed predators maintain diversity by inhibiting regeneration near conspecifics. In Neotropical forests, anthropogenic disturbance can disrupt the Janzen–Connell mechanism, but similar data are unavailable for South East Asia. We investigated the effects of conspecific density (two spatial scales) and distance from fruiting trees on seed and seedling survival of the canopy tree Parashorea malaanonan in unlogged and logged forests in Sabah, Malaysia. The production of mature seeds was higher in unlogged forest, perhaps because high adult densities facilitate pollination or satiate pre-dispersal predators. In both forest types, post-dispersal survival was reduced by small-scale (1 m2) conspecific density, but not by proximity to the nearest fruiting tree. Large-scale conspecific density (seeds per fruiting tree) reduced predation, probably by satiating predators. Higher seed production in unlogged forest, in combination with slightly higher survival, meant that recruitment was almost entirely limited to unlogged forest. Thus, while logging might not affect the Janzen–Connell mechanism at this site, it may influence the recruitment of particular species. PMID:22006965

How much Dillenia indica seed predation occurs from Asian elephant dung?

NASA Astrophysics Data System (ADS)

Sekar, Nitin; Giam, Xingli; Sharma, Netra Prasad; Sukumar, Raman

2016-01-01

Elephants are thought to be effective seed dispersers, but research on whether elephant dung effectively protects seeds from seed predation is lacking. Quantifying rates of seed predation from elephant dung will facilitate comparisons between elephants and alternative dispersers, helping us understand the functional role of megaherbivores in ecosystems. We conducted an experiment to quantify the predation of Dillenia indica seeds from elephant dung in Buxa Reserve, India from December 2012 to April 2013. Using dung boluses from the same dung pile, we compared the number of seeds in boluses that are a) opened immediately upon detection (control boluses), b) made available only to small seed predators (<3 mm wide) for 1-4 months, and c) made available to all seed predators and secondary dispersers for 1-4 months. Using a model built on this experiment, we estimated that seed predation by small seed predators (most likely ants and termites) destroys between 82.9% and 96.4% of seeds in elephant dung between the time of defecation and the median germination date for D. indica. Exposure to larger seed predators and secondary dispersers did not lead to a significant additional reduction in the number of seeds per dung bolus. Our findings suggest that post-dispersal seed predation by small insects (<3 mm) substantially reduces but does not eliminate the success of elephants as dispersers of D. indica in a tropical moist forest habitat.

Seed size variation in the palm Euterpe edulis and the effects of seed predators on germination and seedling survival

NASA Astrophysics Data System (ADS)

Pizo, Marco A.; Von Allmen, Christiane; Morellato, L. Patricia C.

2006-05-01

Intraspecific variation in seed size is common in wild plant populations and has important consequences for the reproductive success of individual plants. Multiple, often conflicting evolutionary forces mediated by biotic as well as abiotic agents may maintain such a variation. In this paper we assessed seed size variation in a population of the threatened, commercially important palm Euterpe edulis in southeast Brazil. We investigated (i) how this variation affects the probability of attack by vertebrate and invertebrate post-dispersal seed predators, and (ii) if seed size influences the outcome of seeds damaged by beetles in terms of seed germination and early survival of seedlings. Euterpe edulis seeds varied in diameter from 8.3 to 14.1 mm. Neither insects nor rodents selected the seeds they preyed upon based on seed size. Seed germination and total, shoot and root biomasses of one-year seedlings were significantly and positively affected by seed size. Root biomass and seedling survival were negatively affected by seed damage caused by a scolytid beetle ( Coccotrypes palmarum) whose adults bore into seeds to consume part of the endosperm, but do not oviposit on them. Seed size had a marginally significant effect on seedling survival. Therefore, if any advantage is accrued by E. edulis individuals producing large seeds, this is because of greater seed germination success and seedling vigor. If this is so, even a relatively narrow range of variation in seed size as observed in the E. edulis population studied may translate into differential success of individual plants.

Effects of predispersal insect seed predation on the early life history stages of a rare cold sand-desert legume.

PubMed

Han, Yi J; Baskin, Jerry M; Tan, Dun Y; Baskin, Carol C; Wu, Ming Y

2018-02-19

Seed predation by insects is common in seeds of Fabaceae (legume) species with physical dormancy (PY). However, the consequences of insect seed predation on the life history of legumes with PY have been little studied. In the largest genus of seed plants, Astragalus (Fabaceae), only one study has tested the effects of insect predation on germination, and none has tested it directly on seedling survival. Thus, we tested the effects of insect predation on seed germination and seedling growth and survival of Astragalus lehmannianus, a central Asian sand-desert endemic. Under laboratory conditions, seeds lightly predated in the natural habitat of this perennial legume germinated to a much higher percentage than intact seeds, and seedlings from predated and nonpredated seeds survived and grew about equally well. Further, in contrast to our prediction seedlings from predated seeds that germinated "out-of-season" under near-natural conditions in NW China survived over winter. The implication of our results is that individual plants from predated seeds that germinate early (in our case autumn) potentially have a fitness advantage over those from nonpredated seeds, which delay germination until spring of a subsequent year.

Beneficial Effects of Ants and Spiders on the Reproductive Value of Eriotheca gracilipes (Malvaceae) in a Tropical Savanna

PubMed Central

2015-01-01

Predators affect plant fitness when they forage on them and reduce the action of herbivores. Our study evaluates the complementary effects of spiders and ants that visit the extrafloral nectaries of Eriotheca gracilipes (Malvaceae) on the production of fruits and viable seeds of these savanna trees. Four experimental groups were established: control group – with free access of spiders and ants; exclusion group – spiders and ants excluded; ant group – absence of spiders; and spider group – absence of ants. The presence of ants reduced the spider richness; however, the presence of spiders did not affect the ant richness. A significantly higher number of fruits per buds were found in the presence of spiders alone or spiders and ants together (control group) compared with the absence of both predators (exclusion group). The number of seeds per fruits and seed viability were higher in the control group. This is the first study showing that spiders and ants may exert a positive and complementary effect on the reproductive value of an extrafloral nectaried plant. Mostly the impact of ants and/or spiders on herbivores is considered, whereas our study reinforces the importance of evaluating the effect of multiple predators simultaneously, exploring how the interactions among predators with distinct skills may affect the herbivores and the plants on which they forage. PMID:26168036

Beneficial Effects of Ants and Spiders on the Reproductive Value of Eriotheca gracilipes (Malvaceae) in a Tropical Savanna.

PubMed

Stefani, Vanessa; Pires, Tayna Lopes; Torezan-Silingardi, Helena Maura; Del-Claro, Kleber

2015-01-01

Predators affect plant fitness when they forage on them and reduce the action of herbivores. Our study evaluates the complementary effects of spiders and ants that visit the extrafloral nectaries of Eriotheca gracilipes (Malvaceae) on the production of fruits and viable seeds of these savanna trees. Four experimental groups were established: control group - with free access of spiders and ants; exclusion group - spiders and ants excluded; ant group - absence of spiders; and spider group - absence of ants. The presence of ants reduced the spider richness; however, the presence of spiders did not affect the ant richness. A significantly higher number of fruits per buds were found in the presence of spiders alone or spiders and ants together (control group) compared with the absence of both predators (exclusion group). The number of seeds per fruits and seed viability were higher in the control group. This is the first study showing that spiders and ants may exert a positive and complementary effect on the reproductive value of an extrafloral nectaried plant. Mostly the impact of ants and/or spiders on herbivores is considered, whereas our study reinforces the importance of evaluating the effect of multiple predators simultaneously, exploring how the interactions among predators with distinct skills may affect the herbivores and the plants on which they forage.

Postdispersal seed predation limits the abundance of a long-lived perennial forb (Lithospermum ruderale).

PubMed

Bricker, Mary; Maron, John

2012-03-01

Loss of seeds to consumers is common in plant communities, but the degree to which these losses influence plant abundance or population growth is often unclear. This is particularly the case for postdispersal seed predation by rodents, as most studies of rodent seed predation have focused on the sources of spatiotemporal variation in seed loss but not quantified the population consequences of this loss. In previous work we showed that seed predation by deer mice (Peromyscus maniculatus) substantially reduced seedling recruitment and establishment of Lithospermum ruderale (Boraginaceae), a long-lived perennial forb. To shed light on how rodent seed predation and the near-term effects on plant recruitment might influence longer-term patterns of L. ruderale population growth, we combined experimental results with demographic data in stage-based population models. Model outputs revealed that rodent seed predation had a significant impact on L. ruderale population growth rate (lambda). With the removal of postdispersal seed predation, the projected population growth rates increased between 0.06 and 0.12, depending on site (mean deltalambda across sites = 0.08). Seed predation shifted the projected stable stage distribution of populations from one with a high proportion of young plants to one in which larger adult size classes dominate. Elasticities of vital rates also changed, with germination and growth of seedlings and young plants becoming more important with the removal of seed predation. Simulations varying the magnitude of seed predation pressure while holding other vital rates constant showed that seed predation could lower lambda even if only 40% of available seeds were consumed. These results demonstrate that rodent granivory can be a potent force limiting the abundance of a long-lived perennial forb.

Masting behaviour in a Mediterranean pine tree alters seed predator selection on reproductive output.

PubMed

Moreira, X; Abdala-Roberts, L; Zas, R; Merlo, E; Lombardero, M J; Sampedro, L; Mooney, K A

2016-11-01

Context-dependency in species interactions is widespread and can produce concomitant patterns of context-dependent selection. Masting (synchronous production of large seed crops at irregular intervals by a plant population) has been shown to reduce seed predation through satiation (reduction in rates of seed predation with increasing seed cone output) and thus represents an important source of context-dependency in plant-animal interactions. However, the evolutionary consequences of such dynamics are not well understood. Here we describe masting behaviour in a Mediterranean model pine species (Pinus pinaster) and present a test of the effects of masting on selection by seed predators on reproductive output. We predicted that masting, by enhancing seed predator satiation, could in turn strengthen positive selection by seed predators for larger cone output. For this we collected six-year data (spanning one mast year and five non-mast years) on seed cone production and seed cone predation rates in a forest genetic trial composed by 116 P. pinaster genotypes. Following our prediction, we found stronger seed predator satiation during the masting year, which in turn led to stronger seed predator selection for increased cone production relative to non-masting years. These findings provide evidence that masting can alter the evolutionary outcome of plant-seed predator interactions. More broadly, our findings highlight that changes in consumer responses to resource abundance represent a widespread mechanism for predicting and understanding context dependency in plant-consumer evolutionary dynamics. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

Pericarpial nectary-visiting ants do not provide fruit protection against pre-dispersal seed predators regardless of ant species composition and resource availability

PubMed Central

Ré Jorge, Leonardo; Benitez-Vieyra, Santiago; Amorim, Felipe W.

2017-01-01

Extrafloral nectaries can occur in both vegetative and reproductive plant structures. In many Rubiaceae species in the Brazilian Cerrado, after corolla abscission, the floral nectary continues to secret nectar throughout fruit development originating post-floral pericarpial nectaries which commonly attract many ant species. The occurrence of such nectar secreting structures might be strategic for fruit protection against seed predators, as plants are expected to invest higher on more valuable and vulnerable parts. Here, we performed ant exclusion experiments to investigate whether the interaction with ants mediated by the pericarpial nectaries of Tocoyena formosa affects plant reproductive success by reducing the number of pre-dispersal seed predators. We also assessed whether ant protection was dependent on ant species composition and resource availability. Although most of the plants were visited by large and aggressive ant species, such as Ectatomma tuberculatum and species of the genus Camponotus, ants did not protect fruits against seed predators. Furthermore, the result of the interaction was neither related to ant species composition nor to the availability of resources. We suggest that these results may be related to the nature and behavior of the most important seed predators, like Hemicolpus abdominalis weevil which the exoskeleton toughness prevent it from being predated by most ant species. On the other hand, not explored factors, such as reward quality, local ant abundance, ant colony characteristics and/or the presence of alternative energetic sources could also account for variations in ant frequency, composition, and finally ant protective effects, highlighting the conditionality of facultative plant-ant mutualisms. PMID:29211790

Temporal variation in seed predation by insects in a population of Syagrus romanzoffiana (Arecaceae) in Santa Catarina Island, SC, Brazil.

PubMed

da Silva, F R; Begnini, R M; Lopes, B C; Castellani, T T

2012-02-01

Insect seed predation may vary depending on seed production. The present study considers the hypothesis that the rates of seed predation tend to be smaller in years of higher fruit production. Thus, we monitored the production of fruits and predation of seeds of the palm Syagrus romanzoffiana over 2 years in the Atlantic Forest (Parque Municipal da Lagoa do Peri, Florianópolis, SC, Brazil), between July 2006 and June 2008. Plots of 0.25 m(2) were fitted under 20 mother plants and fruits were monthly collected for assessment of abundance and seed predation. There was variation in fruit production between the 2 years and among reproductive plants. Predation rates were high and occurred in the predispersal phase by the Curculionidae Revena rubiginosa Boheman, Anchylorhynchus aegrotus Fahraeus, and Anchylorhynchus variabilis Gyllenhal. Seed predation by these species of Anchylorhynchus is first registered in the present study. In average, about 60% of the seeds monthly produced in the population tend to escape insect predation in year of high or low production, becoming available for recruitment. The predation rate was not related to the amount of fruits produced per reproductive plant. Also, different than expected, there was a positive relation between the rates of seed predation and the total of fruits produced monthly on the plots. Thus, no evidence for the satiation of insect seed predators was found in this study with S. romanzoffiana.

Do flower color and floral scent of silene species affect host preference of Hadena bicruris, a seed-eating pollinator, under field conditions?

PubMed

Page, Paul; Favre, Adrien; Schiestl, Florian P; Karrenberg, Sophie

2014-01-01

Specialization in plant-insect interactions is an important driver of evolutionary divergence; yet, plant traits mediating such interactions are poorly understood. In this study, we investigated how flower color and floral scent are related to seed predation by a seed-eating pollinator. We used field-transplanted recombinant F2 hybrids between Silene latifolia and S. dioica that are the preferred and alternative hosts of the moth Hadena bicruris and crosses within these species for comparison. We scored seed predation and flower color and analyzed floral scent. Pinker S. dioica-like flowers and emission of α-pinene decreased the odds of seed predation while emission of benzyl acetate and 6-methyl-5-hepten-2-one increased the odds of seed predation. Emission of these compounds did not differ significantly between the two Silene species. Our results suggest that flower color plays an important role in the specific interaction of H. bicruris with its preferred host S. latifolia. The compounds α-pinene, benzyl acetate and 6-methyl-5-hepten-2-one could represent non-specific deterrents and attractants to ovipositing moths. Alternatively, emission of these compounds could be related to herbivory or pathogen attack and act as a signal for host quality. This would weaken the predictability of the plant's costs and benefits of the interaction and act to maintain an imperfect degree of specialization.

Do Flower Color and Floral Scent of Silene Species affect Host Preference of Hadena bicruris, a Seed-Eating Pollinator, under Field Conditions?

PubMed Central

Page, Paul; Favre, Adrien; Schiestl, Florian P.; Karrenberg, Sophie

2014-01-01

Specialization in plant–insect interactions is an important driver of evolutionary divergence; yet, plant traits mediating such interactions are poorly understood. In this study, we investigated how flower color and floral scent are related to seed predation by a seed-eating pollinator. We used field-transplanted recombinant F2 hybrids between Silene latifolia and S. dioica that are the preferred and alternative hosts of the moth Hadena bicruris and crosses within these species for comparison. We scored seed predation and flower color and analyzed floral scent. Pinker S. dioica-like flowers and emission of α-pinene decreased the odds of seed predation while emission of benzyl acetate and 6-methyl-5-hepten-2-one increased the odds of seed predation. Emission of these compounds did not differ significantly between the two Silene species. Our results suggest that flower color plays an important role in the specific interaction of H. bicruris with its preferred host S. latifolia. The compounds α-pinene, benzyl acetate and 6-methyl-5-hepten-2-one could represent non-specific deterrents and attractants to ovipositing moths. Alternatively, emission of these compounds could be related to herbivory or pathogen attack and act as a signal for host quality. This would weaken the predictability of the plant's costs and benefits of the interaction and act to maintain an imperfect degree of specialization. PMID:24905986

Effects of frugivore impoverishment and seed predators on the recruitment of a keystone palm

NASA Astrophysics Data System (ADS)

Fadini, Rodrigo F.; Fleury, Marina; Donatti, Camila I.; Galetti, Mauro

2009-03-01

Many plant species are threatened as a result of extinction of their large-bodied frugivores all over the world. Additionally, introduced herbivores and seed predators may cause severe pressure on early stages of plant recruitment. We studied the seed dispersal and seed predation of the keystone palm Euterpe edulis on a land-bridge island with a highly impoverished frugivore fauna and overabundant seed predators, and in a continuous Atlantic forest in Brazil. While the diversity of avian seed dispersers and predators was higher on the mainland, the abundance of seed dispersers was 4-fold higher on the island. Turdus flavipes was responsible for 72% and 96% of seeds removed in the island and mainland, respectively. However, the higher density of T. flaviceps on the island did not result in higher seed removal. In fact, seed removal rate was 1.7 times lower there than on the mainland, probably due to the aggressive behavior of the major seed disperser who defend palm fruits. Seed predation, on the other hand, was markedly higher on the island, where nearly 100% of seeds were preyed upon, but only 0.3% on the mainland. As a consequence of higher seed predation the population of E. edulis has few numbers of seedlings and saplings on the island. Therefore, management of the seed predator populations on the island is a key priority for recovering the natural population of this keystone palm and the frugivores that depend on its fruits.

Adaptive Advantage of Myrmecochory in the Ant-Dispersed Herb Lamium amplexicaule (Lamiaceae): Predation Avoidance through the Deterrence of Post-Dispersal Seed Predators

PubMed Central

Tanaka, Koki; Ogata, Kanako; Mukai, Hiromi; Yamawo, Akira; Tokuda, Makoto

2015-01-01

Seed dispersal by ants (myrmecochory) is found worldwide, but the benefits that plants obtain from this mutualism remain uncertain. In the present study, we conducted laboratory experiments to demonstrate seed predator avoidance as a benefit of myrmecochory using the annual ant-dispersed herb Lamium amplexicaule, the disperser ant Tetramorium tsushimae, and the seed predatory burrower bug Adomerus rotundus. We compared the predation intensity of Lamium amplexicaule seeds by Adomerus rotundus under the presence or absence of Tetramorium tsushimae. Both the number of seeds sucked by Adomerus rotundus adults and the feeding duration of sucked seeds by nymphs were significantly reduced in the presence of ants. This effect was most likely due to the behavioral alteration of Adomerus rotundus in response to the ant presence, because ants seldom predated Adomerus rotundus during the experiment. Our results demonstrated that the presence of ants decreases post-dispersal seed predation, even when the ants do not bury the seeds. The present study thus suggests that the non-consumptive effects of ants on seed predators benefit myrmecochorous plants. PMID:26197397

A test of the predator satiation hypothesis, acorn predator size, and acorn preference

Treesearch

C.H. Greenberg; S.J. Zarnoch

2018-01-01

Mast seeding is hypothesized to satiate seed predators with heavy production and reduce populations with crop failure, thereby increasing seed survival. Preference for red or white oak acorns could influence recruitment among oak species. We tested the predator satiation hypothesis, acorn preference, and predator size by concurrently...

Are Local Filters Blind to Provenance? Ant Seed Predation Suppresses Exotic Plants More than Natives

PubMed Central

Pearson, Dean E.; Icasatti, Nadia S.; Hierro, Jose L.; Bird, Benjamin J.

2014-01-01

The question of whether species’ origins influence invasion outcomes has been a point of substantial debate in invasion ecology. Theoretically, colonization outcomes can be predicted based on how species’ traits interact with community filters, a process presumably blind to species’ origins. Yet, exotic plant introductions commonly result in monospecific plant densities not commonly seen in native assemblages, suggesting that exotic species may respond to community filters differently than natives. Here, we tested whether exotic and native species differed in their responses to a local community filter by examining how ant seed predation affected recruitment of eighteen native and exotic plant species in central Argentina. Ant seed predation proved to be an important local filter that strongly suppressed plant recruitment, but ants suppressed exotic recruitment far more than natives (89% of exotic species vs. 22% of natives). Seed size predicted ant impacts on recruitment independent of origins, with ant preference for smaller seeds resulting in smaller seeded plant species being heavily suppressed. The disproportionate effects of provenance arose because exotics had generally smaller seeds than natives. Exotics also exhibited greater emergence and earlier peak emergence than natives in the absence of ants. However, when ants had access to seeds, these potential advantages of exotics were negated due to the filtering bias against exotics. The differences in traits we observed between exotics and natives suggest that higher-order introduction filters or regional processes preselected for certain exotic traits that then interacted with the local seed predation filter. Our results suggest that the interactions between local filters and species traits can predict invasion outcomes, but understanding the role of provenance will require quantifying filtering processes at multiple hierarchical scales and evaluating interactions between filters. PMID:25099535

Seed Dispersers, Seed Predators, and Browsers Act Synergistically as Biotic Filters in a Mosaic Landscape

PubMed Central

Zamora, Regino; Matías, Luis

2014-01-01

In this study, we analize the functional influence of animals on the plants they interact with in a mediterranean mountain. We hypothesise that seed dispersers, seed predators, and browsers can act as biotic filters for plant communities. We analyse the combined effects of mutualistic (seed dispersal) and antagonistic (seed predation, herbivory) animal interactions in a mosaic landscape of Mediterranean mountains, basing our results on observational and experimental field. Most of the dispersed seeds came from tree species, whereas the population of saplings was composed predominantly of zoochorous shrub species. Seed predators preferentially consumed seeds from tree species, whereas seeds from the dominant fleshy-fruited shrubs had a higher probability of escaping these predators. The same pattern was repeated among the different landscape units by browsers, since they browsed selectively and far more intensely on tree-species saplings than on the surrounding shrubs. In synthesis, our work identifies the major biotic processes that appear to be favoring a community dominated by shrubs versus trees because seed dispersers, predators, and herbivores together favored shrub dispersal and establishment versus trees. PMID:25233342

Identification and Management of Multiple Threats to Rare and Endangered Plant Species

DTIC Science & Technology

2013-07-30

Glynn et. al., 2003), affect fruit removal (Schaefer et. al., 2003) and change the palatability of plants to slugs (Albrectsen et. al., 2004...persistent seed bank. Initial seed bank composition should not be affected by the fence, as we detected no initial difference in flowering or fruiting ...and secondary compounds affect fruit removal. Oikos 102, 318-328. Sessions, L., Kelly, D., 2002. Predator mediated apparent competition between an

Endocarp thickness affects seed removal speed by small rodents in a warm-temperate broad-leafed deciduous forest, China

NASA Astrophysics Data System (ADS)

Zhang, Hongmao; Zhang, Zhibin

2008-11-01

Seed traits are important factors affecting seed predation by rodents and thereby the success of recruitment. Seeds of many tree species have hard hulls. These are thought to confer mechanical protection, but the effect of endocarp thickness on seed predation by rodents has not been well investigated. Wild apricot ( Prunus armeniaca), wild peach ( Amygdalus davidiana), cultivated walnut ( Juglans regia), wild walnut ( Juglans mandshurica Maxim) and Liaodong oak ( Quercus liaotungensis) are very common tree species in northwestern Beijing city, China. Their seeds vary greatly in size, endocarp thickness, caloric value and tannin content. This paper aims to study the effects of seed traits on seed removal speed of these five tree species by small rodents in a temperate deciduous forest, with emphasis on the effect of endocarp thickness. The results indicated that speed of removal of seeds released at stations in the field decreased significantly with increasing endocarp thickness. We found no significant correlations between seed removal speed and other seed traits such as seed size, caloric value and tannin content. In seed selection experiments in small cages, Père David's rock squirrel ( Sciurotamias davidianus), a large-bodied, strong-jawed rodent, selected all of the five seed species, and the selection order among the five seed species was determined by endocarp thickness and the ratio of endocarp mass/seed mass. In contrast, the Korean field mouse ( Apodemus peninsulae) and Chinese white-bellied rat ( Niviventer confucianus), with relatively small bodies and weak jaws, preferred to select small seeds like acorns of Q. liaotungensis and seeds of P. armeniaca, indicating that rodent body size is also an important factor affecting food selection based on seed size. These results suggest endocarp thickness significantly reduces seed removal speed by rodents and then negatively affects dispersal fitness of seeds before seed removal of tree species in the study region. However, effect of endocarp thickness on final dispersal fitness needs further investigation because it may increase seed caching and survival after seed removal.

Functional traits determine formation of mutualism and predation interactions in seed-rodent dispersal system of a subtropical forest

NASA Astrophysics Data System (ADS)

Chang, Gang; Zhang, Zhibin

2014-02-01

Network structure in plant-animal systems has been widely investigated but the roles of functional traits of plants and animals in formation of mutualism and predation interactions and community structure are still not fully understood. In this study, we quantitatively assessed interaction strength of mutualism and predation between 5 tree species and 7 rodent species by using semi-natural enclosures in a subtropical forest in southwest China. Seeds with high handling-time and nutrition traits (for both rat and mouse species) or high tannin trait (for mouse species) show high mutualism but low predation with rodents; while seeds with low handling-time and low nutrition traits show high predation but low mutualism with rodents. Large-sized rat species are more linked to seeds with high handling-time and high nutrition traits, while small-sized mouse species are more connected with seeds with low handling-time, low nutrition value and high tannin traits. Anti-predation seed traits tend to increase chance of mutualism instead of reducing predation by rodents, suggesting formation of mutualism may be connected with that of predation. Our study demonstrates that seed and animal traits play significant roles in the formation of mutualism and predation and network structure of the seed-rodent dispersal system.

Contagious seed dispersal beneath heterospecific fruiting trees and its consequences.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwit, Charles; Levey, Douglas, J.; Greenberg, Cathyrn, H.

2004-05-03

Kwit, Charles, D.J. Levey and Cathryn H. Greenberg. 2004. Contagious seed dispersal beneath heterospecific fruiting trees and its consequences. Oikos. 107:303-308 A n hypothesized advantage of seed dispersal is avoidance of high per capita mortality (i.e. density-dependent mortality) associated with dense populations of seeds and seedlings beneath parent trees. This hypothesis, inherent in nearly all seed dispersal studies, assumes that density effects are species-specific. Yet because many tree species exhibit overlapping fruiting phenologies and share dispersers, seeds may be deposited preferentially under synchronously fruiting heterospecific trees, another location where they may be particularly vulnerable to mortality, in this case bymore » generalist seed predators. We demonstrate that frugivores disperse higher densities of Cornus florida seeds under fruiting (female) I lex opaca trees than under non-fruiting (male) I lex trees in temperate hardwood forest settings in South Carolina, U SA . To determine if density of Cornus and/or I lex seeds influences survivorship of dispersed Cornus seeds, we followed the fates of experimentally dispersed Cornus seeds in neighborhoods of differing, manipulated background densities of Cornus and I lex seeds. We found that the probability of predation on dispersed Cornus seeds was a function of both Cornus and I lex background seed densities. H igher densities of I lex seeds negatively affected Cornus seed survivorship, and this was particularly evident as background densities of dispersed Cornus seeds increased. These results illustrate the importance of viewing seed dispersal and predation in a community context, as the pattern and intensity of density-dependent mortality may not be solely a function of conspecific densities.« less

Seed predation and climate impacts on reproductive variation in temperate forests of the southeastern USA

Treesearch

David M. Bell; James S. Clark

2016-01-01

Climatic effects on tree recruitment will be determined by the interactive effects of fecundity and seed predation. Evaluating how insect and vertebrate seed predators mediate tree reproductive responses to climate depends on long-term studies of seed production, development, and predation. In this study, our objectives were to (1) assess the effects of...

Advantages of masting in European beech: timing of granivore satiation and benefits of seed caching support the predator dispersal hypothesis.

PubMed

Zwolak, Rafał; Bogdziewicz, Michał; Wróbel, Aleksandra; Crone, Elizabeth E

2016-03-01

The predator satiation and predator dispersal hypotheses provide alternative explanations for masting. Both assume satiation of seed-eating vertebrates. They differ in whether satiation occurs before or after seed removal and caching by granivores (predator satiation and predator dispersal, respectively). This difference is largely unrecognized, but it is demographically important because cached seeds are dispersed and often have a microsite advantage over nondispersed seeds. We conducted rodent exclosure experiments in two mast and two nonmast years to test predictions of the predator dispersal hypothesis in our study system of yellow-necked mice (Apodemus flavicollis) and European beech (Fagus sylvatica). Specifically, we tested whether the fraction of seeds removed from the forest floor is similar during mast and nonmast years (i.e., lack of satiation before seed caching), whether masting decreases the removal of cached seeds (i.e., satiation after seed storage), and whether seed caching increases the probability of seedling emergence. We found that masting did not result in satiation at the seed removal stage. However, masting decreased the removal of cached seeds, and seed caching dramatically increased the probability of seedling emergence relative to noncached seeds. European beech thus benefits from masting through the satiation of scatterhoarders that occurs only after seeds are removed and cached. Although these findings do not exclude other evolutionary advantages of beech masting, they indicate that fitness benefits of masting extend beyond the most commonly considered advantages of predator satiation and increased pollination efficiency.

The Effect of Conservation Tillage and Cover Crop Residue on Beneficial Arthropods and Weed Seed Predation in Acorn Squash.

PubMed

Quinn, N F; Brainard, D C; Szendrei, Z

2016-12-01

Conservation tillage combined with cover crops or mulching may enhance natural enemy activity in agroecosystems by reducing soil disturbance and increasing habitat structural complexity. In particular, weed seed predation can increase with vegetation cover and reduced tillage, indicating that mulches may improve the quality of the habitat for weed seed foraging. The purpose of this study was to quantify the effects of tillage and mulching for conservation biological control in cucurbit fields. The effects of mulch and reduced tillage on arthropods and rates of weed seed loss from arenas were examined in field trials on sandy soils in 2014 and 2015. Experimental factors included tillage and cover crop, each with two levels: strip-tillage or full-tillage, and cover crop mulch (rye residue) or no cover crop mulch (unmulched). Arthropod abundance on the crop foliage was not affected by tillage or cover crops. Contrary to expectations, epigeal natural enemies of insects and rates of weed seed removal either did not respond to treatments or were greater in full-tilled plots and plots without mulch. Our study demonstrates the potential importance of weed seed predators in reducing weed seedbanks in vegetable agroecosystems, and suggests that early-season tillage may not be detrimental to epigeal predator assemblages. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Fruit Size Determines the Role of Three Scatter-Hoarding Rodents as Dispersers or Seed Predators of a Fleshy-Fruited Atacama Desert Shrub

PubMed Central

Loayza, Andrea P.; Squeo, Francisco A.

2016-01-01

Scatter-hoarding rodents can act as both predators and dispersers for many large-seeded plants because they cache seeds for future use, but occasionally forget them in sites with high survival and establishment probabilities. The most important fruit or seed trait influencing rodent foraging behavior is seed size; rodents prefer large seeds because they have higher nutritional content, but this preference can be counterbalanced by the higher costs of handling larger seeds. We designed a cafeteria experiment to assess whether fruit and seed size of Myrcianthes coquimbensis, an endangered desert shrub, influence the decision-making process during foraging by three species of scatter-hoarding rodents differing in body size: Abrothrix olivaceus, Phyllotis darwini and Octodon degus. We found that the size of fruits and seeds influenced foraging behavior in the three rodent species; the probability of a fruit being harvested and hoarded was higher for larger fruits than for smaller ones. Patterns of fruit size preference were not affected by rodent size; all species were able to hoard fruits within the entire range of sizes offered. Finally, fruit and seed size had no effect on the probability of seed predation, rodents typically ate only the fleshy pulp of the fruits offered and discarded whole, intact seeds. In conclusion, our results reveal that larger M. coquimbensis fruits have higher probabilities of being harvested, and ultimately of its seeds being hoarded and dispersed by scatter-hoarding rodents. As this plant has no other dispersers, rodents play an important role in its recruitment dynamics. PMID:27861550

Small-mammal seed predation limits the recruitment and abundance of two perennial grassland forbs

Treesearch

Mary Bricker; Dean Pearson; John Maron

2010-01-01

Although post-dispersal seed predators are common and often reduce seed density, their influence on plant population abundance remains unclear. On the one hand, increasing evidence suggests that many plant populations are seed limited, implying that seed predators could reduce plant abundance. On the other hand, it is generally uncertain whether the magnitude of seed...

Geographic consistency and variation in conflicting selection generated by pollinators and seed predators.

PubMed

Sun, Shi-Guo; Armbruster, W Scott; Huang, Shuang-Quan

2016-08-01

Floral traits that attract pollinators may also attract seed predators, which, in turn, may generate conflicting natural selection on such traits. Although such selection trade-offs are expected to vary geographically, few studies have investigated selection mediated by pollinators and seed predators across a geographic mosaic of environments and floral variation. Floral traits were investigated in 14 populations of the bumble-bee-pollinated herb, Pedicularis rex, in which tubular flowers are subtended by cupular bracts holding rain water. To study potentially conflicting selection on floral traits generated by pollinators and florivores, stigmatic pollen loads, initial seed set, pre-dispersal seed predation and final viable seed production were measured in 12-14 populations in the field. Generalized Linear Model (GLM) analyses indicated that the pollen load on stigmas was positively related to the exsertion of the corolla beyond the cupular bracts and size of the lower corolla lip, but so too was the rate of seed predation, creating conflicting selection on both floral traits. A geographic mosaic of selection mediated by seed predators, but not pollinators, was indicated by significant variation in levels of seed predation and the inclusion of two-, three- and four-way interaction terms between population and seed predation in the best model [lowest corrected Akaike Information Criterion (AICc)] explaining final seed production. These results indicate opposing selection in operation: pollinators generated selection for greater floral exsertion beyond the bracts, but seed predators generated selection for reduced exsertion above the protective pools of water, although the strength of the latter varied across populations. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Endophyte status of tall fescue (festuca arundinacea) affects seed predation

USDA-ARS?s Scientific Manuscript database

In a preliminary study seed of a tall fescue (Festuca arundinacea Schreb.) variety ‘Jesup’ without endophyte were consumed at a slightly higher rate by common cricket (Acheta domesticus L.) in a standard feeding trial than the same fescue variety with the endophyte. Although, the preference for the...

New approaches to understanding weed seed predation in agroecosystems

USDA-ARS?s Scientific Manuscript database

Postdispersal predation of weed seeds in arable systems can be a valuable ecosystem service, with the potential to support ecological approaches to weed management by reducing inputs to the soil seed bank. Scientific understanding of factors regulating weed seed predation rates is still insufficient...

Indirect interactions among tropical tree species through shared rodent seed predators: a novel mechanism of tree species coexistence.

PubMed

Garzon-Lopez, Carol X; Ballesteros-Mejia, Liliana; Ordoñez, Alejandro; Bohlman, Stephanie A; Olff, Han; Jansen, Patrick A

2015-08-01

The coexistence of numerous tree species in tropical forests is commonly explained by negative dependence of recruitment on the conspecific seed and tree density due to specialist natural enemies that attack seeds and seedlings ('Janzen-Connell' effects). Less known is whether guilds of shared seed predators can induce a negative dependence of recruitment on the density of different species of the same plant functional group. We studied 54 plots in tropical forest on Barro Colorado Island, Panama, with contrasting mature tree densities of three coexisting large seeded tree species with shared seed predators. Levels of seed predation were far better explained by incorporating seed densities of all three focal species than by conspecific seed density alone. Both positive and negative density dependencies were observed for different species combinations. Thus, indirect interactions via shared seed predators can either promote or reduce the coexistence of different plant functional groups in tropical forest. © 2015 John Wiley & Sons Ltd/CNRS.

Temporal scaling of episodic point estimates of weed seed predation to long-term predation rates

USDA-ARS?s Scientific Manuscript database

Weed seed predation is an important ecosystem service supporting weed management in low-external-input agroecosystems. For convenience, measurements of seed predation are often made at very short time scales (< 3 d). However, one of the primary uses of such data, the parameterization of models of cr...

Effects of microhabitat on palm seed predation in two forest fragments in southeast Brazil

NASA Astrophysics Data System (ADS)

Fleury, Marina; Galetti, Mauro

2004-12-01

The establishment of plants depends crucially on where seeds are deposited in the environment. Some authors suggest that in forest understory seed predation is lower than in gaps, and higher than at the forest edge. However, most studies have been carried out in large forest patches and very little is known about the effects of microhabitat conditions on seed predation in forest fragments. We evaluated the effects of three microhabitats (gaps, forest edge, and understory) on seed predation of two palm species ( Euterpe edulis and Syagrus romanzoffiana) in two semi-deciduous forest fragments (230 and 2100 ha) in southeast Brazil. Our objective was to test two hypotheses: (1) Low rodent abundance in small fragments as a result of meso-predator action levels leads to lower seed predation in small fragments. (2) Most mammal species in small fragments are generalists with respect to diet and habitat, so that seed predation is similar in different microhabitats (gaps, forest edge and understory) in the small fragment, but not in the larger one. The study community of small fragments is usually composed of generalist species (in diet and habitat aspects), so we expected the same rate of seed predation among microhabitats (gaps, forest edge and understory) in the tested smaller fragment. The experiment was carried out in the dry season (for E. edulis) and in the wet season (for S. romanzoffiana) in 1999. We conclude that post-dispersal seed predation in forest fragments can be directly connected with mammal communities, reflecting their historical and ecological aspects.

Uncoupling the Effects of Seed Predation and Seed Dispersal by Granivorous Ants on Plant Population Dynamics

PubMed Central

Arnan, Xavier; Molowny-Horas, Roberto; Rodrigo, Anselm; Retana, Javier

2012-01-01

Secondary seed dispersal is an important plant-animal interaction, which is central to understanding plant population and community dynamics. Very little information is still available on the effects of dispersal on plant demography and, particularly, for ant-seed dispersal interactions. As many other interactions, seed dispersal by animals involves costs (seed predation) and benefits (seed dispersal), the balance of which determines the outcome of the interaction. Separate quantification of each of them is essential in order to understand the effects of this interaction. To address this issue, we have successfully separated and analyzed the costs and benefits of seed dispersal by seed-harvesting ants on the plant population dynamics of three shrub species with different traits. To that aim a stochastic, spatially-explicit individually-based simulation model has been implemented based on actual data sets. The results from our simulation model agree with theoretical models of plant response dependent on seed dispersal, for one plant species, and ant-mediated seed predation, for another one. In these cases, model predictions were close to the observed values at field. Nonetheless, these ecological processes did not affect in anyway a third species, for which the model predictions were far from the observed values. This indicates that the balance between costs and benefits associated to secondary seed dispersal is clearly related to specific traits. This study is one of the first works that analyze tradeoffs of secondary seed dispersal on plant population dynamics, by disentangling the effects of related costs and benefits. We suggest analyzing the effects of interactions on population dynamics as opposed to merely analyzing the partners and their interaction strength. PMID:22880125

Fire season and intensity affect shrub recruitment in temperate sclerophyllous woodlands.

PubMed

Knox, K J E; Clarke, P J

2006-10-01

The season in which a fire occurs may regulate plant seedling recruitment because of: (1) the interaction of season and intensity of fire and the temperature requirements for seed release, germination and growth; (2) post-fire rainfall and temperature patterns affecting germination; (3) the interaction of post-fire germination conditions and competition from surrounding vegetation; and (4) the interaction of post-fire germination conditions and seed predators and/or seedling herbivores. This study examined the effects of different fire intensities and fire seasons on the emergence and survival of shrubs representing a range of fire response syndromes from a summer rainfall cool climate region. Replicated experimental burns were conducted in two seasons (spring and autumn) in 2 consecutive years and fuel loads were increased to examine the effects of fire intensity (low intensity and moderate intensity). Post-fire watering treatments partitioned the effects of seasonal temperature from soil moisture. Higher intensity fires resulted in enhanced seedling emergence for hard-seeded species but rarely influenced survival. Spring fires enhanced seedling emergence across all functional groups. Reduced autumn recruitment was related to seasonal temperature inhibiting germination rather than a lack of soil moisture or competition. In Mediterranean-type climate regions, seedling emergence has been related to post-fire rainfall and exposure of seeds to seed predators. We think a similar model may operate in temperate summer rainfall regions where cold-induced dormancy over winter exposes seeds to predators for a longer time and subsequently results in recruitment failure. Our results support the theory that the effect of fire season is more predictable where there are strong seasonal patterns in climate. In this study seasonal temperature rather than rainfall appears to be more influential.

Rodent density and the landscape of fear in the Chihuahaun Desert

USDA-ARS?s Scientific Manuscript database

Small mammals in desert environments are important links in ecosystem energy flow, with their densities often effecting the abundance of their primarily predators. Granivorous small mammals also affect seed dispersal and can shape vegetation characteristics. Consequently, factors affecting small m...

Annual variation in seedfall, postdispersal predation, and recruitment of a neotropical tree

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schupp, E.W.

1990-04-01

Knowledge of the dynamics of seed production and seedling recruitment of individual tree species is crucial for a complete understanding of tropical forest dynamics, yet multiyear studies on the seed and young seedling stages of tropical trees are virtually nonexistent. In a 4-yr study of the understory tree Faramea occidentalis on Barro Colorado Island, Panama, the author quantified natural levels of viable seedfall, seedling emergence, and seedling establishment, and experimentally estimated postdispersal seed predation. The levels of viable seedfall, seed predation, seedling emergence, early seedling survival, and seedling recruitment all differed significantly among years. The proportion of fallen seeds destroyedmore » by predators before germination was not related to the quantity of F. occidentalis seedfall. Within a year, however, F. occidentalis seed predation appeared to be influenced by community-wide seedfall, with high predation rates during times of low seed abundance and very low predation during the late dry season peak in seedfall by the community. Most of the annual variation in recruitment can be explained by the combination of seedfall and seed predation; in 3 of the 4 yr seedling emergence could be predicted from a knowledge of viable seedfall and the probability of a seed surviving until the peak of germination. The 4th yr, however, demonstrated that environmental conditions provide a sporadic, though important, limitation to recruitment. In comparison to many tree species, early seedling survival was relatively high, as was the ratio of seedlings recruited per seed falling. The highly successful recruitment of F. occidentalis is associated with a high population density of both saplings and adults in the study area.« less

A strong conditional mutualism limits and enhances seed dispersal and germination of a tropical palm

USGS Publications Warehouse

Klinger, R.; Rejmanek, M.

2010-01-01

Seed predation and seed dispersal can have strong effects on early life history stages of plants. These processes have often been studied as individual effects, but the degree to which their relative importance co-varies with seed predator abundance and how this influences seed germination rates is poorly understood. Therefore, we used a combination of observations and field experiments to determine the degree to which germination rates of the palm Astrocaryum mexicanum varied with abundance of a small mammal seed predator/disperser, Heteromysdesmarestianus, in a lowland tropical forest. Patterns of abundance of the two species were strongly related; density of H. desmarestianus was low in sites with low density of A. mexicanum and vice versa. Rates of predation and dispersal of A. mexicanum seeds depended on abundance of H. desmarestianus; sites with high densities of H. desmarestianus had the highest rates of seed predation and lowest rates of seed germination, but a greater total number of seeds were dispersed and there was greater density of seedlings, saplings, and adults of A. mexicanum in these sites. When abundance of H. desmarestianus was experimentally reduced, rates of seed predation decreased, but so did dispersal of A. mexicanum seeds. Critically, rates of germination of dispersed seeds were 5 times greater than undispersed seeds. The results suggest that the relationship between A. mexicanum and H. desmarestianus is a conditional mutualism that results in a strong local effect on the abundance of each species. However, the magnitude and direction of these effects are determined by the relative strength of opposing, but related, mechanisms. A. mexicanum nuts provide H. desmarestianus with a critical food resource, and while seed predation on A. mexicanum nuts by H. desmarestianus is very intense, A. mexicanum ultimately benefits because of the relatively high germination rates of its seeds that are dispersed by H. desmarestianus. ?? The Author(s) 2010.

Seed dispersal is more limiting to grassland diversity than competition or seed predation

Treesearch

Sarah M. Pinto; Dean E. Pearson; John L. Maron

2014-01-01

Competition has historically been viewed as the predominant process affecting plant community structure. In particular, it is often assumed that the dominant resident species is the superior competitor and therefore has large impacts on plant community diversity. This assumption, however, is seldom tested. As well, there are a variety of other processes such as...

A Simple Relationship Between Short- and Long-term Seed Predation Rates

USDA-ARS?s Scientific Manuscript database

Weed seed predation is an important ecosystem service supporting weed management in low-external-input agroecosystems. For convenience, measurements of seed predation are often made at very short time scales (< 3 d). However, one of the primary uses of such data, the parameterization of models of cr...

Predation of warm-and cool-season grass seed by the common cricket (Acheta domesticus L.)

USDA-ARS?s Scientific Manuscript database

In field experiments we noted that one of the main predators of tall fescue (Festuca arundinacea Schreb.) and Italian ryegrass (Lolium multiflorum Lam.) seed was the field cricket (Gryllus sp.). To determine if there might be a seed predation preference among forage grasses a laboratory study was ...

Weed-biocontrol insects reduce native-plant recruitment through second-order apparent competition.

PubMed

Pearson, Dean E; Callaway, Ragan M

2008-09-01

Small-mammal seed predation is an important force structuring native-plant communities that may also influence exotic-plant invasions. In the intermountain West, deer mice (Peromyscus maniculatus) are prominent predators of native-plant seeds, but they avoid consuming seeds of certain widespread invasives like spotted knapweed (Centaurea maculosa). These mice also consume the biological-control insects Urophora spp. introduced to control C. maculosa, and this food resource substantially increases deer mouse populations. Thus, mice may play an important role in the invasion and management of C. maculosa through food-web interactions. We examined deer mouse seed predation and its effects on seedling emergence and establishment of a dominant native grass, Pseudoroegneria spicata, and forb, Balsamorhiza sagittata, in C. maculosa-invaded grasslands that were treated with herbicide to suppress C. maculosa or left untreated as controls. Deer mice readily took seeds of both native plants but removed 2-20 times more of the larger B. sagittata seeds than the smaller P. spicata seeds. Seed predation reduced emergence and establishment of both species but had greater impacts on B. sagittata. The intensity of seed predation corresponded with annual and seasonal changes in deer mouse abundance, suggesting that abundance largely determined mouse impacts on native-plant seeds. Accordingly, herbicide treatments that reduced mouse abundance by suppressing C. maculosa and its associated biocontrol food subsidies to mice also reduced seed predation and decreased the impact of deer mice on B. sagittata establishment. These results provide evidence that Urophora biocontrol agents may exacerbate the negative effects of C. maculosa on native plants through a form of second-order apparent competition-a biocontrol indirect effect that has not been previously documented. Herbicide suppressed C. maculosa and Urophora, reducing mouse populations and moderating seed predation on native plants, but the herbicide's direct negative effects on native forb seedlings overwhelmed the indirect positive effect of reducing deer mouse seed predation. By manipulating this four-level food chain, we illustrate that host-specific biological control agents may impact nontarget plant species through food-web interactions, and herbicides may influence management outcomes through indirect trophic interactions in addition to their direct effects on plants.

Management of Protected Areas and Its Effect on an Ecosystem Function: Removal of Prosopis flexuosa Seeds by Mammals in Argentinian Drylands.

PubMed

Campos, Claudia M; Campos, Valeria E; Miguel, Florencia; Cona, Mónica I

The ecological function of animal seed dispersal depends on species interactions and can be affected by drivers such as the management interventions applied to protected areas. This study was conducted in two protected areas in the Monte Desert: a fenced reserve with grazing exclusion and absence of large native mammals (the Man and Biosphere Ñacuñán Reserve; FR) and an unfenced reserve with low densities of large native and domestic animals (Ischigualasto Park; UFR). The study focuses on Prosopis flexuosa seed removal by different functional mammal groups: "seed predators", "scatter-hoarders", and "opportunistic frugivores". Under both interventions, the relative contribution to seed removal by different functional mammal groups was assessed, as well as how these groups respond to habitat heterogeneity (i.e. vegetation structure) at different spatial scales. Camera traps were used to identify mammal species removing P. flexuosa seeds and to quantify seed removal; remote sensing data helped analyze habitat heterogeneity. In the FR, the major fruit removers were a seed predator (Graomys griseoflavus) and a scatter-hoarder (Microcavia asutralis). In the UFR, the main seed removers were the opportunistic frugivores (Lycalopex griseus and Dolichotis patagonum), who removed more seeds than the seed predator in the FR. The FR shows higher habitat homogeneity than the UFR, and functional groups respond differently to habitat heterogeneity at different spatial scales. In the FR, because large herbivores are locally extinct (e.g. Lama guanicoe) and domestic herbivores are excluded, important functions of large herbivores are missing, such as the maintenance of habitat heterogeneity, which provides habitats for medium-sized opportunistic frugivores with consequent improvement of quality and quantity of seed dispersal services. In the UFR, with low densities of large herbivores, probably one important ecosystem function this group performs is to increase habitat heterogeneity, allowing for the activity of medium-sized mammals who, behaving as opportunistic frugivores, did the most significant seed removal.

Relative Preference and Localized Food Affect Predator Space Use and Consumption of Incidental Prey

PubMed Central

Schartel, Tyler E.; Schauber, Eric M.

2016-01-01

Abundant, localized foods can concentrate predators and their foraging efforts, thus altering both the spatial distribution of predation risk and predator preferences for prey that are encountered incidentally. However, few investigations have quantified the spatial scale over which localized foods affect predator foraging behavior and consumption of incidental prey. In spring 2010, we experimentally tested how point-source foods altered how generalist predators (white-footed mice, Peromyscus leucopus) utilized space and depredated two incidental prey items: almonds (Prunus dulcis; highly profitable) and maple seeds (Acer saccharum; less profitable). We estimated mouse population densities with trapping webs, quantified mouse consumption rates of these incidental prey items, and measured local mouse activity with track plates. We predicted that 1) mouse activity would be elevated near full feeders, but depressed at intermediate distances from the feeder, 2) consumption of both incidental prey would be high near feeders providing less-preferred food and, 3) consumption of incidental prey would be contingent on predator preference for prey relative to feeders providing more-preferred food. Mouse densities increased significantly from pre- to post-experiment. Mean mouse activity was unexpectedly greatest in control treatments, particularly <15 m from the control (empty) feeder. Feeders with highly preferred food (sunflower seeds) created localized refuges for incidental prey at intermediate distances (15 to 25m) from the feeder. Feeders with less-preferred food (corn) generated localized high risk for highly preferred almonds <10 m of the feeder. Our findings highlight the contingent but predictable effects of locally abundant food on risk experienced by incidental prey, which can be positive or negative depending on both spatial proximity and relative preference. PMID:26978659

Relative Preference and Localized Food Affect Predator Space Use and Consumption of Incidental Prey.

PubMed

Schartel, Tyler E; Schauber, Eric M

2016-01-01

Abundant, localized foods can concentrate predators and their foraging efforts, thus altering both the spatial distribution of predation risk and predator preferences for prey that are encountered incidentally. However, few investigations have quantified the spatial scale over which localized foods affect predator foraging behavior and consumption of incidental prey. In spring 2010, we experimentally tested how point-source foods altered how generalist predators (white-footed mice, Peromyscus leucopus) utilized space and depredated two incidental prey items: almonds (Prunus dulcis; highly profitable) and maple seeds (Acer saccharum; less profitable). We estimated mouse population densities with trapping webs, quantified mouse consumption rates of these incidental prey items, and measured local mouse activity with track plates. We predicted that 1) mouse activity would be elevated near full feeders, but depressed at intermediate distances from the feeder, 2) consumption of both incidental prey would be high near feeders providing less-preferred food and, 3) consumption of incidental prey would be contingent on predator preference for prey relative to feeders providing more-preferred food. Mouse densities increased significantly from pre- to post-experiment. Mean mouse activity was unexpectedly greatest in control treatments, particularly <15 m from the control (empty) feeder. Feeders with highly preferred food (sunflower seeds) created localized refuges for incidental prey at intermediate distances (15 to 25m) from the feeder. Feeders with less-preferred food (corn) generated localized high risk for highly preferred almonds <10 m of the feeder. Our findings highlight the contingent but predictable effects of locally abundant food on risk experienced by incidental prey, which can be positive or negative depending on both spatial proximity and relative preference.

The effect of rodent seed predation on four species of California annual grasses.

PubMed

Borchert, M I; Jain, S K

1978-01-01

The effect of seed predation by Microtus californicus and Mus musculus on plant numbers of four species of California annual grasses was investigated for one year period on a grassland near Davis, California. In winter, mice utilized dead star thistle plants for cover when grasses in open areas were short, but moved into open areas when grass grew tall in spring.Using exclosures and plots sown with known quantities of seed, it was estimated that a mouse population (approximate density 120/acre) consumed 75% of Avena fatua seed, 44% of Hordeum leporinum seed, and 37% of Bromus diandrus seed. Mice showed a strong preference for Avena seed.Plant numbers of Avena and Hordeum were reduced by 62% and 30%, respectively. Hordeum, Lolium, and to a lesser extent, Bromus responded to a competitive release from Avena by increases in plant size and reproductive output. In addition, seed predation markedly increased seed to adult plant survivorship of Avena, Hordeum, and Bromus.Vertebrate seed predation is discussed as a potentially important factor in the yearly patterns of plant population regulation in California annual grasslands.

Ecological Interactions Shape the Dynamics of Seed Predation in Acrocomia aculeata (Arecaceae)

PubMed Central

Pereira, Anielle C. F.; Fonseca, Francine S. A.; Mota, Gleicielle R.; Fernandes, Ane K. C.; Fagundes, Marcílio; Reis-Júnior, Ronaldo; Faria, Maurício L.

2014-01-01

Background The complex network of direct and indirect relationships determines not only the species abundances but also the community characteristics such as diversity and stability. In this context, seed predation is a direct interaction that affects the reproductive success of the plant. For Acrocomia aculeata, the seed predation by Pachymerus cardo and Speciomerus revoili in post-dispersal may destroy more than 70% of the propagules and is influenced by the herbivory of the fruits during pre-dispersal. Fruits of plants with a higher level of herbivory during pre-dispersal are less attacked by predators in post-dispersal. We proposed a hypothesis that describes this interaction as an indirect defense mediated by fungi in a multitrophic interaction. As explanations, we proposed the predictions: i) injuries caused by herbivores in the fruits of A. aculeata favor fungal colonization and ii) the colonization of A. acuelata fruit by decomposing fungi reduces the selection of the egg-laying site by predator. Methodology/Principal Findings For prediction (i), differences in the fungal colonization in fruits with an intact or damaged epicarp were evaluated in fruits exposed in the field. For prediction (ii), we performed fruit observations in the field to determine the number of eggs of P. cardo and/or S. revoili per fruit and the amount of fungal colonization in the fruits. In another experiment, in the laboratory, we use P. cardo females in a triple-choice protocol. Each insect to choose one of the three options: healthy fruits, fruits with fungus, or an empty pot. The proposed hypothesis was corroborated. Fruits with injuries in the epicarp had a higher fungal colonization, and fruits colonized by fungi were less attractive for egg-laying by seed predators. Conclusion/Significance This study emphasizes the importance of exploring the networks of interactions between multitrophic systems to understand the dynamics and maintenance of natural populations. PMID:24875386

Invasive exotic shrub modifies a classic animal-habitat relationship and alters patterns of vertebrate seed predation.

PubMed

Guiden, Peter W; Orrock, John L

2017-02-01

Recent evidence suggests that invasive exotic plants can provide novel habitats that alter animal behavior. However, it remains unclear whether classic animal-habitat associations that influence the spatial distribution of plant-animal interactions, such as small mammal use of downed woody debris, persist in invaded habitats. We removed an invasive exotic shrub (buckthorn, Rhamnus cathartica) from 7 of 15 plots in Wisconsin. In each plot, we deployed 200 tagged Quercus rubra seeds in November 2014. After five months, tags were recovered to track spatial patterns of small mammal seed predation. Most recovered tags were associated with consumed seeds (95%); live-trapping, ancillary camera-trapping, and previous behavioral studies suggest that white-footed mice (Peromyscus leucopus) were responsible for most seed predation. In habitats without R. cathartica, most seed predation occurred near woody debris. In habitats with R. cathartica, small mammals rarely consumed seeds near woody debris, and seed predation occurred farther from the plot center and was less spatially clustered. Our results illustrate that invasive exotic shrubs can disrupt an otherwise common animal-habitat relationship. Failing to account for changes in habitat use may diminish our ability to predict animal distributions and outcomes of species interactions in novel habitats created by invasive exotic plants. © 2016 by the Ecological Society of America.

Impact of seed predators on the herb Baptista lanceolata (Fabales: Fabacae).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scott Horn; James L. Hanula.

2004-09-01

Leguminous seeds are a concentrated source of nutrition (Brashier 2000). In a nutrient-poor habitat, these seeds are important resources for many of the animal species residing there. Several insect predators are known to feed on Baptisia seeds. One such insect is Apion rostrum Say (Coleoptera: Curculionidae), a weevil that feeds on seeds of several wild indigo species. Females lay eggs in developing seed pods where the larvae eat the seeds.

Differential predation of forage seed

USDA-ARS?s Scientific Manuscript database

In recent field experiments we observed that the main invertebrate seed predators of overseeded tall fescue (Festuca arundinacea Schreb.) or Italian ryegrass (Lolium multiflorum Lam.) seed in unimproved pastures were harvester ants (Pogonomyrmex sp.) and common field crickets (Gryllus sp.) To determ...

Choices and consequences of oviposition by a pollinating seed predator, Hadena ectypa (Noctuidae), on its host plant, Silene stellata (Caryophyllaceae).

PubMed

Kula, Abigail A R; Dudash, Michele R; Fenster, Charles B

2013-06-01

Pollinating seed predators are models for the study of mutualisms. These insects have dual effects on host-plant fitness, through pollination as adults and flower and fruit predation as larvae. A rarely examined question is whether pollinating seed-predator oviposition choices are influenced by plant floral and size traits and the potential consequences of oviposition for host-plant reproduction. • We quantified oviposition by a pollinating seed predator, Hadena ectypa, on its host, Silene stellata, to determine if oviposition was associated with specific plant traits and whether oviposition was significantly correlated with fruit initiation or flower and fruit predation over three years. We also quantified whether stigmatic pollen loads of flowers visited by Hadena that both fed on nectar and oviposited were greater than when Hadena only fed on nectar. • Hadena had significant preference for plants having flowers with long corolla tubes in all three years. Moth oviposition was correlated with other traits only in some years. Oviposition did not increase stigmatic pollen loads. We observed significant positive relationships between both oviposition and fruit initiation and oviposition and flower/fruit predation. • Hadena ectypa oviposition choices were based consistently on floral tube length differences among individuals, and the consequences of oviposition include both fruit initiation (due to pollination while feeding on nectar prior to oviposition) and larval flower/fruit predation. The positive association between oviposition and fruit initiation may explain the long-term maintenance of facultative pollinating seed-predator interactions.

The role of dung beetles as a secondary seed disperser after dispersal by frugivore mammals in a temperate deciduous forest

NASA Astrophysics Data System (ADS)

Koike, Shinsuke; Morimoto, Hideto; Kozakai, Chinatsu; Arimoto, Isao; Soga, Masashi; Yamazaki, Koji; Koganezawa, Masaaki

2012-05-01

We studied the effects of dung beetles on the fates of endozoochorous seeds of five species (Prunus jamasakura, Prunus verecunda, Prunus grayana, Swida controversa, and Vitis coignetiae) in a temperate deciduous forest in Japan during 2004-2006. In field experiments using dung of the Asiatic black bear (Ursus thibetanus), we investigated the depths that dung beetles (Onthophagus atripennis, Onthophagus lenzii, and Phelotrupes auratus) buried seeds (4.8-6.8 mm diameter) and plastic markers (2 or 5 mm diameter), the levels of predation on buried and unburied seeds, and germination rates of seeds buried to different depths. All three species buried the 2-mm markers, but only P. auratus buried the seeds and 5-mm markers. There were seasonal differences in mean seed burial rates (range, 27-51%) and depths (range, 1-27 mm). Significantly more seeds were buried in June, July, and September than in August or October, and the mean burial depth was significantly deeper in June and July. Most seeds and markers were buried to a 3-6 cm depth. Germination of seeds that were positioned at depths of 1-4 cm was significantly greater than that of seeds left on the surface or buried at greater depths. Buried seeds were less likely to disappear than seeds at the surface, which may reflect differential predation. These results suggested that dung beetles, especially P. auratus, acted as a secondary seed disperser that affected the survival and distribution of seeds dispersed by a frugivore.

Flower color preferences of insects and livestock: effects on Gentiana lutea reproductive success.

PubMed

Sobral, Mar; Losada, María; Veiga, Tania; Guitián, Javier; Guitián, José; Guitián, Pablo

2016-01-01

Angiosperms diversification was primarily driven by pollinator agents, but non-pollinator agents also promoted floral evolution. Gentiana lutea shows pollinator driven flower color variation in NW Spain. We test whether insect herbivores and livestock, which frequently feed in G.lutea, play a role in G. lutea flower color variation, by answering the following questions: (i) Do insect herbivores and grazing livestock show flower color preferences when feeding on G. lutea? (ii) Do mutualists (pollinators) and antagonists (seed predators, insect herbivores and livestock) jointly affect G. lutea reproductive success? Insect herbivores fed more often on yellow flowering individuals but they did not affect seed production, whereas livestock affected seed production but did not show clear color preferences. Our data indicate that flower color variation of G. lutea is not affected by insect herbivores or grazing livestock.

Flower color preferences of insects and livestock: effects on Gentiana lutea reproductive success

PubMed Central

Losada, María; Veiga, Tania; Guitián, Javier; Guitián, José; Guitián, Pablo

2016-01-01

Angiosperms diversification was primarily driven by pollinator agents, but non-pollinator agents also promoted floral evolution. Gentiana lutea shows pollinator driven flower color variation in NW Spain. We test whether insect herbivores and livestock, which frequently feed in G.lutea, play a role in G. lutea flower color variation, by answering the following questions: (i) Do insect herbivores and grazing livestock show flower color preferences when feeding on G. lutea? (ii) Do mutualists (pollinators) and antagonists (seed predators, insect herbivores and livestock) jointly affect G. lutea reproductive success? Insect herbivores fed more often on yellow flowering individuals but they did not affect seed production, whereas livestock affected seed production but did not show clear color preferences. Our data indicate that flower color variation of G. lutea is not affected by insect herbivores or grazing livestock. PMID:27014509

Endangered plant-parrot mutualisms: seed tolerance to predation makes parrots pervasive dispersers of the Parana pine

PubMed Central

Tella, José L.; Dénes, Francisco V.; Zulian, Viviane; Prestes, Nêmora P.; Martínez, Jaime; Blanco, Guillermo; Hiraldo, Fernando

2016-01-01

Parrots are largely considered plant antagonists as they usually destroy the seeds they feed on. However, there is evidence that parrots may also act as seed dispersers. We evaluated the dual role of parrots as predators and dispersers of the Critically Endangered Parana pine (Araucaria angustifolia). Eight of nine parrot species predated seeds from 48% of 526 Parana pines surveyed. Observations of the commonest parrot indicated that 22.5% of the picked seeds were dispersed by carrying them in their beaks. Another five parrot species dispersed seeds, at an estimated average distance of c. 250 m. Dispersal distances did not differ from those observed in jays, considered the main avian dispersers. Contrary to jays, parrots often dropped partially eaten seeds. Most of these seeds were handled by parrots, and the proportion of partially eaten seeds that germinated was higher than that of undamaged seeds. This may be explained by a predator satiation effect, suggesting that the large seeds of the Parana pine evolved to attract consumers for dispersal. This represents a thus far overlooked key plant-parrot mutualism, in which both components are threatened with extinction. The interaction is becoming locally extinct long before the global extinction of the species involved. PMID:27546381

Endangered plant-parrot mutualisms: seed tolerance to predation makes parrots pervasive dispersers of the Parana pine.

PubMed

Tella, José L; Dénes, Francisco V; Zulian, Viviane; Prestes, Nêmora P; Martínez, Jaime; Blanco, Guillermo; Hiraldo, Fernando

2016-08-22

Parrots are largely considered plant antagonists as they usually destroy the seeds they feed on. However, there is evidence that parrots may also act as seed dispersers. We evaluated the dual role of parrots as predators and dispersers of the Critically Endangered Parana pine (Araucaria angustifolia). Eight of nine parrot species predated seeds from 48% of 526 Parana pines surveyed. Observations of the commonest parrot indicated that 22.5% of the picked seeds were dispersed by carrying them in their beaks. Another five parrot species dispersed seeds, at an estimated average distance of c. 250 m. Dispersal distances did not differ from those observed in jays, considered the main avian dispersers. Contrary to jays, parrots often dropped partially eaten seeds. Most of these seeds were handled by parrots, and the proportion of partially eaten seeds that germinated was higher than that of undamaged seeds. This may be explained by a predator satiation effect, suggesting that the large seeds of the Parana pine evolved to attract consumers for dispersal. This represents a thus far overlooked key plant-parrot mutualism, in which both components are threatened with extinction. The interaction is becoming locally extinct long before the global extinction of the species involved.

Yucca brevifolia fruit production, predispersal seed predation, and fruit removal by rodents during two years of contrasting reproduction

USGS Publications Warehouse

Borchert, Mark I.; DeFalco, Lesley

2016-01-01

PREMISE OF THE STUDY: The distribution of Yucca brevifolia, a keystone species of the Mojave Desert, may contract with climate change, yet reproduction and dispersal are poorly understood. We tracked reproduction, seed predation, and fruit dispersal for two years and discuss whether Y. brevifolia is a masting species. METHODS: Fruit maturation, seed predation (larval yucca moths), and fruit dispersal (rodents) were monitored on a random sample of panicles during 2013 and 2014, which were years of high and low reproduction, respectively. Fates of fruits placed on the ground and in canopies were also tracked. Rodents were live-trapped to assess abundance and species composition. KEY RESULTS: In 2013, 66% of inflorescences produced fruit of which 53% escaped larval predation; 19.5% of seeds were destroyed in infested fruits. Total seed production was estimated to be >100 times greater in 2013 than 2014. One-third of the fruit crop fell to the ground and was removed by rodents over the course of 120 d. After ground fruits became scarce, rodents exploited canopy fruits. Rodent numbers were low in 2013, so fruits remained in canopies for 370 d. In 2014, fruit production was approximately 20% lower. Larvae infested the majority of fruits, and almost twice the number of seeds were damaged. Fruits were exploited by rodents within 65 d. CONCLUSIONS: High fertilization, prolific seed production, and low predispersal predation in 2013 suggests that pollinator attraction and satiation of seed predators influence masting in Y. brevifolia. Abundant, prolonged fruit availability to seed-dispersing rodents likely extends recruitment opportunities during mast years.

Annual post-dispersal weed seed predation in contrasting field environments

USDA-ARS?s Scientific Manuscript database

Interest in weed seed predation as an ecological weed management tactic has led to a growing number of investigations of agronomic and environmental effects on predation rates. Whereas the measurements in most of these studies have taken place at very short time scales, from days to weeks, measureme...

Seed tolerance to predation: Evidence from the toxic seeds of the buckeye tree (Aesculus californica; Sapindaceae).

PubMed

Mendoza, Eduardo; Dirzo, Rodolfo

2009-07-01

Tolerance, the capacity of plants to withstand attack by animals, as opposed to resistance, has been poorly examined in the context of seed predation. We investigated the role that the seed mass of the large-seeded endemic tree Aesculus californica plays as a tolerance trait to rodent attack by comparing, under greenhouse conditions, patterns of germination, and subsequent seedling growth, of seeds with a wide range of natural damage. Germination percentage was reduced by 50% and time to germination by 64% in attacked compared to intact seeds, and germination probability was negatively correlated with damage. Seedlings that emerged from intact seeds were taller and bore more leaves than those from damaged seeds. This species' large seed mass favors tolerance to damage because heavily damaged seeds are able to germinate and produce seedlings. This finding is significant given that seeds of this species are known to contain chemical compounds toxic to vertebrates, a resistance trait. We posit that this combination of tolerance and resistance traits might be a particularly effective antipredation strategy when seeds are exposed to a variety of vertebrate predators.

Weed biocontrol insects reduce native plant recruitment through second-order apparent competition

Treesearch

Dean E. Pearson; Ragan M. Callaway

2008-01-01

Small-mammal seed predation is an important force structuring native-plant communities that may also influence exotic-plant invasions. In the intermountain West, deer mice (Peromyscus maniculatus) are prominent predators of native-plant seeds, but they avoid consuming seeds of certain widespread invasives like spotted knapweed (Centaurea...

Small-mammal seed predation limits the recruitment and abundance of two perennial grassland forbs.

PubMed

Bricker, Mary; Pearson, Dean; Maron, John

2010-01-01

Although post-dispersal seed predators are common and often reduce seed density, their influence on plant population abundance remains unclear. On the one hand, increasing evidence suggests that many plant populations are seed limited, implying that seed predators could reduce plant abundance. On the other hand,.it is generally uncertain whether the magnitude of seed limitation imposed by granivores is strong enough to overcome density-dependent processes that could compensate for seed loss at later stages. We examined the impact of seed predation by small mammals, primarily deer mice (Peromyscus maniculatus), on seedling recruitment and subsequent plant establishment of two perennial grassland forbs in western Montana, USA: Lupinus sericeus (Fabaceae) and Lithospermum ruderale (Boraginaceae). The experiment combined graded densities of seed addition for each species with a small-mammal exclusion treatment. Seedling recruitment and plant establishment were monitored in the experimental plots for up to three years. For both species, small-mammal exclusion increased the total number of seedlings that emerged, and these effects were still significant three years after seed addition, resulting in greater numbers of established plants inside exclosures than in control plots. We also found evidence of seed limitation, with increasing density of seeds added leading to increased numbers of seedlings. Results from seed addition and small-mammal exclusion experiments in later years also revealed significant impacts of small mammals on seedling emergence. These results suggest that granivores can have potentially important impacts in limiting forb abundance in grasslands communities.

Genetic variation in flowering phenology and avoidance of seed predation in native populations of Ulex europaeus.

PubMed

Atlan, A; Barat, M; Legionnet, A S; Parize, L; Tarayre, M

2010-02-01

The genetic variation in flowering phenology may be an important component of a species' capacity to colonize new environments. In native populations of the invasive species Ulex europaeus, flowering phenology has been shown to be bimodal and related to seed predation. The aim of the present study was to determine if this bimodality has a genetic basis, and to investigate whether the polymorphism in flowering phenology is genetically linked to seed predation, pod production and growth patterns. We set up an experiment raising maternal families in a common garden. Based on mixed analyses of variance and correlations among maternal family means, we found genetic differences between the two main flowering types and confirmed that they reduced seed predation in two different ways: escape in time or predator satiation. We suggest that this polymorphism in strategy may facilitate maintain high genetic diversity for flowering phenology and related life-history traits in native populations of this species, hence providing high evolutionary potential for these traits in invaded areas.

Titmouse calling and foraging are affected by head and body orientation of cat predator models and possible experience with real cats.

PubMed

Book, D L; Freeberg, Todd M

2015-09-01

Although anti-predator behavior systems have been studied in diverse taxa, less is known about how prey species detect and assess the immediate threat posed by a predator based on its behavior. In this study, we evaluated a potential cue that some species may utilize when assessing predation threat-the predator's body and head orientation. We tested the effect of this orientation cue on signaling and predation-risk-sensitive foraging of a prey species, tufted titmice (Baeolophus bicolor). Earlier work revealed sensitivity of titmice and related species to the presence of predator stimuli. Here, we manipulated cat models to face either toward or away from a food source preferred by titmice and then measured titmouse calling and seed-taking behavior. Titmice showed greater feeder avoidance when the cat predator models faced the feeder, compared to when the models faced away from the feeder or when titmice were exposed to control stimuli. Titmouse calling was also sensitive to predator head/body orientation, depending upon whether titmice were from sites where real cats had been observed or not. This study experimentally demonstrated that both calling and foraging of prey species can be affected by the head and body orientation of an important terrestrial predator. Prey species may therefore signal in strategic ways to conspecifics not just about predator presence, but also urgency of threat related to the more subtle cue of the head and body orientation of the predator. These findings hold potential implications for understanding animal cognition and learning processes.

Interaction between juniper Juniperus communis L. and its fruit pest insects: Pest abundance, fruit characteristics and seed viability

NASA Astrophysics Data System (ADS)

García, Daniel

1998-12-01

The relationships between the fruit features of Juniperus communis and the presence of fruit pests were studied in Sierra Nevada, SE Spain. The abundance of two insect species — a pulp-sucking scale and a seed-predator wasp — was surveyed with respect both to fruit characteristics and to viability of seeds contained therein. Seed-predator pressure was not significantly related to any fruit characteristics; however, pulp suckers tended to be more abundant in plants with low pulp: seed ratios and high fruit-water content. In addition, fruits with high levels of pulp-sucker attack tended to have higher water content. A multi-factor ANOVA, considering the identity of the plant and the attack of the different pests as factors, showed that plant identity accounts for most of the variation in fruit characteristics. The viability of seeds tended to be lower in plants strongly attacked by both pests. Fruits attacked by seed predators showed significantly lower proportions of viable and unviable seeds than did unattacked fruits. Seed viability was also lower in those fruits heavily attacked by pulp suckers, but this pattern is strongly mediated by plant identity. Pest activity proved to be clearly associated with a direct decrease in juniper reproductive capacity. This loss involved a reduction of the viable-seed number, mainly related to the seed predator, as well as a reduction of fruit attractiveness to frugivorous dispersers, related to the pulp sucker.

Consumer preference for seeds and seedlings of rare species impacts tree diversity at multiple scales.

PubMed

Young, Hillary S; McCauley, Douglas J; Guevara, Roger; Dirzo, Rodolfo

2013-07-01

Positive density-dependent seed and seedling predation, where herbivores selectively eat seeds or seedlings of common species, is thought to play a major role in creating and maintaining plant community diversity. However, many herbivores and seed predators are known to exhibit preferences for rare foods, which could lead to negative density-dependent predation. In this study, we first demonstrate the occurrence of increased predation of locally rare tree species by a widespread group of insular seed and seedling predators, land crabs. We then build computer simulations based on these empirical data to examine the effects of such predation on diversity patterns. Simulations show that herbivore preferences for locally rare species are likely to drive scale-dependent effects on plant community diversity: at small scales these foraging patterns decrease plant community diversity via the selective consumption of rare plant species, while at the landscape level they should increase diversity, at least for short periods, by promoting clustered local dominance of a variety of species. Finally, we compared observed patterns of plant diversity at the site to those obtained via computer simulations, and found that diversity patterns generated under simulations were highly consistent with observed diversity patterns. We posit that preference for rare species by herbivores may be prevalent in low- or moderate-diversity systems, and that these effects may help explain diversity patterns across different spatial scales in such ecosystems.

Pre-dispersal seed predation in a species-rich forest community: Patterns and the interplay with determinants

Treesearch

Yue Xu; Zehao Shen; Daoxin Li; Qinfeng Guo

2015-01-01

Pre-dispersal seed predation (PDSP) is commonly observed in woody plants, and recognized as a driver of seed production variability that is critical for successful regeneration. Earlier studies on PDSP and its determinants were mostly species specific, with community- level PDSP rarely estimated; and the interactions between the temporal...

Floral display size, conspecific density and florivory affect fruit set in natural populations of Phlox hirsuta, an endangered species

PubMed Central

Ruane, Lauren G.; Rotzin, Andrew T.; Congleton, Philip H.

2014-01-01

Background and Aims Natural variation in fruit and seed set may be explained by factors that affect the composition of pollen grains on stigmas. Self-incompatible species require compatible outcross pollen grains to produce seeds. The siring success of outcross pollen grains, however, can be hindered if self (or other incompatible) pollen grains co-occur on stigmas. This study identifies factors that determine fruit set in Phlox hirsuta, a self-sterile endangered species that is prone to self-pollination, and its associated fitness costs. Methods Multiple linear regressions were used to identify factors that explain variation in percentage fruit set within three of the five known populations of this endangered species. Florivorous beetle density, petal colour, floral display size, local conspecific density and pre-dispersal seed predation were quantified and their effects on the ability of flowers to produce fruits were assessed. Key Results In all three populations, percentage fruit set decreased as florivorous beetle density increased and as floral display size increased. The effect of floral display size on fruit set, however, often depended on the density of nearby conspecific plants. High local conspecific densities offset – even reversed – the negative effects of floral display size on percentage fruit set. Seed predation by mammals decreased fruit set in one population. Conclusions The results indicate that seed production in P. hirsuta can be maximized by selectively augmenting populations in areas containing isolated large plants, by reducing the population sizes of florivorous beetles and by excluding mammals that consume unripe fruits. PMID:24557879

Emergence of ratio-dependent and predator-dependent functional responses for pollination mutualism and seed parasitism

USGS Publications Warehouse

DeAngelis, Donald L.; Holland, J. Nathaniel

2006-01-01

Prey (N) dependence [g(N)], predator (P) dependence [g(P) or g(N,P)], and ratio dependence [f(P/N)] are often seen as contrasting forms of the predator's functional response describing predator consumption rates on prey resources in predator–prey and parasitoid–host interactions. Analogously, prey-, predator-, and ratio-dependent functional responses are apparently alternative functional responses for other types of consumer–resource interactions. These include, for example, the fraction of flowers pollinated or seeds parasitized in pollination (pre-dispersal) seed-parasitism mutualisms, such as those between fig wasps and fig trees or yucca moths and yucca plants. Here we examine the appropriate functional responses for how the fraction of flowers pollinated and seeds parasitized vary with the density of pollinators (predator dependence) or the ratio of pollinator and flower densities (ratio dependence). We show that both types of functional responses can emerge from minor, but biologically important variations on a single model. An individual-based model was first used to describe plant–pollinator interactions. Conditional upon on whether the number of flowers visited by the pollinator was limited by factors other than search time (e.g., by the number of eggs it had to lay, if it was also a seed parasite), and on whether the pollinator could directly find flowers on a plant, or had to search, the simulation results lead to either a predator-dependent or a ratio-dependent functional response. An analytic model was then used to show mathematically how these two cases can arise.

The Roles of Dispersal, Fecundity, and Predation in the Population Persistence of an Oak (Quercus engelmannii) under Global Change

PubMed Central

Conlisk, Erin; Lawson, Dawn; Syphard, Alexandra D.; Franklin, Janet; Flint, Lorraine; Flint, Alan; Regan, Helen M.

2012-01-01

A species’ response to climate change depends on the interaction of biotic and abiotic factors that define future habitat suitability and species’ ability to migrate or adapt. The interactive effects of processes such as fire, dispersal, and predation have not been thoroughly addressed in the climate change literature. Our objective was to examine how life history traits, short-term global change perturbations, and long-term climate change interact to affect the likely persistence of an oak species - Quercus engelmannii (Engelmann oak). Specifically, we combined dynamic species distribution models, which predict suitable habitat, with stochastic, stage-based metapopulation models, which project population trajectories, to evaluate the effects of three global change factors – climate change, land use change, and altered fire frequency – emphasizing the roles of dispersal and seed predation. Our model predicted dramatic reduction in Q. engelmannii abundance, especially under drier climates and increased fire frequency. When masting lowers seed predation rates, decreased masting frequency leads to large abundance decreases. Current rates of dispersal are not likely to prevent these effects, although increased dispersal could mitigate population declines. The results suggest that habitat suitability predictions by themselves may under-estimate the impact of climate change for other species and locations. PMID:22623955

Analysis of how ant behaviors affect germination in a tropical myrmecochore Calathea microcephala (P. & E.) Koernicke (Marantaceae): Microsite selection and aril removal by neotropical ants, Odontomachus, Pachycondyla, and Solenopsis (Formicidae).

PubMed

Horvitz, C C

1981-10-01

The evolutionary effects of a tropical ant-seed interaction are examined by posing questions about the fate of Calathea seeds carried by neotropical ants. Where do ants take seeds and what do they do with them? How do ant behaviors affect seed germination? Treatment of seeds by ants is determined by a series of seed-fate trials in captive colonies. There is no evidence of seed predation by ants. Odontomachus laticeps, Pachycondyla spp, and Solenopsis geminata rapidly displace seeds to ant nests, determine the microsites of seeds, and remove the seed arils for food. The seed arils are rich in lipids. The effects on germination of microsite selection and aril removal are quantitatively evaluated. Seeds which are immediately taken to a consistently moist spot germinate readily; 72% germinate, with a mean germination speed of 29 days. For such seeds aril removal does not significantly affect germination. In contrast, seeds which experience a delay before encountering appropriate germination conditions seem to exhibit an induced dormancy (sensu, Harper 1977) and a lower germination percentage. They take longer to germinate (up to 85 days) even after conditions become appropriate. It appears that their germination is enhanced by aril removal, which may act as an environmental cue to break dormancy. Such a mechanism would indicate that ant-handling of seeds is predictive of favorable conditions for seedling growth and establishment. The exact nature of such conditions and the effects on plant population dynamics remain to be seen.

The role of rodents in the seed fate of a thorny shrub in an ancient wood pasture

NASA Astrophysics Data System (ADS)

Scheper, Jeroen; Smit, Christian

2011-03-01

Thorny shrubs play a crucial role for the diversity and dynamics in wood pastures: they protect non-defended plants from large herbivores and thus facilitate tree establishment in the landscape through associational resistance. How thorny shrubs themselves establish in wood pastures - the main bottleneck for a dynamic shifting of grassland - shrub - woodland mosaics - is an essential unanswered question. We studied post-primary dispersal seed fate - i.e. removal, predation, secondary dispersal and survival of seeds after primary dispersal - of the thorny shrub blackthorn ( Prunus spinosa) in an ancient wood pasture in the Netherlands. Blackthorn seeds are primarily dispersed by frugivorous birds and may secondarily be dispersed by scatter-hoarding rodents. We performed two cafeteria-style experiments with blackthorn seeds placed on dishes in the dominant vegetation types. In the first we monitored seed removal in grassland, swards or blackthorn shrubs and determined rodent species abundance by live-trapping. In the second we followed tagged blackthorn seeds under shrubs and in swards to determine seed removal, predation, survival and secondary dispersal patterns. Tagged seeds were retrieved using a metal detector and by visual means. We recorded dispersal direction and distance, vegetation type, seed handling (burial, consumption) and rodent species responsible via bite marks. Seed removal and number of live-trapped rodents differed between vegetation types, with higher removal and rodent captures under shrubs than in swards and grassland. All retrieved seeds were depredated, predominantly by the wood mouse ( Apodemus sylvaticus). Disproportionally high seed numbers were retrieved in the vegetation type where originally placed (shrubs or swards). Our study suggests that rodents play an important role for blackthorn in wood pastures, predominantly as seed predators rather than secondary seed dispersers. Predation is particularly high under blackthorn shrubs, suggesting that primary seed dispersal by birds away from shrubs into grassland or swards is a prerequisite for blackthorn recruitment in wood pastures.

Cheating on the mutualistic contract: nutritional gain through seed predation in the frugivorous bat Chiroderma villosum (Phyllostomidae).

PubMed

Wagner, Insa; Ganzhorn, Jörg U; Kalko, Elisabeth K V; Tschapka, Marco

2015-04-01

Most frugivorous bats are efficient seed dispersers, as they typically do not damage seeds and transport them over long distances. In contrast, bats of the phyllostomid genus Chiroderma cheat fig trees by acting more as seed predators than as seed dispersers. The bats initially separate seeds from fruit pulp in the mouth. After extracting the juice from the fruit pulp, they thoroughly chew the seeds and spit out small seed fragments in a pellet. Consequently, the faeces contain almost no viable seeds. We compared the nutrient content of intact fig seeds with ejecta and faecal samples from both Chiroderma villosum and the 'conventional' frugivorous bat Artibeus watsoni. We show that C. villosum can extract nutrients from the seeds, especially protein and fat. The processing time of figs showed no significant difference between the two bat species. Food-choice experiments showed that C. villosum preferred fig species with more seeds over those with fewer seeds. This preference, in combination with the specialized seed-chewing behaviour, leads to an increased nutrient intake per fig. This unique strategy enables C. villosum to satisfy its nutritional requirements with a lower number of figs than other species, which decreases the amount of energy necessary for foraging flights as well as the predation risk during foraging. © 2015. Published by The Company of Biologists Ltd.

The influence of habitat fragmentation on multiple plant-animal interactions and plant reproduction.

PubMed

Brudvig, Lars A; Damschen, Ellen I; Haddad, Nick M; Levey, Douglas J; Tewksbury, Joshua J

2015-10-01

Despite broad recognition that habitat loss represents the greatest threat to the world's biodiyersity, a mechanistic understanding of how habitat loss and associated fragmentation affect ecological systems has proven remarkably challenging. The challenge stems from the multiple interdependent ways that landscapes change following fragmentation and the ensuing complex impacts on populations and communities of interacting species. We confronted these challenges by evaluating how fragmentation affects individual plants through interactions with animals, across five herbaceous species native to longleaf pine savannas. We created a replicated landscape experiment that provides controlled tests of three major fragmentation effects (patch isolation, patch shape [i.e., edge-to-area ratio], and distance to edge), established experimental founder populations of the five species to control for spatial distributions and densities of individual plants, and employed structural equation modeling to evaluate the effects of fragmentation on plant reproductive output and the degree to which these impacts are mediated through altered herbivory, pollination, or pre-dispersal seed predation. Across species, the most consistent response to fragmentation was a reduction in herbivory. Herbivory, however, had little impact.on plant reproductive output, and thus we found little evidence for any resulting benefit to plants in fragments. In contrast, fragmentation rarely impacted pollination or pre-dispersal seed predation, but both of these interactions had strong and consistent impacts on plant reproductive output. As a result, our models robustly predicted plant reproductive output (r2 = 0.52-0.70), yet due to the weak effects of fragmentation on pollination and pre-dispersal seed predation, coupled with the weak effect of herbivory on plant reproduction, the effects of fragmentation on reproductive output were generally small in magnitude and inconsistent. This work provides mechanistic insight into landscape-scale variation in plant reproductive success, the relative importance of plant-animal interactions for structuring these dynamics, and the nuanced nature of how habitat fragmentation can affect populations and communities of interacting species.

Hydrated mucilage reduces post-dispersal seed removal of a sand desert shrub by ants in a semiarid ecosystem.

PubMed

Yang, Xuejun; Baskin, Carol C; Baskin, Jerry M; Gao, Ruiru; Yang, Fan; Wei, Lingling; Li, Leilei; He, Hongju; Huang, Zhenying

2013-12-01

Post-dispersal seed removal by animals can lead to extensive seed loss and thus is an important factor in structuring plant communities. However, we know much less about post-dispersal seed predation than about other forms of herbivory. Mucilage plays many ecological roles in adaptation of plants to diverse environments; nevertheless, until now the role of mucilage in ant-mediated seed movement remains largely hypothetical. We studied the role of mucilage in seed removal of Artemisia sphaerocephala by ants in Mu Us Sandland in Inner Mongolia, China. Messor aciculatus was the most active seed predator of Artemisia sphaerocephala. Time to first ant collecting (T 1st) of wet intact seeds was longest and significantly different from that for dry intact seeds, wet demucilaged seeds, and dry demucilaged seeds; number of seeds removed to ant nests was lowest for wet intact seeds. After they were collected by ants, 5 % of wet intact seeds were dropped during transport. Our results indicate that seed mucilage of Artemisia sphaerocephala may play a significant role in post-dispersal seed removal by (1) making seeds less attractive to ants, thus resulting in a delay of collection time; (2) forming a strong bond to soil particles, making it difficult for ants to remove seeds; and (3) making seeds more likely to be dropped during transport, thereby allowing them to escape from predation even after collection by ants. This study demonstrates the importance of mucilage in reducing seed removal by ants and thus in anchoring seeds of desert plants in the vicinity of mother plants.

Short-term effects of springtime prescribed fires on adult populations of soil-emerging weevils in Central Appalachian hardwood stands

Treesearch

David P. McCann; David W. McGill; Thomas M. Schuler; W. Mark Ford

2006-01-01

Numerous biotic and abiotic factors interact to affect oak regeneration in the central Appalachians. Fire, white-tailed deer, rodents, other vertebrate seed predators, invasive plants, insects, fungi, climate, and tree physiology contribute singularly or additively to oak regeneration problems. Moreover, fire suppression has significantly enhanced the deleterious...

Short-term effects of springtime prescribed fires on adult populations of soil-emerging weevils in Central Appalachian hardwood stands

Treesearch

David P. McCann; David W. McGill; Thomas M. Schuler; W. Mark Ford

2006-01-01

Numerous biotic and abiotic factors interact to affect oak regeneration in the central Appalachians. Fire, whitetailed deer, rodents, other vertebrate seed predators, invasive plants, insects, fungi, climate, and tree physiology contribute singularly or additively to oak regeneration problems. Moreover, fire suppression has significantly enhanced the deleterious...

Management of Protected Areas and Its Effect on an Ecosystem Function: Removal of Prosopis flexuosa Seeds by Mammals in Argentinian Drylands

PubMed Central

Campos, Valeria E.; Miguel, Florencia; Cona, Mónica I.

2016-01-01

The ecological function of animal seed dispersal depends on species interactions and can be affected by drivers such as the management interventions applied to protected areas. This study was conducted in two protected areas in the Monte Desert: a fenced reserve with grazing exclusion and absence of large native mammals (the Man and Biosphere Ñacuñán Reserve; FR) and an unfenced reserve with low densities of large native and domestic animals (Ischigualasto Park; UFR). The study focuses on Prosopis flexuosa seed removal by different functional mammal groups: “seed predators”, “scatter-hoarders”, and “opportunistic frugivores”. Under both interventions, the relative contribution to seed removal by different functional mammal groups was assessed, as well as how these groups respond to habitat heterogeneity (i.e. vegetation structure) at different spatial scales. Camera traps were used to identify mammal species removing P. flexuosa seeds and to quantify seed removal; remote sensing data helped analyze habitat heterogeneity. In the FR, the major fruit removers were a seed predator (Graomys griseoflavus) and a scatter-hoarder (Microcavia asutralis). In the UFR, the main seed removers were the opportunistic frugivores (Lycalopex griseus and Dolichotis patagonum), who removed more seeds than the seed predator in the FR. The FR shows higher habitat homogeneity than the UFR, and functional groups respond differently to habitat heterogeneity at different spatial scales. In the FR, because large herbivores are locally extinct (e.g. Lama guanicoe) and domestic herbivores are excluded, important functions of large herbivores are missing, such as the maintenance of habitat heterogeneity, which provides habitats for medium-sized opportunistic frugivores with consequent improvement of quality and quantity of seed dispersal services. In the UFR, with low densities of large herbivores, probably one important ecosystem function this group performs is to increase habitat heterogeneity, allowing for the activity of medium-sized mammals who, behaving as opportunistic frugivores, did the most significant seed removal. PMID:27655222

Invasive plant species alters consumer behavior by providing refuge from predation.

PubMed

Dutra, Humberto P; Barnett, Kirk; Reinhardt, Jason R; Marquis, Robert J; Orrock, John L

2011-07-01

Understanding the effects of invasive plants on native consumers is important because consumer-mediated indirect effects have the potential to alter the dynamics of coexistence in native communities. Invasive plants may promote changes in consumer pressure due to changes in protective cover (i.e., the architectural complexity of the invaded habitat) and in food availability (i.e., subsidies of fruits and seeds). No experimental studies have evaluated the relative interplay of these two effects. In a factorial experiment, we manipulated cover and food provided by the invasive shrub Amur honeysuckle (Lonicera maackii) to evaluate whether this plant alters the foraging activity of native mammals. Using tracking plates to quantify mammalian foraging activity, we found that removal of honeysuckle cover, rather than changes in the fruit resources it provides, reduced the activity of important seed consumers, mice in the genus Peromyscus. Two mesopredators, Procyon lotor and Didelphis virginiana, were also affected. Moreover, we found rodents used L. maackii for cover only on cloudless nights, indicating that the effect of honeysuckle was weather-dependent. Our work provides experimental evidence that this invasive plant species changes habitat characteristics, and in so doing alters the behavior of small- and medium-sized mammals. Changes in seed predator behavior may lead to cascading effects on the seeds that mice consume.

Frugivory and seed dispersal by tapirs: an insight on their ecological role.

PubMed

O'Farrill, Georgina; Galetti, Mauro; Campos-Arceiz, Ahimsa

2013-03-01

Tapirs are one of the last extant megafauna species that survived the Pleistocene extinctions. Given their size and digestive system characteristics, tapirs might be the last potential seed disperser of plant species that were previously dispersed by other large mammal species that are now extinct. We compiled evidence from 39 published scientific studies showing that tapirs have a key role as seed dispersers and seed predators. Tapirs play an important role either through seed predation or by facilitating the recruitment of seeds over long distances, therefore influencing the diversity of plant species in the ecosystem. Neotropical tapirs might have a unique role as long-distance seed dispersers of large seeds (<20 mm) because they are capable of depositing viable large seeds in favorable places for germination that even large-bodied primates cannot disperse. Given the high diversity of seed species found in tapir diet, more information is needed on the identification of seed traits that allow the survival of seeds in the tapir's gut. Moreover, further studies are necessary on the role of tapirs as seed dispersers and predators; in particular considering spatial patterns of dispersed seeds, seed viability, effect of dung, and seed density in tapir latrines, and the effect of deposition sites on germination and seedling survival. Because all tapir species are highly threatened, it is paramount to identify gaps in our knowledge on the ecological role of tapirs and, in particular, on critical and endangered plant-tapir interactions to avoid possible trophic cascading effects on ecosystem function. © 2012 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS.

Preferential predation of cool season grass seed by the common cricket (Acheta domesticus)

USDA-ARS?s Scientific Manuscript database

To determine if there might be a seed predation preference among forage grasses a laboratory study was conducted using the common cricket (Acheta domesticus L.). Six cool-season grasses were selected and feeding studies were conducted over a three day period. The study was designed as a randomized ...

Fire and mice: Seed predation moderates fire's influence on conifer recruitment

Treesearch

Rafal Zwolak; Dean E. Pearson; Yvette K. Ortega; Elizabeth E. Crone

2010-01-01

In fire-adapted ecosystems, fire is presumed to be the dominant ecological force, and little is known about how consumer interactions influence forest regeneration. Here, we investigated seed predation by deer mice (Peromyscus maniculatus) and its effects on recruitment of ponderosa pine (Pinus ponderosa) and Douglas-fir (Pseudotsuga menziesii) seedlings in unburned...

Tree squirrel habitat selection and predispersal seed predation in a declining subalpine conifer

Treesearch

Shawn T. McKinney; Carl E. Fiedler

2009-01-01

Differential responses by species to modern perturbations in forest ecosystems may have undesirable impacts on plant-animal interactions. If such disruptions cause declines in a plant species without corresponding declines in a primary seed predator, the effects on the plant could be exacerbated. We examined one such interaction between Pinus...

Integrated management of Scotch broom, Cytisus scoparius: is control enhanced when seed predation is combined with prescribed fire or mowing?

USDA-ARS?s Scientific Manuscript database

Integrated weed management (IWM) strategies are being advocated and employed to control invasive plants species. Prescribed fire, mechanical removal, and biological control (seed predator Exapion fuscirostre) are used to manage the invasive plant, Cytisus scoparius, in prairies at Fort Lewis, Washi...

Impact of the newly arrived seed-predating beetle Specularius impressithorax (Coleoptera: Chrysomelidae: Bruchinae) in Hawai'i

USGS Publications Warehouse

Medeiros, A.C.; Von Allmen, E.; Fukada, M.; Samuelson, A.; Lau, T.

2008-01-01

Prior to 2001, seed predation was virtually absent in the endemic Wiliwili Erythrina sandwicensis (Fabaceae: Degener), dominant tree species of lower-elevation Hawaiian dryland forests. The African bruchine chrysomelid Specularius impressithorax (Pic) (Coleoptera: Chrysomelidae: Bruchinae) was first detected in Hawai'i in 2001 and became established on all main islands within the next two years. The mode of entry for this invasive Erythrina seed predator into Hawai'i is unknown, but likely occurred with the importation of trinket jewelry from Africa containing characteristically brightly-colored Erythrina seeds. The initial establishment of this insect likely occurred on a non-native host, the widely cultivated coral tree E. variegata. Within three years of its first record, S. impressithorax accounted for 77.4% mean seed crop loss in 12 populations of Wiliwili on six main Hawaiian islands. Specularius impressithorax, dispersed through international commerce and established via E. variegata, has become a threat to a unique Hawaiian forest type and may threaten other Erythrina, especially New World representatives.

Large herbivores facilitate savanna tree establishment via diverse and indirect pathways.

PubMed

Goheen, Jacob R; Palmer, Todd M; Keesing, Felicia; Riginos, Corinna; Young, Truman P

2010-03-01

1. Savanna ecosystems are defined largely by tree-grass mixtures, and tree establishment is a key driver of community structure and ecosystem function in these systems. The factors controlling savanna tree establishment are understudied, but likely involve some combination of seed, microsite and predator/fire limitation. In African savannas, suppression and killing of adult trees by large mammals like elephants (Loxodonta africana Blumenbach, 1797) and giraffes (Giraffa camelopardalis Linnaeus, 1758) can maintain tree-grass co-dominance, although the impacts of even these conspicuous herbivores on tree establishment also are poorly understood. 2. We combined seed addition and predator exclusion experiments with a large-scale, long-term field manipulation of large herbivores to investigate the relative importance of seeds, microsites and predators in limiting establishment of a monodominant tree (Acacia drepanolobium Sjostedt) in a Kenyan savanna. 3. Both wild and domestic (i.e. cattle; Bos taurus Linnaeus, 1758) large herbivores facilitated tree establishment by suppressing abundances of rodents, the most important seed and seedling predators. However, this indirect, positive effect of wild herbivores was negated by wild herbivores' suppression of seed production. Cattle did not have this direct, negative impact; rather, they further assisted tree establishment by reducing cover of understorey grasses. Thus, the impacts of both groups of large herbivores on tree establishment were largely routed through other taxa, with a negligible net effect of wild herbivores and a positive net effect of cattle on tree establishment. 4. The distinction between the (positive) net effect of cattle and (neutral) net effect of wild herbivores is due to the inclusion of browsers and mixed feeders within the assemblage of wild herbivores. Browsing by wild herbivores limited seed production, which reduced tree recruitment; grazing by cattle was more pronounced than that by wild herbivores, and thus promoted germination and subsequent establishment of small trees. 5. Our study is the first to link seed fates to tree establishment in savanna ecosystems in experimentally-manipulated herbivore communities. Further, our results highlight how large herbivores can modify a suite of independent factors - seed production, competition with understorey species, and seed and seedling predation - to collectively drive tree establishment.

Impact of Seed Predators on the Herb Baptisia Lanceolata (Fabales: Fabaceae)

Treesearch

Scott Horn; James L. Hanula

2004-01-01

The reproductive success of plants is a complex interaction among beneficial organisms such as pollinators, and destructive ones such as defoliators or seed predators that eat plant tissue. Many insects that consume reproductive tissue destroy much of a plant's reproductive output (Breedlove & Ehrlich 1968; Janzen 1971; Evans et al. 1989). In particular, the...

Small mammals of the Bitterroot National Forest: Ecological significance and guidelines for management

Treesearch

Dean E. Pearson

2000-01-01

Small mammal literature was reviewed to assess the ecological role of small mammals on the Bitterroot National Forest of western Montana. Small mammals fulfill numerous important roles in forest ecosystems by supporting a wide range of predators, dispersing seeds and mycorrhizal spores, altering vegetation through herbivory and seed predation, and preying on insects....

Carabid larvae as predators of weed seeds: granivory in larvae of Amara eurynota (Coleoptera: Carabidae).

PubMed

Saska, Pavel

2004-01-01

Up to date we do not have much information about predation on seeds by larvae of ground beetles. One of the reasons why such knowledge is important is that granivorous larvae contribute to predation of weed seeds. In this study, the food requirements of larvae of autumn breeding carabid species Amara eurynota (Panzer) were investigated in the laboratory and a hypothesis, that they are granivorous was tested. Insect diet (Tenebrio molitor larvae), three seed diets (seeds of Artemisia vulgaris, Tripleurospermum inodorum or Urtica dioica or a mixed diet (T. molitor + A. uulgaris) were used as food. For larvae of A. eurynota, seeds are essential for successful completion of development, because all those fed pure insect diet died before pupation. However, differences in suitability were observed between pure seed diets. Larvae fed seeds of A. vulgaris had the lowest mortality and fastest development of the seed diets. Those fed seeds of T. inodorum had also low mortality, but the development was prolonged in the third instar. In contrast, development of larvae reared on seeds of U. dioica was slowest of the tested diets and could not be completed, as all individuals died before pupation. When insects were included to seed diet of A. vulgaris (mixed diet), the duration of development shortened, but mortality remained the same when compared to seed diet of A. vulgaris. According to the results it was concluded that larvae of A. eurynota are granivorous. A mixed diet and seed diets of A. uulgaris and T. inodorum were suitable and insect diet and seeds of U. dioica were unsuitable diets in this experiment.

Rodent seed predation as a biotic filter influencing exotic plant abundance and distribution

Treesearch

D. E. Pearson; J. L. Hierro; M. Chiuffo; D. Villarreal

2014-01-01

Biotic resistance is commonly invoked to explain why many exotic plants fail to thrive in introduced ranges, but the role of seed predation as an invasion filter is understudied. Abiotic conditions may also influence plant populations and can interact with consumers to determine plant distributions, but how these factors jointly influence invasions is poorly understood...

Straw mulch prevents loss of fall-sown seeds to cold temperatures and wildlife predation

Treesearch

J. Wichman; R. Hawkins; P.M. Pijut

2005-01-01

A combination of cover crops and straw mulch effectively protect fall-sown hardwood seeds from cold temperature damage and predation at our nursery in central Indiana. Before using this treatment, we experienced 30% to 90% crop losses on a regular basis, but now our seedbed densities are consistently at target and the resulting seedlings are larger. Specialized...

Remote Cameras Reveal Experimental Artifact in a Study of Seed Predation in a Semi-Arid Shrubland.

PubMed

Brown, Alissa J; Deutschman, Douglas H; Braswell, Jessica; McLaughlin, Dana

2016-01-01

Granivorous animals may prefer to predate or cache seed of certain plant species over others. Multiple studies have documented preference for larger, non-native seed by granivores. To accomplish this, researchers have traditionally used indirect inference by relating patterns of seed removal to the species composition of the granivorous animal community. To measure seed removal, researchers present seed to granivorous animals in the field using equipment intended to exclude certain animal taxa while permitting access to others. This approach allows researchers to differentiate patterns of seed removal among various taxa (e.g., birds, small mammals, and insects); however, it is unclear whether the animals of interest are freely using the exclusion devices, which may be a hindrance to discovering the seed dishes. We used video observation to perform a study of seed predation using a custom-built, infrared digital camera and recording system. We presented native and non-native seed mixtures in partitioned Petri dishes both within and outside of exclusion cages. The exclusion cages were intended to allow entrance by rodent taxa while preventing entrance by rabbits and birds. We documented all seed removal visits by granivorous animals, which we identified to the genus level. Genera exhibited varying seed removal patterns based on seed type (native vs. non-native) and dish type (open vs. enclosed). We documented avoidance of the enclosed dishes by all but one rodent taxa, even though these dishes were intended to be used freely by rodents. This suggests that preference for non-native seed occurs differentially among granivorous animals in this system; however, interpretation of these nuanced results would be difficult without the benefit of video observation. When feasible, video observation should accompany studies using in situ equipment to ensure incorrect assumptions do not lead to inappropriate interpretation of results.

Neighborhoods have little effect on fungal attack or insect predation of developing seeds in a grassland biodiversity experiment.

PubMed

Beckman, Noelle G; Dybzinski, Ray; Tilman, G David

2014-02-01

Numerous observational studies have documented conspecific negative density-dependence that is consistent with the Janzen-Connell Hypothesis (JCH) of diversity maintenance. However, there have been few experimental tests of a central prediction of the JCH: that removing host-specific enemies should lead to greater increases in per capita recruitment in areas of higher host density or lower relative phylogenetic diversity. Using spatially randomized plots of high and low host biomass in a temperate grassland biodiversity experiment, we treated developing seedheads of six prairie perennials to factorial applications of fungicide and insecticide. We measured predispersal seed production, seed viability, and seedling biomass. Results were highly species-specific and idiosyncratic. Effects of insect seed predators and fungal pathogens on predispersal responses varied with neither conspecific biomass nor phylogenetic diversity, suggesting that-at least at the predispersal stage and for the insect and fungal seed predators we were able to exclude-the JCH is not sufficient to contribute to negative conspecific density-dependence for these dominant prairie species.

Improvements on a Reliable Oak Seed Trap

Treesearch

Carl N. Phillips; Thomas B. Hunnicutt

1995-01-01

The need for seed trap longevity, capture of heavy seed, and protection from predation in several forest types for long-term studies of seed production prompted seed trap design improvements. Critical improvements were achieved by painting the trap with a latex exterior gloss house paint, raising traps above water lines in areas tbat flooded, and enclosing the seed...

Cache placement, pilfering, and a recovery advantage in a seed-dispersing rodent: Could predation of scatter hoarders contribute to seedling establishment?

NASA Astrophysics Data System (ADS)

Steele, Michael A.; Bugdal, Melissa; Yuan, Amy; Bartlow, Andrew; Buzalewski, Jarrod; Lichti, Nathan; Swihart, Robert

2011-11-01

Scatter-hoarding mammals are thought to rely on spatial memory to relocate food caches. Yet, we know little about how long these granivores (primarily rodents) recall specific cache locations or whether individual hoarders have an advantage when recovering their own caches. Indeed, a few recent studies suggest that high rates of pilferage are common and that individual hoarders may not have a retriever's advantage. We tested this hypothesis in a high-density (>7 animals/ha) population of eastern gray squirrels ( Sciurus carolinensis) by presenting individually marked animals (>20) with tagged acorns, mapping cache sites, and following the fate of seed caches. PIT tags allowed us to monitor individual seeds without disturbing cache sites. Acorns only remained in the caches for 12-119 h (0.5-5 d). However, when we live-trapped and removed some animals from the site immediately after they stored seeds (thus simulating predation), their seed caches remained intact for significantly longer periods (16-27 d). Cache duration corresponded roughly to the time at which squirrels were returned to the study area. These results suggest that squirrels have a retriever's advantage and may remember specific cache sites longer than previously thought. We further suggest that predation of scatter hoarders who store seeds for long periods and also possess a recovery advantage may be one important mechanism by which seed establishment is achieved.

An overlooked plant–parakeet mutualism counteracts human overharvesting on an endangered tree

PubMed Central

Gleiser, Gabriela; Tella, José L.; Hiraldo, Fernando; Aizen, Marcelo A.

2018-01-01

The exponential growth of the human population often causes the overexploitation of resources and disruption of ecological interactions. Here, we propose that the antagonist effect of humans on exploited species might be alleviated with the advent of a second predator species. We focused on the complex interactions between an endangered conifer (Araucaria araucana) and two seed exploiters: the Austral parakeet (Enicognathus ferrugineus) and human seed collectors. We tested the importance of partial seed consumption by parakeets as an escape from human seed harvesting. Although parakeets frequently ate whole seeds, a substantial proportion of the seeds found under trees were only partially eaten and avoided by human seed collectors. These seeds germinated at a similar proportion but faster than intact seeds under laboratory conditions. Our results revealed an overlooked mutualism between parakeets and an endangered tree. Incomplete seed eating by parakeets, plus selection against these eaten seeds by humans, may enhance regeneration possibilities for this conifer species subject to human seed collection, turning the scale of the antagonism–mutualism continuum to the mutualistic side. In this context, parakeets might be providing an important service in those forests subject to human harvesting by allowing a fraction of seeds to escape human predation. PMID:29410848

Seed feeding beetles (Bruchidae, Curculionidae, Brentidae) from legumes (Dalea ornata, Astragalus filipes) and other forbs needed for restoring rangelands of the Intermountain West

USDA-ARS?s Scientific Manuscript database

Larval seed beetles are common seed predators that feed within individual seeds, and legume plants are especially plagued by seed beetles. This can be problematic for seed growers who raise seeds of North American legumes native to the Intermountain Region of the western U.S. for use in the reveget...

Differential foraging preferences on seed size by rodents result in higher dispersal success of medium-sized seeds.

PubMed

Cao, Lin; Wang, Zhenyu; Yan, Chuan; Chen, Jin; Guo, Cong; Zhang, Zhibin

2016-11-01

Rodent preference for scatter-hoarding large seeds has been widely considered to favor the evolution of large seeds. Previous studies supporting this conclusion were primarily based on observations at earlier stages of seed dispersal, or on a limited sample of successfully established seedlings. Because seed dispersal comprises multiple dispersal stages, we hypothesized that differential foraging preference on seed size by animal dispersers at different dispersal stages would ultimately result in medium-sized seeds having the highest dispersal success rates. In this study, by tracking a large number of seeds for 5 yr, we investigated the effects of seed size on seed fates from seed removal to seedling establishment of a dominant plant Pittosporopsis kerrii (Icacinaceae) dispersed by scatter-hoarding rodents in tropical forest in southwest China. We found that small seeds had a lower survival rate at the early dispersal stage where more small seeds were predated at seed stations and after removal; large seeds had a lower survival rate at the late dispersal stage, more large seeds were recovered, predated after being cached, or larder-hoarded. Medium-sized seeds experienced the highest dispersal success. Our study suggests that differential foraging preferences by scatter-hoarding rodents at different stages of seed dispersal could result in conflicting selective pressures on seed size and higher dispersal success of medium-sized seeds. © 2016 by the Ecological Society of America.

Vertebrate predators have minimal cascading effects on plant production or seed predation in an intact grassland ecosystem

Treesearch

John L. Maron; Dean E. Pearson

2011-01-01

The strength of trophic cascades in terrestrial habitats has been the subject of considerable interest and debate. We conducted an 8-year experiment to determine how exclusion of vertebrate predators, ungulates alone (to control for ungulate exclusion from predator exclusion plots) or none of these animals influenced how strongly a three-species assemblage of rodent...

UV induced visual cues in grasses

PubMed Central

Baby, Sabulal; Johnson, Anil John; Govindan, Balaji; Lukose, Sujith; Gopakumar, Bhaskaran; Koshy, Konnath Chacko

2013-01-01

Grasses are traditionally considered as wind pollinated, however, field observations confirmed frequent insect visits to grass flowers, suggesting insect pollination. Fruit and seed predators inflict heavy losses to cereals and millets during their growth, maturation and storage. The actual factors guiding insects and predators to grass flowers, fruits and seeds are not clear. Here, we report attractive blue fluorescence emissions on grass floral parts such as glumes, lemma, palea, lodicules, staminal filaments, pollens and fruits in ultraviolet (UV) 366 nm, whereas the stigmatic portions were not blue, but red fluorescent. We characterized the blue fluorescent constituent in grass reproductive structures as ferulic acid (FA). Fluorescence spectra of blue-emitting grass floral, seed extracts and isolated FA on excitation at 366 nm showed their emissions at 420–460 nm. We propose these FA-based blue fluorescence emissions in grass reproductive structures as visual cues that attract pollinators, predators and even pests towards them. PMID:24061408

Evolutionary optimization of material properties of a tropical seed

PubMed Central

Lucas, Peter W.; Gaskins, John T.; Lowrey, Timothy K.; Harrison, Mark E.; Morrogh-Bernard, Helen C.; Cheyne, Susan M.; Begley, Matthew R.

2012-01-01

Here, we show how the mechanical properties of a thick-shelled tropical seed are adapted to permit them to germinate while preventing their predation. The seed has evolved a complex heterogeneous microstructure resulting in hardness, stiffness and fracture toughness values that place the structure at the intersection of these competing selective constraints. Analyses of different damage mechanisms inflicted by beetles, squirrels and orangutans illustrate that cellular shapes and orientations ensure damage resistance to predation forces imposed across a broad range of length scales. This resistance is shown to be around the upper limit that allows cracking the shell via internal turgor pressure (i.e. germination). Thus, the seed appears to strike an exquisitely delicate adaptive balance between multiple selection pressures. PMID:21613287

Remote Cameras Reveal Experimental Artifact in a Study of Seed Predation in a Semi-Arid Shrubland

PubMed Central

Deutschman, Douglas H.; Braswell, Jessica; McLaughlin, Dana

2016-01-01

Granivorous animals may prefer to predate or cache seed of certain plant species over others. Multiple studies have documented preference for larger, non-native seed by granivores. To accomplish this, researchers have traditionally used indirect inference by relating patterns of seed removal to the species composition of the granivorous animal community. To measure seed removal, researchers present seed to granivorous animals in the field using equipment intended to exclude certain animal taxa while permitting access to others. This approach allows researchers to differentiate patterns of seed removal among various taxa (e.g., birds, small mammals, and insects); however, it is unclear whether the animals of interest are freely using the exclusion devices, which may be a hindrance to discovering the seed dishes. We used video observation to perform a study of seed predation using a custom-built, infrared digital camera and recording system. We presented native and non-native seed mixtures in partitioned Petri dishes both within and outside of exclusion cages. The exclusion cages were intended to allow entrance by rodent taxa while preventing entrance by rabbits and birds. We documented all seed removal visits by granivorous animals, which we identified to the genus level. Genera exhibited varying seed removal patterns based on seed type (native vs. non-native) and dish type (open vs. enclosed). We documented avoidance of the enclosed dishes by all but one rodent taxa, even though these dishes were intended to be used freely by rodents. This suggests that preference for non-native seed occurs differentially among granivorous animals in this system; however, interpretation of these nuanced results would be difficult without the benefit of video observation. When feasible, video observation should accompany studies using in situ equipment to ensure incorrect assumptions do not lead to inappropriate interpretation of results. PMID:27764200

Investment in seed physical defence is associated with species' light requirement for regeneration and seed persistence: evidence from Macaranga species in Borneo

USDA-ARS?s Scientific Manuscript database

The life stage from seed dispersal to seedling emergence is often critical in determining the regeneration success of plants. During this period seeds must survive an array of seed predators and pathogens and germinate under conditions favorable for seedling establishment. To maximise recruitment s...

A repellent to reduce mouse damage to longleaf pine seed

Treesearch

Dale L. Nolte; James P. Barnett

2000-01-01

Direct seeding is a potential method for reforestation of pines on many southern sites. The success of direct seeding, however, depends, at least in part, in reducing seed predation by birds and rodents. We conducted a series of tests to assess the efficacy of capsicum and thiram in reducing mouse damage to longleaf pine (Pinus palustris) seeds....

Seedling establishment in a masting desert shrub parallels the pattern for forest trees

NASA Astrophysics Data System (ADS)

Meyer, Susan E.; Pendleton, Burton K.

2015-05-01

The masting phenomenon along with its accompanying suite of seedling adaptive traits has been well studied in forest trees but has rarely been examined in desert shrubs. Blackbrush (Coleogyne ramosissima) is a regionally dominant North American desert shrub whose seeds are produced in mast events and scatter-hoarded by rodents. We followed the fate of seedlings in intact stands vs. small-scale disturbances at four contrasting sites for nine growing seasons following emergence after a mast year. The primary cause of first-year mortality was post-emergence cache excavation and seedling predation, with contrasting impacts at sites with different heteromyid rodent seed predators. Long-term establishment patterns were strongly affected by rodent activity in the weeks following emergence. Survivorship curves generally showed decreased mortality risk with age but differed among sites even after the first year. There were no detectable effects of inter-annual precipitation variability or site climatic differences on survival. Intraspecific competition from conspecific adults had strong impacts on survival and growth, both of which were higher on small-scale disturbances, but similar in openings and under shrub crowns in intact stands. This suggests that adult plants preempted soil resources in the interspaces. Aside from effects on seedling predation, there was little evidence for facilitation or interference beneath adult plant crowns. Plants in intact stands were still small and clearly juvenile after nine years, showing that blackbrush forms cohorts of suppressed plants similar to the seedling banks of closed forests. Seedling banks function in the absence of a persistent seed bank in replacement after adult plant death (gap formation), which is temporally uncoupled from masting and associated recruitment events. This study demonstrates that the seedling establishment syndrome associated with masting has evolved in desert shrublands as well as in forests.

Taste and physiological responses to glucosinolates: seed predator versus seed disperser.

PubMed

Samuni-Blank, Michal; Izhaki, Ido; Gerchman, Yoram; Dearing, M Denise; Karasov, William H; Trabelcy, Beny; Edwards, Thea M; Arad, Zeev

2014-01-01

In contrast to most other plant tissues, fleshy fruits are meant to be eaten in order to facilitate seed dispersal. Although fleshy fruits attract consumers, they may also contain toxic secondary metabolites. However, studies that link the effect of fruit toxins with seed dispersal and predation are scarce. Glucosinolates (GLSs) are a family of bitter-tasting compounds. The fleshy fruit pulp of Ochradenus baccatus was previously found to harbor high concentrations of GLSs, whereas the myrosinase enzyme, which breaks down GLSs to produce foul tasting chemicals, was found only in the seeds. Here we show the differential behavioral and physiological responses of three rodent species to high dose (80%) Ochradenus' fruits diets. Acomys russatus, a predator of Ochradenus' seeds, was the least sensitive to the taste of the fruit and the only rodent to exhibit taste-related physiological adaptations to deal with the fruits' toxins. In contrast, Acomys cahirinus, an Ochradenus seed disperser, was more sensitive to a diet containing the hydrolyzed products of the GLSs. A third rodent (Mus musculus) was deterred from Ochradenus fruits consumption by the GLSs and their hydrolyzed products. We were able to alter M. musculus avoidance of whole fruit consumption by soaking Ochradenus fruits in a water solution containing 1% adenosine monophosphate, which blocks the bitter taste receptor in mice. The observed differential responses of these three rodent species may be due to evolutionary pressures that have enhanced or reduced their sensitivity to the taste of GLSs.

Testing hypotheses for excess flower production and low fruit-to-flower ratios in a pollinating seed-consuming mutualism

USGS Publications Warehouse

Holland, J. Nathaniel; Bronstein, Judith L.; DeAngelis, Donald L.

2004-01-01

Pollinator attraction, pollen limitation, resource limitation, pollen donation and selective fruit abortion have all been proposed as processes explaining why hermaphroditic plants commonly produce many more flowers than mature fruit. We conducted a series of experiments in Arizona to investigate low fruit-to-flower ratios in senita cacti, which rely exclusively on pollinating seed-consumers. Selective abortion of fruit based on seed predators is of particular interest in this case because plants relying on pollinating seed-consumers are predicted to have such a mechanism to minimize seed loss. Pollinator attraction and pollen dispersal increased with flower number, but fruit set did not, refuting the hypothesis that excess flowers increase fruit set by attracting more pollinators. Fruit set of natural- and hand-pollinated flowers were not different, supporting the resource, rather than pollen, limitation hypothesis. Senita did abort fruit, but not selectively based on pollen quantity, pollen donors, or seed predators. Collectively, these results are consistent with sex allocation theory in that resource allocation to excess flower production can increase pollen dispersal and the male fitness function of flowers, but consequently results in reduced resources available for fruit set. Inconsistent with sex allocation theory, however, fruit production and the female fitness function of flowers may actually increase with flower production. This is because excess flower production lowers pollinator-to-flower ratios and results in fruit abortion, both of which limit the abundance and hence oviposition rates, of pre-dispersal seed predators.

Fires can benefit plants by disrupting antagonistic interactions.

PubMed

García, Y; Castellanos, M C; Pausas, J G

2016-12-01

Fire has a key role in the ecology and evolution of many ecosystems, yet its effects on plant-insect interactions are poorly understood. Because interacting species are likely to respond to fire differently, disruptions of the interactions are expected. We hypothesized that plants that regenerate after fire can benefit through the disruption of their antagonistic interactions. We expected stronger effects on interactions with specialist predators than with generalists. We studied two interactions between two Mediterranean plants (Ulex parviflorus, Asphodelus ramosus) and their specialist seed predators after large wildfires. In A. ramosus we also studied the generalist herbivores. We sampled the interactions in burned and adjacent unburned areas during 2 years by estimating seed predation, number of herbivores and fruit set. To assess the effect of the distance to unburned vegetation we sampled plots at two distance classes from the fire perimeter. Even 3 years after the fires, Ulex plants experienced lower seed damage by specialists in burned sites. The presence of herbivores on Asphodelus decreased in burned locations, and the variability in their presence was significantly related to fruit set. Generalist herbivores were unaffected. We show that plants can benefit from fire through the disruption of their antagonistic interactions with specialist seed predators for at least a few years. In environments with a long fire history, this effect might be one additional mechanism underlying the success of fire-adapted plants.

Wood thrush nest success and post-fledging survival across a temporal pulse of small mammal abundance in an oak forest.

PubMed

Schmidt, Kenneth A; Rush, Scott A; Ostfeld, Richard S

2008-07-01

1. Synchronized mass production of seed crops, such as acorns, produces a resource pulse that may have far-reaching consequences for songbird populations through its effects on avian predators. Seed production in these forests represents only the first of several pulsed events. Secondary pulses emerge as mast-consuming rodents numerically respond to seed production and tertiary pulses emerge as generalist predators, such as raptors, numerically respond to rodents. In turn, these two groups reduce nest productivity and juvenile survivorship 1 and 2 years, respectively, after the initial pulse in seed production. 2. At our study site in south-eastern New York, USA, autumn acorn abundance (primary pulse) largely determines rodent abundance (secondary pulse) the following spring. We tested the hypotheses that the population dynamics of a shrub-nesting passerine (wood thrush Hylocichla mustelina), is influenced by rodents through the: (a) direct effect of predation by rodents; (b) indirect effect of rodents on the abundance of raptors (tertiary pulse); and (c) indirect effect of rodent abundance on raptor diet. The latter specifically hypothesizes that a crash in the rodent population in the wake of region-wide failure of acorn production leads to an extreme diet shift in raptors that increases post-fledging mortality in birds. 3. We conducted a 3-year study to examine variation in wood thrush nest success and fledgling survival, using radio telemetry, across a pulse of rodent abundance (i.e. low, medium and high). We also updated and reanalysed regional wood thrush population growth rates as a function of the annual variation in rodent abundance. 4. Fledgling survivorship, but not nest success, varied in relation to annual rodent abundance. Raptors and eastern chipmunks Tamias striatus were the most commonly identified predators on fledglings. Fledgling survivorship was greatest at intermediate rodent abundance consistent with a shift in raptor diet. Regional rate of wood thrush population growth showed a unimodal relationship with rodent abundance, peaking during years with intermediate rodent abundance. This unimodal pattern was due to wood thrush population growth rates near or below zero during rodent population crashes. 5. The telemetry study, pattern of regional abundance and synchronized population dynamics of coexisting thrushes suggest a common mechanism of behavioural changes in raptors in response to declines in rodent prey, which in turn affects thrush population dynamics.

How mammalian predation contributes to tropical tree community structure.

PubMed

Paine, C E Timothy; Beck, Harald; Terborgh, John

2016-12-01

The recruitment of seedlings from seeds is the key demographic transition for rain forest trees. Though tropical forest mammals are known to consume many seeds, their effects on tree community structure remain little known. To evaluate their effects, we monitored 8,000 seeds of 24 tree species using exclosure cages that were selectively permeable to three size classes of mammals for up to 4.4 years. Small and medium-bodied mammals removed many more seeds than did large mammals, and they alone generated beta diversity and negative density dependence, whereas all mammals reduced diversity and shaped local species composition. Thus, small and medium-bodied mammals more strongly contributed to community structure and promoted species coexistence than did large mammals. Given that seedling recruitment is seed limited for most species, alterations to the composition of the community of mammalian seed predators is expected to have long-term consequences for tree community structure in tropical forests. © 2016 by the Ecological Society of America.

Rise and fall of cotton aphid (Hemiptera: Aphididae) populations in southeastern cotton production systems.

PubMed

Abney, Mark R; Ruberson, John R; Herzog, Gary A; Kring, Timothy J; Steinkraus, Donald C; Roberts, Phillip M

2008-02-01

The impact of natural enemies on cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), populations in cotton, Gossypium hirsutum L., production systems in the southeastern United States was evaluated over 3 yr in irrigated commercial cotton fields. Fungal epizootics caused by the entomopathogen Neozygites fresenii (Nowakowski) Batko reduced aphid numbers to subthreshold levels in 1999, 2000, and 2001 and occurred consistently in early to mid-July in all 3 yr. Scymnus spp. were the most abundant aphidophagous predators, although other coccinellid species and generalist predators such as spiders, fire ants, heteropterans, and neuropterans also were present. Studies using arthropod exclusion cages demonstrated little impact of predators or parasitoids on aphid populations before fungal epizootics. Arthropod natural enemies were most abundant after epizootics and may have suppressed aphid populations late in the season. Seed cotton yield, and lint quality were not affected by aphicide applications in any year of the study. Implications of these findings for aphid management in the southeastern United States are discussed.

Natural selection drives chemical resistance of Datura stramonium

PubMed Central

Miranda-Pérez, Adán; Castillo, Guillermo; Hernández-Cumplido, Johnattan; Valverde, Pedro L.; Borbolla, María; Cruz, Laura L.; Tapia-López, Rosalinda; Fornoni, Juan; Flores-Ortiz, César M.

2016-01-01

Plant resistance to herbivores involves physical and chemical plant traits that prevent or diminish damage by herbivores, and hence may promote coevolutionary arm-races between interacting species. Although Datura stramonium’s concentration of tropane alkaloids is under selection by leaf beetles, it is not known whether chemical defense reduces seed predation by the specialist weevil, Trichobaris soror, and if it is evolving by natural selection. We measured infestation by T. soror as well as the concentration of the plants’ two main tropane alkaloids in 278 D. stramonium plants belonging to 31 populations in central Mexico. We assessed whether the seed predator exerted preferences on the levels of both alkaloids and whether they affect plant fitness. Results show great variation across populations in the concentration of scopolamine and atropine in both leaves and seeds of plants of D. stramonium, as well as in the intensity of infestation and the proportion of infested fruits by T. soror. The concentration of scopolamine in seeds and leaves are negatively associated across populations. We found that scopolamine concentration increases plant fitness. Our major finding was the detection of a positive relationship between the population average concentrations of scopolamine with the selection differentials of scopolamine. Such spatial variation in the direction and intensity of selection on scopolamine may represent a coevolutionary selective mosaic. Our results support the view that variation in the concentration of scopolamine among-populations of D. stramonium in central Mexico is being driven, in part, by selection exerted by T. soror, pointing an adaptive role of tropane alkaloids in this plant species. PMID:27114866

Different effects of variation in Xanthium strumarium L. (Compositae) on two insect seed predators.

PubMed

Hare, J Daniel; Futuyma, Douglas J

1978-01-01

To determine the relative importance of variation in several plant characters on susceptibility to herbivores, we examined patterns of seed predation by two monophagous insect species and patterns of variation in ten populations of the cocklebur, Xanthium strumarium. Multiple regression analysis disclosed that one seed predator was most influenced by plant chemical variation, the other was significantly influenced by both chemical and morphological variation, but variation in yet another character, general burr size, was most important in conferring resistance to both insects simultaneously. The plant populations differed most in this character. Although many of the plant characters were correlated with each other, those important in determining susceptibility to each insect species were uncorrelated and independent of those conferring resistance to both insects simultaneously.These results imply that ecological similar herbivores may be influenced by different aspects of plant variation, and that predictions of evolutionary responses of local plant populations to herbivory may require knowledge of the structure of local herbivore communities and the dynamics of their establishment.

Spatial variation in post-dispersal seed removal in an Atlantic forest: Effects of habitat, location and guilds of seed predators

NASA Astrophysics Data System (ADS)

Christianini, Alexander V.; Galetti, Mauro

2007-11-01

Studies of post-dispersal seed removal in the Neotropics have rarely examined the magnitude of seed removal by different types of granivores. The relative impact of invertebrates, small rodents, and birds on seed removal was investigated in a 2,178 ha Atlantic forest fragment in southeastern Brazil. We used popcorn kernels ( Zea mays—Poaceae) to investigate seed removal in a series of selective exclosure treatments in a replicated, paired design experiment that included forest understory, gaps, and forest edge sites. We recorded the vegetation around the experimental seed stations in detail in order to evaluate the influence of microhabitat traits on seed removal. Vertebrate granivores (rodents and birds) were surveyed to determine whether granivore abundance was correlated with seed removal levels. Seed removal varied spatially and in unpredictable ways at the study site. Seed encounter and seed use varied with treatments, but not with habitat type. However, seed removal by invertebrates was negatively correlated with gap-related traits, which suggested an avoidance of large gaps by granivorous ants. The abundance of small mammals was remarkably low, but granivorous birds (tinamous and doves) were abundant at the study site. Birds were the main seed consumers in open treatments, but there was no correlation between local granivorous bird abundance and seed removal. These results emphasize the stochastic spatial pattern of seed removal, and, contrary to previous studies, highlight the importance of birds as seed predators in forest habitats.

Seed consumption and dispersal of ant-dispersed plants by slugs.

PubMed

Türke, Manfred; Heinze, Eric; Andreas, Kerstin; Svendsen, Sarah M; Gossner, Martin M; Weisser, Wolfgang W

2010-07-01

In beech-dominated forests in Central Europe, many spring geophytes show adaptations to seed dispersal by ants (myrmecochory). Ants, however, can be rare in such moist forests. Motivated by observations of slug feeding on seeds we investigated the seed consumption of two plant species, Anemone nemorosa and Asarum europaeum, by slugs, in a series of experiments. In a seed predation experiment in a beech forest, we found that seed removal was strongly reduced when gastropods were excluded from the seed depots. The contribution of insects, including ants, and rodents to seed removal was relatively less but differed between May and July. In the laboratory, slug species, in particular Arion sp., consumed seeds of both plant species. Slugs either consumed the elaiosomes of seeds or swallowed seeds intact. Swallowed seeds were defecated undamaged and germinated as well as control seeds when buried overwinter, indicating the potential for seed dispersal by slugs. We also recovered seeds of myrmecochores in the faeces of several slugs caught in forests. In a slug release experiment in the forest, slugs moved up to 14.6 m (mean 4.4 m) in 15 h, which is the median gut passage time of seeds based on measurements made in the laboratory. We also found that when slug-defecated seeds were offered to rodents, these were less attractive than control seeds, suggesting that passage through the slug gut reduces seed predation risk. Our results demonstrate that slugs are significant consumers of elaiosomes or entire seeds of ant-dispersed plants and that they can function as seed dispersers of these plants.

Post-dispersal seed removal by ground-feeding rodents in tropical peatlands, Central Kalimantan, Indonesia

PubMed Central

Blackham, Grace V.; Corlett, Richard T.

2015-01-01

Forested tropical peatlands in Southeast Asia are being rapidly converted to agriculture or degraded into non-forest vegetation. Although large areas have been abandoned, there is little evidence for subsequent forest recovery. As part of a study of forest degradation and recovery, we used seed removal experiments and rodent surveys to investigate the potential role of post-dispersal seed predation in limiting the regeneration of woody plants. Two 14-day seed removal trials were done in deforested and forested peatland habitat in Central Kalimantan, Indonesia. Seeds of Nephelium lappaceum, Syzygium muelleri, Artocarpus heterophyllus (all animal-dispersed) and Combretocarpus rotundatus (wind-dispersed) were tested. Significantly more seeds (82.8%) were removed in forest than non-forest (38.1%) and Combretocarpus had the lowest removal in both habitats. Most handled seeds were eaten in situ and little caching was observed. Six species of rodents were captured in forest and five in non-forest. The most trapped taxa were three Maxomys spp. in forest (85.5% of individuals) and Rattus tiomanicus in non-forest (74.8%). Camera traps confirmed that rodents were responsible for seed removal. Seed predation in deforested areas, which have a much lower seed rain than forest, may contribute to the low density and diversity of regenerating forest. PMID:26369444

Post-dispersal seed removal by ground-feeding rodents in tropical peatlands, Central Kalimantan, Indonesia.

PubMed

Blackham, Grace V; Corlett, Richard T

2015-09-15

Forested tropical peatlands in Southeast Asia are being rapidly converted to agriculture or degraded into non-forest vegetation. Although large areas have been abandoned, there is little evidence for subsequent forest recovery. As part of a study of forest degradation and recovery, we used seed removal experiments and rodent surveys to investigate the potential role of post-dispersal seed predation in limiting the regeneration of woody plants. Two 14-day seed removal trials were done in deforested and forested peatland habitat in Central Kalimantan, Indonesia. Seeds of Nephelium lappaceum, Syzygium muelleri, Artocarpus heterophyllus (all animal-dispersed) and Combretocarpus rotundatus (wind-dispersed) were tested. Significantly more seeds (82.8%) were removed in forest than non-forest (38.1%) and Combretocarpus had the lowest removal in both habitats. Most handled seeds were eaten in situ and little caching was observed. Six species of rodents were captured in forest and five in non-forest. The most trapped taxa were three Maxomys spp. in forest (85.5% of individuals) and Rattus tiomanicus in non-forest (74.8%). Camera traps confirmed that rodents were responsible for seed removal. Seed predation in deforested areas, which have a much lower seed rain than forest, may contribute to the low density and diversity of regenerating forest.

Relationship of seed microsite to germination and survival of lodgepole pine on high-elevation clearcuts in northeastern Utah

Treesearch

Deborah S. Page-Dumroese; R. Kasten Dumroese; Connie M. Carpenter; David L. Wenny

2002-01-01

On two high-elevation sites (~3,000 m) in northeastern Utah, lodgepole pine (Pinus contorta var. latifolia) seeds germinated best (53 percent) on large mineral microsites (5 x 5 m), and percentage survival of germinating seeds was best on microsites covered with forest floor material. Seed predation was severe at both study sites;...

The numerical and functional responses of a granivorous rodent and the fate of Neotropical tree seeds

USGS Publications Warehouse

Klinger, R.; Rejmanek, M.

2009-01-01

Despite their potential to provide mechanistic explanations of rates of seed dispersal and seed fate, the functional and numerical responses of seed predators have never been explicitly examined within this context. Therefore, we investigated the numerical response of a small-mammal seed predator, Heteromys desmarestianus, to disturbance-induced changes in food availability and evaluated the degree to which removal and fate of seeds of eight tree species in a lowland tropical forest in Belize were related to the functional response of H. desmarestianus to varying seed densities. Mark-recapture trapping was used to estimate abundance of H. desmarestianus in six 0.5-ha grids from July 2000 to September 2002. Fruit availability and seed fate were estimated in each grid, and two experiments nested within the grids were used to determine (1) the form of the functional response for nine levels of fruit density (2-32 fruits/m 2), (2) the removal rate and handling times, and (3) the total proportion of fruits removed. The total proportion of fruits removed was determined primarily by the numerical response of H. desmarestianus to fruit availability, while removal rates and the proportion of seeds eaten or cached were related primarily to the form of the functional response. However, the numerical and functional responses interacted; H. desmarestianus showed strong spatial and temporal numerical responses to total fruit availability, and their density relative to fruit availability resulted in variation in the form of the functional response. Types I, II, and III functional responses were observed, as were density-independent responses, and these responses varied both among and within fruit species. The highest proportions of fruits were eaten when the Type III functional response was detected, which was when fruit availability was high relative to H. desmarestianus population density. Numerous idiosyncratic influences on seed fate have been documented, but our results indicate that shifts in the numerical and functional responses of seed predators to seasonal and interannual variation in seed availability potentially provide a general mechanistic explanation for patterns of removal and fate for vertebrate-dispersed seeds. ?? 2009 by the Ecological Society of America.

Dense understory dwarf bamboo alters the retention of canopy tree seeds

NASA Astrophysics Data System (ADS)

Qian, Feng; Zhang, Tengda; Guo, Qinxue; Tao, Jianping

2016-05-01

Tree seed retention is thought to be an important factor in the process of forest community regeneration. Although dense understory dwarf bamboo has been considered to have serious negative effects on the regeneration of forest community species, little attention has been paid to the relationship between dwarf bamboo and seed retention. In a field experiment we manipulated the density of Fargesia decurvata, a common understory dwarf bamboo, to investigate the retention of seeds from five canopy tree species in an evergreen and deciduous broad-leaved mixed forest in Jinfoshan National Nature Reserve, SW China. We found that the median survival time and retention ratio of seeds increased with the increase in bamboo density. Fauna discriminately altered seed retention in bamboo groves of different densities. Arthropods reduced seed survival the most, and seeds removed decreased with increasing bamboo density. Birds removed or ate more seeds in groves of medium bamboo density and consumed fewer seeds in dense or sparse bamboo habitats. Rodents removed a greater number of large and highly profitable seeds in dense bamboo groves but more small and thin-husked seeds in sparse bamboo groves. Seed characteristics, including seed size, seed mass and seed profitability, were important factors affecting seed retention. The results suggested that dense understory dwarf bamboo not only increased seeds concealment and reduced the probability and speed of seed removal but also influenced the trade-off between predation and risk of animal predatory strategies, thereby impacting the quantity and composition of surviving seeds. Our results also indicated that dense understory dwarf bamboo and various seed characteristics can provide good opportunities for seed storage and seed germination and has a potential positive effect on canopy tree regeneration.

Seed predation by bonobos (Pan paniscus) at Kokolopori, Democratic Republic of the Congo.

PubMed

Georgiev, Alexander V; Thompson, Melissa Emery; Lokasola, Albert Lotana; Wrangham, Richard W

2011-10-01

We compared the feeding ecology of the Hali-Hali community of bonobos (Pan paniscus) at Kokolopori, a new field site in the Democratic Republic of the Congo, between two periods 5 months apart. During the first study period (SP1), bonobos relied heavily on the dry seeds of Guibourtia (Caesalpiniaceae), mostly eaten from the ground. The second period (SP2) was characterized by high consumption of ripe tree fruit. Terrestrial herbaceous vegetation (THV) contributed little to the diet in either study period. The low amount of ripe fruit and the high reliance on seeds in the diet during SP1 were associated with high cortisol production and low levels of urinary C-peptide in females, suggesting nutritional stress. However, female gregariousness was not constrained during the fruit-poor period, probably because high seed abundance on the ground ameliorated scramble feeding competition. This is the first description of extensive seed predation by bonobos. It suggests that bonobo feeding ecology may be more similar to that of chimpanzees than previously recognized.

Does retained-seed priming drive the evolution of serotiny in drylands? An assessment using the cactus Mammillaria hernandezii.

PubMed

Santini, Bianca A; Martorell, Carlos

2013-02-01

Serotinous plants retain their seeds for a long time. In deserts, retained seeds undergo hydration-dehydration cycles and thus may become primed. Priming enhances germination and seedling vigor. We test the hypothesis that serotiny evolves because it provides a site protected from predators in which seeds can become primed. Rainfall-cued dispersal of primed seeds may enhance this effect. We tested this hypothesis with Mammillaria hernandezii through protein-content analyses; field and laboratory germination experiments with primed, unprimed, and retained seeds; and fitness estimations from demographic models. Hydration-dehydration cycles induced priming, enhancing germination. Artificial priming and retention in the parent plant for 1 yr induced similar changes in seed protein patterns, suggesting that priming occurs naturally while seeds are retained. Under field conditions, germination of seeds retained for 1 yr more than doubled that of seeds of the same cohort that were not primed or that remained buried for 1 yr. The first seeds to germinate died rapidly. Serotinous plants whose seeds underwent priming had higher fitness than those whose seeds were in the soil seed bank or that did not experience priming. Priming in soil seed banks may be costly because of high predation, so seed protection during priming is sufficient to promote the evolution of serotiny. Bet hedging contributes to this process. Rapid germination of primed seeds that respond to brief rainfall events is disadvantageous because such rainfall is insufficient for seedling survival. Serotinous species counteract this cost by cueing dispersal with heavy precipitation.

Invasive mammals and habitat modification interact to generate unforeseen outcomes for indigenous fauna.

PubMed

Norbury, Grant; Byrom, Andrea; Pech, Roger; Smith, James; Clarke, Dean; Anderson, Dean; Forrester, Guy

2013-10-01

Biotic invasions and habitat modification are two drivers of global change predicted to have detrimental impacts on the persistence of indigenous biota worldwide. Few studies have investigated how they operate synergistically to alter trophic interactions among indigenous and nonindigenous species in invaded ecosystems. We experimentally manipulated a suite of interacting invasive mammals, including top predators (cat Felis catus, ferret Mustela furo, stoat M. erminea), herbivores (rabbit Oryctolagus cuniculus, hare Lepus europaeus), and an insectivore (hedgehog Erinaceus europaeus occidentalis), and measured their effects on indigenous lizards and invertebrates and on an invasive mesopredator (house mouse Mus musculus). The work was carried out in a grassland/shrubland ecosystem that had been subjected to two types of habitat modification (widespread introduction of high-seed-producing pasture species, and areas of land use intensification by fertilization and livestock grazing). We also quantified food productivity for indigenous and invasive fauna by measuring pasture biomass, as well as seed and fruit production by grasses and shrubs. Indigenous fauna did not always increase following top-predator suppression: lizards increased on one of two sites; invertebrates did not increase on either site. Mesopredator release of mice was evident at the site where lizards did not increase, suggesting negative effects of mice on lizard populations. High mouse abundance occurred only on the predator-suppression site with regular production of pasture seed, indicating that this food resource was the main driver of mouse populations. Removal of herbivores increased pasture and seed production, which further enhanced ecological release of mice, particularly where pasture swards were overtopped by shrubs. An effect of landscape supplementation was also evident where nearby fertilized pastures boosted rabbit numbers and the associated top predators. Other studies have shown that both suppression of invasive predators and retiring land from grazing can benefit indigenous species, but our results suggest that the ensuing vegetation changes and complex interactions among invasive species can block recovery of indigenous fauna vulnerable to mesopredators. Top-down and bottom-up ecological release of mesopredators and landscape supplementation of top predators are key processes to consider when managing invaded communities in complex landscapes.

Effects of dilution on dissolved oxygen depletion and microbial populations in the biochemical oxygen demand determination.

PubMed

Seo, Kyo Seong; Chang, Ho Nam; Park, Joong Kon; Choo, Kwang-Ho

2007-09-01

The biochemical oxygen demand (BOD) value is still a key parameter that can determine the level of organics, particularly the content of biodegradable organics in water. In this work, the effects of sample dilution, which should be done inevitably to get appropriate dissolved oxygen (DO) depletion, on the measurement of 5-day BOD (BOD(5)), was investigated with and without seeding using natural and synthetic water. The dilution effects were also evaluated for water samples taken in different seasons such as summer and winter because water temperature can cause a change in the types of microbial species, thus leading to different oxygen depletion profiles during BOD testing. The predation phenomenon between microbial cells was found to be dependent on the inorganic nutrients and carbon sources, showing a change in cell populations according to cell size after 5-day incubation. The dilution of water samples for BOD determination was linked to changes in the environment for microbial growth such as nutrition. The predation phenomenon between microbial cells was more important with less dilution. BOD(5) increased with the specific amount of inorganic nutrient per microbial mass when the natural water was diluted. When seeding was done for synthetic water samples, the seed volume also affected BOD due to the rate of organic uptake by microbes. BOD(5) increased with the specific bacterial population per organic source supplied at the beginning of BOD measurement. For more accurate BOD measurements, specific guidelines on dilution should be established.

Biological invasions as disruptors of plant reproductive mutualisms.

PubMed

Traveset, Anna; Richardson, David M

2006-04-01

Invasive alien species affect the composition and functioning of invaded ecosystems in many ways, altering ecological interactions that have arisen over evolutionary timescales. Specifically, disruptions to pollination and seed-dispersal mutualistic interactions are often documented, although the profound implications of such impacts are not widely recognized. Such disruptions can occur via the introduction of alien pollinators, seed dispersers, herbivores, predators or plants, and we define here the many potential outcomes of each situation. The frequency and circumstances under which each category of mechanisms operates are also poorly known. Most evidence is from population-level studies, and the implications for global biodiversity are difficult to predict. Further insights are needed on the degree of resilience in interaction networks, but the preliminary picture suggests that invasive species frequently cause profound disruptions to plant reproductive mutualisms.

Harmonia axyridis (Coleoptera: Coccinellidae) Exhibits No Preference between Bt and Non-Bt Maize Fed Spodoptera frugiperda (Lepidoptera: Noctuidae)

PubMed Central

Dutra, Carla C.; Koch, Robert L.; Burkness, Eric C.; Meissle, Michael; Romeis, Joerg; Hutchison, William D.; Fernandes, Marcos G.

2012-01-01

A recent shift in managing insect resistance to genetically engineered (GE) maize consists of mixing non-GE seed with GE seed known as “refuge in a bag”, which increases the likelihood of predators encountering both prey fed Bt and prey fed non-Bt maize. We therefore conducted laboratory choice-test feeding studies to determine if a predator, Harmonia axyridis, shows any preference between prey fed Bt and non-Bt maize leaves. The prey species was Spodoptera frugiperda, which were fed Bt maize (MON-810), expressing the single Cry1Ab protein, or non-Bt maize. The predators were third instar larvae and female adults of H. axyridis. Individual predators were offered Bt and non-Bt fed prey larvae that had fed for 24, 48 or 72 h. Ten and 15 larvae of each prey type were offered to third instar and adult predators, respectively. Observations of arenas were conducted at 1, 2, 3, 6, 15 and 24 h after the start of the experiment to determine the number and type of prey eaten by each individual predator. Prey larvae that fed on non-Bt leaves were significantly larger than larvae fed Bt leaves. Both predator stages had eaten nearly all the prey by the end of the experiment. However, in all combinations of predator stage and prey age, the number of each prey type consumed did not differ significantly. ELISA measurements confirmed the presence of Cry1Ab in leaf tissue (23–33 µg/g dry weight) and S. frugiperda (2.1–2.2 µg/g), while mean concentrations in H. axyridis were very low (0.01–0.2 µg/g). These results confirm the predatory status of H. axyridis on S. frugiperda and that both H. axyridis adults and larvae show no preference between prey types. The lack of preference between Bt-fed and non-Bt-fed prey should act in favor of insect resistance management strategies using mixtures of GE and non-GE maize seed. PMID:23024772

Synchrony between fruit maturation and effective dispersers' foraging activity increases seed protection against seed predators

PubMed Central

Boulay, Raphaël; Carro, Francisco; Soriguer, Ramón C; Cerdá, Xim

2007-01-01

The evolution of pollination and seed dispersal mutualisms is conditioned by the spatial and temporal co-occurrence of animals and plants. In the present study we explore the timing of seed release of a myrmecochorous plant (Helleborus foetidus) and ant activity in two populations in southern Spain during 2 consecutive years. The results indicate that fruit dehiscence and seed shedding occur mostly in the morning and correspond to the period of maximum foraging activity of the most effective ant dispersers. By contrast, ant species that do not transport seeds and/or that do not abound near the plants are active either before or after H. foetidus diaspores are released. Experimental analysis of diet preference for three kinds of food shows that effective ant dispersers are mostly scavengers that readily feed on insect corpses and sugars. Artificial seed depots suggest that seeds deposited on the ground out of the natural daily time window of diaspore releasing are not removed by ants and suffer strong predation by nocturnal rodents Apodemus sylvaticus. Nevertheless, important inter-annual variations in rodent populations cast doubts on their real importance as selection agents. We argue that traits allowing synchrony between seed presentation and effective partners may constitute a crucial pre-adaptation for the evolution of plant–animal mutualisms involving numerous animal partners. PMID:17698486

Determinants of spatial behavior of a tropical forest seed predator: The roles of optimal foraging, dietary diversification, and home range defense.

PubMed

Palminteri, Suzanne; Powell, George V N; Peres, Carlos A

2016-05-01

Specialized seed predators in tropical forests may avoid seasonal food scarcity and interspecific feeding competition but may need to diversify their daily diet to limit ingestion of any given toxin. Seed predators may, therefore, adopt foraging strategies that favor dietary diversity and resource monitoring, rather than efficient energy intake, as suggested by optimal foraging theory. We tested whether fine-scale space use by a small-group-living seed predator-the bald-faced saki monkey (Pithecia irrorata)-reflected optimization of short-term foraging efficiency, maximization of daily dietary diversity, and/or responses to the threat of territorial encroachment by neighboring groups. Food patches across home ranges of five adjacent saki groups were widely spread, but areas with higher densities of stems or food species were not allocated greater feeding time. Foraging patterns-specifically, relatively long daily travel paths that bypassed available fruiting trees and relatively short feeding bouts in undepleted food patches-suggest a strategy that maximizes dietary diversification, rather than "optimal" foraging. Travel distance was unrelated to the proportion of seeds in the diet. Moreover, while taxonomically diverse, the daily diets of our study groups were no more species-rich than randomly derived diets based on co-occurring available food species. Sakis preferentially used overlapping areas of their HRs, within which adjacent groups shared many food trees, yet the density of food plants or food species in these areas was no greater than in other HR areas. The high likelihood of depletion by neighboring groups of otherwise enduring food sources may encourage monitoring of peripheral food patches in overlap areas, even if at the expense of immediate energy intake, suggesting that between-group competition is a key driver of fine-scale home range use in sakis. © 2015 Wiley Periodicals, Inc.

Impacts of habitat alterations and predispersal seed predation on the reproductive success of Great Basin forbs

Treesearch

Robert L. Johnson

2008-01-01

Sexual reproductive success in wild plant populations is dependent upon the ability to bank seed for when environmental conditions favor seedling recruitment. Seed production in many plant populations requires the pollination services of local bee populations. A loss in bee diversity as a result of exotic plant invasion or revegetation practices which do not adequately...

Identification of Albizia lebbeck seed coat chitin-binding vicilins (7S globulins) with high toxicity to the larvae of the bruchid Callosobruchus maculatus

PubMed Central

Souza, A.J.; Ferreira, A.T.S.; Perales, J.; Beghini, D.G.; Fernandes, K.V.S.; Xavier-Filho, J.; Venancio, T.M.; Oliveira, A.E.A.

2011-01-01

Seed coat is a specialized maternal tissue that interfaces the embryo and the external environment during embryogenesis, dormancy and germination. In addition, it is the first defensive barrier against penetration by pathogens and herbivores. Here we show that Albizia lebbeck seed coat dramatically compromises the oviposition, eclosion and development of the bruchid Callosobruchus maculatus. Dietary supplementation of bruchid larvae with A. lebbeck seed coat flour causes severe weight loss and reduces survival. By means of protein purification, mass spectrometry and bioinformatic analyses, we show that chitinbinding vicilins are the main source of A. lebbeck tegumental toxicity to C. maculatus. At concentrations as low as 0.1%, A. lebbeck vicilins reduce larval mass from 8.1 ± 1.7 (mass of control larvae) to 1.8 ± 0.5 mg, which corresponds to a decrease of 78%. Seed coat toxicity constitutes an efficient defense mechanism, hindering insect predation and preventing embryo damage. We hypothesize that A. lebbeck vicilins are good candidates for the genetic transformation of crop legumes to enhance resistance to bruchid predation. PMID:22267002

Identification of Albizia lebbeck seed coat chitin-binding vicilins (7S globulins) with high toxicity to the larvae of the bruchid Callosobruchus maculatus.

PubMed

Souza, A J; Ferreira, A T S; Perales, J; Beghini, D G; Fernandes, K V S; Xavier-Filho, J; Venancio, T M; Oliveira, A E A

2012-02-01

Seed coat is a specialized maternal tissue that interfaces the embryo and the external environment during embryogenesis, dormancy and germination. In addition, it is the first defensive barrier against penetration by pathogens and herbivores. Here we show that Albizia lebbeck seed coat dramatically compromises the oviposition, eclosion and development of the bruchid Callosobruchus maculatus. Dietary supplementation of bruchid larvae with A. lebbeck seed coat flour causes severe weight loss and reduces survival. By means of protein purification, mass spectrometry and bioinformatic analyses, we show that chitin-binding vicilins are the main source of A. lebbeck tegumental toxicity to C. maculatus. At concentrations as low as 0.1%, A. lebbeck vicilins reduce larval mass from 8.1 ± 1.7 (mass of control larvae) to 1.8 ± 0.5 mg, which corresponds to a decrease of 78%. Seed coat toxicity constitutes an efficient defense mechanism, hindering insect predation and preventing embryo damage. We hypothesize that A. lebbeck vicilins are good candidates for the genetic transformation of crop legumes to enhance resistance to bruchid predation.

Evidence for a Trade-Off Strategy in Stone Oak (Lithocarpus) Seeds between Physical and Chemical Defense Highlights Fiber as an Important Antifeedant

PubMed Central

Chen, Xi; Cannon, Charles H.; Conklin-Brittan, Nancy Lou

2012-01-01

Trees in the beech or oak family (Fagaceae) have a mutualistic relationship with scatter-hoarding rodents. Rodents obtain nutrients and energy by consuming seeds, while providing seed dispersal for the tree by allowing some cached seeds to germinate. Seed predation and caching behavior of rodents is primarily affected by seed size, mechanical protection, macronutrient content, and chemical antifeedants. To enhance seed dispersal, trees must optimize trade-offs in investment between macronutrients and antifeedants. Here, we examine this important chemical balance in the seeds of tropical stone oak species with two substantially different fruit morphologies. These two distinct fruit morphologies in Lithocarpus differ in the degree of mechanical protection of the seed. For ‘acorn’ fruit, a thin exocarp forms a shell around the seed while for ‘enclosed receptacle’ (ER) fruit, the seed is embedded in a woody receptacle. We compared the chemical composition of numerous macronutrient and antifeedant in seeds from several Lithocarpus species, focusing on two pairs of sympatric species with different fruit morphologies. We found that macronutrients, particularly total non-structural carbohydrate, was more concentrated in seeds of ER fruits while antifeedants, primarily fibers, were more concentrated in seeds of acorn fruits. The trade-off in these two major chemical components was more evident between the two sympatric lowland species than between two highland species. Surprisingly, no significant difference in overall tannin concentrations in the seeds was observed between the two fruit morphologies. Instead, the major trade-off between macronutrients and antifeedants involved indigestible fibers. Future studies of this complex mutualism should carefully consider the role of indigestible fibers in the foraging behavior of scatter-hoarding rodents. PMID:22457722

Proteomic analysis of Metarhizium anisopliae secretion in the presence of the insect pest Callosobruchus maculatus.

PubMed

Murad, André M; Noronha, Eliane F; Miller, Robert N G; Costa, Fabio T; Pereira, Caroline D; Mehta, Angela; Caldas, Ruy A; Franco, Octávio L

2008-12-01

Crop improvement in agriculture generally focuses on yield, seed quality and nutritional characteristics, as opposed to resistance to biotic stresses. Consequently, natural antifeedant toxins are often rare in seed material, with commercial crops being prone to insect pest predation. In the specific case of cowpea (Vigna unguiculata), smallholder cropping is affected by insect pests that reproduce inside the stored seeds. Entomopathogenic organisms can offer an alternative to conventional pesticides for pest control, producing hydrolases that degrade insect exoskeleton. In this study, protein secretions of the ascomycete Metarhizium anisopliae, which conferred bioinsecticidal activity against Callosobruchus maculatus, were characterized via 2D electrophoresis and mass spectrometry. Proteases, reductases and acetyltransferase enzymes were detected. These may be involved in degradation and nutrient uptake from dehydrated C. maculatus. Proteins identified in this work allowed description of metabolic pathways. Their potential applications in biotechnology include both novel compound development and production of genetically modified plants resistant to insect pests.

The effect of pollen source vs. flower type on progeny performance and seed predation under contrasting light environments in a cleistogamous herb.

PubMed

Munguía-Rosas, Miguel A; Campos-Navarrete, María J; Parra-Tabla, Víctor

2013-01-01

Dimorphic cleistogamy is a specialized form of mixed mating system where a single plant produces both open, potentially outcrossed chasmogamous (CH) and closed, obligately self-pollinated cleistogamous (CL) flowers. Typically, CH flowers and seeds are bigger and energetically more costly than those of CL. Although the effects of inbreeding and floral dimorphism are critical to understanding the evolution and maintenance of cleistogamy, these effects have been repeatedly confounded. In an attempt to separate these effects, we compared the performance of progeny derived from the two floral morphs while controlling for the source of pollen. That is, flower type and pollen source effects were assessed by comparing the performance of progeny derived from selfed CH vs. CL and outcrossed CH vs. selfed CH flowers, respectively. The experiment was carried out with the herb Ruellia nudiflora under two contrasting light environments. Outcrossed progeny generally performed better than selfed progeny. However, inbreeding depression ranges from low (1%) to moderate (36%), with the greatest value detected under shaded conditions when cumulative fitness was used. Although flower type generally had less of an effect on progeny performance than pollen source did, the progeny derived from selfed CH flowers largely outperformed the progeny from CL flowers, but only under shaded conditions and when cumulative fitness was taken into account. On the other hand, the source of pollen and flower type influenced seed predation, with selfed CH progeny the most heavily attacked by predators. Therefore, the effects of pollen source and flower type are environment-dependant and seed predators may increase the genetic differences between progeny derived from CH and CL flowers. Inbreeding depression alone cannot account for the maintenance of a mixed mating system in R. nudiflora and other unidentified mechanisms must thus be involved.

Vertebrate seed dispersers maintain the composition of tropical forest seedbanks

PubMed Central

Wandrag, E. M.; Dunham, A. E.; Miller, R. H.; Rogers, H. S.

2015-01-01

The accumulation of seeds in the soil (the seedbank) can set the template for the early regeneration of habitats following disturbance. Seed dispersal is an important factor determining the pattern of seed rain, which affects the interactions those seeds experience. For this reason, seed dispersal should play an important role in structuring forest seedbanks, yet we know little about how that happens. Using the functional extirpation of frugivorous vertebrates from the island of Guam, together with two nearby islands (Saipan and Rota) that each support relatively intact disperser assemblages, we aimed to identify the role of vertebrate dispersers in structuring forest seedbanks. We sampled the seedbank on Guam where dispersers are absent, and compared this with the seedbank on Saipan and Rota where they are present. Almost twice as many species found in the seedbank on Guam, when compared with Saipan and Rota, had a conspecific adult within 2 m. This indicates a strong role of vertebrate dispersal in determining the identity of seeds in the seedbank. In addition, on Guam, a greater proportion of samples contained no seeds and overall species richness was lower than on Saipan. Differences in seed abundance and richness between Guam and Rota were less clear, as seedbanks on Rota also contained fewer species than Saipan, possibly due to increased post-dispersal seed predation. Our findings suggest that vertebrate seed dispersers can have a strong influence on the species composition of seedbanks. Regardless of post-dispersal processes, without dispersal, seedbanks no longer serve to increase the species pool of recruits during regeneration. PMID:26578741

Status and limiting factors of three rare plant species in the coastal lowlands and mid-elevation woodlands of Hawai`i Volcanoes National Park

USGS Publications Warehouse

Pratt, Linda W.; VanDeMark, Joshua R.; Euaparadorn, Melody

2011-01-01

Two endangered plant species (Portulaca sclerocarpa, `ihi mākole, and Sesbania tomentosa, `ōhai) and a species of concern (Bobea timonioides, `ahakea) native to the coastal lowlands and dry mid-elevation woodlands of Hawai`i Volcanoes National Park were studied for more than two years to determine their stand structure, short-term mortality rates, patterns of reproductive phenology, success of fruit production, seed germination rates in the greenhouse, presence of soil seed bank, and survival of both natural and planted seedlings. The role of rodents as fruit and seed predators was evaluated using exclosures and seed offerings in open and closed stations or cages. Rodents were excluded from randomly selected plants of P. sclerocarpa and from branches of S. tomentosa, and flower and fruit production were compared to that of adjacent unprotected plants. Tagged S. tomentosa fruit were also monitored monthly to detect rodent predation.

Role of predation by zooplankton in transport and fate of protozoan (oo)cysts in granular activated carbon filtration.

PubMed

Bichai, Françoise; Barbeau, Benoit; Dullemont, Yolanda; Hijnen, Wim

2010-02-01

The significance of zooplankton in the transport and fate of pathogenic organisms in drinking water is poorly understood, although many hints of the role of predation in the persistence of microorganisms through water treatment processes can be found in literature. The objective of this study was to assess the impact of predation by natural zooplankton on the transport and fate of protozoan (oo)cysts in granular activated carbon (GAC) filtration process. UV-irradiated unlabelled Cryptosporidium parvum and Giardia lamblia (oo)cysts were seeded into two pilot-scale GAC filtration columns operated under full-scale conditions. In a two-week period after seeding, a reduction of free (oo)cysts retained in the filter bed was observed. Zooplankton was isolated from the filter bed and effluent water on a 30 microm net before and during the two-week period after seeding; it was enumerated and identified. Rotifers, which are potential predators of (oo)cysts, accounted for the major part of the isolated zooplankton. Analytical methods were developed to detect (oo)cysts internalized in natural zooplankton isolated from the filter bed and effluent water. Sample sonication was optimized to disrupt zooplankton organisms and release internalized microorganisms. (Oo)cysts released from zooplankton after sonication were isolated by IMS and stained (EasyStain) for microscopic counting. Both Cryptosporidium and Giardia (oo)cysts were detected in association with zooplankton in the filter bed samples as well as in the effluent of GAC filters. The results of this study suggest that predation by zooplankton can play a role in the remobilization of persistent pathogens such as Cryptosporidium and Giardia (oo)cysts retained in GAC filter beds, and consequently in the transmission of these pathogens in drinking water. Copyright 2009 Elsevier Ltd. All rights reserved.

Neotropical fish-fruit interactions: eco-evolutionary dynamics and conservation.

PubMed

Correa, Sandra Bibiana; Costa-Pereira, Raul; Fleming, Theodore; Goulding, Michael; Anderson, Jill T

2015-11-01

Frugivorous fish play a prominent role in seed dispersal and reproductive dynamics of plant communities in riparian and floodplain habitats of tropical regions worldwide. In Neotropical wetlands, many plant species have fleshy fruits and synchronize their fruiting with the flood season, when fruit-eating fish forage in forest and savannahs for periods of up to 7 months. We conducted a comprehensive analysis to examine the evolutionary origin of fish-fruit interactions, describe fruit traits associated with seed dispersal and seed predation, and assess the influence of fish size on the effectiveness of seed dispersal by fish (ichthyochory). To date, 62 studies have documented 566 species of fruits and seeds from 82 plant families in the diets of 69 Neotropical fish species. Fish interactions with flowering plants are likely to be as old as 70 million years in the Neotropics, pre-dating most modern bird-fruit and mammal-fruit interactions, and contributing to long-distance seed dispersal and possibly the radiation of early angiosperms. Ichthyochory occurs across the angiosperm phylogeny, and is more frequent among advanced eudicots. Numerous fish species are capable of dispersing small seeds, but only a limited number of species can disperse large seeds. The size of dispersed seeds and the probability of seed dispersal both increase with fish size. Large-bodied species are the most effective seed dispersal agents and remain the primary target of fishing activities in the Neotropics. Thus, conservation efforts should focus on these species to ensure continuity of plant recruitment dynamics and maintenance of plant diversity in riparian and floodplain ecosystems. © 2015 Cambridge Philosophical Society.

Seed wasp invasions promoted by unregulated seed trade affect vegetal and animal biodiversity.

PubMed

Auger-Rozenberg, Marie-Anne; Roques, Alain

2012-09-01

Cone and seed insects are considered the most important predators of tree seeds during the pre-dispersal phase of development. Among them, exotic seed chalcids in the genus Megastigmus invaded Europe as a result of the rapidly-increasing and mostly unregulated seed trade for afforestation and ornamental plantations. Unlike their economic impact in seed orchards, until recently, little attention was paid to the ecological impact of these insects. In the present study, selected case studies of alien Megastigmus spp. were considered to assess their specific impact on the potential of natural regeneration of native woody plants and on the native entomofauna competing for seed resource. We re-analyzed data from former studies that did not focus on these ecological interactions and, here, present previously unpublished results. Seeds of Douglas-fir, true cedars, true firs and wild roses were sampled all over Europe, and the relative importance of the native and invasive chalcid species was assessed as well as their specific impact on seed yield. In most cases, the recent arrival of alien chalcids resulted in a significant decrease in the regeneration potential of the host trees. In the absence of competitors, alien chalcids occupied the entire seed niche in Douglas-fir, but their impact tended to decrease after the arrival of invasive seed bugs. In firs, alien chalcids tended to displace the native chalcids, but not in wild roses and cedars, where their damage was increasing. Different biological traits that might explain invasive success of alien chalcids are discussed. However, no general invasive patterns seem to exist. © 2012 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS.

Direct and indirect effects of a dense understory on tree seedling recruitment in temperate forests: habitat-mediated predation versus competition

Treesearch

Alejandro A. Royo; Walter P. Carson

2008-01-01

In forests characterized by a dense woody and herbaceous understory layer, seedling recruitment is often directly suppressed via interspecific competition. Alternatively, these dense layers may indirectly lower tree recruitment by providing a haven for seed and seedling predators that prey on neighboring plant species. To simultaneously...

Strong dependence of a pioneer shrub on seed dispersal services provided by an endemic endangered lizard in a Mediterranean island ecosystem.

PubMed

Neghme, Constanza; Santamaría, Luís; Calviño-Cancela, María

2017-01-01

The accelerating rate of vertebrate extinctions and population declines threatens to disrupt important ecological interactions, altering key ecosystem processes such as animal seed dispersal. The study of highly specialized mutualistic interactions is crucial to predict the consequences of population declines and extinctions. Islands offer unique opportunities to study highly specialized interactions, as they often have naturally depauperated faunas and are experiencing high rates of human-driven extinctions. In this study, we assess the effect of seed dispersal on seedling recruitment of Ephedra fragilis (Ephedraceae) on a Mediterranean island ecosystem. We used field data and stochastic simulation modeling to estimate seed fate and recruitment patterns of this pioneer shrub typical of arid and semiarid areas, and to estimate the dependence of recruitment on the lizard Podarcis lilfordi (Lacertidae), its only known seed disperser. Ephedra fragilis recruitment highly depended on lizards: lizards produced 3.8 times more newly-emerged seedlings than non-dispersed seeds and no seedlings from undispersed seeds survived the study period. Seed dispersal by lizards was mostly to open sites, which was key for the increased success observed, while undispersed seeds, falling under mother plants, suffered higher predation and lower seedling emergence and survival. The ability of this pioneer shrub to get established in open ground is crucial for vegetation colonization and restoration, especially on degraded lands affected by desertification, where they act as nurse plants for other species. Lizards are key in this process, which has important consequences for community structure and ecosystem functioning.

Strong dependence of a pioneer shrub on seed dispersal services provided by an endemic endangered lizard in a Mediterranean island ecosystem

PubMed Central

Santamaría, Luís; Calviño-Cancela, María

2017-01-01

The accelerating rate of vertebrate extinctions and population declines threatens to disrupt important ecological interactions, altering key ecosystem processes such as animal seed dispersal. The study of highly specialized mutualistic interactions is crucial to predict the consequences of population declines and extinctions. Islands offer unique opportunities to study highly specialized interactions, as they often have naturally depauperated faunas and are experiencing high rates of human-driven extinctions. In this study, we assess the effect of seed dispersal on seedling recruitment of Ephedra fragilis (Ephedraceae) on a Mediterranean island ecosystem. We used field data and stochastic simulation modeling to estimate seed fate and recruitment patterns of this pioneer shrub typical of arid and semiarid areas, and to estimate the dependence of recruitment on the lizard Podarcis lilfordi (Lacertidae), its only known seed disperser. Ephedra fragilis recruitment highly depended on lizards: lizards produced 3.8 times more newly-emerged seedlings than non-dispersed seeds and no seedlings from undispersed seeds survived the study period. Seed dispersal by lizards was mostly to open sites, which was key for the increased success observed, while undispersed seeds, falling under mother plants, suffered higher predation and lower seedling emergence and survival. The ability of this pioneer shrub to get established in open ground is crucial for vegetation colonization and restoration, especially on degraded lands affected by desertification, where they act as nurse plants for other species. Lizards are key in this process, which has important consequences for community structure and ecosystem functioning. PMID:28827820

How to be an ant on figs

NASA Astrophysics Data System (ADS)

Bain, Anthony; Harrison, Rhett D.; Schatz, Bertrand

2014-05-01

Mutualistic interactions are open to exploitation by one or other of the partners and a diversity of other organisms, and hence are best understood as being embedded in a complex network of biotic interactions. Figs participate in an obligate mutualism in that figs are dependent on agaonid fig wasps for pollination and the wasps are dependent on fig ovules for brood sites. Ants are common insect predators and abundant in tropical forests. Ants have been recorded on approximately 11% of fig species, including all six subgenera, and often affect the fig-fig pollinator interaction through their predation of either pollinating and parasitic wasps. On monoecious figs, ants are often associated with hemipterans, whereas in dioecious figs ants predominantly prey on fig wasps. A few fig species are true myrmecophytes, with domatia or food rewards for ants, and in at least one species this is linked to predation of parasitic fig wasps. Ants also play a role in dispersal of fig seeds and may be particularly important for hemi-epiphytic species, which require high quality establishment microsites in the canopy. The intersection between the fig-fig pollinator and ant-plant systems promises to provide fertile ground for understanding mutualistic interactions within the context of complex interaction networks.

Vertebrate seed dispersers maintain the composition of tropical forest seedbanks.

PubMed

Wandrag, E M; Dunham, A E; Miller, R H; Rogers, H S

2015-11-16

The accumulation of seeds in the soil (the seedbank) can set the template for the early regeneration of habitats following disturbance. Seed dispersal is an important factor determining the pattern of seed rain, which affects the interactions those seeds experience. For this reason, seed dispersal should play an important role in structuring forest seedbanks, yet we know little about how that happens. Using the functional extirpation of frugivorous vertebrates from the island of Guam, together with two nearby islands (Saipan and Rota) that each support relatively intact disperser assemblages, we aimed to identify the role of vertebrate dispersers in structuring forest seedbanks. We sampled the seedbank on Guam where dispersers are absent, and compared this with the seedbank on Saipan and Rota where they are present. Almost twice as many species found in the seedbank on Guam, when compared with Saipan and Rota, had a conspecific adult within 2 m. This indicates a strong role of vertebrate dispersal in determining the identity of seeds in the seedbank. In addition, on Guam, a greater proportion of samples contained no seeds and overall species richness was lower than on Saipan. Differences in seed abundance and richness between Guam and Rota were less clear, as seedbanks on Rota also contained fewer species than Saipan, possibly due to increased post-dispersal seed predation. Our findings suggest that vertebrate seed dispersers can have a strong influence on the species composition of seedbanks. Regardless of post-dispersal processes, without dispersal, seedbanks no longer serve to increase the species pool of recruits during regeneration. Published by Oxford University Press on behalf of the Annals of Botany Company.

Cover crops increase foraging activity of omnivorous predators in seed patches and facilitate weed biological control

USDA-ARS?s Scientific Manuscript database

Omnivores are important consumers of both weed seeds and insect pests, and habitat provisions like cover crops are suggested to promote their ecosystem services in agricultural systems. However, few studies establish direct links between cover, food, and pest suppression because they are entangled a...

Pondberry (Lindera   melissifolia, Lauraceae) seed and seedling dispersers and predators

Treesearch

Andreza M. Martins; Fernanda M. Abilio; Plinio Gonçalves de Oliveira; Raquel Partelli Feltrin; Fernanda Scheffer Alves de Lima; Priscilla de O. Antonelli; Daniela Teixeira Vilela; Carl G. Smith III; Collin Tidwell; Paul Hamel; Margaret Devall; Kristina Connor; Theodor Leininger; Nathan Schiff; A. Dan Wilson

2015-01-01

Pondberry (Lindera melissifolia(Walter) Blume) is an endangered dioecious, clonal shrub that grows in periodically flooded forests of the southeastern United States. The probability of survival of dispersed pondberry seeds and new germinants is unknown, but few seedlings are noted in the forest. This study was undertaken to: (1) identify herbivores...

The Effect of Pollen Source vs. Flower Type on Progeny Performance and Seed Predation under Contrasting Light Environments in a Cleistogamous Herb

PubMed Central

Munguía-Rosas, Miguel A.; Campos-Navarrete, María J.; Parra-Tabla, Víctor

2013-01-01

Dimorphic cleistogamy is a specialized form of mixed mating system where a single plant produces both open, potentially outcrossed chasmogamous (CH) and closed, obligately self-pollinated cleistogamous (CL) flowers. Typically, CH flowers and seeds are bigger and energetically more costly than those of CL. Although the effects of inbreeding and floral dimorphism are critical to understanding the evolution and maintenance of cleistogamy, these effects have been repeatedly confounded. In an attempt to separate these effects, we compared the performance of progeny derived from the two floral morphs while controlling for the source of pollen. That is, flower type and pollen source effects were assessed by comparing the performance of progeny derived from selfed CH vs. CL and outcrossed CH vs. selfed CH flowers, respectively. The experiment was carried out with the herb Ruellia nudiflora under two contrasting light environments. Outcrossed progeny generally performed better than selfed progeny. However, inbreeding depression ranges from low (1%) to moderate (36%), with the greatest value detected under shaded conditions when cumulative fitness was used. Although flower type generally had less of an effect on progeny performance than pollen source did, the progeny derived from selfed CH flowers largely outperformed the progeny from CL flowers, but only under shaded conditions and when cumulative fitness was taken into account. On the other hand, the source of pollen and flower type influenced seed predation, with selfed CH progeny the most heavily attacked by predators. Therefore, the effects of pollen source and flower type are environment-dependant and seed predators may increase the genetic differences between progeny derived from CH and CL flowers. Inbreeding depression alone cannot account for the maintenance of a mixed mating system in R. nudiflora and other unidentified mechanisms must thus be involved. PMID:24260515

Convergent evolution of plant and animal embryo defences by hyperstable non-digestible storage proteins.

PubMed

Pasquevich, María Yanina; Dreon, Marcos Sebastián; Qiu, Jian-Wen; Mu, Huawei; Heras, Horacio

2017-11-20

Plants have evolved sophisticated embryo defences by kinetically-stable non-digestible storage proteins that lower the nutritional value of seeds, a strategy that have not been reported in animals. To further understand antinutritive defences in animals, we analysed PmPV1, massively accumulated in the eggs of the gastropod Pomacea maculata, focusing on how its structure and structural stability features affected its capacity to withstand passage through predator guts. The native protein withstands >50 min boiling and resists the denaturing detergent sodium dodecyl sulphate (SDS), indicating an unusually high structural stability (i.e., kinetic stability). PmPV1 is highly resistant to in vitro proteinase digestion and displays structural stability between pH 2.0-12.0 and 25-85 °C. Furthermore, PmPV1 withstands in vitro and mice digestion and is recovered unchanged in faeces, supporting an antinutritive defensive function. Subunit sequence similarities suggest a common origin and tolerance to mutations. This is the first known animal genus that, like plant seeds, lowers the nutritional value of eggs by kinetically-stable non-digestible storage proteins that survive the gut of predators unaffected. The selective pressure of the harsh gastrointestinal environment would have favoured their appearance, extending by convergent evolution the presence of plant-like hyperstable antinutritive proteins to unattended reproductive stages in animals.

Autumn predation of northern red oak seed crops

Treesearch

Kim C. Steiner

1995-01-01

Production and autumn predation of northern red oak acorns was measured over four years in five Pennsylvania stands dominated by this species. Mean annual production was 41,779/acre, of which an average of 7.9% was destroyed by insects or decay following insect attack, and an average of 38.6% was destroyed or removed by vertebrates. White-tailed deer appeared to be the...

Pre-dispersal seed predator dynamics at the northern limits of limber pine distribution

Treesearch

Vernon S. Peters

2011-01-01

Limber pine (Pinus flexilis) is listed provincially as endangered in the northern part of its geographic range (Alberta) due to the high mortality caused by white pine blister rust (WPBR) (Cronartium ribicola) and mountain pine beetle (Dendroctonus ponderosae), and limited regeneration opportunities due to fire exclusion. In the case of an endangered species, seed...

Pondberry (Lindera melissifolia) seed predators

Treesearch

Fernanda Maria Abilio; Carl Smith; Colin Tidwell; Paul Hamel; Margaret Devall; Ted Leininger

2008-01-01

Pondberry is an endangered, dioecious, deciduous shrub that grows in periodically flooded forests of the southeastern United States of America. Pondbeny is a clonal plant. Each female stem grows up to two meters tall and may produce many red drupes. The probability of dispersed seeds to survive to germination and beyond is unknown in the species. For this study, six...

Field observations of climbing behavior and seed predation by adult ground beetles (Coleoptera: Carabidae) in a lowland area of the temperate zone.

PubMed

Sasakawa, Kôji

2010-10-01

Granivory is a specialized food habit in the predominantly carnivorous beetle family Carabidae. Most studies of carabid granivory have been conducted under laboratory conditions; thus, our knowledge of the feeding ecology of granivorous carabids in the field is insufficient. I conducted field observations of climbing behavior and seed predation by adult carabids in a lowland area of eastern Japan, from early October to late November in 2008. This is the first systematic field observation of the feeding ecology of granivorous carabids in the temperate zone. In total, 176 carabid individuals of 11 species were observed, with 108 individuals feeding on plant seeds/flowers. Each carabid species was primarily observed feeding on a particular plant species. Frequently observed combinations were: Amara gigantea Motschulsky on Humulus scandens (Loureiro) Merrill (Moraceae) seed, Amara lucens Baliani on Artemisia indica Willdenow (Asteraceae) flower, and Amara macronota (Solsky) and Harpalus (Pseudoophonus) spp. on Digitaria ciliaris (Retzius) Koeler (Poaceae) seed. In all but one species, the sex ratio of individuals observed feeding was female-biased. In Am. gigantea and Am. macronota, a larger proportion of females than males ate seeds. In the three Amara species, copulations on plants, with the female feeding on its seeds/flowers, were often observed. These observations may indicate that, whereas females climb onto plants to feed on seeds, males climb to seek females for copulation rather than forage. Because granivorous carabids play important roles as weed-control agents in temperate agro-ecosystems, the present results would provide valuable basic information for future studies on this subject.

Reversing functional extinction of mammals prompts a rethink of paradigms about seed fate in arid Australia

PubMed Central

2018-01-01

Functional extinction of once abundant species has frequently preceded understanding of their ecological roles. Consequently, our understanding of ecosystems is prone to shifting baselines because it often relies on observations made on depauperate species assemblages. In Australian deserts, current paradigms are that ants are the dominant granivores, mammals are unimportant seed predators and that myrmecochory in many Australian shrubs is an adaptation to increase dispersal distance and direct seeds to favourable germination sites. Here, we ask whether these paradigms could be artefacts of mammal extinction. We take advantage of a predator-proof reserve within which locally extinct native mammals have been reintroduced to compare seed removal by ants and mammals. Using foraging trays that selectively excluded mammals and ants we show that a reintroduced mammal, the woylie (Bettongia penicillata) was at least as important as ants in the removal of seeds of two shrub species (Dodonaea viscosa and Acacia ligulata). Our results provide evidence that the dominance of ants as granivores and current understanding of the adaptive benefit of myrmecochory in arid Australia may be artefacts of the functional extinction of mammals. Our study shows how reversing functional extinction can provide the opportunity to rethink contemporary understanding of ecological processes. PMID:29410877

Reversing functional extinction of mammals prompts a rethink of paradigms about seed fate in arid Australia.

PubMed

Mills, Charlotte H; Letnic, Mike

2018-01-01

Functional extinction of once abundant species has frequently preceded understanding of their ecological roles. Consequently, our understanding of ecosystems is prone to shifting baselines because it often relies on observations made on depauperate species assemblages. In Australian deserts, current paradigms are that ants are the dominant granivores, mammals are unimportant seed predators and that myrmecochory in many Australian shrubs is an adaptation to increase dispersal distance and direct seeds to favourable germination sites. Here, we ask whether these paradigms could be artefacts of mammal extinction. We take advantage of a predator-proof reserve within which locally extinct native mammals have been reintroduced to compare seed removal by ants and mammals. Using foraging trays that selectively excluded mammals and ants we show that a reintroduced mammal, the woylie ( Bettongia penicillata ) was at least as important as ants in the removal of seeds of two shrub species ( Dodonaea viscosa and Acacia ligulata ). Our results provide evidence that the dominance of ants as granivores and current understanding of the adaptive benefit of myrmecochory in arid Australia may be artefacts of the functional extinction of mammals. Our study shows how reversing functional extinction can provide the opportunity to rethink contemporary understanding of ecological processes.

Food preferences and mound-building behaviour of the mound-building mice Mus spicilegus

NASA Astrophysics Data System (ADS)

Hölzl, Michaela; Krištofík, Ján; Darolová, Alžbeta; Hoi, Herbert

2011-10-01

Optimal foraging strategies and food choice are influenced by various factors, e.g. availability, size and caloric content of the food type and predation risk. However, food choice criteria may change when food is not eaten immediately but has to be carried to a storage site for later use. For example, handling time in terms of harvesting and transport time should be optimized, particularly when the risk of predation is high. Thus, it is not clear whether food selected by hoarding animals reflects their food preference due to intrinsic features of the food type, e.g. size, caloric or lipid content, or whether the food type selected is a compromise that also considers the handling time required for harvesting and transport. We investigate this question in relation to food hoarding behaviour in mound-building mice. In autumn, mound-building mice Mus spicilegus collect seeds and other plant material and cover it with soil. Such above-ground storage is quite unusual for rodents. Here, we investigated whether there is a relationship between the seed species preferred as building materials and those preferred for food. We conducted a seed preference test using three most collected weed species for mound building. Controlling factors like food availability or predation risk, mice prefer Setaria spp. as food, although Amaranthus spp. and Chenopodium spp. were preferentially harvested and stored. By including the availability of the three species, our experimental results were confirmed, namely, a clear preference for Setaria spp. Also, handling time and seed size revealed to influence plant choice.

Biochemical characterisation of α-amylase inhibitors from Achyranthes aspera and their interactions with digestive amylases of coleopteran and lepidopteran insects.

PubMed

Hivrale, Vandana K; Chougule, Nanasaheb P; Giri, Ashok P; Chhabda, Pavan J; Kachole, Manvendra S

2011-08-15

Starchy seeds are an important food and a source of dietary ingredients in many countries. However, they suffer from extensive predation by bruchids (weevils) and other pests. α-Amylase inhibitors are attractive candidates for the control of seed weevils, as these insects are highly dependent on starch as an energy source. A proteinaceous α-amylase inhibitor from the seeds of Achyranthes aspera was identified, purified and characterised. In electrophoretic analysis, two prominent amylase inhibitor activity bands (AI1 and AI2) were detected. The inhibitor was purified 9.99-fold with 1206.95 total amylase inhibitor units mg⁻¹ protein. The molecular weight of the purified inhibitor was around 6 kDa. The isolated α-amylase inhibitor was found to be resistant to heat and proteolysis. Feeding analysis of Callosobruchus maculatus larvae on a diet containing seed powder of A. aspera revealed that survival of the larvae was severely affected, with the highest mortality rate occurring on the fifth day of feeding. The isolated inhibitor inhibited the majority of amylase isoforms of C. maculatus, Tribolium confusum and Helicoverpa armigera in electrophoretic analysis and solution assays. The information obtained in the present investigation could be useful for a genetic engineering approach that would make seeds resistant to storage pest infestations. Copyright © 2011 Society of Chemical Industry.

Meta-analysis of the effects of forest fragmentation on interspecific interactions.

PubMed

Magrach, Ainhoa; Laurance, William F; Larrinaga, Asier R; Santamaria, Luis

2014-10-01

Forest fragmentation dramatically alters species persistence and distribution and affects many ecological interactions among species. Recent studies suggest that mutualisms, such as pollination and seed dispersal, are more sensitive to the negative effects of forest fragmentation than antagonisms, such as predation or herbivory. We applied meta-analytical techniques to evaluate this hypothesis and quantified the relative contributions of different components of the fragmentation process (decreases in fragment size, edge effects, increased isolation, and habitat degradation) to the overall effect. The effects of fragmentation on mutualisms were primarily driven by habitat degradation, edge effects, and fragment isolation, and, as predicted, they were consistently more negative on mutualisms than on antagonisms. For the most studied interaction type, seed dispersal, only certain components of fragmentation had significant (edge effects) or marginally significant (fragment size) effects. Seed size modulated the effect of fragmentation: species with large seeds showed stronger negative impacts of fragmentation via reduced dispersal rates. Our results reveal that different components of the habitat fragmentation process have varying impacts on key mutualisms. We also conclude that antagonistic interactions have been understudied in fragmented landscapes, most of the research has concentrated on particular types of mutualistic interactions such as seed dispersal, and that available studies of interspecific interactions have a strong geographical bias (arising mostly from studies carried out in Brazil, Chile, and the United States). © 2014 Society for Conservation Biology.

Forest fragmentation and selective logging have inconsistent effects on multiple animal-mediated ecosystem processes in a tropical forest.

PubMed

Schleuning, Matthias; Farwig, Nina; Peters, Marcell K; Bergsdorf, Thomas; Bleher, Bärbel; Brandl, Roland; Dalitz, Helmut; Fischer, Georg; Freund, Wolfram; Gikungu, Mary W; Hagen, Melanie; Garcia, Francisco Hita; Kagezi, Godfrey H; Kaib, Manfred; Kraemer, Manfred; Lung, Tobias; Naumann, Clas M; Schaab, Gertrud; Templin, Mathias; Uster, Dana; Wägele, J Wolfgang; Böhning-Gaese, Katrin

2011-01-01

Forest fragmentation and selective logging are two main drivers of global environmental change and modify biodiversity and environmental conditions in many tropical forests. The consequences of these changes for the functioning of tropical forest ecosystems have rarely been explored in a comprehensive approach. In a Kenyan rainforest, we studied six animal-mediated ecosystem processes and recorded species richness and community composition of all animal taxa involved in these processes. We used linear models and a formal meta-analysis to test whether forest fragmentation and selective logging affected ecosystem processes and biodiversity and used structural equation models to disentangle direct from biodiversity-related indirect effects of human disturbance on multiple ecosystem processes. Fragmentation increased decomposition and reduced antbird predation, while selective logging consistently increased pollination, seed dispersal and army-ant raiding. Fragmentation modified species richness or community composition of five taxa, whereas selective logging did not affect any component of biodiversity. Changes in the abundance of functionally important species were related to lower predation by antbirds and higher decomposition rates in small forest fragments. The positive effects of selective logging on bee pollination, bird seed dispersal and army-ant raiding were direct, i.e. not related to changes in biodiversity, and were probably due to behavioural changes of these highly mobile animal taxa. We conclude that animal-mediated ecosystem processes respond in distinct ways to different types of human disturbance in Kakamega Forest. Our findings suggest that forest fragmentation affects ecosystem processes indirectly by changes in biodiversity, whereas selective logging influences processes directly by modifying local environmental conditions and resource distributions. The positive to neutral effects of selective logging on ecosystem processes show that the functionality of tropical forests can be maintained in moderately disturbed forest fragments. Conservation concepts for tropical forests should thus include not only remaining pristine forests but also functionally viable forest remnants.

Forest Fragmentation and Selective Logging Have Inconsistent Effects on Multiple Animal-Mediated Ecosystem Processes in a Tropical Forest

PubMed Central

Schleuning, Matthias; Farwig, Nina; Peters, Marcell K.; Bergsdorf, Thomas; Bleher, Bärbel; Brandl, Roland; Dalitz, Helmut; Fischer, Georg; Freund, Wolfram; Gikungu, Mary W.; Hagen, Melanie; Garcia, Francisco Hita; Kagezi, Godfrey H.; Kaib, Manfred; Kraemer, Manfred; Lung, Tobias; Schaab, Gertrud; Templin, Mathias; Uster, Dana; Wägele, J. Wolfgang; Böhning-Gaese, Katrin

2011-01-01

Forest fragmentation and selective logging are two main drivers of global environmental change and modify biodiversity and environmental conditions in many tropical forests. The consequences of these changes for the functioning of tropical forest ecosystems have rarely been explored in a comprehensive approach. In a Kenyan rainforest, we studied six animal-mediated ecosystem processes and recorded species richness and community composition of all animal taxa involved in these processes. We used linear models and a formal meta-analysis to test whether forest fragmentation and selective logging affected ecosystem processes and biodiversity and used structural equation models to disentangle direct from biodiversity-related indirect effects of human disturbance on multiple ecosystem processes. Fragmentation increased decomposition and reduced antbird predation, while selective logging consistently increased pollination, seed dispersal and army-ant raiding. Fragmentation modified species richness or community composition of five taxa, whereas selective logging did not affect any component of biodiversity. Changes in the abundance of functionally important species were related to lower predation by antbirds and higher decomposition rates in small forest fragments. The positive effects of selective logging on bee pollination, bird seed dispersal and army-ant raiding were direct, i.e. not related to changes in biodiversity, and were probably due to behavioural changes of these highly mobile animal taxa. We conclude that animal-mediated ecosystem processes respond in distinct ways to different types of human disturbance in Kakamega Forest. Our findings suggest that forest fragmentation affects ecosystem processes indirectly by changes in biodiversity, whereas selective logging influences processes directly by modifying local environmental conditions and resource distributions. The positive to neutral effects of selective logging on ecosystem processes show that the functionality of tropical forests can be maintained in moderately disturbed forest fragments. Conservation concepts for tropical forests should thus include not only remaining pristine forests but also functionally viable forest remnants. PMID:22114695

Non-climatic constraints on upper elevational plant range expansion under climate change

PubMed Central

Brown, Carissa D.; Vellend, Mark

2014-01-01

We are limited in our ability to predict climate-change-induced range shifts by our inadequate understanding of how non-climatic factors contribute to determining range limits along putatively climatic gradients. Here, we present a unique combination of observations and experiments demonstrating that seed predation and soil properties strongly limit regeneration beyond the upper elevational range limit of sugar maple, a tree species of major economic importance. Most strikingly, regeneration beyond the range limit occurred almost exclusively when seeds were experimentally protected from predators. Regeneration from seed was depressed on soil from beyond the range edge when this soil was transplanted to sites within the range, with indirect evidence suggesting that fungal pathogens play a role. Non-climatic factors are clearly in need of careful attention when attempting to predict the biotic consequences of climate change. At minimum, we can expect non-climatic factors to create substantial time lags between the creation of more favourable climatic conditions and range expansion. PMID:25253462

Phenological and ecological consequences of changes in winter snowpack in the Colorado Rocky Mountains

NASA Astrophysics Data System (ADS)

Inouye, D. W.; McKinney, A. M.

2012-12-01

The date the snowpack disappears in spring is an important seasonal event at high altitudes because it determines the beginning of the growing season, which in turn influences the phenology of plant growth and flowering, and thus the availability of these resources for animal consumers. At our study site at 2,900m in the Colorado Rocky Mountains, the Rocky Mountain Biological Laboratory, snowmelt now averages two weeks earlier than in 1975. Earlier snowmelt results from a combination of lower snowfall (38 cm less since 1975), dust storms (increasing in frequency, which reduces the snowpack albedo), and warmer spring temperatures (April minimum temperature has increased 3.1°C since 1973; 2012 April mean temperature was 3.4°C above the 38-year mean). There is also a trend of increasing annual precipitation falling as rain instead of snow. We have monitored flowering phenology and abundance for about 100 species of plants in permanent plots since 1973, and use this record to look at how the change in timing of snowmelt has affected flowering. There is significant variation among years in flowering phenology (e.g., about six weeks difference between 2011 and 2012), with a mid-season decline in flowering abundance becoming apparent as the growing season starts earlier. The date of the last hard frost has not been changing in concert with the earlier growing season, with the consequence that many species now have flower buds developed that are then damaged or killed by frost. In 2012, snowmelt date was 23 April, and frost events on 27 May (-11.7°C) and 11 June (-5.6°C) did significant damage to vegetation of some species and to flower buds of many species. For example, flower abundance of the aspen sunflower Helianthella quinquenervis was 0.002% of 2011's flowering. In the absence of seed production, the demography of some plant species is likely being affected. Some animal species are also being affected by the changes in length and temperature of winter. New species of mammals, birds, and insects have begun to reproduce and overwinter at our field site in the past decade, and hibernators have changed the phenology of emergence from hibernation. Marmots now put on much more fat before entering hibernation. Interactions among species such as pollination and seed predation have also been affected by the changes in snowpack and phenology. For example, although both migratory hummingbirds and their floral resources are changing phenology, they are not changing at the same rate, leading to mismatches in their historical synchrony; hummingbirds now arrive well after their earliest food plant has begun to flower. A similar loss of synchrony appears to be affecting bumble bees as they emerge from overwintering underground, and one of their earliest nectar sources. Seed predator flies and moths, and their parasitoids, are probably being affected by the absence of seeds from species sensitive to frost. Thus many aspects of high-altitude ecological communities are being affected by the ongoing changes in depth of winter snowpack and the timing of its melting.

Impact of cogongrass management strategies on generalist predators in cogongrass-infested longleaf pine plantations.

PubMed

Sells, Sallie M; Held, David W; Enloe, Stephen F; Loewenstein, Nancy J; Eckhardt, Lori G

2015-03-01

Cogongrass (Imperata cylindrica Beav.) is an aggressive, invasive weed with a global distribution. In North America, it threatens the integrity of southeastern pine agroecosystems, including longleaf pine (Pinus palustris Mill.). While studies have examined the impacts of cogongrass and various vegetation management strategies on longleaf pine understory plant communities, little is known about how they impact associated insect communities. To understand the effect of cogongrass management strategies on arthropod natural enemies and bark beetles, a split-plot design was used to test fire (whole-plot) and four subplot treatments (control, herbicide, seeding and herbicide plus seeding). Arthropods were sampled using pitfall traps and sweep samples. After 2 years of sampling, total natural enemies were not significantly affected by subplot treatment but were affected by burn treatment. Upon subdividing natural enemies into groups, only spiders were significantly affected by subplot treatment, but predatory beetles and ants were significantly affected by burn treatment. The abundance of root-feeding bark beetles (Hylastes spp.) was not significant by subplot or whole-plot treatments. Multiple applications of herbicide remain the most effective way to manage cogongrass in longleaf pine. In this study, we found limited evidence that cogongrass management with herbicides would negatively impact arthropod natural enemies associated with longleaf pine or locally increase root-feeding bark beetles. © 2014 Society of Chemical Industry.

From seed production to seedling establishment: Important steps in an invasive process

NASA Astrophysics Data System (ADS)

Ferreras, Ana Elisa; Galetto, Leonardo

2010-03-01

It is widely accepted that exotic invasive species are one of the most important ecological and economic problems. Reproductive and establishment traits are considered key features of a population expansion process, but few works have studied many of these simultaneously. This work examines how large the differences are in reproductive and establishment traits between two Fabaceae, the exotic invasive, Gleditsia triacanthos and the native, Acacia aroma. Gleditsia is a serious leguminous woody invader in various parts of the world and Acacia is a common native tree of Argentina. Both species have similar dispersal mechanisms and their reproductive phenology overlaps. We chose 17 plants of each species in a continuous forest of the Chaco Serrano Forest of Córdoba, Argentina. In each plant we measured fruit production, fruit removal (exclusion experiments), seed predation (pre- and post-dispersal), seed germination, seed bank (on each focal tree, three sampling periods during the year), and density of seedlings (around focal individuals and randomly in the study site). Gleditsia presented some traits that could favour the invasion process, such as a higher number of seeds per plant, percentage of scarified seed germination and density of seedlings around the focal individuals, than Acacia. On the other hand, Gleditsia presented a higher percentage of seed predation. The seed bank was persistent in both species and no differences were observed in fruit removal. This work highlights the importance of simultaneously studying reproductive and establishment variables involved in the spreading of an exotic invasive species. It also gives important insight into the variables to be considered when planning management strategies. The results are discussed from the perspective of some remarkable hypotheses on invasive species and may contribute to rethinking some aspects of the theory on invasive species.

Risk of predation makes foragers less choosy about their food.

PubMed

Charalabidis, Alice; Dechaume-Moncharmont, François-Xavier; Petit, Sandrine; Bohan, David A

2017-01-01

Animals foraging in the wild have to balance speed of decision making and accuracy of assessment of a food item's quality. If resource quality is important for maximizing fitness, then the duration of decision making may be in conflict with other crucial and time consuming tasks, such as anti-predator behaviours or competition monitoring. Individuals facing the risk of predation and/or competition should adjust the duration of decision making and, as a consequence, their level of choosiness for resources. When exposed to predation, the forager could either maintain its level of choosiness for food items but accept a reduction in the amount of food items consumed or it could reduce its level of choosiness and accept all prey items encountered. Under competition risk, individuals are expected to reduce their level of choosiness as slow decision making exposes individuals to a higher risk of opportunity costs. To test these predictions, the level of choosiness of a seed-eating carabid beetle, Harpalus affinis, was examined under 4 different experimental conditions of risk: i) predation risk; ii) intraspecific competition; iii) interspecific competition; and, iv) control. All the risks were simulated using chemical cues from individual conspecifics or beetles of different species that are predatory or granivorous. Our results show that when foraging under the risk of predation, H. affinis individuals significantly reduce their level of choosiness for seeds. Reductions in level of choosiness for food items might serve as a sensible strategy to reduce both the total duration of a foraging task and the cognitive load of the food quality assessment. No significant differences were observed when individuals were exposed to competition cues. Competition, (i.e opportunity cost) may not be perceived as risk high enough to induce changes in the level of choosiness. Our results suggest that considering the amount of items consumed, alone, would be a misleading metric when assessing individual response to a risk of predation. Foraging studies should therefore also take in account the decision making process.

Power lines, roads, and avian nest survival: effects on predator identity and predation intensity

PubMed Central

DeGregorio, Brett A; Weatherhead, Patrick J; Sperry, Jinelle H

2014-01-01

1 Anthropogenic alteration of landscapes can affect avian nest success by influencing the abundance, distribution, and behavior of predators. Understanding avian nest predation risk necessitates understanding how landscapes affect predator distribution and behavior. 2 From a sample of 463 nests of 17 songbird species, we evaluated how landscape features (distance to forest edge, unpaved roads, and power lines) influenced daily nest survival. We also used video cameras to identify nest predators at 137 nest predation events and evaluated how landscape features influenced predator identity. Finally, we determined the abundance and distribution of several of the principal predators using surveys and radiotelemetry. 3 Distance to power lines was the best predictor of predator identity: predation by brown-headed cowbirds (Molothrus ater), corvids (Corvus sp. and Cyanocitta cristata), racers (Coluber constrictor), and coachwhips (Masticophis flagellum) increased with proximity to power lines, whereas predation by rat snakes (Elaphe obsoleta) and raptors decreased. In some cases, predator density may reliably indicate nest predation risk because racers, corvids, and cowbirds frequently used power line right-of-ways. 4 Of five bird species with enough nests to analyze individually, daily nest survival of only indigo buntings (Passerina cyanea) decreased with proximity to power lines, despite predation by most predators at our site being positively associated with power lines. For all nesting species combined, distance to unpaved road was the model that most influenced daily nest survival. This pattern is likely a consequence of rat snakes, the locally dominant nest predator (28% of predation events), rarely using power lines and associated areas. Instead, rat snakes were frequently associated with road edges, indicating that not all edges are functionally similar. 5 Our results suggest that interactions between predators and landscape features are likely to be specific to both the local predators and landscape. Thus, predicting how anthropogenic changes to landscapes affect nesting birds requires that we know more about how landscape changes affect the behavior of nest predators and which nest predators are locally important. PMID:24967077

Power lines, roads, and avian nest survival: effects on predator identity and predation intensity.

PubMed

DeGregorio, Brett A; Weatherhead, Patrick J; Sperry, Jinelle H

2014-05-01

1 Anthropogenic alteration of landscapes can affect avian nest success by influencing the abundance, distribution, and behavior of predators. Understanding avian nest predation risk necessitates understanding how landscapes affect predator distribution and behavior. 2 From a sample of 463 nests of 17 songbird species, we evaluated how landscape features (distance to forest edge, unpaved roads, and power lines) influenced daily nest survival. We also used video cameras to identify nest predators at 137 nest predation events and evaluated how landscape features influenced predator identity. Finally, we determined the abundance and distribution of several of the principal predators using surveys and radiotelemetry. 3 Distance to power lines was the best predictor of predator identity: predation by brown-headed cowbirds (Molothrus ater), corvids (Corvus sp. and Cyanocitta cristata), racers (Coluber constrictor), and coachwhips (Masticophis flagellum) increased with proximity to power lines, whereas predation by rat snakes (Elaphe obsoleta) and raptors decreased. In some cases, predator density may reliably indicate nest predation risk because racers, corvids, and cowbirds frequently used power line right-of-ways. 4 Of five bird species with enough nests to analyze individually, daily nest survival of only indigo buntings (Passerina cyanea) decreased with proximity to power lines, despite predation by most predators at our site being positively associated with power lines. For all nesting species combined, distance to unpaved road was the model that most influenced daily nest survival. This pattern is likely a consequence of rat snakes, the locally dominant nest predator (28% of predation events), rarely using power lines and associated areas. Instead, rat snakes were frequently associated with road edges, indicating that not all edges are functionally similar. 5 Our results suggest that interactions between predators and landscape features are likely to be specific to both the local predators and landscape. Thus, predicting how anthropogenic changes to landscapes affect nesting birds requires that we know more about how landscape changes affect the behavior of nest predators and which nest predators are locally important.

Seed release in serotinous lodgepole pine forests after mountain pine beetle outbreak.

PubMed

Teste, François P; Lieffers, Victor J; Landhausser, Simon M

2011-01-01

There are concerns that large-scale stand mortality due to mountain pine beetle (MPB) could greatly reduce natural regeneration of serotinous Rocky Mountain (RM) lodgepole pine (Pinus contorta var. latifolia) because the closed cones are held in place without the fire cue for cone opening. We selected 20 stands (five stands each of live [control], 3 years since MPB [3-yr-MPB], 6 years since MPB [6-yr-MPB], and 9 years since MPB [9-yr-MPB] mortality) in north central British Columbia, Canada. The goal was to determine partial loss of serotiny due to fall of crown-stored cones via breakage of branches and in situ opening of canopy cones throughout the 2008 and 2009 growing seasons. We also quantified seed release by the opening of forest-floor cones, loss of seed from rodent predation, and cone burial. Trees killed by MPB three years earlier dropped approximately 3.5 times more cones via branch breakage compared to live stands. After six years, MPB-killed stands had released 45% of their canopy seed bank through cone opening, cone fall due to breakage, and squirrel predation. Further losses of canopy seed banks are expected with time since we found 9-yr-MPB stands had 38% more open canopy cones. This was countered by the development of a modest forest-floor seed bank (6% of the original canopy seed bank) from burial of cones; this seed bank may be ecologically important if a fire or anthropogenic disturbance reexposes these cones. If adequate levels of regeneration are to occur, disturbances to create seedbeds must occur shortly after tree mortality, before the seed banks are lost. Our findings also suggest that the sustained seed rain (over at least nine years) after MPB outbreak may be beneficial for population growth of ground-foraging vertebrates. Our study adds insight to the seed ecology of serotinous pines under a potentially continental-wide insect outbreak, threatening vast forests adapted to regeneration after fire. Key words: biotic disturbance; cone burial; cone opening; Dendroctonus ponderosae; ground-foraging vertebrates; mountain pine beetle; natural regeneration; Pinus contorta var. latifolia; Rocky Mountain lodgepole pine; seed banks; serotiny (canopy seed storage); Tamiasciurus hudsonicus.

Meta-analysis reveals that seed-applied neonicotinoids and pyrethroids have similar negative effects on abundance of arthropod natural enemies

PubMed Central

Tooker, John F.

2016-01-01

Background Seed-applied neonicotinoids are widely used in agriculture, yet their effects on non-target species remain incompletely understood. One important group of non-target species is arthropod natural enemies (predators and parasitoids), which contribute considerably to suppression of crop pests. We hypothesized that seed-applied neonicotinoids reduce natural-enemy abundance, but not as strongly as alternative insecticide options such as soil- and foliar-applied pyrethroids. Furthermore we hypothesized that seed-applied neonicotinoids affect natural enemies through a combination of toxin exposure and prey scarcity. Methods To test our hypotheses, we compiled datasets comprising observations from randomized field studies in North America and Europe that compared natural-enemy abundance in plots that were planted with seed-applied neonicotinoids to control plots that were either (1) managed without insecticides (20 studies, 56 site-years, 607 observations) or (2) managed with pyrethroid insecticides (eight studies, 15 site-years, 384 observations). Using the effect size Hedge’s d as the response variable, we used meta-regression to estimate the overall effect of seed-applied neonicotinoids on natural-enemy abundance and to test the influence of potential moderating factors. Results Seed-applied neonicotinoids reduced the abundance of arthropod natural enemies compared to untreated controls (d = −0.30 ± 0.10 [95% confidence interval]), and as predicted under toxin exposure this effect was stronger for insect than for non-insect taxa (QM = 8.70, df = 1, P = 0.003). Moreover, seed-applied neonicotinoids affected the abundance of arthropod natural enemies similarly to soil- or foliar-applied pyrethroids (d = 0.16 ± 0.42 or −0.02 ± 0.12; with or without one outlying study). Effect sizes were surprisingly consistent across both datasets (I2 = 2.7% for no-insecticide controls; I2 = 0% for pyrethroid controls), suggesting little moderating influence of crop species, neonicotinoid active ingredients, or methodological choices. Discussion Our meta-analysis of nearly 1,000 observations from North American and European field studies revealed that seed-applied neonicotinoids reduced the abundance of arthropod natural enemies similarly to broadcast applications of pyrethroid insecticides. These findings suggest that substituting pyrethroids for seed-applied neonicotinoids, or vice versa, will have little net affect on natural enemy abundance. Consistent with previous lab work, our results also suggest that seed-applied neonicotinoids are less toxic to spiders and mites, which can contribute substantially to biological control in many agricultural systems. Finally, our ability to interpret the negative effect of neonicotinoids on natural enemies is constrained by difficulty relating natural-enemy abundance to biological control function; this is an important area for future study. PMID:27957400

Meta-analysis reveals that seed-applied neonicotinoids and pyrethroids have similar negative effects on abundance of arthropod natural enemies.

PubMed

Douglas, Margaret R; Tooker, John F

2016-01-01

Seed-applied neonicotinoids are widely used in agriculture, yet their effects on non-target species remain incompletely understood. One important group of non-target species is arthropod natural enemies (predators and parasitoids), which contribute considerably to suppression of crop pests. We hypothesized that seed-applied neonicotinoids reduce natural-enemy abundance, but not as strongly as alternative insecticide options such as soil- and foliar-applied pyrethroids. Furthermore we hypothesized that seed-applied neonicotinoids affect natural enemies through a combination of toxin exposure and prey scarcity. To test our hypotheses, we compiled datasets comprising observations from randomized field studies in North America and Europe that compared natural-enemy abundance in plots that were planted with seed-applied neonicotinoids to control plots that were either (1) managed without insecticides (20 studies, 56 site-years, 607 observations) or (2) managed with pyrethroid insecticides (eight studies, 15 site-years, 384 observations). Using the effect size Hedge's d as the response variable, we used meta-regression to estimate the overall effect of seed-applied neonicotinoids on natural-enemy abundance and to test the influence of potential moderating factors. Seed-applied neonicotinoids reduced the abundance of arthropod natural enemies compared to untreated controls ( d = -0.30 ± 0.10 [95% confidence interval]), and as predicted under toxin exposure this effect was stronger for insect than for non-insect taxa ( Q M = 8.70, df = 1, P = 0.003). Moreover, seed-applied neonicotinoids affected the abundance of arthropod natural enemies similarly to soil- or foliar-applied pyrethroids ( d = 0.16 ± 0.42 or -0.02 ± 0.12; with or without one outlying study). Effect sizes were surprisingly consistent across both datasets ( I 2  = 2.7% for no-insecticide controls; I 2  = 0% for pyrethroid controls), suggesting little moderating influence of crop species, neonicotinoid active ingredients, or methodological choices. Our meta-analysis of nearly 1,000 observations from North American and European field studies revealed that seed-applied neonicotinoids reduced the abundance of arthropod natural enemies similarly to broadcast applications of pyrethroid insecticides. These findings suggest that substituting pyrethroids for seed-applied neonicotinoids, or vice versa, will have little net affect on natural enemy abundance. Consistent with previous lab work, our results also suggest that seed-applied neonicotinoids are less toxic to spiders and mites, which can contribute substantially to biological control in many agricultural systems. Finally, our ability to interpret the negative effect of neonicotinoids on natural enemies is constrained by difficulty relating natural-enemy abundance to biological control function; this is an important area for future study.

Barriers to seed and seedling survival of once-common Hawaiian palms: the role of invasive rats and ungulates

PubMed Central

Shiels, Aaron B.; Drake, Donald R.

2015-01-01

Mammalian herbivores can limit plant recruitment and affect forest composition. Loulu palms (Pritchardia spp.) once dominated many lowland ecosystems in Hawai‘i, and non-native rats (Rattus spp.), ungulates (e.g. pigs Sus scrofa, goats Capra hircus) and humans have been proposed as major causes of their decline. In lowland wet forest, we experimentally determined the vulnerability of seeds and seedlings of two species of Pritchardia, P. maideniana and P. hillebrandii, by measuring their removal by introduced vertebrates; we also used motion-sensing cameras to identify the animals responsible for Pritchardia removal. We assessed potential seed dispersal of P. maideniana by spool-and-line tracking, and conducted captive-feeding trials with R. rattus and seeds and seedlings of both Pritchardia species. Seed removal from the forest floor occurred rapidly for both species: >50 % of Pritchardia seeds were removed from the vertebrate-accessible stations within 6 days and >80 % were removed within 22 days. Although rats and pigs were both common to the study area, motion-sensing cameras detected only rats (probably R. rattus) removing Pritchardia seeds from the forest floor. Captive-feeding trials and spool-and-line tracking revealed that vertebrate seed dispersal is rare; rats moved seeds up to 8 m upon collection and subsequently destroyed them (100 % mortality in 24–48 h in captivity). Surprisingly, seedlings did not suffer vertebrate damage in field trials, and although rats damaged seedlings in captivity, they rarely consumed them. Our findings are consistent with the hypothesis generated from palaeoecological studies, indicating that introduced rats may have assisted in the demise of native insular palm forests. These findings also imply that the seed stage of species in this Pacific genus is particularly vulnerable to rats; therefore, future conservation efforts involving Pritchardia should prioritize the reduction of rat predation on the plant recruitment stages preceding seedling establishment. PMID:26019231

A field experiment demonstrating plant life-history evolution and its eco-evolutionary feedback to seed predator populations.

PubMed

Agrawal, Anurag A; Johnson, Marc T J; Hastings, Amy P; Maron, John L

2013-05-01

The extent to which evolutionary change occurs in a predictable manner under field conditions and how evolutionary changes feed back to influence ecological dynamics are fundamental, yet unresolved, questions. To address these issues, we established eight replicate populations of native common evening primrose (Oenothera biennis). Each population was planted with 18 genotypes in identical frequency. By tracking genotype frequencies with microsatellite DNA markers over the subsequent three years (up to three generations, ≈5,000 genotyped plants), we show rapid and consistent evolution of two heritable plant life-history traits (shorter life span and later flowering time). This rapid evolution was only partially the result of differential seed production; genotypic variation in seed germination also contributed to the observed evolutionary response. Since evening primrose genotypes exhibited heritable variation for resistance to insect herbivores, which was related to flowering time, we predicted that evolutionary changes in genotype frequencies would feed back to influence populations of a seed predator moth that specializes on O. biennis. By the conclusion of the experiment, variation in the genotypic composition among our eight replicate field populations was highly predictive of moth abundance. These results demonstrate how rapid evolution in field populations of a native plant can influence ecological interactions.

Seedling ecology and restoration of blackbrush (Coleogyne ramosissima) in the Mojave Desert, United States

USGS Publications Warehouse

Jones, Lisa C.; Schwinning, Susanne; Esque, Todd C.

2014-01-01

Increases in fire frequency are disrupting many ecological communities not historically subjected to fire. In the southwestern United States, the blackbrush (Coleogyne ramosissima) community is among the most threatened, often replaced by invasive annual grasses after fire. This long-lived shrub is vulnerable because it recruits sporadically, partially due to mast seeding and the absence of a seed bank. The goal of this study was to evaluate if shrub restoration can be enhanced by identifying and ameliorating recruitment limitations. Specifically, we tested the effect of encapsulating seeds in predation-deterring “seed balls.” We also tested the effects of nurse plants and mammalian exclusion cages on seedling emergence, growth, and survivorship. These experiments were conducted in a full-factorial design across three sites differing in elevation. Over 2 years, 13% of all planted seeds emerged and the effect of seed balls was overwhelmingly negative because of low emergence. Nurse plants had overall positive effects at Low Elevation, but negative effects at Mid- and High Elevation. Emergence and survival were highest in caged plots everywhere, and effect sizes increased with elevation. Interactions between the cage and the nurse plant treatments indicated that nurse plants tended to attract mammalian predators, lowering emergence and seedling survivorship, particularly at higher elevations. Findings conform to the stress-gradient hypothesis in that interactions among seedlings and mature plants shifted from facilitation to competition as environmental stress decreased with increasing elevation, suggesting that they are transferable to ecologically similar communities elsewhere. Knowledge of site-specific recruitment limitations can help minimize ineffective restoration efforts.

An island-wide predator manipulation reveals immediate and long-lasting matching of risk by prey.

PubMed

Orrock, John L; Fletcher, Robert J

2014-06-07

Anti-predator behaviour affects prey population dynamics, mediates cascading effects in food webs and influences the likelihood of rapid extinctions. Predator manipulations in natural settings provide a rare opportunity to understand how prey anti-predator behaviour is affected by large-scale changes in predators. Here, we couple a long-term, island-wide manipulation of an important rodent predator, the island fox (Urocyon littoralis), with nearly 6 years of measurements on foraging by deer mice (Peromyscus maniculatus) to provide unequivocal evidence that prey closely match their foraging behaviour to the number of fox predators present on the island. Peromyscus maniculatus foraging among exposed and sheltered microhabitats (a measure of aversion to predation risk) closely tracked fox density, but the nature of this effect depended upon nightly environmental conditions known to affect rodent susceptibility to predators. These effects could not be explained by changes in density of deer mice over time. Our work reveals that prey in natural settings are cognizant of the dynamic nature of their predators over timescales that span many years, and that predator removals spanning many generations of prey do not result in a loss of anti-predator behaviour.

You'd better walk alone: Changes in forest composition affect pollination efficiency and pre-dispersal cone damage in Iberian Juniperus thurifera forests.

PubMed

Rodríguez-García, E; Mezquida, E T; Olano, J M

2017-11-01

Changes in land-use patterns are a major driver of global environmental change. Cessation of traditional land-use practices has led to forest expansion and shifts in forest composition. Consequently, former monospecific forests maintained by traditional management are progressing towards mixed forests. However, knowledge is scarce on how the presence of other tree species will affect reproduction of formerly dominant species. We explored this question in the wind-pollinated tree Juniperus thurifera. We hypothesised that the presence of heterospecific trees would have a negative effect on cone production and on the proportion of cones attacked by specialised predators. We assessed the relative importance of forest composition on cone production, seed development and pre-dispersal cone damage on nine paired pure and mixed J. thurifera forests in three regions across the Iberian Peninsula. The effects of forest composition on crop size, cone and seed characteristics, as well as damage by pre-dispersal arthropods were tested using mixed models. Cone production was lower and seed abortion higher in mixed forests, suggesting higher pollination failure. In contrast, cone damage by arthropods was higher in pure forests, supporting the hypothesis that presence of non-host plants reduces damage rates. However, the response of each arthropod to forest composition was species-specific and the relative rates of cone damage varied depending on individual tree crops. Larger crop sizes in pure forests compensated for the higher cone damage rates, leading to a higher net production of sound seeds compared to mixed forests. This study indicates that ongoing changes in forest composition after land abandonment may impact tree reproduction. © 2017 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.

Notes on spider (Theridiidae, Salticidae) predation of the harvester ant, Pogonomyrmex salinus Olsen (Hymenoptera: Formicidae: Myrmicinae), and a possible parasitoid fly (Chloropidae)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, W.H.; Blom, P.E.

1992-12-01

Spiders are known predators of ants. Pressure exerted by consistent spider predation can alter the behavior of ant colonies (MacKay 1982) and may be a selective pressure contributing to the seed-harvesting behavior of Pogonomyrmex (MacKay and MacKay 1984). The authors observed the spider Euryopis formosa Banks (Araneae: Theridiidae) capture and transport workers of the harvester ant (Pogonomyrmex salinus Olsen [Hymenoptera: Formicidae, Myrmicinae]) in southeastern Idaho. Additional observations revealed a crab spider of the genus Xysticus preying on P. salinus and the presence of a chloropid fly (Incertella) that may have been parasitizing the moribund prey subdued by the spider.

The earliest seeds

USGS Publications Warehouse

Gillespie, W.H.; Rothwell, G.W.; Scheckler, S.E.

1981-01-01

Lagenostomalean-type seeds in bifurcating cupule systems have been discovered in the late Devonian Hampshire Formation of Randolph County, West Virginia, USA (Fig. 1). The associated megaflora, plants from coal balls, and vertebrate and invertebrate faunas demonstrate that the material is Famennian; the microflora indicates a more specific Fa2c age. Consequently, these seeds predate Archaeosperma arnoldii1 from the Fa2d of northeastern Pennsylvania, the oldest previously reported seed. By applying precision fracture, transfer, de??gagement, and thin-section techniques to selected cupules from the more than 100 specimens on hand, we have determined the three-dimensional morphology and histology of the seeds (Fig. 2a-h, k) and cupule systems. A comparison with known late Devonian to early Carboniferous seeds reveals that ours are more primitively organized than all except Genomosperma2,3. ?? 1981 Nature Publishing Group.

Does Ferocactus wislizeni (Cactaceae) have a between-year seed bank?

USGS Publications Warehouse

Bowers, Janice E.

2000-01-01

Field and laboratory experiments at Tumamoc Hill, Tucson, Arizona, U.S.A., demonstrated that Ferocactus wislizeni, a common perennial cactus in the northern Sonoran Desert, has a between-year seed bank. In laboratory studies, F. wislizeni seeds lost dormancy during storage at room temperature and had a light requirement for germination. Field experiments suggested that as much as 2% of the annual seed crop might escape post-dispersal predation even when unprotected; where suitable safe sites exist, a higher percentage might escape. Germination of seed recovered monthly from above- and below-ground components of an artificial seed bank showed that seeds can survive at least 18 months in and on the soil. Seed banks enable F. wislizeni to take advantage of favorable rains and temperatures throughout the growing season, thus increasing the number of opportunities for germination. Moreover, seed banks enable F. wislizeni to respond hugely when the climate seems especially favorable, thus producing the large cohorts necessary to compensate for high seedling mortality. (C) 2000 Academic Press.

Plant defences limit herbivore population growth by changing predator-prey interactions.

PubMed

Kersch-Becker, Mônica F; Kessler, André; Thaler, Jennifer S

2017-09-13

Plant quality and predators are important factors affecting herbivore population growth, but how they interact to regulate herbivore populations is not well understood. We manipulated jasmonate-induced plant resistance, exposure to the natural predator community and herbivore density to test how these factors jointly and independently affect herbivore population growth. On low-resistance plants, the predator community was diverse and abundant, promoting high predator consumption rates. On high-resistance plants, the predator community was less diverse and abundant, resulting in low predator consumption rate. Plant resistance only directly regulated aphid population growth on predator-excluded plants. When predators were present, plant resistance indirectly regulated herbivore population growth by changing the impact of predators on the herbivorous prey. A possible mechanism for the interaction between plant resistance and predation is that methyl salicylate, a herbivore-induced plant volatile attractive to predators, was more strongly induced in low-resistance plants. Increased plant resistance reduced predator attractant lures, preventing predators from locating their prey. Low-resistance plants may regulate herbivore populations via predators by providing reliable information on prey availability and increasing the effectiveness of predators. © 2017 The Author(s).

Local adaptation of Ruellia nudiflora (Acanthaceae) to biotic counterparts: complex scenarios revealed when two herbivore guilds are considered.

PubMed

Ortegón-Campos, I; Parra-Tabla, V; Abdala-Roberts, L; Herrera, C M

2009-11-01

This study evaluated whether the herb Ruellia nudiflora is locally adapted to a specialist insect seed predator (SP) and insect folivores, and if plant local adaptation (LA) to the former is more likely. A reciprocal transplant experiment was conducted using three sites in Yucatan (Mexico) (n = 864 plants). A third of the plants of each origin were placed at each site, and we recorded the following during a 9-month period: fruit number, leaf damage, and fruits attacked by SP. Results indicated lack of plant LA for all the variables measured. Instead, seed predation was c. 100% greater for native plants at one study site, suggesting insect LA or plant maladaptation; folivory was homogeneous across sites/origins. Based on these results, we discuss differences in the potential each herbivore guild has to promote plant LA, as well as divergent evolutionary outcomes of plant-herbivore interactions across sites.

Dispersal of mimetic seeds of three species of Ormosia (Leguminosae)

USGS Publications Warehouse

Foster, M.S.; DeLay, L.S.

1998-01-01

Seeds with 'imitation arils' appear wholly or partially covered by pulp or aril but actually carry no fleshy material. The mimetic seed hypothesis to explain this phenomenon proposes a parasitic relationship in which birds are deceived into dispersing seeds that resemble bird-dispersed fruits, without receiving a nutrient reward. The hard-seed for grit hypothesis proposes a mutualistic relationship in which large, terrestrial birds swallow the exceptionally hard 'mimetic' seeds as grit for grinding the softer seeds on which they feed. They defecate, dispersing the seeds, and abrade the seed surface, enhancing germination. Any fruit mimicry is incidental. Fruiting trees of Ormosia spp. (Leguminosae: Papilionoideae) were observed to ascertain mechanisms of seed dispersal and the role of seemingly mimetic characteristics of the seeds in that dispersal. Seed predation and seed germination were also examined. Ormosia isthamensis and O. macrocalyx (but not O. bopiensis) deceived arboreally-foraging frugivorous birds into taking their mimetic seeds, although rates of seed dispersal were low. These results are consistent with the mimetic seed hypothesis. On the other hand, the rates of disappearance of seeds from the ground under the Ormosia trees, hardness of the seeds, and enhancement of germination with the abrasion of the seed coat are all consistent with the hard-seed for grit hypothesis.

The Interplay among Acorn Abundance and Rodent Behavior Drives the Spatial Pattern of Seedling Recruitment in Mature Mediterranean Oak Forests.

PubMed

Sunyer, Pau; Boixadera, Ester; Muñoz, Alberto; Bonal, Raúl; Espelta, Josep Maria

2015-01-01

The patterns of seedling recruitment in animal-dispersed plants result from the interactions among environmental and behavioral variables. However, we know little on the contribution and combined effect of both kinds of variables. We designed a field study to assess the interplay between environment (vegetation structure, seed abundance, rodent abundance) and behavior (seed dispersal and predation by rodents, and rooting by wild boars), and their contribution to the spatial patterns of seedling recruitment in a Mediterranean mixed-oak forest. In a spatially explicit design, we monitored intensively all environmental and behavioral variables in fixed points at a small spatial scale from autumn to spring, as well as seedling emergence and survival. Our results revealed that the spatial patterns of seedling emergence were strongly related to acorn availability on the ground, but not by a facilitation effect of vegetation cover. Rodents changed seed shadows generated by mother trees by dispersing most seeds from shrubby to open areas, but the spatial patterns of acorn dispersal/predation had no direct effect on recruitment. By contrast, rodents had a strong impact on recruitment as pilferers of cached seeds. Rooting by wild boars also reduced recruitment by reducing seed abundance, but also by changing rodent's behavior towards higher consumption of acorns in situ. Hence, seed abundance and the foraging behavior of scatter-hoarding rodents and wild boars are driving the spatial patterns of seedling recruitment in this mature oak forest, rather than vegetation features. The contribution of vegetation to seedling recruitment (e.g. facilitation by shrubs) may be context dependent, having a little role in closed forests, or being overridden by directed seed dispersal from shrubby to open areas. We warn about the need of using broad approaches that consider the combined action of environment and behavior to improve our knowledge on the dynamics of natural regeneration in forests.

The Interplay among Acorn Abundance and Rodent Behavior Drives the Spatial Pattern of Seedling Recruitment in Mature Mediterranean Oak Forests

PubMed Central

Boixadera, Ester; Bonal, Raúl

2015-01-01

The patterns of seedling recruitment in animal-dispersed plants result from the interactions among environmental and behavioral variables. However, we know little on the contribution and combined effect of both kinds of variables. We designed a field study to assess the interplay between environment (vegetation structure, seed abundance, rodent abundance) and behavior (seed dispersal and predation by rodents, and rooting by wild boars), and their contribution to the spatial patterns of seedling recruitment in a Mediterranean mixed-oak forest. In a spatially explicit design, we monitored intensively all environmental and behavioral variables in fixed points at a small spatial scale from autumn to spring, as well as seedling emergence and survival. Our results revealed that the spatial patterns of seedling emergence were strongly related to acorn availability on the ground, but not by a facilitationeffect of vegetation cover. Rodents changed seed shadows generated by mother trees by dispersing most seeds from shrubby to open areas, but the spatial patterns of acorn dispersal/predation had no direct effect on recruitment. By contrast, rodents had a strong impact on recruitment as pilferers of cached seeds. Rooting by wild boars also reduced recruitment by reducing seed abundance, but also by changing rodent’s behavior towards higher consumption of acorns in situ. Hence, seed abundance and the foraging behavior of scatter-hoarding rodents and wild boars are driving the spatial patterns of seedling recruitment in this mature oak forest, rather than vegetation features. The contribution of vegetation to seedling recruitment (e.g. facilitation by shrubs) may be context dependent, having a little role in closed forests, or being overridden by directed seed dispersal from shrubby to open areas. We warn about the need of using broad approaches that consider the combined action of environment and behavior to improve our knowledge on the dynamics of natural regeneration in forests. PMID:26070129

Perceived Risk of Predation Affects Reproductive Life-History Traits in Gambusia holbrooki, but Not in Heterandria formosa

PubMed Central

Mukherjee, Shomen; Heithaus, Michael R.; Trexler, Joel C.; Ray-Mukherjee, Jayanti; Vaudo, Jeremy

2014-01-01

Key to predicting impacts of predation is understanding the mechanisms through which predators impact prey populations. While consumptive effects are well-known, non-consumptive predator effects (risk effects) are increasingly being recognized as important. Studies of risk effects, however, have focused largely on how trade-offs between food and safety affect fitness. Less documented, and appreciated, is the potential for predator presence to directly suppress prey reproduction and affect life-history characteristics. For the first time, we tested the effects of visual predator cues on reproduction of two prey species with different reproductive modes, lecithotrophy (i.e. embryonic development primarily fueled by yolk) and matrotrophy (i.e. energy for embryonic development directly supplied by the mother to the embryo through a vascular connection). Predation risk suppressed reproduction in the lecithotrophic prey (Gambusia holbrokii) but not the matrotroph (Heterandria formosa). Predator stress caused G. holbrooki to reduce clutch size by 43%, and to produce larger and heavier offspring compared to control females. H. formosa, however, did not show any such difference. In G. holbrooki we also found a significantly high percentage (14%) of stillbirths in predator-exposed treatments compared to controls (2%). To the best of our knowledge, this is the first direct empirical evidence of predation stress affecting stillbirths in prey. Our results suggest that matrotrophy, superfetation (clutch overlap), or both decrease the sensitivity of mothers to environmental fluctuation in resource (food) and stress (predation risk) levels compared to lecithotrophy. These mechanisms should be considered both when modeling consequences of perceived risk of predation on prey-predator population dynamics and when seeking to understand the evolution of reproductive modes. PMID:24551171

Adaptive and selective seed abortion reveals complex conditional decision making in plants.

PubMed

Meyer, Katrin M; Soldaat, Leo L; Auge, Harald; Thulke, Hans-Hermann

2014-03-01

Behavior is traditionally attributed to animals only. Recently, evidence for plant behavior is accumulating, mostly from plant physiological studies. Here, we provide ecological evidence for complex plant behavior in the form of seed abortion decisions conditional on internal and external cues. We analyzed seed abortion patterns of barberry plants exposed to seed parasitism and different environmental conditions. Without abortion, parasite infestation of seeds can lead to loss of all seeds in a fruit. We statistically tested a series of null models with Monte Carlo simulations to establish selectivity and adaptiveness of the observed seed abortion patterns. Seed abortion was more frequent in parasitized fruits and fruits from dry habitats. Surprisingly, seed abortion occurred with significantly greater probability if there was a second intact seed in the fruit. This strategy provides a fitness benefit if abortion can prevent a sibling seed from coinfestation and if nonabortion of an infested but surviving single seed saves resources invested in the fruit coat. Ecological evidence for complex decision making in plants thus includes a structural memory (the second seed), simple reasoning (integration of inner and outer conditions), conditional behavior (abortion), and anticipation of future risks (seed predation).

Selective Pressure along a Latitudinal Gradient Affects Subindividual Variation in Plants

PubMed Central

Sobral, Mar; Guitián, José; Guitián, Pablo; Larrinaga, Asier R.

2013-01-01

Individual plants produce repeated structures such as leaves, flowers or fruits, which, although belonging to the same genotype, are not phenotypically identical. Such subindividual variation reflects the potential of individual genotypes to vary with micro-environmental conditions. Furthermore, variation in organ traits imposes costs to foraging animals such as time, energy and increased predation risk. Therefore, animals that interact with plants may respond to this variation and affect plant fitness. Thus, phenotypic variation within an individual plant could be, in part, an adaptive trait. Here we investigated this idea and we found that subindividual variation of fruit size of Crataegus monogyna, in different populations throughout the latitudinal gradient in Europe, was explained at some extent by the selective pressures exerted by seed-dispersing birds. These findings support the hypothesis that within-individual variation in plants is an adaptive trait selected by interacting animals which may have important implications for plant evolution. PMID:24069297

A trophic cascade induced by predatory ants in a fig-fig wasp mutualism.

PubMed

Wang, Bo; Geng, Xiang-Zong; Ma, Li-Bin; Cook, James M; Wang, Rui-Wu

2014-09-01

A trophic cascade occurs when predators directly decrease the densities, or change the behaviour, of herbivores and thus indirectly increase plant productivity. The predator-herbivore-plant context is well known, but some predators attack species beneficial to plants (e.g. pollinators) and/or enemies of herbivores (e.g. parasites), and their role in the dynamics of mutualisms remains largely unexplored. We surveyed the predatory ant species and studied predation by the dominant ant species, the weaver ant Oecophylla smaragdina, associated with the fig tree Ficus racemosa in southwest China. We then tested the effects of weaver ants on the oviposition behaviour of pollinating and non-pollinating fig wasps in an ant-exclusion experiment. The effects of weaver ants on fig wasp community structure and fig seed production were then compared between trees with and without O. smaragdina. Oecophylla smaragdina captured more non-pollinating wasps (Platyneura mayri) than pollinators as the insects arrived to lay eggs. When ants were excluded, more non-pollinators laid eggs into figs and fewer pollinators entered figs. Furthermore, trees with O. smaragdina produced more pollinator offspring and fewer non-pollinator offspring, shifting the community structure significantly. In addition, F. racemosa produced significantly more seeds on trees inhabited by weaver ants. Oecophylla smaragdina predation reverses the dominance of the two commonest wasp species at the egg-laying stage and favours the pollinators. This behavioural pattern is mirrored by wasp offspring production, with pollinators' offspring dominating figs produced by trees inhabited by weaver ants, and offspring of the non-pollinator P. mayri most abundant in figs on trees inhabited by other ants. Overall, our results suggest that predation by weaver ants limits the success of the non-pollinating P. mayri and therefore indirectly benefits the mutualism by increasing the reproductive success of both the pollinators and the plant. Predation is thus a key functional factor that can shape the community structure of a pollinator-plant mutualistic system. © 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society.

Nutrient balance affects foraging behaviour of a trap-building predator

PubMed Central

Mayntz, David; Toft, Søren; Vollrath, Fritz

2009-01-01

Predator foraging may be affected by previous prey capture, but it is unknown how nutrient balance affects foraging behaviour. Here, we use a trap-building predator to test whether nutrients from previous prey captures affect foraging behaviour. We fed orb-weaving spiders (Zygiella x-notata) prey flies of different nutrient composition and in different amounts during their first instar and measured the subsequent frequency of web building and aspects of web architecture. We found that both the likelihood of web building and the number of radii in the web were affected by prey nutrient composition while prey availability affected capture area and mesh height. Our results show that both the balance of nutrients in captured prey and the previous capture rate may affect future foraging behaviour of predators. PMID:19640870

Revisiting the origin and diversification of vascular plants through a comprehensive Bayesian analysis of the fossil record.

PubMed

Silvestro, Daniele; Cascales-Miñana, Borja; Bacon, Christine D; Antonelli, Alexandre

2015-07-01

Plants have a long evolutionary history, during which mass extinction events dramatically affected Earth's ecosystems and its biodiversity. The fossil record can shed light on the diversification dynamics of plant life and reveal how changes in the origination-extinction balance have contributed to shaping the current flora. We use a novel Bayesian approach to estimate origination and extinction rates in plants throughout their history. We focus on the effect of the 'Big Five' mass extinctions and on estimating the timing of origin of vascular plants, seed plants and angiosperms. Our analyses show that plant diversification is characterized by several shifts in origination and extinction rates, often matching the most important geological boundaries. The estimated origin of major plant clades predates the oldest macrofossils when considering the uncertainties associated with the fossil record and the preservation process. Our findings show that the commonly recognized mass extinctions have affected each plant group differently and that phases of high extinction often coincided with major floral turnovers. For instance, after the Cretaceous-Paleogene boundary we infer negligible shifts in diversification of nonflowering seed plants, but find significantly decreased extinction in spore-bearing plants and increased origination rates in angiosperms, contributing to their current ecological and evolutionary dominance. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Oak habitat recovery on California's largest islands: Scenarios for the role of corvid seed dispersal

USGS Publications Warehouse

Pesendorfer, Mario B.; Baker, Christopher M.; Stringer, Martin; McDonald-Madden, Eve; Bode, Michael; McEachern, A. Kathryn; Morrison, Scott A.; Sillett, T. Scott

2018-01-01

Seed dispersal by birds is central to the passive restoration of many tree communities. Reintroduction of extinct seed dispersers can therefore restore degraded forests and woodlands. To test this, we constructed a spatially explicit simulation model, parameterized with field data, to consider the effect of different seed dispersal scenarios on the extent of oak populations. We applied the model to two islands in California's Channel Islands National Park (USA), one of which has lost a key seed disperser.We used an ensemble modelling approach to simulate island scrub oak (Quercus pacifica) demography. The model was developed and trained to recreate known population changes over a 20-year period on 250-km2 Santa Cruz Island, and incorporated acorn dispersal by island scrub-jays (Aphelocoma insularis), deer mice (Peromyscus maniculatus) and gravity, as well as seed predation. We applied the trained model to 215-km2 Santa Rosa Island to examine how reintroducing island scrub-jays would affect the rate and pattern of oak population expansion. Oak habitat on Santa Rosa Island has been greatly reduced from its historical extent due to past grazing by introduced ungulates, the last of which were removed by 2011.Our simulation model predicts that a seed dispersal scenario including island scrub-jays would increase the extent of the island scrub oak population on Santa Rosa Island by 281% over 100 years, and by 544% over 200 years. Scenarios without jays would result in little expansion. Simulated long-distance seed dispersal by jays also facilitates establishment of discontinuous patches of oaks, and increases their elevational distribution.Synthesis and applications. Scenario planning provides powerful decision support for conservation managers. We used ensemble modelling of plant demographic and seed dispersal processes to investigate whether the reintroduction of seed dispersers could provide cost-effective means of achieving broader ecosystem restoration goals on California's second-largest island. The simulation model, extensively parameterized with field data, suggests that re-establishing the mutualism with seed-hoarding jays would accelerate the expansion of island scrub oak, which could benefit myriad species of conservation concern.

Harnessing ant defence at fruits reduces bruchid seed predation in a symbiotic ant-plant mutualism.

PubMed

Pringle, Elizabeth G

2014-06-22

In horizontally transmitted mutualisms, mutualists disperse separately and reassemble in each generation with partners genetically unrelated to those in the previous generation. Because of this, there should be no selection on either partner to enhance the other's reproductive output directly. In symbiotic ant-plant mutualisms, myrmecophytic plants host defensive ant colonies, and ants defend the plants from herbivores. Plants and ants disperse separately, and, although ant defence can indirectly increase plant reproduction by reducing folivory, it is unclear whether ants can also directly increase plant reproduction by defending seeds. The neotropical tree Cordia alliodora hosts colonies of Azteca pittieri ants. The trees produce domatia where ants nest at stem nodes and also at the node between the peduncle and the rachides of the infloresence. Unlike the stem domatia, these reproductive domatia senesce after the tree fruits each year. In this study, I show that the tree's resident ant colony moves into these ephemeral reproductive domatia, where they tend honeydew-producing scale insects and patrol the nearby developing fruits. The presence of ants significantly reduced pre-dispersal seed predation by Amblycerus bruchid beetles, thereby directly increasing plant reproductive output.

Harnessing ant defence at fruits reduces bruchid seed predation in a symbiotic ant–plant mutualism

PubMed Central

Pringle, Elizabeth G.

2014-01-01

In horizontally transmitted mutualisms, mutualists disperse separately and reassemble in each generation with partners genetically unrelated to those in the previous generation. Because of this, there should be no selection on either partner to enhance the other's reproductive output directly. In symbiotic ant–plant mutualisms, myrmecophytic plants host defensive ant colonies, and ants defend the plants from herbivores. Plants and ants disperse separately, and, although ant defence can indirectly increase plant reproduction by reducing folivory, it is unclear whether ants can also directly increase plant reproduction by defending seeds. The neotropical tree Cordia alliodora hosts colonies of Azteca pittieri ants. The trees produce domatia where ants nest at stem nodes and also at the node between the peduncle and the rachides of the infloresence. Unlike the stem domatia, these reproductive domatia senesce after the tree fruits each year. In this study, I show that the tree's resident ant colony moves into these ephemeral reproductive domatia, where they tend honeydew-producing scale insects and patrol the nearby developing fruits. The presence of ants significantly reduced pre-dispersal seed predation by Amblycerus bruchid beetles, thereby directly increasing plant reproductive output. PMID:24807259

Predator Dispersal Determines the Effect of Connectivity on Prey Diversity

PubMed Central

Limberger, Romana; Wickham, Stephen A.

2011-01-01

Linking local communities to a metacommunity can positively affect diversity by enabling immigration of dispersal-limited species and maintenance of sink populations. However, connectivity can also negatively affect diversity by allowing the spread of strong competitors or predators. In a microcosm experiment with five ciliate species as prey and a copepod as an efficient generalist predator, we analysed the effect of connectivity on prey species richness in metacommunities that were either unconnected, connected for the prey, or connected for both prey and predator. Presence and absence of predator dispersal was cross-classified with low and high connectivity. The effect of connectivity on local and regional richness strongly depended on whether corridors were open for the predator. Local richness was initially positively affected by connectivity through rescue of species from stochastic extinctions. With predator dispersal, however, this positive effect soon turned negative as the predator spread over the metacommunity. Regional richness was unaffected by connectivity when local communities were connected only for the prey, while predator dispersal resulted in a pronounced decrease of regional richness. The level of connectivity influenced the speed of richness decline, with regional species extinctions being delayed for one week in weakly connected metacommunities. While connectivity enabled rescue of prey species from stochastic extinctions, deterministic extinctions due to predation were not overcome through reimmigration from predator-free refuges. Prey reimmigrating into these sink habitats appeared to be directly converted into increased predator abundance. Connectivity thus had a positive effect on the predator, even when the predator was not dispersing itself. Our study illustrates that dispersal of a species with strong negative effects on other community members shapes the dispersal-diversity relationship. When connections enable the spread of a generalist predator, positive effects of connectivity on prey species richness are outweighed by regional extinctions through predation. PMID:22194992

Turbidity interferes with foraging success of visual but not chemosensory predators.

PubMed

Lunt, Jessica; Smee, Delbert L

2015-01-01

Predation can significantly affect prey populations and communities, but predator effects can be attenuated when abiotic conditions interfere with foraging activities. In estuarine communities, turbidity can affect species richness and abundance and is changing in many areas because of coastal development. Many fish species are less efficient foragers in turbid waters, and previous research revealed that in elevated turbidity, fish are less abundant whereas crabs and shrimp are more abundant. We hypothesized that turbidity altered predatory interactions in estuaries by interfering with visually-foraging predators and prey but not with organisms relying on chemoreception. We measured the effects of turbidity on the predation rates of two model predators: a visual predator (pinfish, Lagodon rhomboides) and a chemosensory predator (blue crabs, Callinectes sapidus) in clear and turbid water (0 and ∼100 nephelometric turbidity units). Feeding assays were conducted with two prey items, mud crabs (Panopeus spp.) that rely heavily on chemoreception to detect predators, and brown shrimp (Farfantepenaus aztecus) that use both chemical and visual cues for predator detection. Because turbidity reduced pinfish foraging on both mud crabs and shrimp, the changes in predation rates are likely driven by turbidity attenuating fish foraging ability and not by affecting prey vulnerability to fish consumers. Blue crab foraging was unaffected by turbidity, and blue crabs were able to successfully consume nearly all mud crab and shrimp prey. Turbidity can influence predator-prey interactions by reducing the feeding efficiency of visual predators, providing a competitive advantage to chemosensory predators, and altering top-down control in food webs.

Species and temporal factors affect predator-specific rates of nest predation for forest songbirds in the midwest

Treesearch

W. Andrew Cox; Frank R. III Thompson; John Faaborg

2012-01-01

Knowledge of the relative contributions of predator species to overall rates of nest predation can improve our understanding of why predation risk varies, but the identity of predators is seldom known. We used video technology to identify nest predators of the tree-nesting Acadian Flycatcher (Empidonax virescens) and the shrub-nesting Indigo Bunting...

Maternal intraguild predation risk affects offspring anti-predator behavior and learning in mites.

PubMed

Seiter, Michael; Schausberger, Peter

2015-10-09

Predation risk is a strong selective force shaping prey morphology, life history and behavior. Anti-predator behaviors may be innate, learned or both but little is known about the transgenerational behavioral effects of maternally experienced predation risk. We examined intraguild predation (IGP) risk-induced maternal effects on offspring anti-predator behavior, including learning, in the predatory mite Phytoseiulus persimilis. We exposed predatory mite mothers during egg production to presence or absence of the IG predator Amblyseius andersoni and assessed whether maternal stress affects the anti-predator behavior, including larval learning ability, of their offspring as protonymphs. Protonymphs emerging from stressed or unstressed mothers, and having experienced IGP risk as larvae or not, were subjected to choice situations with and without IG predator traces. Predator-experienced protonymphs from stressed mothers were the least active and acted the boldest in site choice towards predator cues. We argue that the attenuated response of the protonymphs to predator traces alone represents optimized risk management because no immediate risk existed. Such behavioral adjustment could reduce the inherent fitness costs of anti-predator behaviors. Overall, our study suggests that P. persimilis mothers experiencing IGP risk may prime their offspring to behave more optimally in IGP environments.

Maternal intraguild predation risk affects offspring anti-predator behavior and learning in mites

PubMed Central

Seiter, Michael; Schausberger, Peter

2015-01-01

Predation risk is a strong selective force shaping prey morphology, life history and behavior. Anti-predator behaviors may be innate, learned or both but little is known about the transgenerational behavioral effects of maternally experienced predation risk. We examined intraguild predation (IGP) risk-induced maternal effects on offspring anti-predator behavior, including learning, in the predatory mite Phytoseiulus persimilis. We exposed predatory mite mothers during egg production to presence or absence of the IG predator Amblyseius andersoni and assessed whether maternal stress affects the anti-predator behavior, including larval learning ability, of their offspring as protonymphs. Protonymphs emerging from stressed or unstressed mothers, and having experienced IGP risk as larvae or not, were subjected to choice situations with and without IG predator traces. Predator-experienced protonymphs from stressed mothers were the least active and acted the boldest in site choice towards predator cues. We argue that the attenuated response of the protonymphs to predator traces alone represents optimized risk management because no immediate risk existed. Such behavioral adjustment could reduce the inherent fitness costs of anti-predator behaviors. Overall, our study suggests that P. persimilis mothers experiencing IGP risk may prime their offspring to behave more optimally in IGP environments. PMID:26449645

Predator community structure and trophic linkage strength to a focal prey.

PubMed

Lundgren, Jonathan G; Fergen, Janet K

2014-08-01

Predator abundance and community structure can affect the suppression of lower trophic levels, although studies of these interactions under field conditions are relatively few. We investigated how the frequency of consumption (measured using PCR-based gut content analysis) is affected by predator abundance, community diversity and evenness under realistic conditions. Soil arthropod communities in sixteen maize fields were measured (number of predators, diversity [Shannon H] and evenness [J]), and predator guts were searched for DNA of the focal subterranean herbivore, the corn rootworm (Diabrotica virgifera). Predator abundance and diversity were positively correlated with trophic linkage strength (the proportion positive for rootworm DNA), although the latter characteristic was not significantly so. The diversity and evenness of the predator community with chewing mouthparts were strongly correlated with their linkage strength to rootworms, whereas the linkage strength of fluid-feeding predators was unaffected by their community characteristics. Within this community, chewing predators are more affected by the rootworm's hemolymph defence. This research clearly shows that predator abundance and diversity influence the strength of a community's trophic linkage to a focal pest and that these community characteristics may be particularly important for less palatable or protected prey species. We also make the case for conserving diverse and abundant predator communities within agroecosystems as a form of pest management. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Foraging decisions in wild versus domestic Mus musculus: What does life in the lab select for?

PubMed

Troxell-Smith, Sandra M; Tutka, Michal J; Albergo, Jessica M; Balu, Deebika; Brown, Joel S; Leonard, John P

2016-01-01

What does domestication select for in terms of foraging and anti-predator behaviors? We applied principles of patch use and foraging theory to test foraging strategies and fear responses of three strains of Mus musculus: wild-caught, control laboratory, and genetically modified strains. Foraging choices were quantified using giving-up densities (GUDs) under three foraging scenarios: (1) patches varying in microhabitat (covered versus open), and initial resource density (low versus high); (2) daily variation in auditory cues (aerial predators and control calls); (3) patches with varying seed aggregations. Overall, both domestic strains harvested significantly more food than wild mice. Each strain revealed a significant preference for foraging under cover compared to the open, and predator calls had no detectable effects on foraging. Both domestic strains biased their harvest toward high quality patches; wild mice did not. In terms of exploiting favorable and avoiding unfavorable distributions of seeds within patches, the lab strain performed best, the wild strain worst, and the mutant strain in between. Our study provides support for hypothesis that domestic animals have more energy-efficient foraging strategies than their wild counterparts, but retain residual fear responses. Furthermore, patch-use studies can reveal the aptitudes and priorities of both domestic and wild animals. Copyright © 2015 Elsevier B.V. All rights reserved.

Foraging Activity Pattern Is Shaped by Water Loss Rates in a Diurnal Desert Rodent.

PubMed

Levy, Ofir; Dayan, Tamar; Porter, Warren P; Kronfeld-Schor, Noga

2016-08-01

Although animals fine-tune their activity to avoid excess heat, we still lack a mechanistic understanding of such behaviors. As the global climate changes, such understanding is particularly important for projecting shifts in the activity patterns of populations and communities. We studied how foraging decisions vary with biotic and abiotic pressures. By tracking the foraging behavior of diurnal desert spiny mice in their natural habitat and estimating the energy and water costs and benefits of foraging, we asked how risk management and thermoregulatory requirements affect foraging decisions. We found that water requirements had the strongest effect on the observed foraging decisions. In their arid environment, mice often lose water while foraging for seeds and cease foraging even at high energetic returns when water loss is high. Mice also foraged more often when energy expenditure was high and for longer times under high seed densities and low predation risks. Gaining insight into both energy and water balance will be crucial to understanding the forces exerted by changing climatic conditions on animal energetics, behavior, and ecology.

Barriers to seed and seedling survival of once-common Hawaiian palms: the role of invasive rats and ungulates.

PubMed

Shiels, Aaron B; Drake, Donald R

2015-05-27

Mammalian herbivores can limit plant recruitment and affect forest composition. Loulu palms (Pritchardia spp.) once dominated many lowland ecosystems in Hawai'i, and non-native rats (Rattus spp.), ungulates (e.g. pigs Sus scrofa, goats Capra hircus) and humans have been proposed as major causes of their decline. In lowland wet forest, we experimentally determined the vulnerability of seeds and seedlings of two species of Pritchardia, P. maideniana and P. hillebrandii, by measuring their removal by introduced vertebrates; we also used motion-sensing cameras to identify the animals responsible for Pritchardia removal. We assessed potential seed dispersal of P. maideniana by spool-and-line tracking, and conducted captive-feeding trials with R. rattus and seeds and seedlings of both Pritchardia species. Seed removal from the forest floor occurred rapidly for both species: >50 % of Pritchardia seeds were removed from the vertebrate-accessible stations within 6 days and >80 % were removed within 22 days. Although rats and pigs were both common to the study area, motion-sensing cameras detected only rats (probably R. rattus) removing Pritchardia seeds from the forest floor. Captive-feeding trials and spool-and-line tracking revealed that vertebrate seed dispersal is rare; rats moved seeds up to 8 m upon collection and subsequently destroyed them (100 % mortality in 24-48 h in captivity). Surprisingly, seedlings did not suffer vertebrate damage in field trials, and although rats damaged seedlings in captivity, they rarely consumed them. Our findings are consistent with the hypothesis generated from palaeoecological studies, indicating that introduced rats may have assisted in the demise of native insular palm forests. These findings also imply that the seed stage of species in this Pacific genus is particularly vulnerable to rats; therefore, future conservation efforts involving Pritchardia should prioritize the reduction of rat predation on the plant recruitment stages preceding seedling establishment. Published by Oxford University Press on behalf of the Annals of Botany Company 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Emergent Properties of Patch Shapes Affect Edge Permeability to Animals

PubMed Central

Nams, Vilis O.

2011-01-01

Animal travel between habitat patches affects populations, communities and ecosystems. There are three levels of organization of edge properties, and each of these can affect animals. At the lowest level are the different habitats on each side of an edge, then there is the edge itself, and finally, at the highest level of organization, is the geometry or structure of the edge. This study used computer simulations to (1) find out whether effects of edge shapes on animal behavior can arise as emergent properties solely due to reactions to edges in general, without the animals reacting to the shapes of the edges, and to (2) generate predictions to allow field and experimental studies to test mechanisms of edge shape response. Individual animals were modeled traveling inside a habitat patch that had different kinds of edge shapes (convex, concave and straight). When animals responded edges of patches, this created an emergent property of responding to the shape of the edge. The response was mostly to absolute width of the shapes, and not the narrowness of them. When animals were attracted to edges, then they tended to collect in convexities and disperse from concavities, and the opposite happened when animals avoided edges. Most of the responses occurred within a distance of 40% of the perceptual range from the tip of the shapes. Predictions were produced for directionality at various locations and combinations of treatments, to be used for testing edge behavior mechanisms. These results suggest that edge shapes tend to either concentrate or disperse animals, simply because the animals are either attracted to or avoid edges, with an effect as great as 3 times the normal density. Thus edge shape could affect processes like pollination, seed predation and dispersal and predator abundance. PMID:21747965

Effects of prescribed fire, supplemental feeding, and mammalian predator exclusion on hispid cotton rat populations.

PubMed

Morris, Gail; Hostetler, Jeffrey A; Conner, L Mike; Oli, Madan K

2011-12-01

Predation and food resources can strongly affect small mammal population dynamics directly by altering vital rates or indirectly by influencing behaviors. Fire may also strongly influence population dynamics of species inhabiting fire-adapted habitats because fire can alter food and cover availability. We used capture-mark-recapture and radio-telemetry studies to experimentally examine how supplemental feeding, mammalian predator exclusion, and prescribed fire affected survival, abundance, and reproduction of hispid cotton rats (Sigmodon hispidus) in southwestern Georgia, USA. Prescribed fire reduced survival, abundance, and rates of transitions to reproductive states. Food supplementation increased survival, transitions to reproductive states, and abundance, but was not sufficient to prevent post-fire declines in any of these parameters. Mammalian predator exclusion did not strongly affect any of the considered parameters. Our results show that fire strongly influenced cotton rat populations in our study site, primarily by reducing cover and increasing predation risk from non-mammalian predators.

Turbidity interferes with foraging success of visual but not chemosensory predators

PubMed Central

Smee, Delbert L.

2015-01-01

Predation can significantly affect prey populations and communities, but predator effects can be attenuated when abiotic conditions interfere with foraging activities. In estuarine communities, turbidity can affect species richness and abundance and is changing in many areas because of coastal development. Many fish species are less efficient foragers in turbid waters, and previous research revealed that in elevated turbidity, fish are less abundant whereas crabs and shrimp are more abundant. We hypothesized that turbidity altered predatory interactions in estuaries by interfering with visually-foraging predators and prey but not with organisms relying on chemoreception. We measured the effects of turbidity on the predation rates of two model predators: a visual predator (pinfish, Lagodon rhomboides) and a chemosensory predator (blue crabs, Callinectes sapidus) in clear and turbid water (0 and ∼100 nephelometric turbidity units). Feeding assays were conducted with two prey items, mud crabs (Panopeus spp.) that rely heavily on chemoreception to detect predators, and brown shrimp (Farfantepenaus aztecus) that use both chemical and visual cues for predator detection. Because turbidity reduced pinfish foraging on both mud crabs and shrimp, the changes in predation rates are likely driven by turbidity attenuating fish foraging ability and not by affecting prey vulnerability to fish consumers. Blue crab foraging was unaffected by turbidity, and blue crabs were able to successfully consume nearly all mud crab and shrimp prey. Turbidity can influence predator–prey interactions by reducing the feeding efficiency of visual predators, providing a competitive advantage to chemosensory predators, and altering top-down control in food webs. PMID:26401444

Seed rain, soil seed bank, seed loss and regeneration of Castanopsis fargesii (Fagaceae) in a subtropical evergreen broad-leaved forest

USGS Publications Warehouse

Du, X.; Guo, Q.; Gao, X.; Ma, K.

2007-01-01

Understanding the seed rain and seed loss dynamics in the natural condition has important significance for revealing the natural regeneration mechanisms. We conducted a 3-year field observation on seed rain, seed loss and natural regeneration of Castanopsis fargesii Franch., a dominant tree species in evergreen broad-leaved forests in Dujiangyan, southwestern China. The results showed that: (1) there were marked differences in (mature) seed production between mast (733,700 seeds in 2001) and regular (51,200 and 195,600 seeds in 2002 and 2003, respectively) years for C. fargesii. (2) Most seeds were dispersed in leaf litter, humus and 0-2 cm depth soil in seed bank. (3) Frequency distributions of both DBH and height indicated that C. fargesii had a relatively stable population. (4) Seed rain, seed ground density, seed loss, and leaf fall were highly dynamic and certain quantity of seeds were preserved on the ground for a prolonged time due to predator satiation in both the mast and regular years so that the continuous presence of seed bank and seedling recruitments in situ became possible. Both longer time observations and manipulative experiments should be carried out to better understand the roles of seed dispersal and regeneration process in the ecosystem performance. ?? 2006 Elsevier B.V. All rights reserved.

Feeding on Host Plants with Different Concentrations and Structures of Pyrrolizidine Alkaloids Impacts the Chemical-Defense Effectiveness of a Specialist Herbivore

PubMed Central

Cunha, Beatriz P.; Solferini, Vera N.

2015-01-01

Sequestration of chemical defenses from host plants is a strategy widely used by herbivorous insects to avoid predation. Larvae of the arctiine moth Utetheisa ornatrix feeding on unripe seeds and leaves of many species of Crotalaria (Leguminosae) sequester N-oxides of pyrrolizidine alkaloids (PAs) from these host plants, and transfer them to adults through the pupal stage. PAs confer protection against predation on all life stages of U. ornatrix. As U. ornatrix also uses other Crotalaria species as host plants, we evaluated whether the PA chemical defense against predation is independent of host plant use. We fed larvae from hatching to pupation with either leaves or seeds of one of eight Crotalaria species (C. incana, C. juncea, C. micans, C. ochroleuca, C. pallida, C. paulina, C. spectabilis, and C. vitellina), and tested if adults were preyed upon or released by the orb-weaving spider Nephila clavipes. We found that the protection against the spider was more effective in adults whose larvae fed on seeds, which had a higher PA concentration than leaves. The exceptions were adults from larvae fed on C. paulina, C. spectabilis and C. vitellina leaves, which showed high PA concentrations. With respect to the PA profile, we describe for the first time insect-PAs in U. ornatrix. These PAs, biosynthesized from the necine base retronecine of plant origin, or monocrotaline- and senecionine-type PAs sequestered from host plants, were equally active in moth chemical defense, in a dose-dependent manner. These results are also partially explained by host plant phylogeny, since PAs of the host plants do have a phylogenetic signal (clades with high and low PA concentrations in leaves) which is reflected in the adult defense. PMID:26517873

Feeding on Host Plants with Different Concentrations and Structures of Pyrrolizidine Alkaloids Impacts the Chemical-Defense Effectiveness of a Specialist Herbivore.

PubMed

Martins, Carlos H Z; Cunha, Beatriz P; Solferini, Vera N; Trigo, José R

2015-01-01

Sequestration of chemical defenses from host plants is a strategy widely used by herbivorous insects to avoid predation. Larvae of the arctiine moth Utetheisa ornatrix feeding on unripe seeds and leaves of many species of Crotalaria (Leguminosae) sequester N-oxides of pyrrolizidine alkaloids (PAs) from these host plants, and transfer them to adults through the pupal stage. PAs confer protection against predation on all life stages of U. ornatrix. As U. ornatrix also uses other Crotalaria species as host plants, we evaluated whether the PA chemical defense against predation is independent of host plant use. We fed larvae from hatching to pupation with either leaves or seeds of one of eight Crotalaria species (C. incana, C. juncea, C. micans, C. ochroleuca, C. pallida, C. paulina, C. spectabilis, and C. vitellina), and tested if adults were preyed upon or released by the orb-weaving spider Nephila clavipes. We found that the protection against the spider was more effective in adults whose larvae fed on seeds, which had a higher PA concentration than leaves. The exceptions were adults from larvae fed on C. paulina, C. spectabilis and C. vitellina leaves, which showed high PA concentrations. With respect to the PA profile, we describe for the first time insect-PAs in U. ornatrix. These PAs, biosynthesized from the necine base retronecine of plant origin, or monocrotaline- and senecionine-type PAs sequestered from host plants, were equally active in moth chemical defense, in a dose-dependent manner. These results are also partially explained by host plant phylogeny, since PAs of the host plants do have a phylogenetic signal (clades with high and low PA concentrations in leaves) which is reflected in the adult defense.

Numerical and behavioral effects within a pulse-driven system: consequences for shared prey.

PubMed

Schmidt, Kenneth A; Ostfeld, Richard S

2008-03-01

Some of the clearest examples of the ramifying effects of resource pulses exist in deciduous forests dominated by mast-producing trees, such as oaks, beech, and hornbeam. Seed production in these forests represents only the first of several pulsed events. Secondary pulses emerge as mast-consuming small rodents numerically respond to seed production and tertiary pulses emerge as generalist predators numerically respond to rodents. Raptors may also respond behaviorally (i.e., diet shifts) to subsequent crashes in small rodents following the crash phase in seed production. In oak-dominated forest in the Hudson Valley, New York, these various pulse and crash phases act synergistically, although not simultaneously, to influence thrush population dynamics through predation on nests, juveniles, and adults. As a consequence, factors limiting population growth rate and their age-specific action vary as a function of past acorn production. We highlight these interactions based on our eight-year study of thrush demography, acorn production, and small mammal abundance coupled with information on regional adult thrush population trends from the Breeding Bird Survey. We use these data sets to demonstrate the sequence of primary to tertiary pulses and how they influence breeding thrush populations. To extend our discussion beyond masting phenomena in the eastern United States, we briefly review the literature of alternative avian prey within pulsed systems to show (1) numerical and behavioral responses by generalist predators are ubiquitous in pulsed systems, and this contributes to (2) variability in reproduction and survivorship of avian prey linked to the underlying dynamics of the pulse. We conclude by exploring the broad consequences of cascading resource pulses for alternative prey based upon the indirect interaction of apparent competition among shared prey and the nature of temporal variability on populations.

Crop damage of Eriotheca gracilipes (Bombacaceae) by the Blue-Fronted Amazon (Amazona aestiva, Psittacidae), in the Brazilian Cerrado.

PubMed

Ragusa-Netto, J

2014-11-01

Seed predation has major effects on the reproductive success of individuals, spatial patterns of populations, genetic variability, interspecific interactions and ultimately in the diversity of tree communities. At a Brazilian savanna, I evaluated the proportional crop loss of Eriotheca gracilipes due the Blue-Fronted Amazon (Amazona aestiva) during a fruiting period. Also, I analyzed the relationship between proportional crop loss to Amazons and both fruit crop size and the distance from the nearest damaged conspecific. Trees produced from 1 to 109 fruits, so that Amazons foraged more often on trees bearing larger fruit crop size, while seldom visited less productive trees. Moreover, the relationship between fruit crop sizes and the number of depredated fruits was significant. However, when only damaged trees were assessed, I found a negative and significant relation between fruit crop size and proportional crop loss to Blue-Fronted Amazons. Taking into account this as a measure more directly related to the probability of seed survival, a negative density dependent effect emerged. Also, Amazons similarly damaged the fruit crops of either close or distant neighboring damaged trees. Hence, in spite of Blue-Fronted Amazons searched for E. gracilipes bearing large fruit crops, they were swamped due to the presence of more fruits than they could eat. Moderate seed predation by Blue-Fronted Amazons either at trees with large fruit crops or in areas where fruiting trees were aggregated implies in an enhanced probability of E. gracilipes seed survival and consequent regeneration success.

Plant chemical defence: a partner control mechanism stabilising plant - seed-eating pollinator mutualisms

PubMed Central

Ibanez, Sébastien; Gallet, Christiane; Dommanget, Fanny; Després, Laurence

2009-01-01

Background Mutualisms are inherently conflictual as one partner always benefits from reducing the costs imposed by the other. Despite the widespread recognition that mutualisms are essentially reciprocal exploitation, there are few documented examples of traits that limit the costs of mutualism. In plant/seed-eating pollinator interactions the only mechanisms reported so far are those specific to one particular system, such as the selective abortion of over-exploited fruits. Results This study shows that plant chemical defence against developing larvae constitutes another partner sanction mechanism in nursery mutualisms. It documents the chemical defence used by globeflower Trollius europaeus L. (Ranunculaceae) against the seed-eating larvae of six pollinating species of the genus Chiastocheta Pokorny (Anthomyiidae). The correlative field study carried out shows that the severity of damage caused by Chiastocheta larvae to globeflower fruits is linked to the accumulation in the carpel walls of a C-glycosyl-flavone (adonivernith), which reduces the larval seed predation ability per damaged carpel. The different Chiastocheta species do not exploit the fruit in the same way and their interaction with the plant chemical defence is variable, both in terms of induction intensity and larval sensitivity to adonivernith. Conclusion Adonivernith accumulation and larval predation intensity appear to be both the reciprocal cause and effect. Adonivernith not only constitutes an effective chemical means of partner control, but may also play a key role in the sympatric diversification of the Chiastocheta genus. PMID:19887006

Selective Pressures Explain Differences in Flower Color among Gentiana lutea Populations.

PubMed

Sobral, Mar; Veiga, Tania; Domínguez, Paula; Guitián, Javier A; Guitián, Pablo; Guitián, José M

2015-01-01

Flower color variation among plant populations might reflect adaptation to local conditions such as the interacting animal community. In the northwest Iberian Peninsula, flower color of Gentiana lutea varies longitudinally among populations, ranging from orange to yellow. We explored whether flower color is locally adapted and the role of pollinators and seed predators as agents of selection by analyzing the influence of flower color on (i) pollinator visitation rate and (ii) escape from seed predation and (iii) by testing whether differences in pollinator communities correlate with flower color variation across populations. Finally, (iv) we investigated whether variation in selective pressures explains flower color variation among 12 G. lutea populations. Flower color influenced pollinator visits and differences in flower color among populations were related to variation in pollinator communities. Selective pressures on flower color vary among populations and explain part of flower color differences among populations of G. lutea. We conclude that flower color in G. lutea is locally adapted and that pollinators play a role in this adaptation.

Jasmonic acid protects etiolated seedlings of Arabidopsis thaliana against herbivorous arthropods

PubMed Central

Boex-Fontvieille, Edouard; Rustgi, Sachin; Von Wettstein, Diter; Pollmann, Stephan; Reinbothe, Steffen; Reinbothe, Christiane

2016-01-01

ABSTRACT Seed predators can cause mass ingestion of larger seed populations. As well, herbivorous arthropods attempt to attack etiolated seedlings and chose the apical hook for ingestion, aimed at dropping the cotyledons for later consumption. Etiolated seedlings, as we show here, have established an efficient mechanism of protecting their Achilles' heel against these predators, however. Evidence is provided for a role of jasmonic acid (JA) in this largely uncharacterized plant-herbivore interaction during skotomorphogenesis and that this comprises the temporally and spatially tightly controlled synthesis of a cysteine protease inhibitors of the Kunitz family. Interestingly, the same Kunitz protease inhibitor was found to be expressed in flowers of Arabidopsis where endogenous JA levels are high for fertility. Because both the apical hook and inflorescences were preferred isopod targets in JA-deficient plants that could be rescued by exogenously administered JA, our data identify a JA-dependent mechanism of plant arthropod deterrence that is recalled in different organs and at quite different times of plant development. PMID:27485473

Selective Pressures Explain Differences in Flower Color among Gentiana lutea Populations

PubMed Central

Domínguez, Paula; Guitián, Javier A.; Guitián, Pablo; Guitián, José M.

2015-01-01

Flower color variation among plant populations might reflect adaptation to local conditions such as the interacting animal community. In the northwest Iberian Peninsula, flower color of Gentiana lutea varies longitudinally among populations, ranging from orange to yellow. We explored whether flower color is locally adapted and the role of pollinators and seed predators as agents of selection by analyzing the influence of flower color on (i) pollinator visitation rate and (ii) escape from seed predation and (iii) by testing whether differences in pollinator communities correlate with flower color variation across populations. Finally, (iv) we investigated whether variation in selective pressures explains flower color variation among 12 G. lutea populations. Flower color influenced pollinator visits and differences in flower color among populations were related to variation in pollinator communities. Selective pressures on flower color vary among populations and explain part of flower color differences among populations of G. lutea. We conclude that flower color in G. lutea is locally adapted and that pollinators play a role in this adaptation. PMID:26172378

Predation of Songbird Nests Differs By Predator and Between Field and Forest Habitats

Treesearch

Frank R., III Thompson; Dirk E. Burhans

2003-01-01

Our understanding of factors affecting nest predation and ability to mitigate high nest predation rates is hampered by a lack of information on the importance of various nest predator species in different habitats and landscapes. We identified predators of songbird nests in old-field and forest habitats in central Missouri, USA, with miniature video cameras. We used an...

Life history traits influence the strength of distance- and density-dependence at different life stages of two Amazonian palms.

PubMed

Choo, Juanita; Carasco, Cecilia; Alvarez-Loayza, Patricia; Simpson, Beryl B; Economo, Evan P

2017-07-01

Natural enemies are known to be important in regulating plant populations and contributing to species coexistence (Janzen-Connell effects). The strength of Janzen-Connell effects (both distance- and density-effects) varies across species, but the life history traits that may mediate such a variation are not well understood. This study examined Janzen-Connell effects across the life stages (seed through adult stages) of two sympatric palm species with distinct phenologies and shade tolerances, two traits that may mediate the strength and timing of Janzen-Connell effects. Populations of two common palm species, Attalea phalerata and Astrocaryum murumuru , were studied in Manu National Park, Peru. Seed predation experiments were conducted to assess Janzen-Connell effects at the seed stage. In the post-seed stages, spatial point pattern analyses of the distributions of individuals and biomass were used to infer the strength of distance- and density-effects. Seed predation was both negative distance- and density-dependent consistent with the Janzen-Connell effects. However, only seedling recruitment for asynchronously fruiting Attalea phalerata was depressed near adults while recruitment remained high for synchronously fruiting Astrocaryum murumuru , consistent with weak distance-effects. Negative density-effects were strong in the early stages for shade-intolerant Attalea phalerata but weak or absent in shade-tolerant Astrocaryum murumuru. Distance- and density-effects varied among the life stages of the two palm species in a manner that corresponded to their contrasting phenology and shade tolerance. Generalizing such connections across many species would provide a route to understanding how trait-mediated Janzen-Connell effects scale up to whole communities of species. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com

A latitudinal gradient in seed nutrients of the forest herb Anemone nemorosa.

PubMed

De Frenne, P; Kolb, A; Graae, B J; Decocq, G; Baltora, S; De Schrijver, A; Brunet, J; Chabrerie, O; Cousins, S A O; Dhondt, R; Diekmann, M; Gruwez, R; Heinken, T; Hermy, M; Liira, J; Saguez, R; Shevtsova, A; Baskin, C C; Verheyen, K

2011-05-01

The nutrient concentration in seeds determines many aspects of potential success of the sexual reproductive phase of plants, including the seed predation probability, efficiency of seed dispersal and seedling performance. Despite considerable research interest in latitudinal gradients of foliar nutrients, a similar gradient for seeds remains unexplored. We investigated a potential latitudinal gradient in seed nutrient concentrations within the widespread European understorey forest herb Anemone nemorosa L. We sampled seeds of A. nemorosa in 15 populations along a 1900-km long latitudinal gradient at three to seven seed collection dates post-anthesis and investigated the relative effects of growing degree-hours >5 °C, soil characteristics and latitude on seed nutrient concentrations. Seed nitrogen, nitrogen:phosphorus ratio and calcium concentration decreased towards northern latitudes, while carbon:nitrogen ratios increased. When taking differences in growing degree-hours and measured soil characteristics into account and only considering the most mature seeds, the latitudinal decline remained particularly significant for seed nitrogen concentration. We argue that the decline in seed nitrogen concentration can be attributed to northward decreasing seed provisioning due to lower soil nitrogen availability or greater investment in clonal reproduction. This pattern may have large implications for the reproductive performance of this forest herb as the degree of seed provisioning ultimately co-determines seedling survival and reproductive success. © 2010 German Botanical Society and The Royal Botanical Society of the Netherlands.

Insect herbivores drive real-time ecological and evolutionary change in plant populations.

PubMed

Agrawal, Anurag A; Hastings, Amy P; Johnson, Marc T J; Maron, John L; Salminen, Juha-Pekka

2012-10-05

Insect herbivores are hypothesized to be major factors affecting the ecology and evolution of plants. We tested this prediction by suppressing insects in replicated field populations of a native plant, Oenothera biennis, which reduced seed predation, altered interspecific competitive dynamics, and resulted in rapid evolutionary divergence. Comparative genotyping and phenotyping of nearly 12,000 O. biennis individuals revealed that in plots protected from insects, resistance to herbivores declined through time owing to changes in flowering time and lower defensive ellagitannins in fruits, whereas plant competitive ability increased. This independent real-time evolution of plant resistance and competitive ability in the field resulted from the relaxation of direct selective effects of insects on plant defense and through indirect effects due to reduced herbivory on plant competitors.

Effects of urbanization on direct and indirect interactions in a tri-trophic system.

PubMed

Tabea, Turrini; Dirk, Sanders; Eva, Knop

2016-04-01

While effects of urbanization on species assemblages are receiving increasing attention, effects on ecological interactions remain largely unexplored. We investigated how urbanization influences the strength of direct and indirect trophic interactions in a tri- trophic system. In a field experiment including five cities and nearby farmed areas, we used potted Vicia faba plants and manipulated the presence of Megoura viciae aphids and that of naturally occurring aphid predators. When predators could access aphids, they reduced their abundance less in the urban than in the agricultural ecosystem. Compared to aphid abundance on plants without predator access, abundance on plants with predator access was 2.58 times lower in urban and 5.27 times lower in agricultural areas. This indicates that urbanization limited top-down control of aphids by predators. In both ecosystems, plant biomass was negatively affected by herbivores and positively affected by predators, but the positive indirect predator effect was weaker in cities. Compared to aphid-infested plants without predator access, plants with predator access were 1.89 times heavier in urban and 2.12 times heavier in agricultural areas. Surprisingly, differences between ecosystems regarding the indirect predator effect on plants were not explained by the differentially strong herbivore suppression. Instead, the urban environment limited plant biomass per se, thereby mitigating the scope of a positive predator effect. Our results show that urbanization can influence direct and indirect trophic interactions through effects on biotic top-down forces and on plant growth. In order to understand how urbanization affects biodiversity and ecosystem functioning, it is fundamental to not only consider species assemblages, but also species interactions.

Critical Stages in the Recruitment Process of Rhamnus alaternus L.

PubMed Central

GULIAS, J.; TRAVESET, A.; RIERA, N.; MUS, M.

2004-01-01

• Background and Aims Rhamnus alaternus is a Mediterranean shrub commonly used in reforestation programs. Although several aspects of its reproductive biology have been studied, little is known about the importance of the different recruitment stages in the overall regeneration process of this species, which limits its proper use in Mediterranean forests and shrubland management. The aim of the present work was to quantify the importance of the different recruitment stages in the regeneration process of R. alaternus. • Methods Two populations of Rhamnus alaternus on the island of Mallorca that differ in climatic conditions, type of habitat and sex ratio were studied. The importance of seed production, seed dispersal and predation, seedling emergence and seedling survival for the regeneration of this species were quantified. • Key Results In both populations, fruit set and fruit removal by animals were not critical stages, since almost half of the flowers became mature fruits and 90 % of those were dispersed. Most seeds were deposited under female conspecifics (86 and 47 %, at Lloret and Esporles, respectively), and very few were found in open inter‐spaces (1 and 5 %). Post‐dispersal seed predation (mostly by ants and rodents) was very high in both populations. Seedling emergence took place during autumn and early winter and it ranged from 31 to 68 % depending upon year and microhabitat. The majority of emerged seedlings died during the first year, mainly due to desiccation; such mortality was influenced by rainfall and differed among microhabitats (varying from 67 to 100 %). The general spatial distribution of seed rain was concordant with the seedling emergence and survival pattern in both populations. • Conclusions The recruitment of Rhamnus alaternus appeared to be mainly limited by seed and seedling survival, regardless of the type of habitat in which the species is found. PMID:15150073

Linking Foraging Decisions to Residential Yard Bird Composition

PubMed Central

Lerman, Susannah B.; Warren, Paige S.; Gan, Hilary; Shochat, Eyal

2012-01-01

Urban bird communities have higher densities but lower diversity compared with wildlands. However, recent studies show that residential urban yards with native plantings have higher native bird diversity compared with yards with exotic vegetation. Here we tested whether landscape designs also affect bird foraging behavior. We estimated foraging decisions by measuring the giving-up densities (GUD; amount of food resources remaining when the final forager quits foraging on an artificial food patch, i.e seed trays) in residential yards in Phoenix, AZ, USA. We assessed how two yard designs (mesic: lush, exotic vegetation; xeric: drought-tolerant and native vegetation) differed in foraging costs. Further, we developed a statistical model to calculate GUDs for every species visiting the seed tray. Birds foraging in mesic yards depleted seed trays to a lower level (i.e. had lower GUDs) compared to birds foraging in xeric yards. After accounting for bird densities, the lower GUDs in mesic yards appeared largely driven by invasive and synanthropic species. Furthermore, behavioral responses of individual species were affected by yard design. Species visiting trays in both yard designs had lower GUDs in mesic yards. Differences in resource abundance (i.e., alternative resources more abundant and of higher quality in xeric yards) contributed to our results, while predation costs associated with foraging did not. By enhancing the GUD, a common method for assessing the costs associated with foraging, our statistical model provided insights into how individual species and bird densities influenced the GUD. These differences we found in foraging behavior were indicative of differences in habitat quality, and thus our study lends additional support for native landscapes to help reverse the loss of urban bird diversity. PMID:22927974

Outrun or Outmaneuver: Predator-Prey Interactions as a Model System for Integrating Biomechanical Studies in a Broader Ecological and Evolutionary Context.

PubMed

Moore, Talia Y; Biewener, Andrew A

2015-12-01

Behavioral studies performed in natural habitats provide a context for the development of hypotheses and the design of experiments relevant both to biomechanics and to evolution. In particular, predator-prey interactions are a model system for integrative study because success or failure of predation has a direct effect on fitness and drives the evolution of specialized performance in both predator and prey. Although all predators share the goal of capturing prey, and all prey share the goal of survival, the behavior of predators and prey are diverse in nature. This article presents studies of some predator-prey interactions sharing common predation strategies that reveal general principles governing the behaviors of predator and prey, even in distantly related taxa. Studies of predator-prey interactions also reveal that maximal performance observed in a laboratory setting is not necessarily the performance that determines fitness. Thus, considering locomotion in the context of predation ecology can aid in evolutionarily relevant experimental design. Classification by strategy reveals that displaying unpredictable trajectories is a relevant anti-predator behavior in response to multiple predation strategies. A predator's perception and pursuit of prey can be affected indirectly by divergent locomotion of similar animals that share an ecosystem. Variation in speed and direction of locomotion that directly increases the unpredictability of a prey's trajectory can be increased through genetic mutation that affects locomotor patterns, musculoskeletal changes that affect maneuverability, and physical interactions between an animal and the environment. By considering the interconnectedness of ecology, physical constraints, and the evolutionary history of behavior, studies in biomechanics can be designed to inform each of these fields. © The Author 2015. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

Sowing pregerminated northern red oak acorns

Treesearch

Richard M. Godman; Gilbert A. Mattson

1992-01-01

Northern red oak is extremely difficult to regenerate, although it has produced good acorn crops nearly half of the last 32 years in northern Wisconsin. Field trials have shown that for successful seeding, you must protect acorns from predation by wildlife and sow them when temperatures are most favorable for germination.

Does Predation Risk Affect Mating Behavior? An Experimental Test in Dumpling Squid (Euprymna tasmanica)

PubMed Central

Franklin, Amanda M.; Squires, Zoe E.; Stuart-Fox, Devi

2014-01-01

Introduction One of the most important trade-offs for many animals is that between survival and reproduction. This is particularly apparent when mating increases the risk of predation, either by increasing conspicuousness, reducing mobility or inhibiting an individual's ability to detect predators. Individuals may mitigate the risk of predation by altering their reproductive behavior (e.g. increasing anti-predator responses to reduce conspicuousness). The degree to which individuals modulate their reproductive behavior in relation to predation risk is difficult to predict because both the optimal investment in current and future reproduction (due to life-history strategies) and level of predation risk may differ between the sexes and among species. Here, we investigate the effect of increased predation risk on the reproductive behavior of dumpling squid (Euprymna tasmanica). Results Females, but not males, showed a substantial increase in the number of inks (an anti-predator behavior) before mating commenced in the presence of a predator (sand flathead Platycephalus bassensis). However, predation risk did not affect copulation duration, the likelihood of mating, female anti-predator behavior during or after mating or male anti-predator behavior at any time. Conclusions Inking is a common anti-predator defense in cephalopods, thought to act like a smokescreen, decoy or distraction. Female dumpling squid are probably using this form of defense in response to the increase in predation risk prior to mating. Conversely, males were undeterred by the increase in predation risk. A lack of change in these variables may occur if the benefit of completing mating outweighs the risk of predation. Prioritizing current reproduction, even under predation risk, can occur when the chance of future reproduction is low, there is substantial energetic investment into mating, or the potential fitness payoffs of mating are high. PMID:25551378

Complex foraging ecology of the red harvester ant and its effect on the soil seed bank

NASA Astrophysics Data System (ADS)

Luna, Pedro; García-Chávez, Juan Héctor; Dáttilo, Wesley

2018-01-01

Granivory is an important interaction in the arid and semi-arid zones of the world, since seeds form an abundant and nutritious resource in these areas. While species of the genus Pogonomyrmex have been studied in detail as seed predators, their impact on seed abundance in the soil has not yet been explored in sufficient depth. We studied the impact of the harvesting activities of the ant Pogonomyrmex barbatus on seed abundance in the soil of the Zapotitlán valley, Mexico. We found that P. barbatus activity significantly impacts the abundance of seeds in the soil, which is lower in the sites where P. barbatus forages than it is in sites with no recorded foraging. We also found that P. barbatus distributes intact seeds of three tree species, two of which are nurse plants, and could consequently be promoting the establishment of these species. Using tools derived from graph theory, we observed that the ant-seed interactions exhibit a nested pattern; where more depredated seed species seem to be the more spatially abundant in the environment. This study illustrates the complex foraging ecology of the harvester ant P. barbatus and elucidates its effect on the soil seed bank in a semi-arid environment.

Relationships of habitat patch size to predator community and survival of duck nests

USGS Publications Warehouse

Sovada, M.A.; Zicus, M.C.; Greenwood, R.J.; Rave, D.P.; Newton, W.E.; Woodward, R.O.; Beiser, J.A.

2000-01-01

We studied duck nest success and predator community composition in relation to size of discrete patches of nesting cover in the Prairie Pothole Region (PPR) of the United States in 1993-95. We focused on nests in uplands that were seeded to perennial grasses and forbs and enrolled in the Conservation Reserve Program (CRP) in Minnesota, North Dakota, and South Dakota. We estimated daily survival rates (DSRs) of upland duck nests and indices of activity for red foxes (Vulpes vulpes), coyotes (Canis latrans), American badgers (Taxidea taxus), striped skunks (Mephitis mephitis), and Franklin's ground squirrels (Spermophilus franklinii), and related these variables to habitat patch size. The effect of patch size (small vs. large) on estimated annual mean DSR was dependent on date of nest initiation (early vs. late) and year. Examination of within-year comparisons for early and late nests suggested that DSR was generally greater in larger habitat patches. Activity indices for the 5 mammalian nest predators were influenced differently by year, location, and patch size. Activity indices of the red fox were greatest in small patches. Coyote indices were the most inconsistent, demonstrating a year X location X patch size interaction. Activity indices of the striped skunk and American badger varied only among years. Franklin's ground squirrel indices were affected by study area location, with higher indices in the southeast than the northwest. Red fox activity was weakly correlated with that of the striped skunk and coyote. Although a positive relationship between habitat patch size and nest success probably exists, we believe the experiment to fully test this hypothesis will continue to be elusive.

Folivory or fruit/seed predation for Mesopithecus, an earliest colobine from the late Miocene of Eurasia?

PubMed

Merceron, Gildas; Scott, Jessica; Scott, Robert S; Geraads, Denis; Spassov, Nikolai; Ungar, Peter S

2009-12-01

Here we compare dental microwear textures from specimens of the fossil genus Mesopithecus (Cercopithecidae, Colobinae) from the late Miocene of Eastern Europe with dental microwear textures from four extant primate species with known dietary differences. Results indicate that the dental microwear textures of Mesopithecus differ from those of extant leaf eaters Alouatta palliata and Trachypithecus cristatus and instead resemble more closely those of the occasional hard-object feeders Cebus apella and Lophocebus albigena. Microwear texture data presented here in combination with results from previous analyses suggest that Mesopithecus was a widespread, opportunistic feeder that often consumed hard seeds. These data are consistent with the hypothesis that early colobines may have preferred hard seeds to leaves.

Competition between harvester ants and rodents in the cold desert

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landeen, D.S.; Jorgensen, C.D.; Smith, H.D.

1979-09-30

Local distribution patterns of three rodent species (Perognathus parvus, Peromyscus maniculatus, Reithrodontomys megalotis) were studied in areas of high and low densities of harvester ants (Pogonomyrmex owyheei) in Raft River Valley, Idaho. Numbers of rodents were greatest in areas of high ant-density during May, but partially reduced in August; whereas, the trend was reversed in areas of low ant-density. Seed abundance was probably not the factor limiting changes in rodent populations, because seed densities of annual plants were always greater in areas of high ant-density. Differences in seasonal population distributions of rodents between areas of high and low ant-densities weremore » probably due to interactions of seed availability, rodent energetics, and predation.« less

Interactions among predators and plant specificity protect herbivores from top predators.

PubMed

Bosc, Christopher; Pauw, Anton; Roets, Francois; Hui, Cang

2018-05-04

The worldwide loss of top predators from natural and agricultural systems has heightened the need to understand how important they are in controlling herbivore abundance. The effect of top predators on herbivore species is likely to depend on 1) the importance of the consumption of intermediate predators by top predators (intra-guild predation; IGP), but also on 2) plant specificity by herbivores, because specialists may defend themselves better (enemy-free space; EFS). Insectivorous birds, as top predators, are generally known to effectively control herbivorous insects, despite also consuming intermediate predators such as spiders, but how this effect varies among herbivore species in relation to the cascading effects of IGP and EFS is not known. To explore this, we excluded birds from natural fynbos vegetation in South Africa using large netted cages and recorded changes in abundance relative to control plots for 199 plant-dwelling intermediate predator and 341 herbivore morpho-species that varied in their estimated plant specificity. We found a strong negative effect of birds on the total abundance of all intermediate predators, with especially clear effects on spiders (strong IGP). In contrast with previous studies, which document a negative effect of birds on herbivores, we found an overall neutral effect of birds on herbivore abundance, but the effect varied among species: some species were negatively affected by birds, suggesting that they were mainly consumed by birds, whereas others, likely released from spiders by IGP, were positively affected. Some species were also effectively neutrally affected by birds. These tended to be more specialized to plants compared to the other species, which may imply that some plant specialists benefited from protection provided by EFS from both birds and spiders. These results suggest that the response of herbivore species to top predators may depend on cascading effects of interactions among predators and on their degree of plant specificity. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Effects of clay turbidity and density of pikeperch (Sander lucioperca) larvae on predation by perch (Perca fluviatilis).

PubMed

Pekcan-Hekim, Zeynep; Lappalainen, Jyrki

2006-07-01

Increased turbidity reduces visibility in the water column, which can negatively affect vision-oriented fish and their ability to detect prey. Young fish could consequently benefit from high turbidity levels that can provide a protective cover, reducing predation pressure. Perch (Perca fluviatilis) are commonly found in littoral zones of temperate lakes and coastal areas of the Baltic Sea. Pikeperch (Sander lucioperca) spawn in these areas, so perch is a potential predator for pikeperch larvae. We conducted laboratory experiments to test the predation of perch on pikeperch larvae at different turbidity levels (5-85 nephelometric turbidity units), densities of pikeperch larvae (2-21 individuals l(-1)) and volumes of water (10-45 l). The logistic regression showed that the probability of larvae eaten depended significantly on turbidity and volume of water in the bags, while density of larvae was not significant. However, because container size is known to affect predation, the data was divided into two groups based on water volume (10-20 and 25-45 l) to reduce the effects of container size. In either group, probability of predation did not significantly depend on volume, whereas turbidity was significant in both groups, while density was significant in larger water volumes. Thus, high turbidity impaired perch predation and protected pikeperch larvae from perch predation. Because density of larvae was also a significant factor affecting predation of perch, the dispersal of pikeperch larvae from spawning areas should also increase the survival of larvae.

Predation risk affects growth and reproduction of an invasive snail and its lethal effect depends on prey size

PubMed Central

Guo, Jing; Martín, Pablo R.; Zhang, Chunxia

2017-01-01

The behavior of invasive species under predation risk has been studied extensively, but their growth and reproductive responses have rarely been investigated. We conducted experiments with juveniles and adults of the invasive freshwater snail Pomacea canaliculata, and we observed changes in growth and reproduction in response to predation risk from a caged predator (Trachemys scripta elegans). P. canaliculata produced eggs earlier in the presence of predators and injured conspecifics compared with the control group (no risk), although the total number of egg masses laid by per female was exceeded by that of the controls after 15 days. Egg hatching success noticeably decreased under predation risk, and the incubation period was significantly prolonged; however, the oviposition height of the snails was not affected. A lethal effect of predation risk was detected in juvenile snails but not in adults. The growth of juvenile P. canaliculata was inhibited under predation risk, probably due to a reduction in food intake. Adult females exhibited a greater reduction in growth under predation risk than males, which likely resulted in part from the high reproductive investment of females in egg laying. These results indicate that P. canaliculata snails under predation risk face a trade-off between predator avoidance and growth and reproduction, where the lethal effect of predation risk is linked to the size of the prey. PMID:29136660

Ants have a negative rather than a positive effect on extrafloral nectaried Crotalaria pallida performance

NASA Astrophysics Data System (ADS)

Pereira, Marcela Fernandes; Trigo, José Roberto

2013-08-01

Crotalaria pallida (Fabaceae) is a pantropical plant with extrafloral nectaries (EFNs) near the reproductive structures. EFN-visiting ants attack and remove arctiid moth Utetheisa ornatrix larvae, the main pre-dispersal seed predator, but the impact of ants on C. pallida fitness is unknown. To assess this impact, we controlled ant presence on plants and evaluated the reproductive output of C. pallida with and without ants. Predatory wasps also visit EFNs, prey upon U. ornatrix larvae, and may be driven out by ants during EFN feeding. Does this agonistic interaction affect the multitrophic interaction outcome? We found it difficult to evaluate the effect of both visitors because cages excluding wasps affect plant growth and do not allow U. ornatrix oviposition. Therefore, we verified whether ant presence inhibited wasp EFN visitation and predicted that (1) if ants confer a benefit for C. pallida, any negative effect of ants on wasps would be negligible for the plant because ants would be the best guardians, and (2) if ants are poor guardians, they would negatively affect wasps and negatively impact the fitness of C. pallida. Surprisingly, we found that the number of seeds/pods significantly increased, ca. 4.7 times, after ant removal. Additionally, we unexpectedly verified that controls showed a higher percentage of herbivore bored pods than ant-excluded plants. We found that wasps spent less time visiting EFNs patrolled by ants (ca. 299 s less). These results support our second prediction and suggest that the outcome of multitrophic interactions may vary with natural enemy actors.

Sparrowhawk movement, calling, and presence of dead conspecifics differentially impact blue tit (Cyanistes caeruleus) vocal and behavioral mobbing responses.

PubMed

Carlson, Nora V; Pargeter, Helen M; Templeton, Christopher N

2017-01-01

Many animals alter their anti-predator behavior in accordance to the threat level of a predator. While much research has examined variation in mobbing responses to different predators, few studies have investigated how anti-predator behavior is affected by changes in a predator's own state or behavior. We examined the effect of sparrowhawk ( Accipiter nisus ) behavior on the mobbing response of wild blue tits ( Cyanistes caeruleus ) using robotic taxidermy sparrowhawks. We manipulated whether the simulated predator moved its head, produced vocalizations, or held a taxidermy blue tit in its talons. When any sparrowhawk model was present, blue tits decreased foraging and increased anti-predator behavior and vocalizations. Additionally, each manipulation of the model predator's state (moving, vocalizing, or the presence of a dead conspecific) impacted different types of blue tit anti-predator behavior and vocalizations. These results indicate that different components of mobbing vary according to the specific state of a given predator-beyond its presence or absence-and suggest that each might play a different role in the overall mobbing response. Last, our results indicate that using more life-like predator stimuli-those featuring simple head movements and audio playback of vocalizations-changes how prey respond to the predator; these 'robo-raptor' models provide a powerful tool to provide increased realism in simulated predator encounters without sacrificing experimental control. Anti-predatory behavior is often modulated by the threat level posed by a particular predator. While much research has tested how different types of predators change prey behavior, few experiments have examined how predator behavior affects anti-predatory responses of prey. By experimentally manipulating robotic predators, we show that blue tits not only respond to the presence of a sparrowhawk, by decreasing feeding and increasing anti-predator behavior and vocalizations, but that they vary specific anti-predator behaviors when encountering differently behaving predators (moving, vocalizing, or those with captured prey), suggesting that prey pay attention to their predators' state and behavior.

Predator identity and time of day interact to shape the risk-reward trade-off for herbivorous coral reef fishes.

PubMed

Catano, Laura B; Barton, Mark B; Boswell, Kevin M; Burkepile, Deron E

2017-03-01

Non-consumptive effects (NCEs) of predators occur as prey alters their habitat use and foraging decisions to avoid predation. Although NCEs are recognized as being important across disparate ecosystems, the factors influencing their strength and importance remain poorly understood. Ecological context, such as time of day, predator identity, and prey condition, may modify how prey species perceive and respond to risk, thereby altering NCEs. To investigate how predator identity affects foraging of herbivorous coral reef fishes, we simulated predation risk using fiberglass models of two predator species (grouper Mycteroperca bonaci and barracuda Sphyraena barracuda) with different hunting modes. We quantified how predation risk alters herbivory rates across space (distance from predator) and time (dawn, mid-day, and dusk) to examine how prey reconciles the conflicting demands of avoiding predation vs. foraging. When we averaged the effect of both predators across space and time, they suppressed herbivory similarly. Yet, they altered feeding differently depending on time of day and distance from the model. Although feeding increased strongly with increasing distance from the predators particularly during dawn, we found that the barracuda model suppressed herbivory more strongly than the grouper model during mid-day. We suggest that prey hunger level and differences in predator hunting modes could influence these patterns. Understanding how context mediates NCEs provides insight into the emergent effects of predator-prey interactions on food webs. These insights have broad implications for understanding how anthropogenic alterations to predator abundances can affect the spatial and temporal dynamics of important ecosystem processes.

Diet overlap and predation between largemouth bass and walleye in Wisconsin lakes using DNA barcoding to improve taxonomic resolution

USGS Publications Warehouse

Kelling, Craig J.; Isermann, Daniel A.; Sloss, Brian L.; Turnquist, Keith N.

2016-01-01

Over the last decade, the abundance of Largemouth Bass Micropterus salmoides has increased in many northern Wisconsin lakes, causing concern among anglers and biologists regarding the potential for Largemouth Bass to negatively affect populations of Walleye Sander vitreus through predation or competition for prey. Our objectives were to determine whether (1) diet overlap and predation occurred between adult Walleyes and Largemouth Bass in four northern Wisconsin lakes and (2) the use of DNA barcoding to reduce unidentifiable fish in diet samples affected conclusions regarding diet overlap. A single occurrence of Walleye predation was observed in the diets of 945 Largemouth Bass. Moderate to high diet overlap was observed between Largemouth Bass and Walleyes throughout much of the study period. The use of DNA barcoding reduced the amount of unidentified fish in diets to <1% and showed that failure to identify fish or fish parts can affect conclusions regarding diet overlap. Largemouth Bass predation is probably not a primary factor affecting Walleye abundance in the lakes we selected, but observed diet overlap suggests the potential for competition between the two species.

Elementary School Children Contribute to Environmental Research as Citizen Scientists.

PubMed

Miczajka, Victoria L; Klein, Alexandra-Maria; Pufal, Gesine

2015-01-01

Research benefits increasingly from valuable contributions by citizen scientists. Mostly, participating adults investigate specific species, ecosystems or phenology to address conservation issues, but ecosystem functions supporting ecosystem health are rarely addressed and other demographic groups rarely involved. As part of a project investigating seed predation and dispersal as ecosystem functions along an urban-rural gradient, we tested whether elementary school children can contribute to the project as citizen scientists. Specifically, we compared data estimating vegetation cover, measuring vegetation height and counting seeds from a seed removal experiment, that were collected by children and scientists in schoolyards. Children counted seeds similarly to scientists but under- or overestimated vegetation cover and measured different heights. We conclude that children can be involved as citizen scientists in research projects according to their skill level. However, more sophisticated tasks require specific training to become familiarized with scientific experiments and the development of needed skills and methods.

Palila (Loxioides bailleui)

USGS Publications Warehouse

Banko, Paul C.; Johnson, Luanne; Lindsey, Gerald D.; Fancy, Steven G.; Pratt, Thane K.; Jacobi, James; Banko, Winston E.

2002-01-01

One of the last surviving of the extraordinary “finch-billed” Hawaiian honeycreepers (Drepanidinae), the Palila epitomizes specialization for seed-eating as it relies almost entirely on immature (soft) seeds, flowers, and other resources produced or supported by mämane (Sophora chrysophylla: Fabaceae), an endemic dry-forest tree. Mämane seeds are highly nutritious, but a strong, sharp bill is necessary to remove and rip open the tough, fibrous pods that protect them. In addition, the seeds contain high levels of potentially toxic secondary compounds, which may also explain why they are eaten by so few other native or alien species. The Palila's close association with mämane influences not only its foraging behavior but also its distribution, abundance, dispersal, and breeding ecology. Like most drepanidines, the Palila produces small clutches, usually only 2 eggs. However, Palila embryos and chicks develop slowly, so eggs and nestlings are threatened by storms and predators for a longer time than many other small passerine species.

Marginal predation: do encounter or confusion effects explain the targeting of prey group edges?

PubMed

Duffield, Callum; Ioannou, Christos C

2017-01-01

Marginal predation, also known as the edge effect, occurs when aggregations of prey are preferentially targeted on their periphery by predators and has long been established in many taxa. Two main processes have been used to explain this phenomenon, the confusion effect and the encounter rate between predators and prey group edges. However, it is unknown at what size a prey group needs to be before marginal predation is detectable and to what extent each mechanism drives the effect. We conducted 2 experiments using groups of virtual prey being preyed upon by 3-spined sticklebacks ( Gasterosteus aculeatus ) to address these questions. In Experiment 1, we show that group sizes do not need to be large for marginal predation to occur, with this being detectable in groups of 16 or more. In Experiment 2, we find that encounter rate is a more likely explanation for marginal predation than the confusion effect in this system. We find that while confusion does affect predatory behaviors (whether or not predators make an attack), it does not affect marginal predation. Our results suggest that marginal predation is a more common phenomenon than originally thought as it also applies to relatively small groups. Similarly, as marginal predation does not need the confusion effect to occur, it may occur in a wider range of predator-prey species pairings, for example those where the predators search for prey using nonvisual sensory modalities.

Rodents balancing a variety of risks: invasive fire ants and indirect and direct indicators of predation risk.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orrock, John, L.; Danielson, Brent, J.

2004-06-08

Oecologia (2004) 140: 662 - 667 We used foraging trays to compare how old field mice, Peromyscus polionotus, altered foraging in response to the presence of fire ants, Solenopsisinvicta, and in the presence of direct (predator urine) and indirect (sheltered or exposed micro habitat, moonlight, and precipitation) indicators of predation risk. Foraging reductions elicited by S. invicta were greater than reductions in response to well-documented indicators of risk (i.e., moonlit nights) and the presence of predator urine. The presence of S. invicta always led to reduced foraging, but the overall impact of S. invicta was dependent upon microhabitat and precipitation.more » When S. invicta was not present, foraging was greater in sheltered microhabitats compared to exposed microhabitats. S. invicta made sheltered microhabitats equivalent to more risky exposed microhabitats, and this effect was especially pronounced on nights without precipitation. The effect of S. invicta suggests that interactions with S. invicta may entail a potentially heavy cost or that presence of S. invicta may represent a more reliable indicator of imminent competition or predation compared to indirect cues of risk and predator urine. The presence of S. invicta led to reduced foraging under situations when foraging activity would otherwise be greatest (i.e., under vegetative cover), potentially reducing habitat quality for P. polionotus and the distribution of seeds consumed by rodents.« less

Forest type affects predation on gypsy moth pupae

Treesearch

A.M. Liebhold; K.F. Raffa; A.L. Diss; A.L. Diss

2005-01-01

Predation by small mammals has previously been shown to be the largest source of mortality in low-density gypsy moth, Lymantria dispar (L.), populations in established populations in north-eastern North America. Fluctuations in predation levels are critical in determining changes in population densities. We compared small mammal communities and levels of predation on...

Context dependence of acorn handling by the Algerian mouse (Mus spretus)

NASA Astrophysics Data System (ADS)

Gallego, D.; Morán-López, T.; Torre, I.; Navarro-Castilla, Á.; Barja, I.; Díaz, M.

2017-10-01

Perceived predation risk and competition for acorns are expected to affect scatter-hoarding decisions by Algerian mice (Mus spretus). We manipulated both factors by means of predator fecal scents and ungulate exclosures. We hypothesized that high-risk perception and ungulate presence would promote acorn dispersal. In the former case, it would stimulate acorn mobilization to safe microhabitats rather than in situ consumption. In the latter, increased competition for acorns would promote their storage for later consumption. We also expected that mice would adapt their foraging behavior to previous experience modulating the strength of these effects. In the presence of ungulates, mice focused their foraging activities on food acquisition at the expenses of vigilant behaviors. However, a more efficient foraging did not entail enhanced dispersal services. Lack of anti-predatory cover in tree surroundings may have deterred mice from transporting seeds outside canopies. Increased risk interacted with previous experience. In control trees (no predator odor), mice confidence increased throughout the night resulting in decreased vigilance and enhanced acorn mobilization rates. In contrast, in risky conditions (trees with predator odor) mice maintained a base-line vigilant behavior. Contrary to our expectations, increased risk did not result in higher acorn mobilization, but the opposite. Again, the scarcity of safe microhabitats for mobilization may have been the underlying cause of this behavior. Our results show that successful acorn dispersal depends, at least partly, on plant-animal relationships that are beyond the oak-rodent mutualism. Thus, any conservation policy aimed at restoring natural regeneration of oaks should take into account the interaction network in which oak-rodent encounters are embedded. In addition, they suggest that mice incorporate direct and indirect cues of risks (habitat structure) through recent experience. A better understanding of this process will improve our ability to incorporate such temporal and spatial variability in models of acorn dispersal.

Granivory of invasive, naturalized, and native plants in communities differentially susceptible to invasion

Treesearch

B. M. Connolly; D. E. Pearson; R. N. Mack

2014-01-01

Seed predation is an important biotic filter that can influence abundance and spatial distributions of native species through differential effects on recruitment. This filter may also influence the relative abundance of nonnative plants within habitats and the communities' susceptibility to invasion via differences in granivore identity, abundance, and food...

Oak mast production and animal impacts on acorn survival in the central hardwoods

Treesearch

Kenneth F. Kellner; Jeffery K. Riegel; Nathanael I. Lichti; Robert K. Swihart

2013-01-01

As part of the Hardwood Ecosystem Experiment we measured mast production in white (Quercus alba) and black (Q. velutina) oak, and quantified the impacts of seed predators on acorn survival over a 3-year period. Specifically, we measured the proportion of acorns of each species infested with weevils (Curculio spp...

Consumers limit the abundance and dynamics of a perennial shrub with a seed bank

USGS Publications Warehouse

Kauffman, M.J.; Maron, J.L.

2006-01-01

For nearly 30 years, ecologists have argued that predators of seeds and seedlings seldom have population-level effects on plants with persistent seed banks and density-dependent seedling survival. We parameterized stage-based population models that incorporated density dependence and seed dormancy with data from a 5.5-year experiment that quantified how granivorous mice and herbivorous voles influence bush lupine (Lupinus arboreus) demography. We asked how seed dormancy and density-dependent seedling survival mediate the impacts of these consumers in dune and grassland habitats. In dune habitat, mice reduced analytical ?? (the intrinsic rate of population growth) by 39%, the equilibrium number of above-ground plants by 90%, and the seed bank by 98%; voles had minimal effects. In adjacent grasslands, mice had minimal effects, but seedling herbivory by voles reduced analytical ?? by 15% and reduced both the equilibrium number of aboveground plants and dormant seeds by 63%. A bootstrap analysis demonstrated that these consumer effects were robust to parameter uncertainty. Our results demonstrate that the quantitative strengths of seed dormancy and density-dependent seedling survival-not their mere existence-critically mediate consumer effects. This study suggests that plant population dynamics and distribution may be more strongly influenced by consumers of seeds and seedlings than is currently recognized. ?? 2006 by The University of Chicago.

Skylarks trade size and energy content in weed seeds to maximize total ingested lipid biomass.

PubMed

Gaba, Sabrina; Collas, Claire; Powolny, Thibaut; Bretagnolle, François; Bretagnolle, Vincent

2014-10-01

The trade-off between forage quality and quantity has been particularly studied in herbivore organisms, but much less for seed eating animals, in particular seed-eating birds which constitute the bulk of wintering passerines in European farmlands. The skylark is one of the commonest farmland birds in winter, mainly feeding on seeds. We focus on weed seeds for conservation and management purposes. Weed seeds form the bulk of the diet of skylarks during winter period, and although this is still a matter for discussion, weed seed predation by granivorous has been suggested as an alternative to herbicides used to regulate weed populations in arable crops. Our objectives were to identify whether weed seed traits govern foraging decisions of skylarks, and to characterize key seed traits with respect to size, which is related to searching and handling time, and lipid content, which is essential for migratory birds. We combined a single-offer experiment and a multiple-offer one to test for feeding preferences of the birds by estimating seed intake on weed seed species differing in their seed size and seed lipid content. Our results showed (1) a selective preference for smaller seeds above a threshold of seed size or seed size difference in the pair and, (2) a significant effect of seed lipid biomass suggesting a trade-off between foraging for smaller seeds and selecting seeds rich in lipids. Skylarks foraging decision thus seems to be mainly based on seed size, that is presumably a 'proxy' for weed seed energy content. However, there are clearly many possible combinations of morphological and physiological traits that must play crucial role in the plant-bird interaction such as toxic compound or seed coat. Copyright © 2014 Elsevier B.V. All rights reserved.

Hunting-mediated predator facilitation and superadditive mortality in a European ungulate.

PubMed

Gehr, Benedikt; Hofer, Elizabeth J; Pewsner, Mirjam; Ryser, Andreas; Vimercati, Eric; Vogt, Kristina; Keller, Lukas F

2018-01-01

Predator-prey theory predicts that in the presence of multiple types of predators using a common prey, predator facilitation may result as a consequence of contrasting prey defense mechanisms, where reducing the risk from one predator increases the risk from the other. While predator facilitation is well established in natural predator-prey systems, little attention has been paid to situations where human hunters compete with natural predators for the same prey. Here, we investigate hunting-mediated predator facilitation in a hunter-predator-prey system. We found that hunter avoidance by roe deer ( Capreolus capreolus ) exposed them to increase predation risk by Eurasian lynx ( Lynx lynx ). Lynx responded by increasing their activity and predation on deer, providing evidence that superadditive hunting mortality may be occurring through predator facilitation. Our results reveal a new pathway through which human hunters, in their role as top predators, may affect species interactions at lower trophic levels and thus drive ecosystem processes.

Ocean acidification affects prey detection by a predatory reef fish.

PubMed

Cripps, Ingrid L; Munday, Philip L; McCormick, Mark I

2011-01-01

Changes in olfactory-mediated behaviour caused by elevated CO(2) levels in the ocean could affect recruitment to reef fish populations because larval fish become more vulnerable to predation. However, it is currently unclear how elevated CO(2) will impact the other key part of the predator-prey interaction--the predators. We investigated the effects of elevated CO(2) and reduced pH on olfactory preferences, activity levels and feeding behaviour of a common coral reef meso-predator, the brown dottyback (Pseudochromis fuscus). Predators were exposed to either current-day CO(2) levels or one of two elevated CO(2) levels (∼600 µatm or ∼950 µatm) that may occur by 2100 according to climate change predictions. Exposure to elevated CO(2) and reduced pH caused a shift from preference to avoidance of the smell of injured prey, with CO(2) treated predators spending approximately 20% less time in a water stream containing prey odour compared with controls. Furthermore, activity levels of fish was higher in the high CO(2) treatment and feeding activity was lower for fish in the mid CO(2) treatment; indicating that future conditions may potentially reduce the ability of the fish to respond rapidly to fluctuations in food availability. Elevated activity levels of predators in the high CO(2) treatment, however, may compensate for reduced olfactory ability, as greater movement facilitated visual detection of food. Our findings show that, at least for the species tested to date, both parties in the predator-prey relationship may be affected by ocean acidification. Although impairment of olfactory-mediated behaviour of predators might reduce the risk of predation for larval fishes, the magnitude of the observed effects of elevated CO(2) acidification appear to be more dramatic for prey compared to predators. Thus, it is unlikely that the altered behaviour of predators is sufficient to fully compensate for the effects of ocean acidification on prey mortality.

Predator evasion in zooplankton is suppressed by polyunsaturated fatty acid limitation.

PubMed

Brzeziński, Tomasz; von Elert, Eric

2015-11-01

Herbivorous zooplankton avoid size-selective predation by vertical migration to a deep, cold water refuge. Adaptation to low temperatures in planktonic poikilotherms depends on essential dietary lipids; the availability of these lipids often limits growth and reproduction of zooplankton. We hypothesized that limitation by essential lipids may affect habitat preferences and predator avoidance behavior in planktonic poikilotherms. We used a liposome supplementation technique to enrich the green alga Scenedesmus obliquus and the cyanobacterium Synecchococcus elongatus with the essential lipids, cholesterol and eicosapentaenoic acid (EPA), and an indoor system with a stratified water-column (plankton organ) to test whether the absence of these selected dietary lipids constrains predator avoidance (habitat preferences) in four species of the key-stone pelagic freshwater grazer Daphnia. We found that the capability of avoiding fish predation through habitat shift to the deeper and colder environment was suppressed in Daphnia unless the diet was supplemented with EPA; however, the availability of cholesterol did not affect habitat preferences of the tested taxa. Thus, their ability to access a predator-free refuge and the outcome of predator-prey interactions depends upon food quality (i.e. the availability of an essential fatty acid). Our results suggest that biochemical food quality limitation, a bottom-up factor, may affect the top-down control of herbivorous zooplankton.

Predator encounters have spatially extensive impacts on parental behaviour in a breeding bird community

PubMed Central

Moks, Kadri; Thomson, Robert L.; Calhim, Sara; Järvistö, Pauliina E.; Schuett, Wiebke; Velmala, William; Laaksonen, Toni

2016-01-01

Predation risk has negative indirect effects on prey fitness, partly mediated through changes in behaviour. Evidence that individuals gather social information from other members of the population suggests that events in a community may impact the behaviour of distant individuals. However, spatially wide-ranging impacts on individual behaviour caused by a predator encounter elsewhere in a community have not been documented before. We investigated the effect of a predator encounter (hawk model presented at a focal nest) on the parental behaviour of pied flycatchers (Ficedula hypoleuca), both at the focal nest and at nearby nests different distances from the predator encounter. We show that nest visitation of both focal pairs and nearby pairs were affected, up to 3 h and 1 h, respectively. Parents also appeared to compensate initial disrupted feeding by later increasing nest visitation rates. This is the first evidence showing that the behaviour of nearby pairs was affected away from an immediate source of risk. Our results indicate that the impacts of short-term predator encounters may immediately extend spatially to the broader community, affecting the behaviour of distant individuals. Information about predators is probably quickly spread by cues such as intra- and heterospecific alarm calls, in communities of different taxa. PMID:27030411

Predator identity more than predator richness structures aquatic microbial assemblages in Sarracenia purpurea leaves.

PubMed

Canter, Erin J; Cuellar-Gempeler, Catalina; Pastore, Abigail I; Miller, Thomas E; Mason, Olivia U

2018-03-01

The importance of predators in influencing community structure is a well-studied area of ecology. However, few studies test ecological hypotheses of predation in multi-predator microbial communities. The phytotelmic community found within the water-filled leaves of the pitcher plant, Sarracenia purpurea, exhibits a simple trophic structure that includes multiple protozoan predators and microbial prey. Using this system, we sought to determine whether different predators target distinct microorganisms, how interactions among protozoans affect resource (microorganism) use, and how predator diversity affects prey community diversity. In particular, we endeavored to determine if protozoa followed known ecological patterns such as keystone predation or generalist predation. For these experiments, replicate inquiline microbial communities were maintained for seven days with five protozoan species. Microbial community structure was determined by 16S rRNA gene amplicon sequencing (iTag) and analysis. Compared to the control (no protozoa), two ciliates followed patterns of keystone predation by increasing microbial evenness. In pairwise competition treatments with a generalist flagellate, prey communities resembled the microbial communities of the respective keystone predator in monoculture. The relative abundance of the most common bacterial Operational Taxonomic Unit (OTU) in our system decreased compared to the control in the presence of these ciliates. This OTU was 98% similar to a known chitin degrader and nitrate reducer, important functions for the microbial community and the plant host. Collectively, the data demonstrated that predator identity had a greater effect on prey diversity and composition than overall predator diversity. © 2018 by the Ecological Society of America.

A role for fruit structure in seed survival and germination of Swartzia langsdorffii Raddi beyond dispersal.

PubMed

Vaz, T A A; Rodrigues-Junior, A G; Davide, A C; Nakamura, A T; Toorop, P E

2018-03-01

Diaspore structure has been hypothesised to play a role in seed viability and/or germination of recalcitrant seeds, especially for Swartzia langsdorffii. Thus, this work aims to (i) investigate the in situ contribution of pericarp and aril on seed viability and germination, and (ii) identify morphoanatomical traits of S. langsdorffii diaspores that allow its desiccation-sensitive seeds to remain viable. The role of the pericarp and aril in seed survival and germination was investigated by placing the whole fruit, whole seeds (arillate seed) and bare seeds (without aril) in soil in the forest understorey, assessing germination, emergence, dead, firm and predated seeds, and water content of pericarps, arils and seeds. Correlation analysis was performed between environmental variables and physiological parameters. Histochemical features of diaspores were also investigated. Pericarp water content fell after several months, while the aril maintained its water content. Seeds did not lose water even without the presence of the pericarp and aril. However, presence of the pericarp promoted seed water content, viability and germination long after dispersal. The embryo had a thickened outer periclinal cell wall. Pericarp and aril are not essential to prevent water loss in seeds, but do help to retain seed moisture, favouring viability maintenance and promoting germination during the rainy season. Morphoanatomical features of seeds are suggested as main factors that reduce water loss. Survival of these desiccation-sensitive seeds upon dispersal during the dry season appears to be facilitated by multiple diaspore features that prevent viability loss. © 2017 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.

Prey dispersal rate affects prey species composition and trait diversity in response to multiple predators in metacommunities.

PubMed

Howeth, Jennifer G; Leibold, Mathew A

2010-09-01

1. Recent studies indicate that large-scale spatial processes can alter local community structuring mechanisms to determine local and regional assemblages of predators and their prey. In metacommunities, this may occur when the functional diversity represented in the regional predator species pool interacts with the rate of prey dispersal among local communities to affect prey species diversity and trait composition at multiple scales. 2. Here, we test for effects of prey dispersal rate and spatially and temporally heterogeneous predation from functionally dissimilar predators on prey structure in pond mesocosm metacommunities. An experimental metacommunity consisted of three pond mesocosm communities supporting two differentially size-selective invertebrate predators and their zooplankton prey. In each metacommunity, two communities maintained constant predation and supported either Gyrinus sp. (Coleoptera) or Notonecta ungulata (Hemiptera) predators generating a spatial prey refuge while the third community supported alternating predation from Gyrinus sp. and N. ungulata generating a temporal prey refuge. Mesocosm metacommunities were connected at either low (0.7% day(-1)) or high (10% day(-1)) planktonic prey dispersal. The diversity, composition and body size of zooplankton prey were measured at local and regional (metacommunity) scales. 3. Metacommunities experiencing the low prey dispersal rate supported the greatest regional prey species diversity (H') and evenness (J'). Neither dispersal rate nor predation regime affected local prey diversity or evenness. The spatial prey refuge at low dispersal maintained the largest difference in species composition and body size diversity between communities under Gyrinus and Notonecta predation, suggesting that species sorting was operating at the low dispersal rate. There was no effect of dispersal rate on species diversity or body size distribution in the temporal prey refuge. 4. The frequency distribution, but not the range, of prey body sizes within communities depended upon prey dispersal rate and predator identity. Taken together, these results demonstrate that prey dispersal rate can moderate the strength of predation to influence prey species diversity and the local frequency distribution of prey traits in metacommunities supporting ecologically different predators.

Fasting or fear: disentangling the roles of predation risk and food deprivation in the nitrogen metabolism of consumers.

PubMed

Dalton, Christopher M; Tracy, Karen E; Hairston, Nelson G; Flecker, Alexander S

2018-03-01

Predators can alter nutrient cycles simply by inducing stress in prey. This stress accelerates prey's protein catabolism, nitrogen waste production, and nitrogen cycling. Yet predators also reduce the feeding rates of their prey, inducing food deprivation that is expected to slow protein catabolism and nitrogen cycling. The physiology of prey under predation risk thus balances the influences of predation risk and food deprivation, and this balance is central to understanding the role of predators in nutrient cycles. We explored the separate and combined effects of predation risk and food deprivation on prey physiology and nutrient cycling by exposing guppies (Poecilia reticulata) to predation risk and food deprivation in a 2 × 2 design. We simulated predation risk using chemical cues from a natural predator of guppies, and we created food deprivation by rationing food availability. We measured guppy response as food consumption, growth, tissue energy density, tissue carbon:nitrogen, and nitrogen (N) excretion and assimilation. We found that N-linked physiological processes (N consumption, assimilation, excretion) were strongly affected by predation risk, independent of food consumption. Guppies excreted substantially less under predation risk than they did under food deprivation or control conditions. These results suggest that predation risk, per se, triggers physiological changes in guppies that increase N retention and decrease N excretion. We suggest that slower N metabolism under predation risk is an adaptive response that minimizes protein loss in the face of predictable, predator-induced food restriction. Notably, N metabolism shares common hormonal control with food seeking behavior, and we speculate that increased N retention is a direct and immediate result of reduced food seeking under predation risk. Contrary to predation-stress-based hypotheses for how predators affect nutrient cycling by prey, our result indicates that even short-term exposure to predators may decelerate, rather than accelerate, the speed of N cycling by suppressing N turnover by prey. © 2018 by the Ecological Society of America.

Prey risk allocation in a grazing ecosystem.

PubMed

Gude, Justin A; Garrott, Robert A; Borkowski, John J; King, Fred

2006-02-01

Understanding the behaviorally mediated indirect effects of predators in ecosystems requires knowledge of predator-prey behavioral interactions. In predator-ungulate-plant systems, empirical research quantifying how predators affect ungulate group sizes and distribution, in the context of other influential variables, is particularly needed. The risk allocation hypothesis proposes that prey behavioral responses to predation risk depend on background frequencies of exposure to risk, and it can be used to make predictions about predator-ungulate-plant interactions. We determined non-predation variables that affect elk (Cervus elaphus) group sizes and distribution on a winter range in the Greater Yellowstone Ecosystem (GYE) using logistic and log-linear regression on surveys of 513 1-km2 areas conducted over two years. Employing model selection techniques, we evaluated risk allocation and other a priori hypotheses of elk group size and distributional responses to wolf (Canis lupus) predation risk while accounting for influential non-wolf-predation variables. We found little evidence that wolves affect elk group sizes, which were strongly influenced by habitat type and hunting by humans. Following predictions from the risk allocation hypothesis, wolves likely created a more dynamic elk distribution in areas that they frequently hunted, as elk tended to move following wolf encounters in those areas. This response should dilute elk foraging pressure on plant communities in areas where they are frequently hunted by wolves. We predict that this should decrease the spatial heterogeneity of elk impacts on grasslands in areas that wolves frequently hunt. We also predict that this should decrease browsing pressure on heavily browsed woody plant stands in certain areas, which is supported by recent research in the GYE.

Moonlight avoidance in gerbils reveals a sophisticated interplay among time allocation, vigilance and state-dependent foraging.

PubMed

Kotler, Burt P; Brown, Joel; Mukherjee, Shomen; Berger-Tal, Oded; Bouskila, Amos

2010-05-22

Foraging animals have several tools for managing the risk of predation, and the foraging games between them and their predators. Among these, time allocation is foremost, followed by vigilance and apprehension. Together, their use influences a forager's time allocation and giving-up density (GUD) in depletable resource patches. We examined Allenby's gerbils (Gerbilus andersoni allenbyi) exploiting seed resource patches in a large vivarium under varying moon phases in the presence of a red fox (Vulpes vulpes). We measured time allocated to foraging patches electronically and GUDs from seeds left behind in resource patches. From these, we estimated handling times, attack rates and quitting harvest rates (QHRs). Gerbils displayed greater vigilance (lower attack rates) at brighter moon phases (full < wane < wax < new). Similarly, they displayed higher GUDs at brighter moon phases (wax > full > new > wane). Finally, gerbils displayed higher QHRs at new and waxing moon phases. Differences across moon phases not only reflect changing time allocation and vigilance, but changes in the state of the foragers and their marginal value of energy. Early in the lunar cycle, gerbils rely on vigilance and sacrifice state to avoid risk; later they defend state at the cost of increased time allocation; finally their state can recover as safe opportunities expand. In the predator-prey foraging game, foxes may contribute to these patterns of behaviours by modulating their own activity in response to the opportunities presented in each moon phase.

Demographic parameters of the insecticide-exposed predator Podisus nigrispinus: implications for IPM

USDA-ARS?s Scientific Manuscript database

The predator Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) shows potential for Integrated Pest Management programs of defoliating caterpillars in agricultural and forestry systems. Insecticides can indirectly affect caterpillar predators through consumption of contaminated prey. We examin...

Structural analysis of a type 1 ribosome inactivating protein reveals multiple L-asparagine-N-acetyl-D-glucosamine monosaccharide modifications: Implications for cytotoxicity

PubMed Central

HOGG, TANIS; MENDEL, JAMESON T.; LAVEZO, JONATHAN L.

2015-01-01

Pokeweed antiviral protein (PAP) belongs to the family of type I ribosome-inactivating proteins (RIPs): Ribotoxins, which function by depurinating the sarcin-ricin loop of ribosomal RNA. In addition to its antibacterial and antifungal properties, PAP has shown promise in antiviral and targeted tumor therapy owing to its ability to depurinate viral RNA and eukaryotic rRNA. Several PAP genes are differentially expressed across pokeweed tissues, with natively isolated seed forms of PAP exhibiting the greatest cytotoxicity. To help elucidate the molecular basis of increased cytotoxicity of PAP isoenzymes from seeds, the present study used protein sequencing, mass spectroscopy and X-ray crystallography to determine the complete covalent structure and 1.7 Å X-ray crystal structure of PAP-S1aci isolated from seeds of Asian pokeweed (Phytolacca acinosa). PAP-S1aci shares ~95% sequence identity with PAP-S1 from P. americana and contains the signature catalytic residues of the RIP superfamily, corresponding to Tyr72, Tyr122, Glu175 and Arg178 in PAP-S1aci. A rare proline substitution (Pro174) was identified in the active site of PAP-S1aci, which has no effect on catalytic Glu175 positioning or overall active-site topology, yet appears to come at the expense of strained main-chain geometry at the pre-proline residue Val173. Notably, a rare type of N-glycosylation was detected consisting of N-acetyl-D-glucosamine monosaccharide residues linked to Asn10, Asn44 and Asn255 of PAP-S1aci. Of note, our modeling studies suggested that the ribosome depurination activity of seed PAPs would be adversely affected by the N-glycosylation of Asn44 and Asn255 with larger and more typical oligosaccharide chains, as they would shield the rRNA-binding sites on the protein. These results, coupled with evidence gathered from the literature, suggest that this type of minimal N-glycosylation in seed PAPs and other type I seed RIPs may serve to enhance cytotoxicity by exploiting receptor-mediated uptake pathways of seed predators while preserving ribosome affinity and rRNA recognition. PMID:26238506

Effects of osmotic stress on predation behaviour of Asterias rubens L.

NASA Astrophysics Data System (ADS)

Agüera, Antonio; Schellekens, Tim; Jansen, Jeroen M.; Smaal, Aad C.

2015-05-01

Environmental stress plays an important role in determining ecosystem functioning and structure. In estuarine areas both tidal and seasonal salinity changes may cause osmotic stress on predators, affecting their behaviour and survival. The interaction between these predators and their prey may affect performance, thus influencing predator impact on prey populations. The common starfish, Asterias rubens, inhabits estuarine areas, such as the Dutch Wadden Sea, that exhibit large seasonal variation in salinity (10-32 PSU). In those areas A. rubens exerts top down control on its prey, thus representing an important shellfish predator. This predation may impact on cultured and natural shellfish populations. However, the effects of osmotic stress on A. rubens performance may influence its effect on prey. Although the effect of salinity in A. rubens survival has been extensively studied, the impact on its predation behaviour and acclimation capacity remains unclear. In this study, we analyse the performance of A. rubens preying on mussels (Mytilus edulis) after a salinity decrease and monitor its acclimation capacity over a period of 22 days. Our experiments demonstrated that salinity affected performance by reducing feeding activity and altering size prey selection. Moreover, as acclimation occurred, A. rubens predation performance improved in all sub-lethal treatments. We conclude that osmotic stress caused by decreasing salinity potentially influences A. rubens distribution, abundance, and potential impact on prey populations. However the magnitude of the change in salinity (from 31 to a minimum of 10 PSU) and its timescale (3 weeks) mediate this effect.

The population ecology of two tropical trees, Brachychiton diversifolius (Malvaceae) and Bombax ceiba (Bombaceae), harvested by Indigenous woodcarvers in Arnhem Land, Australia.

PubMed

Koenig, Jennifer; Griffiths, Anthony

2012-10-01

We describe the population ecology of two tropical deciduous trees, Bombax ceiba leiocarpum A. Robyns and Brachychiton diversifolius R. Br., which are in high demand for Indigenous sculpture production in Arnhem Land, Australia. We monitored tagged populations of both species at two locations for 2 years to examine their reproduction, growth, and survival rates and their response to harvest. Both species have similar life histories: they reproduce during the dry season (June-November) producing a high seed load, seed predation was high, seeds did not survive in the soil past the following wet season to form a seed bank, and germination rates were low and variable for both species. Average annual circumference growth rates were 1.07 cm year(-1) for B. ceiba and 0.98 cm year(-1) for B. diversifolius, with most of the growth occurring during the early wet season. Most (65-88 %) of the harvested B. ceiba and B. diversifolius stems coppiced. Coppice and stem size class were the main factors influencing tree growth rates with coppice stems growing up to six times faster than similar sized non-coppice stems. The survival of B. ceiba and B. diversifolius stems was size class dependent and affected by local site factors (e.g. fire and other disturbances) so that the smaller size classes had a low probability of survival. Given the resprouting potential of both species, their wild harvest is likely to have only minimal local impact on wild populations. However, further population modelling is required to determine whether the small and disjunct B. ceiba populations can sustain harvesting at current levels.

Diplochory in western chokecherry: you can't judge a fruit by its mesocarp.

PubMed

Beck, Maurie J; Vander Wall, Stephen B

2011-01-01

Western chokecherry (Prunus virginiana var. demissa, Rosaceae) is dispersed by frugivorous birds and carnivores, but it has large seeds that are potentially attractive to rodents that could act as seed predators and dispersers. Here, we quantify the benefits of primary dispersal by birds and secondary dispersal by scatter-hoarding rodents. In the fall, avian frugivores (mostly American robins, Turdus migratorius, and cedar waxwings, Bombycilla cedrorum) consumed 87% of the fruit crop and dispersed 67% of the fruit crop away from parent plants. Rodents removed 89% of seeds that simulated bird-dispersed seed rain from transects in riparian zones and 58% from transects in upland habitats. Rodents scatter-hoarded 91.6% of the seeds they removed, burying most in small caches (two to eight seeds) 8-25 mm deep. About 39% of the seeds in spring caches produced seedlings. Inside rodent-proof exclosures, 52.1% of seeds buried to simulate rodent caches produced seedlings, 29.7% of which were still alive after 1 year. In contrast, only 3.8% of seeds placed on the soil surface, simulating dispersal by avian frugivores, produced seedlings. Seed dispersal by frugivorous birds likely contributes to colonization of unoccupied habitat through long-range dispersal and to escape from distance-dependent seed mortality near the parent plant. Despite seed losses, rodents offer short-range seed dispersal and bury seeds in more favorable sites for germination, improving seedling emergence and establishment. The combined mechanisms of seed dispersal significantly enhanced chokecherry seedling recruitment by providing more dispersal-related benefits than either frugivorous bird or scatter-hoarding rodents could provide alone.

Reliable Method for Assessing Seed Germination, Dormancy, and Mortality under Field Conditions.

PubMed

Pace, Brian A; Alexander, Helen M; Emry, D Jason; Mercer, Kristin L

2016-11-06

We describe techniques for approximating seed bank dynamics over time using Helianthus annuus as an example study species. Strips of permeable polyester fabric and glue can be folded and glued to construct a strip of compartments that house seeds and identifying information, while allowing contact with soil leachate, water, microorganisms, and ambient temperature. Strips may be constructed with a wide range of compartment numbers and sizes and allow the researcher to house a variety of genotypes within a single species, different species, or seeds that have experienced different treatments. As opposed to individual seed packets, strips are more easily retrieved as a unit. While replicate packets can be included within a strip, different strips can act as blocks or can be retrieved at different times for observation of seed behavior over time. We used a high temperature glue gun to delineate compartments and sealed the strips once the seed and tags identifying block and removal times were inserted. The seed strips were then buried in the field at the desired depth, with the location marked for later removal. Burrowing animal predators were effectively excluded by use of a covering of metal mesh hardware cloth on the soil surface. After the selected time interval for burial, strips were dug up and seeds were assessed for germination, dormancy and mortality. While clearly dead seeds can often be distinguished from ungerminated living ones by eye, dormant seeds were conclusively identified using a standard Tetrazolium chloride colorimetric test for seed viability.

Biting mechanics and niche separation in a specialized clade of primate seed predators

PubMed Central

Luk, Theodora H. Y.; Perry, Jonathan M. G.; Neaux, Dimitri; Wroe, Stephen

2018-01-01

We analyzed feeding biomechanics in pitheciine monkeys (Pithecia, Chiropotes, Cacajao), a clade that specializes on hard-husked unripe fruit (sclerocarpy) and resistant seeds (seed predation). We tested the hypothesis that pitheciine crania are well-suited to generate and withstand forceful canine and molar biting, with the prediction that they generate bite forces more efficiently and better resist masticatory strains than the closely-related Callicebus, which does not specialize on unripe fruits and/or seeds. We also tested the hypothesis that Callicebus-Pithecia-Chiropotes-Cacajao represent a morphocline of increasing sclerocarpic specialization with respect to biting leverage and craniofacial strength, consistent with anterior dental morphology. We found that pitheciines have higher biting leverage than Callicebus and are generally more resistant to masticatory strain. However, Cacajao was found to experience high strain magnitudes in some facial regions. We therefore found limited support for the morphocline hypothesis, at least with respect to the mechanical performance metrics examined here. Biting leverage in Cacajao was nearly identical (or slightly less than) in Chiropotes and strain magnitudes during canine biting were more likely to follow a Cacajao-Chiropotes-Pithecia trend of increasing strength, in contrast to the proposed morphocline. These results could indicate that bite force efficiency and derived anterior teeth were selected for in pitheciines at the expense of increased strain magnitudes. However, our results for Cacajao potentially reflect reduced feeding competition offered by allopatry with other pitheciines, which allows Cacajao species to choose from a wider variety of fruits at various stages of ripeness, leading to reduction in the selection for robust facial features. We also found that feeding biomechanics in sympatric Pithecia and Chiropotes are consistent with data on food structural properties and observations of dietary niche separation, with the former being well-suited for the regular molar crushing of hard seeds and the latter better adapted for breaching hard fruits. PMID:29324822

Use of artificial nests to investigate predation on freshwater turtle nests

Treesearch

Michael N. Marchand; John A. Litvaitis; Thomas J. Maier; Richard M. DeGraaf

2002-01-01

Habitat fragmentation has raised concerns that populations of generalist predators have increased and are affecting a diverse group of prey. Previous research has included the use of artificial nests to investigate the role of predation on birds that nest on or near the ground. Because predation also is a major factor limiting populations of freshwater turtles, we...

Effect of downed woody debris on small mammal anti-predator behavior

Treesearch

Travis M. Hinkelman; John L. Orrock; Susan C Loeb

2011-01-01

Anti-Predator behavior can affect prey growth, reproduction, survival, and generate emergent effects in food webs. Small mammals often lower the cost of predation by altering their behavior in response to shrubs, but the importance of other microhabitat features, such as downed woody debris, for anti-predator behavior is unknown. We used giving-up densities to quantify...

Interspecies conflict affects RNA expression.

PubMed

Whitworth, David E

2018-05-01

Predation is an extreme form of competition between bacteria, involving the secretion of antimicrobial substances by predators, often packaged within outer membrane vesicles (OMVs). Recent studies into the Myxococcus xanthus/Escherichia coli predator/prey relationship have illuminated transcriptional changes during predation, identifying likely targets of predatory attack in the prey and nutrient assimilation strategies of the predator. Abundant non-coding RNAs can be observed in the predator and prey transcriptomes, with evidence of predation-dependent regulation of RNA levels. Given the observed secretion of regulatory RNAs within OMVs by bacteria, it will next be exciting to test whether the intercellular trafficking of regulatory RNAs is employed by predator and/or prey in their survival struggles.

Juvenile exposure to predator cues induces a larger egg size in fish

PubMed Central

Segers, Francisca H. I. D.; Taborsky, Barbara

2012-01-01

When females anticipate a hazardous environment for their offspring, they can increase offspring survival by producing larger young. Early environmental experience determines egg size in different animal taxa. We predicted that a higher perceived predation risk by juveniles would cause an increase in the sizes of eggs that they produce as adults. To test this, we exposed juveniles of the mouthbrooding cichlid Eretmodus cyanostictus in a split-brood experiment either to cues of a natural predator or to a control situation. After maturation, females that had been confronted with predators produced heavier eggs, whereas clutch size itself was not affected by the treatment. This effect cannot be explained by a differential female body size because the predator treatment did not influence growth trajectories. The observed increase of egg mass is likely to be adaptive, as heavier eggs gave rise to larger young and in fish, juvenile predation risk drops sharply with increasing body size. This study provides the first evidence that predator cues perceived by females early in life positively affect egg mass, suggesting that these cues allow her to predict the predation risk for her offspring. PMID:21976689

Corridors and olfactory predator cues affect small mammal behavior.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brinkerhoff, Robert Jory; Haddad, Nick M.; Orrock, John L.

2005-03-30

Abstract The behavior of prey individuals is influenced by a variety of factors including, but not limited to, habitat configuration, risk of predation, and availability of resources, and these habitat-dependent factors may have interactive effects. We studied the responses of mice to an increase in perceived predation risk in a patchy environment to understand how habitat corridors might affect interactions among species in a fragmented landscape. We used a replicated experiment to investigate corridor-mediated prey responses to predator cues in a network of open habitat patches surrounded by a matrix of planted pine forest. Some of the patches were connectedmore » by corridors. We used mark–recapture techniques and foraging trays to monitor the movement, behavior, and abundance of small mammals. Predation threat was manipulated in one-half of the replicates by applying an olfactory predator cue. Corridors synchronized small mammal foraging activity among connected patches. Foraging also was inhibited in the presence of an olfactory predator cue but apparently increased in adjacent connected patches. Small mammal abundance did not change as a result of the predator manipulation and was not influenced by the presence of corridors. This study is among the 1st to indicate combined effects of landscape configuration and predation risk on prey behavior. These changes in prey behavior may, in turn, have cascading effects on community dynamics where corridors and differential predation risk influence movement and patch use.« less

Are local filters blind to provenance? Ant seed predation suppresses exotic plants more than natives

Treesearch

Dean E. Pearson; Nadia S. Icasatti; Jose L. Hierro; Benjamin J. Bird

2014-01-01

The question of whether species' origins influence invasion outcomes has been a point of substantial debate in invasion ecology. Theoretically, colonization outcomes can be predicted based on how species' traits interact with community filters, a process presumably blind to species' origins. Yet, exotic plant introductions commonly result in monospecific...

Ontogenetic and evolutionary effects of predation and competition on nine-spined stickleback (Pungitius pungitius) body size.

PubMed

Välimäki, Kaisa; Herczeg, Gábor

2012-07-01

1. Individual- and population-level variation in body size and growth often correlates with many fitness traits. Predation and food availability are expected to affect body size and growth as important agents of both natural selection and phenotypic plasticity. How differences in predation and food availability affect body size/growth during ontogeny in populations adapted to different predation and competition regimes is rarely studied. 2. Nine-spined stickleback (Pungitius pungitius) populations originating from habitats with varying levels of predation and competition are known to be locally adapted to their respective habitats in terms of body size and growth. Here, we studied how different levels of perceived predation risk and competition during ontogeny affect the reaction norms of body size and growth in (i) marine and pond populations adapted to different levels of predation and competition and (ii) different sexes. We reared nine-spined stickleback in a factorial experiment under two levels of perceived predation risk (present/absent) and competition (high/low food supply). 3. We found divergence in the reaction norms at two levels: (i) predation-adapted marine stickleback had stronger reactions to predatory cues than intraspecific competition-adapted pond stickleback, the latter being more sensitive to available food than the marine fish and (ii) females reacting more strongly to the treatments than males. 4. The repeated, habitat-dependent nature of the differences suggests that natural selection is the agent behind the observed patterns. Our results suggest that genetic adaptation to certain environmental factors also involves an increase in the range of expressible phenotypic plasticity. We found support for this phenomenon at two levels: (i) across populations driven by habitat type and (ii) within populations driven by sex. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.

Biogeographic and ecological regulation of disease: Prevalence of Sin Nombre virus in island mice is related to island area, precipitation, and predator richness

USGS Publications Warehouse

Orrock, John L.; Allan, Brian F.; Drost, Charles A.

2011-01-01

The relative roles of top-down and bottom-up forces in affecting disease prevalence in wild hosts is important for understanding disease dynamics and human disease risk. We found that the prevalence of Sin Nombre virus (SNV), the agent of a severe disease in humans (hantavirus pulmonary syndrome), in island deer mice from the eight California Channel Islands was greater with increased precipitation (a measure of productivity), greater island area, and fewer species of rodent predators. In finding a strong signal of the ecological forces affecting SNV prevalence, our work highlights the need for future work to understand the relative importance of average rodent density, population fluctuations, behavior, and specialist predators as they affect SNV prevalence. In addition to illustrating the importance of both bottom-up and top-down limitation of disease prevalence, our results suggest that predator richness may have important bearing on the risk of exposure to animal-borne diseases that affect humans.

Epichloë uncinata Infection and Loline Content Protect Festulolium Grasses From Crickets (Orthoptera: Gryllidae).

PubMed

Barker, Gary M; Patchett, Brian J; Cameron, Nicholas E

2015-04-01

Experiments with artificial diets demonstrated that black field cricket (Teleogryllus commodus (Walker)) and Lepidogryllus sp. were highly responsive to presence of lolines in their diet-quantities of diet consumed declined exponentially with increasing loline concentration. Amount consumed by black field cricket and Lepidogryllus sp. on diet containing 5,600 µg/g lolines was only 8 and 2% relative to those on loline-free diet, respectively. Additional experiments with Festulolium seeds demonstrated that both cricket species predated heavily on endophyte-free seed but largely avoided Epichloë uncinata-infected seed. By 12 h, black field cricket had destroyed 98.8% of endophyte-free but only 24.8% of E. uncinata-infected, loline-containing seed. By 36 h, Lepidogryllus sp. crickets had destroyed 40% of endophyte-free but had not fed on E. uncinata-infected, loline-containing seed. Glasshouse experiments demonstrated this aversion to lolines greatly reduces the damage potential of black field cricket in E. uncinata-infected Festulolium. When microswards were sown with E. uncinata-infected Festulolium, seedling numbers were reduced 25-26%, and yields 29-40%, by black field crickets relative to microswards sown without insect infestation. This contrasts with 70-78% reduction in seedling numbers and 67-80% reduction in yields in microswards sown to either endophyte-free Festulolium, endophyte-free perennial ryegrass, or Epichloë festucae var. lolii-infected Festulolium. Yields of mature E. uncinata-infected Festulolium plants were not adversely affected by black field crickets, irrespective of the presence of the endophyte-free standard Festulolium sown as a companion. In contrast, yields of endophyte-free Festulolium, endophyte-free perennial ryegrass, and E. festucae var. lolii-infected Festulolium plants were reduced by 56-61% by crickets. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Variation in predator foraging behavior changes predator-prey spatio-temporal dynamics

USDA-ARS?s Scientific Manuscript database

1. Foraging underlies the ability of all animals to acquire essential resources and, thus, provides a critical link to understanding population dynamics. A key issue is how variation in foraging behavior affects foraging efficiency and predator-prey interactions in spatially-heterogeneous environmen...

Effect of Culverts on Predator-Prey Interactions in a Tropical Stream.

NASA Astrophysics Data System (ADS)

Hein, C. L.; Kikkert, D. A.; Crowl, T. A.

2005-05-01

As part of a biocomplexity project in Puerto Rico, we use river and road networks as a platform to understand the interactions between stream biota, the physical environment, and human activity. Specifically, we ask if humans affect aquatic organisms through road building and recreational activities. Culverts have been documented to impede or slow migration of aquatic biota. This is especially important in these streams because all of the freshwater, stream species have diadramous life cycles. If culverts do act as bottlenecks to shrimp migrations, we expect altered predator-prey interactions downstream through density-dependent predation dynamics. In order to determine how roads may affect predation rates on upstream migrating shrimp, we parameterized functional response curves for mountain mullet (Agonostomus monticola) consuming shrimp (Xiphocaris sp.) using artificial mesocosm experiments. We then used data obtained from underwater videography to determine how culverts decrease the rate and number of shrimp moving upstream. These data were combined in a predator-prey model to quantify the effects of culverts on localized shrimp densities and fish predation.

Spatial profiling of maytansine during the germination process of Maytenus senegalensis seeds.

PubMed

Eckelmann, Dennis; Kusari, Souvik; Spiteller, Michael

2017-06-01

The ecological role of maytansine, an important antineoplastic and antimicrobial compound with high cytotoxicity, particularly as a chemical defense compound has remained elusive since its discovery in the 1970s in Maytenus and Putterlickia plants. In the present study, we have used MALDI-imaging-HRMS to visualize the occurrence as well as spatial and temporal distribution of maytansine in a Maytenus senegalensis plant, seeds obtained from the mother plant during seeding stage, through the germination of the seeds, and finally up to the establishment of seedlings (or daughter plants). Although the mother plant was devoid of maytansine, the bioactive compound was found to be distributed in the cotyledons and the endosperm of the seeds with an augmented accretion towards the seed coat. Furthermore, maytansine was always detected in the emerging seedlings, particularly the cortex encompassing the radicle, hypocotyl, and epicotyl. The typical pattern of accumulation of maytansine not only in the seeds but also during germination provides a proof-of-concept that M. senegalensis is ecologically primed to trigger the production of maytansine in vulnerable tissues such as seeds during plant reproduction. By utilizing maytansine as chemical defense compound against predators and/or pathogens, the plant can ensure viability of the seeds and successful germination, thus leading to the next generation of daughter plants. Copyright © 2017 Elsevier B.V. All rights reserved.

Merriam's turkey nest survival and factors affecting nest predation by mammals

Treesearch

Chad P. Lehman; Mark A. Rumble; Lester D. Flake; Daniel J. Thompson

2008-01-01

Nest success is an important parameter affecting population fluctuations of wild turkeys (Meleagris gallopavo). Factors influencing mammalian predation on turkey nests are complicated and not well understood. Therefore, we assessed nest hazard risk by testing competing hypotheses of Merriam's turkey (M. g. merriami) nest...

Predation and protection in the macroevolutionary history of conifer cones

PubMed Central

Leslie, Andrew B.

2011-01-01

Conifers are an excellent group in which to explore how changing ecological interactions may have influenced the allocation of reproductive tissues in seed plants over long time scales, because of their extensive fossil record and their important role in terrestrial ecosystems since the Palaeozoic. Measurements of individual conifer pollen-producing and seed-producing cones from the Pennsylvanian to the Recent show that the relative amount of tissue invested in pollen cones has remained constant through time, while seed cones show a sharp increase in proportional tissue investment in the Jurassic that has continued to intensify to the present day. Since seed size in conifers has remained similar through time, this increase reflects greater investment in protective cone tissues such as robust, tightly packed scales. This shift in morphology and tissue allocation is broadly concurrent with the appearance of new vertebrate groups capable of browsing in tree canopies, as well as a diversification of insect-feeding strategies, suggesting that an important change in plant–animal interactions occurred over the Mesozoic that favoured an increase in seed cone protective tissues. PMID:21345864

Implications of seed size for seedling survival in Carnegiea gigantea and Ferocactus wislizeni (Cactaceae)

USGS Publications Warehouse

Bowers, Janice E.; Pierson, E.A.

2001-01-01

Larger seeds have been shown to convey benefits for seedling survival but the mechanisms of this process are not well understood. In this study, seed size and seedling survival were compared for 2 sympatric cactus species, Carnegiea gigantea (Engelm.) Britt. & Rose and Ferocactus wislizeni (Engelm.) Britt. & Rose, in laboratory and field experiments in the northern Sonoran Desert. Both species have small seeds, but Ferocactus seeds are nearly twice as long and 3 times as heavy as those of Carnegiea. The difference in size is perpetuated after germination: new Ferocactus seedlings have 4 times the estimated volume of new Carnegiea seedlings. In an outdoor experiment, annual survivorship of both species was low but was 6 times higher for Ferocactus (6 seedlings, 8.1%) than Carnegiea (1 seedling, 1.4%). The pattern of seedling mortality in relation to temperature and rain suggests that, after the initial flush of seed and seedling predation, drought and heat took a greater toll on Carnegiea than Ferocactus seedlings, probably because the larger seedling volume of Ferocactus conferred greater drought tolerance. In addition, F. wislizeni could become established without benefit of nurse plants whereas C. gigantea could not; this might reflect differential tolerance to high soil temperatures.

Predator-prey interactions between Synbranchus marmoratus (Teleostei: Synbranchidae) and Hypsiboas pulchellus tadpoles (Amphibia: Hylidae): importance of lateral line in nocturnal predation and effects of fenitrothion exposure.

PubMed

Junges, Celina M; Lajmanovich, Rafael C; Peltzer, Paola M; Attademo, Andres M; Bassó, Agustín

2010-11-01

Environmental contaminants can disrupt interactions between aquatic species by altering community structure. We explored predator-prey interactions between marbled swamp juvenile eels (Synbranchus marmoratus; predator) and anuran tadpoles (Hypsiboas pulchellus; prey) in relation to two aspects: the importance of lateral line in the predator and whether the absence of light modifies predation rates; and the effect of a sub-lethal concentration of fenitrothion on both predator and prey. Eels were tested under two sensory conditions (lateral line intact and lateral line blocked by cobalt chloride) in dark conditions. Predation rates were evaluated using different treatments that combined predator and prey exposed or not to insecticide. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were also measured in muscle samples of eels and tadpoles to explore whether fenitrothion affects predator and prey differentially. Marbled swamp eels were more efficient in feeding on tadpoles during the night than during the day, showing that lateral line makes an important contribution to prey detection and capture. Regarding pesticide effects, short-term (6 h) exposure to an ecologically relevant fenitrothion dose of 2.5 mg L(-1) altered the predator-prey relationship by changing prey behaviour, reducing prey detection and therefore increasing tadpole survival. At this concentration, the outcome of the predator-prey relationship appears biased in favor of the exposed tadpoles, which were released from predation risk, despite their altered behaviour and the higher inhibition percentages of tail BChE (70%) and AChE (51%) than in control individuals. Our study involving these model species and agrochemicals demonstrates that fenitrothion affected the outcome of a predator-prey relationship. Further studies are needed, in these species and other native amphibians, to investigate the nature of the mechanisms responsible for the adverse effects of pesticides on antipredator behaviour and predation efficiency. Copyright © 2010 Elsevier Ltd. All rights reserved.

Tests of landscape influence: Nest predation and brood parasitism in fragmented ecosystems

USGS Publications Warehouse

Tewksbury, J.J.; Garner, L.; Garner, S.; Lloyd, J.D.; Saab, V.; Martin, T.E.

2006-01-01

The effects of landscape fragmentation on nest predation and brood parasitism, the two primary causes of avian reproductive failure, have been difficult to generalize across landscapes, yet few studies have clearly considered the context and spatial scale of fragmentation. Working in two river systems fragmented by agricultural and rural-housing development, we tracked nesting success and brood parasitism in >2500 bird nests in 38 patches of deciduous riparian woodland. Patches on both river systems were embedded in one of two local contexts (buffered from agriculture by coniferous forest, or adjacent to agriculture), but the abundance of agriculture and human habitation within 1 km of each patch was highly variable. We examined evidence for three models of landscape effects on nest predation based on (1) the relative importance of generalist agricultural nest predators, (2) predators associated with the natural habitats typically removed by agricultural development, or (3) an additive combination of these two predator communities. We found strong support for an additive predation model in which landscape features affect nest predation differently at different spatial scales. Riparian habitat with forest buffers had higher nest predation rates than sites adjacent to agriculture, but nest predation also increased with increasing agriculture in the larger landscape surrounding each site. These results suggest that predators living in remnant woodland buffers, as well as generalist nest predators associated with agriculture, affect nest predation rates, but they appear to respond at different spatial scales. Brood parasitism, in contrast, was unrelated to agricultural abundance on the landscape, but showed a strong nonlinear relationship with farm and house density, indicating a critical point at which increased human habitat causes increased brood parasitism. Accurate predictions regarding landscape effects on nest predation and brood parasitism will require an increased appreciation of the multiple scales at which landscape components influence predator and parasite behavior. ?? 2006 by the Ecological Society of America.

Variation in wind and piscivorous predator fields affecting the survival of Atlantic salmon, Salmo salar, in the Gulf of Maine

USGS Publications Warehouse

Friedland, K.D.; Manning, J.P.; Link, Jason S.; Gilbert, J.R.; Gilbert, A.T.; O'Connell, A.F.

2012-01-01

Observations relevant to the North American stock complex of Atlantic salmon, Salmo salar L., suggest that marine mortality is influenced by variation in predation pressure affecting post-smolts during the first months at sea. This hypothesis was tested for Gulf of Maine (GOM) stocks by examining wind pseudostress and the distribution of piscivorous predator fields potentially affecting post-smolts. Marine survival has declined over recent decades with a change in the direction of spring winds, which is likely extending the migration of post-smolts by favouring routes using the western GOM. In addition to changes in spring wind patterns, higher spring sea surface temperatures have been associated with shifting distributions of a range of fish species. The abundance of several pelagic piscivores, which based on their feeding habits may predate on salmon post-smolts, has increased in the areas that serve as migration corridors for post-smolts. In particular, populations of silver hake, Merluccius bilinearis (Mitchell), red hake, Urophycis chuss (Walbaum), and spiny dogfish, Squalus acanthias L., increased in size in the portion of the GOM used by post-smolts. Climate variation and shifting predator distributions in the GOM are consistent with the predator hypothesis of recruitment control suggested for the stock complex.

Advertising to the enemy: enhanced floral fragrance increases beetle attraction and reduces plant reproduction.

PubMed

Theis, Nina; Adler, Lynn S

2012-02-01

Many organisms face challenges in avoiding predation while searching for mates. For plants, emitting floral fragrances to advertise reproductive structures could increase the attraction of detrimental insects along with pollinators. Very few studies have experimentally evaluated the costs and benefits of fragrance emission with explicit consideration of how plant fitness is affected by both pollinators and florivores. To determine the reproductive consequences of increasing the apparency of reproductive parts, we manipulated fragrance, pollination, and florivores in the wild Texas gourd, Cucurbita pepo var. texana. With enhanced fragrance we found an increase in the attraction of florivores, rather than pollinators, and a decrease in seed production. This study is the first to demonstrate that enhanced floral fragrance can increase the attraction of detrimental florivores and decrease plant reproduction, suggesting that florivory as well as pollination has shaped the evolution of floral scent.

Differential effects of habitat complexity, predators and competitors on abundance of juvenile and adult coral reef fishes.

PubMed

Almany, Glenn R

2004-09-01

Greater structural complexity is often associated with greater abundance and diversity, perhaps because high complexity habitats reduce predation and competition. Using 16 spatially isolated live-coral reefs in the Bahamas, I examined how abundance of juvenile (recruit) and adult (non-recruit) fishes was affected by two factors: (1) structural habitat complexity and (2) the presence of predators and interference competitors. Manipulating the abundance of low and high complexity corals created two levels of habitat complexity, which was cross-factored with the presence or absence of resident predators (sea basses and moray eels) plus interference competitors (territorial damselfishes). Over 60 days, predators and competitors greatly reduced recruit abundance regardless of habitat complexity, but did not affect adult abundance. In contrast, increased habitat complexity had a strong positive effect on adult abundance and a weak positive effect on recruit abundance. Differential responses of recruits and adults may be related to the differential effects of habitat complexity on their primary predators. Sedentary recruits are likely most preyed upon by small resident predators that ambush prey, while larger adult fishes that forage widely and use reefs primarily for shelter are likely most preyed upon by large transient predators that chase prey. Increased habitat complexity may have inhibited foraging by transient predators but not resident predators. Results demonstrate the importance of habitat complexity to community dynamics, which is of concern given the accelerated degradation of habitats worldwide.

Effects of the heterogeneous landscape on a predator-prey system

NASA Astrophysics Data System (ADS)

Lee, Sang-Hee

2010-01-01

In order to understand how a heterogeneous landscape affects a predator-prey system, a spatially explicit lattice model consisting of predators, prey, grass, and landscape was constructed. The predators and preys randomly move on the lattice space and the grass grows in its neighboring site according to its growth probability. When predators and preys meet at the same site at the same time, a number of prey, equal to the number of predators are eaten. This rule was also applied to the relationship between the prey and grass. The predator (prey) could give birth to an offspring when it ate prey (grass), with a birth probability. When a predator or prey animal was initially introduced, or newly born, its health state was set at a given high value. This health state decreased by one with every time step. When the state of an animal decreased to less than zero, the animal died and was removed from the system. The heterogeneous landscape was characterized by parameter H, which controlled the heterogeneity according to the neutral model. The simulation results showed that H positively or negatively affected a predator’s survival, while its effect on prey and grass was less pronounced. The results can be understood by the disturbance of the balance between the prey and predator densities in the areas where the animals aggregated.

Consequences of stage-structured predators: cannibalism, behavioral effects, and trophic cascades.

PubMed

Rudolf, Volker H W

2007-12-01

Cannibalistic and asymmetrical behavioral interactions between stages are common within stage-structured predator populations. Such direct interactions between predator stages can result in density- and trait-mediated indirect interactions between a predator and its prey. A set of structured predator-prey models is used to explore how such indirect interactions affect the dynamics and structure of communities. Analyses of the separate and combined effects of stage-structured cannibalism and behavior-mediated avoidance of cannibals under different ecological scenarios show that both cannibalism and behavioral avoidance of cannibalism can result in short- and long-term positive indirect connections between predator stages and the prey, including "apparent mutualism." These positive interactions alter the strength of trophic cascades such that the system's dynamics are determined by the interaction between bottom-up and top-down effects. Contrary to the expectation of simpler models, enrichment increases both predator and prey abundance in systems with cannibalism or behavioral avoidance of cannibalism. The effect of behavioral avoidance of cannibalism, however, depends on how strongly it affects the maturation rate of the predator. Behavioral interactions between predator stages reduce the short-term positive effect of cannibalism on the prey density, but can enhance its positive long-term effects. Both interaction types reduce the destabilizing effect of enrichment. These results suggest that inconsistencies between data and simple models can be resolved by accounting for stage-structured interactions within and among species.

Small but Powerful: Top Predator Local Extinction Affects Ecosystem Structure and Function in an Intermittent Stream

PubMed Central

Rodríguez-Lozano, Pablo; Verkaik, Iraima; Rieradevall, Maria; Prat, Narcís

2015-01-01

Top predator loss is a major global problem, with a current trend in biodiversity loss towards high trophic levels that modifies most ecosystems worldwide. Most research in this area is focused on large-bodied predators, despite the high extinction risk of small-bodied freshwater fish that often act as apex consumers. Consequently, it remains unknown if intermittent streams are affected by the consequences of top-predators’ extirpations. The aim of our research was to determine how this global problem affects intermittent streams and, in particular, if the loss of a small-bodied top predator (1) leads to a ‘mesopredator release’, affects primary consumers and changes whole community structures, and (2) triggers a cascade effect modifying the ecosystem function. To address these questions, we studied the top-down effects of a small endangered fish species, Barbus meridionalis (the Mediterranean barbel), conducting an enclosure/exclosure mesocosm experiment in an intermittent stream where B. meridionalis became locally extinct following a wildfire. We found that top predator absence led to ‘mesopredator release’, and also to ‘prey release’ despite intraguild predation, which contrasts with traditional food web theory. In addition, B. meridionalis extirpation changed whole macroinvertebrate community composition and increased total macroinvertebrate density. Regarding ecosystem function, periphyton primary production decreased in apex consumer absence. In this study, the apex consumer was functionally irreplaceable; its local extinction led to the loss of an important functional role that resulted in major changes to the ecosystem’s structure and function. This study evidences that intermittent streams can be affected by the consequences of apex consumers’ extinctions, and that the loss of small-bodied top predators can lead to large ecosystem changes. We recommend the reintroduction of small-bodied apex consumers to systems where they have been extirpated, to restore ecosystem structure and function. PMID:25714337

Seed dispersal by fishes in tropical and temperate fresh waters: The growing evidence

NASA Astrophysics Data System (ADS)

Horn, Michael H.; Correa, Sandra Bibiana; Parolin, Pia; Pollux, B. J. A.; Anderson, Jill T.; Lucas, Christine; Widmann, Peter; Tjiu, Albertus; Galetti, Mauro; Goulding, Michael

2011-11-01

Fruit-eating by fishes represents an ancient (perhaps Paleozoic) interaction increasingly regarded as important for seed dispersal (ichthyochory) in tropical and temperate ecosystems. Most of the more than 275 known frugivorous species belong to the mainly Neotropical Characiformes (pacus, piranhas) and Siluriformes (catfishes), but cypriniforms (carps, minnows) are more important in the Holarctic and Indomalayan regions. Frugivores are among the most abundant fishes in Neotropical floodplains where they eat the fruits of a wide variety of trees and shrubs. By consuming fruits, fishes gain access to rich sources of carbohydrates, lipids and proteins and act as either seed predators or seed dispersers. With their often high mobility, large size, and great longevity, fruit-eating fishes can play important roles as seed dispersers and exert strong influences on local plant-recruitment dynamics and regional biodiversity. Recent feeding experiments focused on seed traits after gut passage support the idea that fishes are major seed dispersers in floodplain and riparian forests. Overfishing, damming, deforestation and logging potentially diminish ichthyochory and require immediate attention to ameliorate their effects. Much exciting work remains in terms of fish and plant adaptations to ichthyochory, dispersal regimes involving fishes in different ecosystems, and increased use of nondestructive methods such as stomach lavage, stable isotopes, genetic analyses and radio transmitters to determine fish diets and movements.

Intraguild predation by shore crabs affects mortality, behavior, growth, and densities of California horn snails

USGS Publications Warehouse

Lorda, J.; Hechinger, R.F.; Cooper, S. D.; Kuris, A. M.; Lafferty, Kevin D.

2016-01-01

The California horn snail, Cerithideopsis californica, and the shore crabs, Pachygrapsus crassipesand Hemigrapsus oregonensis, compete for epibenthic microalgae, but the crabs also eat snails. Such intraguild predation is common in nature, despite models predicting instability. Using a series of manipulations and field surveys, we examined intraguild predation from several angles, including the effects of stage-dependent predation along with direct consumptive and nonconsumptive predator effects on intraguild prey. In the laboratory, we found that crabs fed on macroalgae, snail eggs, and snails, and the size of consumed snails increased with predator crab size. In field experiments, snails grew less in the presence of crabs partially because snails behaved differently and were buried in the sediment (nonconsumptive effects). Consistent with these results, crab and snail abundances were negatively correlated in three field surveys conducted at three different spatial scales in estuaries of California, Baja California, and Baja California Sur: (1) among 61 sites spanning multiple habitat types in three estuaries, (2) among the habitats of 13 estuaries, and (3) among 34 tidal creek sites in one estuary. These results indicate that shore crabs are intraguild predators on California horn snails that affect snail populations via predation and by influencing snail behavior and performance.

The impact of six insecticides commonly used in control of agricultural pests on the generalist predator Hippodamia convergens (Coleoptera: Coccinellidae).

PubMed

Santos, Kenia Fernanda Aguiar; Zanuzo Zanardi, Odimar; de Morais, Matheus Rovere; Jacob, Cynthia Renata Oliveira; de Oliveira, Monique Bárbara; Yamamoto, Pedro Takao

2017-11-01

Hippodamia convergens is an important predator found in different agroecosystems. We evaluated the impacts of six insecticides on eggs, larvae and adults of this predator. For eggs, all insecticides reduced larval hatching rates, but did not affect egg duration. Chlorpyrifos and phosmet reduced larval survival; and chlorpyrifos, etofenprox and phosmet prolonged the larva development time. The survival and duration of pupae were not affected by all insecticides tested. Chlorpyrifos reduced fecundity, fertility and longevity when eggs were sprayed. For first-instar larvae, chlorpyrifos, etofenprox, phosmet and imidacloprid caused 100% mortality, while azadirachtin and thiamethoxam caused 35.0 and 52.7% mortality, respectively. However, azadirachtin and thiamethoxam did not affect the other biological parameters of the predator. In adults, chlorpyrifos, etofenprox and phosmet reduced adult survival. Chlorpyrifos, etofenprox, and phosmet reduced fecundity and longevity, but did not affect fertility. Azadirachtin, imidacloprid and thiamethoxam did not affect fecundity, fertility or longevity. Based on demographic parameters, all insecticides reduced the net reproductive rate (R o ), intrinsic rate of increase (r) and finite rate of increase (λ) of the predator when eggs were treated directly. Azadirachtin, chlorpyrifos, etofenprox and phosmet increased the mean generation time (T), while the effects of imidacloprid and thiamethoxam were similar to the control. When first-instar larvae were treated, azadirachtin and thiamethoxam reduced the R o , r and λ. Thiamethoxam increased the T value, while the effects of the other insecticides were similar to the control. These insecticides should be used with caution, in order to reduce their harmful effects on the predator in agroecosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.

Diet of generalist predators reflects effects of cropping period and farming system on extra- and intraguild prey.

PubMed

Roubinet, Eve; Birkhofer, Klaus; Malsher, Gerard; Staudacher, Karin; Ekbom, Barbara; Traugott, Michael; Jonsson, Mattias

2017-06-01

The suppression of agricultural pests by natural enemies, including generalist arthropod predators, is an economically important regulating ecosystem service. Besides pests, generalist predators may also consume non-pest extraguild and intraguild prey, which can affect their impact on pest populations. This may either reduce the impact of generalist predators on pest populations, because they are diverted from pest predation, or increase it, as it helps them survive periods of low pest availability. However, the availability of pest prey and alternative, non-pest prey can vary over the crop growing season and between farming systems, potentially affecting predator-prey interactions and the levels of biological control. We have limited information about how farming systems and environmental variation over the crop growing season influence predator diets. This limits our ability to predict the importance of generalist predators as natural enemies of agricultural pests. Here we utilize molecular gut content analyses to assess detection frequencies of extra- and intraguild prey DNA in generalist predator communities in replicated organically and conventionally managed cereal fields at two key periods of the cropping season for aphid biological control. This is done in order to understand how farming system, crop season, prey availability and predator community composition determine the composition of predator diets. Aphid pests and decomposers (springtails) were equally important prey for generalist predators early in the growing season. Later in the season, the importance of aphid prey increased with increasing aphid densities while springtail predation rates were positively correlated to abundance of this prey at both early and late crop growth stages. Intraguild predation was unidirectional: carabids fed on spiders, whereas spiders rarely fed on carabids. Carabids had higher detection frequencies for the two most common spider families in organically compared to conventionally managed fields. Our study documents that predation by generalist predator communities on aphid pests increases with pest numbers independently of their generally widespread consumption of alternative, non-pest prey. Therefore, conservation strategies in agricultural fields could promote biological control services by promoting high levels of alternative non-pest prey for generalist predator communities. © 2017 by the Ecological Society of America.

Insect growth regulator effects of azadirachtin and neem oil on survivorship, development and fecundity of Aphis glycines (Homoptera: Aphididae) and its predator, Harmonia axyridis (Coleoptera: Coccinellidae).

PubMed

Kraiss, Heidi; Cullen, Eileen M

2008-06-01

Aphis glycines Matsumura, an invasive insect pest in North American soybeans, is fed upon by a key biological control agent, Harmonia axyridis Pallas. Although biological control is preferentially relied upon to suppress insect pests in organic agriculture, approved insecticides, such as neem, are periodically utilized to reduce damaging pest populations. The authors evaluated direct spray treatments of two neem formulations, azadirachtin and neem seed oil, under controlled conditions for effects on survivorship, development time and fecundity in A. glycines and H. axyridis. Both azadirachtin and neem seed oil significantly increased aphid nymphal mortality (80 and 77% respectively) while significantly increasing development time of those surviving to adulthood. First-instar H. axyridis survival to adulthood was also significantly reduced by both neem formulations, while only azadirachtin reduced third-instar survivorship. Azadirachtin increased H. axyridis development time to adult when applied to both instars, while neem oil only increased time to adult when applied to first instar. Neither neem formulation affected the fecundity of either insect. Results are discussed within the context of future laboratory and field studies aimed at clarifying if neem-derived insecticides can be effectively integrated with biological control for soybean aphid management in organic soybeans. Copyright (c) 2008 Society of Chemical Industry.

Plasticity as Phenotype: G x E Interaction in a Freshwater Snail

NASA Astrophysics Data System (ADS)

Brunkow, P. E.; Calloway, S. A.

2005-05-01

Plasticity in morphological development allows species to accommodate environmental variation experienced during growth; however, genetic variation for phenotypic plasticity per se has been relatively under-studied. We utilized the well-documented plastic response of shell development to predator cues in a freshwater snail to quantify genetic variation for plasticity in growth rate and shell shape. Field-caught pairs of snails reproduced in the laboratory to create families of full siblings, which were then divided and allowed to grow in control and predator cue treatments. Predator (crayfish) cues had significant effects on both size-corrected growth rate and shell shape; family identity also significantly affected both final shell shape and growth rate. The interaction between predator treatment and family identity significantly affected snail growth rate but not final shell shape, suggesting genetic variation in the plastic response to predator cues for a physiological variable (growth rate) but not for a variable known to mechanically reduce the risk of predation (shell shape), at least in this population of snails. The possibility that risk of multiple modes of predation (i.e., both fish and crayfish) in some populations might maintain genetic variation in morphological plasticity is discussed.

Revisiting the classics: considering nonconsumptive effects in textbook examples of predator-prey interactions.

PubMed

Peckarsky, Barbara L; Abrams, Peter A; Bolnick, Daniel I; Dill, Lawrence M; Grabowski, Jonathan H; Luttbeg, Barney; Orrock, John L; Peacor, Scott D; Preisser, Evan L; Schmitz, Oswald J; Trussell, Geoffrey C

2008-09-01

Predator effects on prey dynamics are conventionally studied by measuring changes in prey abundance attributed to consumption by predators. We revisit four classic examples of predator-prey systems often cited in textbooks and incorporate subsequent studies of nonconsumptive effects of predators (NCE), defined as changes in prey traits (e.g., behavior, growth, development) measured on an ecological time scale. Our review revealed that NCE were integral to explaining lynx-hare population dynamics in boreal forests, cascading effects of top predators in Wisconsin lakes, and cascading effects of killer whales and sea otters on kelp forests in nearshore marine habitats. The relative roles of consumption and NCE of wolves on moose and consequent indirect effects on plant communities of Isle Royale depended on climate oscillations. Nonconsumptive effects have not been explicitly tested to explain the link between planktonic alewives and the size structure of the zooplankton, nor have they been invoked to attribute keystone predator status in intertidal communities or elsewhere. We argue that both consumption and intimidation contribute to the total effects of keystone predators, and that characteristics of keystone consumers may differ from those of predators having predominantly NCE. Nonconsumptive effects are often considered as an afterthought to explain observations inconsistent with consumption-based theory. Consequently, NCE with the same sign as consumptive effects may be overlooked, even though they can affect the magnitude, rate, or scale of a prey response to predation and can have important management or conservation implications. Nonconsumptive effects may underlie other classic paradigms in ecology, such as delayed density dependence and predator-mediated prey coexistence. Revisiting classic studies enriches our understanding of predator-prey dynamics and provides compelling rationale for ramping up efforts to consider how NCE affect traditional predator-prey models based on consumption, and to compare the relative magnitude of consumptive and NCE of predators.

Biotransfer, bioaccumulation and effects of herbivore dietary Co, Cu, Ni, and Zn on growth and development of the insect predator Podisus maculiventris (Say).

PubMed

Cheruiyot, Dorothy J; Boyd, Robert S; Coudron, Thomas A; Cobine, Paul A

2013-06-01

Increased metal availability in the environment can be detrimental for the growth and development of all organisms in a food web. In part, this toxicity is due to biotransfer or bioaccumulation of metals between trophic levels. We evaluated the survival, growth, and development of a generalist Hemipteran predator (Podisus maculiventris) when fed herbivorous prey (Spodoptera exigua) reared on artificial diet amended with Cu, Zn, Ni, and Co. Predator nymphs were fed S. exigua larvae raised on diet amended with sublethal (Minimum Sublethal Concentration or MSC) or lethal (Minimum Lethal Concentration or MLC) concentrations of each metal, as well as control diet. We determined if metals were biotransferred or bioaccumulated from the diet to herbivore and predator, as well as if predator growth or survival was affected by herbivore diet. Podisus maculiventris fed herbivores raised on MLC levels of both Cu and Zn took significantly longer to mature to adults, whereas their overall survival was not affected by prey diet metal concentration for any metal. Adult weights were significantly reduced for predators raised on herbivores reared on diets amended with the MLC of Cu and Zn. Copper and Zn were bioaccumulated from diet to herbivore and from herbivore to predator, whereas Ni was biotransferred (although concentrations decreased as trophic level increased). The pattern for Co was more complex, with biotransfer the main outcome. Our results show that availability of metals in a food web can affect growth and development of a hemipteran predator, and that metals are transferred between trophic levels, with metal-specific biotransfer and bioaccumulation outcomes.

Predator-prey interactions mediated by prey personality and predator hunting mode.

PubMed

Belgrad, Benjamin A; Griffen, Blaine D

2016-04-13

Predator-prey interactions are important drivers in structuring ecological communities. However, despite widespread acknowledgement that individual behaviours and predator species regulate ecological processes, studies have yet to incorporate individual behavioural variations in a multipredator system. We quantified a prevalent predator avoidance behaviour to examine the simultaneous roles of prey personality and predator hunting mode in governing predator-prey interactions. Mud crabs, Panopeus herbstii, reduce their activity levels and increase their refuge use in the presence of predator cues. We measured mud crab mortality and consistent individual variations in the strength of this predator avoidance behaviour in the presence of predatory blue crabs, Callinectes sapidus, and toadfish, Opsanus tau We found that prey personality and predator species significantly interacted to affect mortality with blue crabs primarily consuming bold mud crabs and toadfish preferentially selecting shy crabs. Additionally, the strength of the predator avoidance behaviour depended upon the predation risk from the predator species. Consequently, the personality composition of populations and predator hunting mode may be valuable predictors of both direct and indirect predator-prey interaction strength. These findings support theories postulating mechanisms for maintaining intraspecies diversity and have broad implications for community dynamics. © 2016 The Author(s).

A mathematical model of the effect of a predator on species diversity

NASA Technical Reports Server (NTRS)

Weston, C. R.; Yang, J. N.

1970-01-01

Mathematical model determines reaction between new predator and microbe competitor when the competitor is the predator's sole nutrient resource. The model utilizes differential equations to describe the interactions with the specific growth rates, and analyzes these growth rates as they are affected by population density and nutrient concentration.

Personality and morphological traits affect pigeon survival from raptor attacks.

PubMed

Santos, Carlos D; Cramer, Julia F; Pârâu, Liviu G; Miranda, Ana C; Wikelski, Martin; Dechmann, Dina K N

2015-10-22

Personality traits have recently been shown to impact fitness in different animal species, potentially making them similarly relevant drivers as morphological and life history traits along the evolutionary pathways of organisms. Predation is a major force of natural selection through its deterministic effects on individual survival, but how predation pressure has helped to shape personality trait selection, especially in free-ranging animals, remains poorly understood. We used high-precision GPS tracking to follow whole flocks of homing pigeons (Columba livia) with known personalities and morphology during homing flights where they were severely predated by raptors. This allowed us to determine how the personality and morphology traits of pigeons may affect their risk of being predated by raptors. Our survival model showed that individual pigeons, which were more tolerant to human approach, slower to escape from a confined environment, more resistant to human handling, with larger tarsi, and with lighter plumage, were more likely to be predated by raptors. We provide rare empirical evidence that the personality of prey influences their risk of being predated under free-ranging circumstances.

Personality and morphological traits affect pigeon survival from raptor attacks

PubMed Central

Santos, Carlos D.; Cramer, Julia F.; Pârâu, Liviu G.; Miranda, Ana C.; Wikelski, Martin; Dechmann, Dina K. N.

2015-01-01

Personality traits have recently been shown to impact fitness in different animal species, potentially making them similarly relevant drivers as morphological and life history traits along the evolutionary pathways of organisms. Predation is a major force of natural selection through its deterministic effects on individual survival, but how predation pressure has helped to shape personality trait selection, especially in free-ranging animals, remains poorly understood. We used high-precision GPS tracking to follow whole flocks of homing pigeons (Columba livia) with known personalities and morphology during homing flights where they were severely predated by raptors. This allowed us to determine how the personality and morphology traits of pigeons may affect their risk of being predated by raptors. Our survival model showed that individual pigeons, which were more tolerant to human approach, slower to escape from a confined environment, more resistant to human handling, with larger tarsi, and with lighter plumage, were more likely to be predated by raptors. We provide rare empirical evidence that the personality of prey influences their risk of being predated under free-ranging circumstances. PMID:26489437

Separating spatial search and efficiency rates as components of predation risk

PubMed Central

DeCesare, Nicholas J.

2012-01-01

Predation risk is an important driver of ecosystems, and local spatial variation in risk can have population-level consequences by affecting multiple components of the predation process. I use resource selection and proportional hazard time-to-event modelling to assess the spatial drivers of two key components of risk—the search rate (i.e. aggregative response) and predation efficiency rate (i.e. functional response)—imposed by wolves (Canis lupus) in a multi-prey system. In my study area, both components of risk increased according to topographic variation, but anthropogenic features affected only the search rate. Predicted models of the cumulative hazard, or risk of a kill, underlying wolf search paths validated well with broad-scale variation in kill rates, suggesting that spatial hazard models provide a means of scaling up from local heterogeneity in predation risk to population-level dynamics in predator–prey systems. Additionally, I estimated an integrated model of relative spatial predation risk as the product of the search and efficiency rates, combining the distinct contributions of spatial heterogeneity to each component of risk. PMID:22977145

On the relative contributions of wind vs. animals to seed dispersal of four Sierra Nevada pines.

PubMed

Vander Wall, Stephen B

2008-07-01

Selective pressures that influence the form of seed dispersal syndromes are poorly understood. Morphology of plant propagules is often used to infer the means of dispersal, but morphology can be misleading. Several species of pines, for example, have winged seeds adapted for wind dispersal but owe much of their establishment to scatter-hoarding animals. Here the relative importance of wind vs. animal dispersal is assessed for four species of pines of the eastern Sierra Nevada that have winged seeds but differed in seed size: lodgepole pine (Pinus contorta murrayana, 8 mg); ponderosa pine (Pinus ponderosa ponderosa, 56 mg); Jeffrey pine (Pinus jeffreyi, 160 mg); and sugar pine (Pinus lambertiana, 231 mg). Pre-dispersal seed mortality eliminated much of the ponderosa pine seed crop (66%), but had much less effect on Jeffrey pine (32% of seeds destroyed), lodgepole pine (29%), and sugar pine (7%). When cones opened most filled seeds were dispersed by wind. Animals removed > 99% of wind-dispersed Jeffrey and sugar pine seeds from the ground within 60 days, but animals gathered only 93% of lodgepole pine seeds and 38% of ponderosa pine seeds during the same period. Animals gathered and scatter hoarded radioactively labeled ponderosa, Jeffrey, and sugar pine seeds, making a total of 2103 caches over three years of study. Only three lodgepole pine caches were found. Caches typically contained 1-4 seeds buried 5-20 mm deep, depths suitable for seedling emergence. Although Jeffrey and sugar pine seeds are initially wind dispersed, nearly all seedlings arise from animal caches. Lodgepole pine is almost exclusively wind dispersed, with animals acting as seed predators. Animals treated ponderosa pine in an intermediate fashion. Two-phased dispersal of large, winged pine seeds appears adaptive; initial wind dispersal helps to minimize pre-dispersal seed mortality whereas scatter hoarding by animals places seeds in sites with a higher probability of seedling establishment.

Habitat edges affect patterns of artificial nest predation along a wetland-meadow boundary

NASA Astrophysics Data System (ADS)

Suvorov, Petr; Svobodová, Jana; Albrecht, Tomáš

2014-08-01

Wetland habitats are among the most endangered ecosystems in the world. However, little is known about factors affecting the nesting success of birds in pristine grass-dominated wetlands. During three breeding periods we conducted an experiment with artificial ground nests to test two basic mechanisms (the matrix and ecotonal effects) that may result in edge effects on nest predation in grass-dominated wetland habitats. Whereas the matrix effect model supposes that predator penetrate from habitat of higher predator density to habitat of lower predator density, thus causing an edge effect in the latter, according to the ecotonal effect model predators preferentially use edge habitats over habitat interiors. In addition, we tested the edge effect in a wetland habitat using artificial shrub nests that simulated the real nests of small open-cup nesting passerines. In our study area, the lowest predation rates on ground nests were found in wetland interiors and were substantially higher along the edges of both wetland and meadow habitat. However, predation was not significantly different between meadow and wetland interiors, indicating that both mechanisms can be responsible for the edge effect in wetland edges. An increased predation rate along wetland edges was also observed for shrub nests, and resembled the predation pattern of real shrub nests in the same study area. Though we are not able to distinguish between the two mechanisms of the edge effect found, our results demonstrate that species nesting in wetland edges bordering arable land may be exposed to higher predation. Therefore, an increase in the size of wetland patches that would lead to a reduced proportion of edge areas might be a suitable management practice to protect wetland bird species in cultural European landscapes.

Predicting the effects of ocean acidification on predator-prey interactions: a conceptual framework based on coastal molluscs.

PubMed

Kroeker, Kristy J; Sanford, Eric; Jellison, Brittany M; Gaylord, Brian

2014-06-01

The influence of environmental change on species interactions will affect population dynamics and community structure in the future, but our current understanding of the outcomes of species interactions in a high-CO2 world is limited. Here, we draw upon emerging experimental research examining the effects of ocean acidification on coastal molluscs to provide hypotheses of the potential impacts of high-CO2 on predator-prey interactions. Coastal molluscs, such as oysters, mussels, and snails, allocate energy among defenses, growth, and reproduction. Ocean acidification increases the energetic costs of physiological processes such as acid-base regulation and calcification. Impacted molluscs can display complex and divergent patterns of energy allocation to defenses and growth that may influence predator-prey interactions; these include changes in shell properties, body size, tissue mass, immune function, or reproductive output. Ocean acidification has also been shown to induce complex changes in chemoreception, behavior, and inducible defenses, including altered cue detection and predator avoidance behaviors. Each of these responses may ultimately alter the susceptibility of coastal molluscs to predation through effects on predator handling time, satiation, and search time. While many of these effects may manifest as increases in per capita predation rates on coastal molluscs, the ultimate outcome of predator-prey interactions will also depend on how ocean acidification affects the specified predators, which also exhibit complex responses to ocean acidification. Changes in predator-prey interactions could have profound and unexplored consequences for the population dynamics of coastal molluscs in a high-CO2 ocean. © 2014 Marine Biological Laboratory.

Immediate or lagged responses of a red squirrel population to pulsed resources.

PubMed

Selonen, Vesa; Varjonen, Rauno; Korpimäki, Erkki

2015-02-01

According to producer-consumer models, consumers should follow pulsed resources with a time lag. This view has been challenged by studies demonstrating that individuals may anticipate future resource pulses by increasing reproduction just before the pulse. We studied population fluctuations and reproduction in European red squirrels, Sciurus vulgaris, in relation to seed masting of the main food resource (the Norway spruce) in boreal coniferous forests between 1979 and 2013. Red squirrels are pre-dispersal seed predators, and previous studies have shown that they can anticipate the coming seed mast. We did not find any indication that anticipation of masting (year t ) increased red squirrel reproduction in the preceding spring to early summer. Instead, the reproductive output of the squirrels was highest in the spring following the mast, indicating that the population had to be at its largest size in the autumn after the mast (year(t+1)), when lots of subadults were around. However, we surmised, based on snow tracks and squirrel nest data, that the population crashed during the following winter (year(t+1)). These data reflected the adult population during winter, which peaked at the same time as the resource pulse. We can therefore conclude that the time lag between the resource pulse and the attainment of the peak number of squirrels was less than one year, and that the resource crash affected more juveniles and subadults than adults. The population increase overlapped with the occurrence of masting, but there was also a lagged response, supporting the classical view of producer-consumer models.

Management effect on bird and arthropod interaction in suburban woodlands

PubMed Central

2011-01-01

Background Experiments from a range of ecosystems have shown that insectivorous birds are important in controlling the populations of their invertebrate prey. Here, we report on a large field experiment testing the hypothesis that management for enhancing recreational values in suburban woodlands affects the intensity of bird predation on canopy-living arthropods. Bird exclosures were used in two types of management (understory clearance and dense understory) at two foraging heights in oak Quercus robur canopies and the experiment was replicated at two sites. Results The biomass and abundance of arthropods were high on net-enclosed branches but strongly reduced on control branches in both types of management. In woods with dense understory, the effect of bird predation on arthropod abundance was about twice as high as in woods with understory clearance. The effect of bird predation on arthropod biomass was not significantly affected by management. Conclusions Our data provide experimental evidence to support the idea that bird predation on arthropods can be affected by forest management. We suggest that the mechanism is twofold: reduction of bird abundance and shift of foraging behaviour. In urban woodlands, there may be a management trade-off between enhancing recreational values and promoting bird predation rates on arthropods. PMID:21362174

Silence is not golden: the hissing calls of tits affect the behaviour of a nest predator.

PubMed

Zub, Karol; Czeszczewik, Dorota; Ruczyński, Ireneusz; Kapusta, Anna; Walankiewicz, Wiesław

2017-01-01

Nest predation is one of the most important mortality factors of birds. Field observations showed that tits (Paridae) produce hissing calls and, usually, have lower breeding losses than nesting Ficedula flycatchers, which do not make such calls. We hypothesise that differences in fledgling success can be directly attributed to the vocal reaction of tits. We tested experimentally whether the hissing calls can affect the behaviour of a potential predator, analysing the response of the Yellow-necked Mouse Apodemus flavicollis to playback of calls of three Parid species. The number of visits by mice to two types of cavities (with playback and control) was not significantly different, but the average time spent by mice in cavities with playback (3.9 s) was significantly shorter than in cavities without playback (26.3 s). This suggests that hissing behaviour of tits significantly changes the exploration activity of predators, which may ultimately increase the breeding success of this group of birds relative to the flycatchers. Nest predation is one of the most important mortality factors of small land birds, but some anti-predatory mechanisms are still poorly recognised. Numerous studies demonstrate that incubating tits make hissing sounds, when a predator is near, but despite almost a century of research, there is little evidence these calls indeed affect behaviour of predators. By using a simple laboratory experiment, we demonstrated that the hissing acoustic signals used by tits may change the behaviour of yellow-necked mice, which are an important predator of cavity-nesting birds in temperate forests. Intruding mice withdrew from cavities where hissing sounds were played back. Our results suggest that the hissing behaviour of tits can change the exploration activity of potential predators and may increase breeding success of this group of birds relative to the flycatchers, which stay silent when their nest is threatened.

Rainfall and hydrological stability alter the impact of top predators on food web structure and function.

PubMed

Marino, Nicholas A C; Srivastava, Diane S; MacDonald, A Andrew M; Leal, Juliana S; Campos, Alice B A; Farjalla, Vinicius F

2017-02-01

Climate change will alter the distribution of rainfall, with potential consequences for the hydrological dynamics of aquatic habitats. Hydrological stability can be an important determinant of diversity in temporary aquatic habitats, affecting species persistence and the importance of predation on community dynamics. As such, prey are not only affected by drought-induced mortality but also the risk of predation [a non-consumptive effect (NCE)] and actual consumption by predators [a consumptive effect (CE)]. Climate-induced changes in rainfall may directly, or via altered hydrological stability, affect predator-prey interactions and their cascading effects on the food web, but this has rarely been explored, especially in natural food webs. To address this question, we performed a field experiment using tank bromeliads and their aquatic food web, composed of predatory damselfly larvae, macroinvertebrate prey and bacteria. We manipulated the presence and consumption ability of damselfly larvae under three rainfall scenarios (ambient, few large rainfall events and several small rainfall events), recorded the hydrological dynamics within bromeliads and examined the effects on macroinvertebrate colonization, nutrient cycling and bacterial biomass and turnover. Despite our large perturbations of rainfall, rainfall scenario had no effect on the hydrological dynamics of bromeliads. As a result, macroinvertebrate colonization and nutrient cycling depended on the hydrological stability of bromeliads, with no direct effect of rainfall or predation. In contrast, rainfall scenario determined the direction of the indirect effects of predators on bacteria, driven by both predator CEs and NCEs. These results suggest that rainfall and the hydrological stability of bromeliads had indirect effects on the food web through changes in the CEs and NCEs of predators. We suggest that future studies should consider the importance of the variability in hydrological dynamics among habitats as well as the biological mechanisms underlying the ecological responses to climate change. © 2016 John Wiley & Sons Ltd.

Determining nest predators of the Least Bell's Vireo through point counts, tracking stations, and video photography

USGS Publications Warehouse

Peterson, Bonnie L.; Kus, Barbara E.; Deutschman, Douglas H.

2004-01-01

We compared three methods to determine nest predators of the Least Bell's Vireo (Vireo bellii pusillus) in San Diego County, California, during spring and summer 2000. Point counts and tracking stations were used to identify potential predators and video photography to document actual nest predators. Parental behavior at depredated nests was compared to that at successful nests to determine whether activity (frequency of trips to and from the nest) and singing vs. non-singing on the nest affected nest predation. Yellow-breasted Chats (Icteria virens) were the most abundant potential avian predator, followed by Western Scrub-Jays (Aphelocoma californica). Coyotes (Canis latrans) were abundant, with smaller mammalian predators occurring in low abundance. Cameras documented a 48% predation rate with scrub-jays as the major nest predators (67%), but Virginia opossums (Didelphis virginiana, 17%), gopher snakes (Pituophis melanoleucus, 8%) and Argentine ants (Linepithema humile, 8%) were also confirmed predators. Identification of potential predators from tracking stations and point counts demonstrated only moderate correspondence with actual nest predators. Parental behavior at the nest prior to depredation was not related to nest outcome.

Cone and seed traits of two Juniperus species influence roles of frugivores and scatter-hoarding rodents as seed dispersal agents

NASA Astrophysics Data System (ADS)

Dimitri, Lindsay A.; Longland, William S.; Vander Wall, Stephen B.

2017-11-01

Seed dispersal in Juniperus is generally attributed to frugivores that consume the berry-like female cones. Some juniper cones are fleshy and resinous such as those of western juniper (Juniperus occidentalis), while others are dry and leathery such as those of Utah juniper (J. osteosperma). Rodents have been recorded harvesting Juniperus seeds and cones but are mostly considered seed predators. Our study sought to determine if rodents play a role in dispersal of western and Utah juniper seeds. We documented rodent harvest of cones and seeds of the locally-occurring juniper species and the alternate (non-local) juniper species in removal experiments at a western juniper site in northeastern California and a Utah juniper site in western Nevada. Characteristics of western and Utah juniper cones appeared to influence removal, as cones from the local juniper species were preferred at both sites. Conversely, removal of local and non-local seeds was similar. Piñon mice (Peromyscus truei) were responsible for most removal of cones and seeds at both sites. We used radioactively labeled seeds to follow seed fate and found many of these seeds in scattered caches (western juniper: 415 seeds in 82 caches, 63.0% of seeds found; Utah juniper: 458 seeds in 127 caches, 39.5% of seeds found) most of which were attributed to piñon mice. We found little evidence of frugivores dispersing Utah juniper seeds, thus scatter-hoarding rodents appear to be the main dispersal agents. Western juniper cones were eaten by frugivores, and scatter-hoarding is a complimentary or secondary form of seed dispersal. Our results support the notion that Utah juniper has adapted to xeric environments by conserving water through the loss of fleshy fruits that attract frugivores and instead relies on scatter-hoarding rodents as effective dispersal agents.

Background level of risk and the survival of predator-naive prey: can neophobia compensate for predator naivety in juvenile coral reef fishes?

PubMed

Ferrari, Maud C O; McCormick, Mark I; Meekan, Mark G; Chivers, Douglas P

2015-01-22

Neophobia--the generalized fear response to novel stimuli--provides the first potential strategy that predator-naive prey may use to survive initial predator encounters. This phenotype appears to be highly plastic and present in individuals experiencing high-risk environments, but rarer in those experiencing low-risk environments. Despite the appeal of this strategy as a 'solution' for prey naivety, we lack evidence that this strategy provides any fitness benefit to prey. Here, we compare the relative effect of environmental risk (high versus low) and predator-recognition training (predator-naive versus predator-experienced individuals) on the survival of juvenile fish in the wild. We found that juveniles raised in high-risk conditions survived better than those raised in low-risk conditions, providing the first empirical evidence that environmental risk, in the absence of any predator-specific information, affects the way naive prey survive in a novel environment. Both risk level and experience affected survival; however, the two factors did not interact, indicating that the information provided by both factors did not interfere or enhance each other. From a mechanistic viewpoint, this indicates that the combination of the two factors may increase the intensity, and hence efficacy, of prey evasion strategies, or that both factors provide qualitatively separate benefits that would result in an additive survival success.

Environmental Impact Research Program and Defense Natural Resources Program: Maximilian Sunflower (Helianthus maximiliani), Section 7.4.3, US Army Corps of Engineers Wildlife Resources Management Manual.

DTIC Science & Technology

1992-02-01

black - bird predation on sunflower seed becomes a serious problem...Calamosplza melanocorys Vesper sparrow Pooecetes gramineus Lark sparrow Chondestes grammacus American tree sparrow Spizella arborea Field sparrow ...8217. pusilla Harris’ sparrow Zonotrichla querula White-crowned sparrow Z. leucophrys White- throated sparrow Z. albicollis Lincoln’s sparrow

No free lunch: Observations on seed predation, cone collection, and controlled germination of whitebark pine from the Canadian Rockies

Treesearch

Adrian Leslie; Brendan Wilson

2011-01-01

Whitebark pine is a keystone species of high elevation forests in western North America that is experiencing rapid decline due to fire exclusion policies, mountain pine beetle, and the introduced pathogen, white pine blister rust. Restoration activities include collecting cones and growing seedlings from individuals that show mechanisms for resistance to blister rust...

The need for silvicultural practices and collection of butternut germplasm for species conservation

Treesearch

M. E. Ostry; B. Ellingson; D. Seekins; W. Ruckheim

2003-01-01

Butternut is a short-lived tree and is declining in numbers for a variety of reasons ranging from changing land use to aging forest stands, seed predation and lack of suitable conditions for reproduction. However, the major reason for the dramatic decrease in butternut populations throughout its range in North America is the lethal canker disease caused by the fungus...

Edge, height and visibility effects on nest predation by birds and mammals in the Brazilian cerrado

NASA Astrophysics Data System (ADS)

Dodonov, Pavel; Paneczko, Ingrid Toledo; Telles, Marina

2017-08-01

Edge influence is one of the main impacts in fragmented landscapes; yet, most of studies on edge influence have focused on high-contrast edges, and the impacts of low-contrast edges and narrow linear openings are less understood. Edge influence often affects bird nest predation, but these effects are not ubiquitous and may depend on characteristics such as nest height and visibility. We performed an experiment on nest predation in a migratory passerine, Elaenia chiriquensis (Lesser Elaenia; Passeriformes: Tyrannidae), in a savanna vegetation of the Brazilian Cerrado biome in South-Eastern Brazil. We used 89 real E. chiriquensis nests, collected during previous reproductive seasons, with two plasticine eggs in each, and randomly distributed them at two locations (edge - up to 20 m from a firebreak edge and interior - approx. 150-350 m from the edge) and two heights (low - 60-175 cm and high - 190-315 cm above ground). We also measured leaf and branch density around each nest. We performed this study on two 15-days campaigns, checking the nests every 2-3 days and removing those with predation marks. We sorted the predation marks into those made by birds, mammals, or unidentified predators, and used generalized linear models to assess the effects of location, height and leaf density on survival time and predator type. Only four nests had not been predated during the experiment; 55 nests were predated by birds, 7 by mammals, and 23 by unidentified predators. Low nests in the interior tended to have larger survival times whereas high nests at the edge tended to be more predated by birds and less predated by mammals. Thus, even a low-contrast (firebreak) edge may significantly increase nest predation, which is also affected by the nest's height, mainly due to predation by birds. These effects may be due to predator movement along the edge as well as to edge-related changes in vegetation structure. We suggest that higher-contrast edges which may also be used as movement conduits, for example powerline openings, may have even stronger effects, demanding further studies.

Coevolution between Hispaniolan crossbills and pine: does more time allow for greater phenotypic escalation at lower latitude?

PubMed

Parchman, Thomas L; Benkman, Craig W; Mezquida, Eduardo T

2007-09-01

Crossbills (Aves: Loxia) and several conifers have coevolved in predator-prey arms races over the last 10,000 years. However, the extent to which coevolutionary arms races have contributed to the adaptive radiation of crossbills or to any other adaptive radiation is largely unknown. Here we extend our previous studies of geographically structured coevolution by considering a crossbill-conifer interaction that has persisted for a much longer time period and involves a conifer with more variable annual seed production. We examined geographic variation in the cone and seed traits of two sister species of pines, Pinus occidentalis and P. cubensis, on the islands of Hispaniola and Cuba, respectively. We also compared the Hispaniolan crossbill (Loxia megaplaga) to its sister taxa the North American white-winged crossbill (Loxia leucoptera leucoptera). The Hispaniolan crossbill is endemic to Hispaniola whereas Cuba lacks crossbills. In addition and in contrast to previous studies, the variation in selection experienced by these pines due to crossbills is not confounded by the occurrence of selection by tree squirrels (Tamiasciurus and Sciurus). As predicted if P. occidentalis has evolved defenses in response to selection exerted by crossbills, cones of P. occidentalis have scales that are 53% thicker than those of P. cubensis. Cones of P. occidentalis, but not P. cubensis, also have well-developed spines, a known defense against vertebrate seed predators. Consistent with patterns of divergence seen in crossbills coevolving locally with other conifers, the Hispaniolan crossbill has evolved a bill that is 25% deeper than the white-winged crossbill. Together with phylogenetic analyses, our results suggest that predator-prey coevolution between Hispaniolan crossbills and P. occidentalis over approximately 600,000 years has caused substantial morphological evolution in both the crossbill and pine. This also indicates that cone crop fluctuations do not prevent crossbills and conifers from coevolving. Furthermore, because the traits at the phenotypic interface of the interaction apparently remain the same over at least several hundred thousand years, divergence as a result of coevolution is greater at lower latitude where crossbill-conifer interactions have been less interrupted by Pleistocene events.

[Frugivory and seed dispersal Oenocarpus bataua palm (Arecaceae) in a forest from the Colombian Andes].

PubMed

Rojas-Robles, Rosario; Stiles, F Gary; Muñoz-Saba, Yaneth

2012-12-01

Seed dispersal is a key process that determines the spatial structure and dynamics of populations of plants, establishes the potential area of recruitment and in this way, the basis for subsequent processes such as predation, germination, competition and growth. The purpose of this research was to identify the guild of frugivores of the Oenocapus bataua palm in fragments of Andean forest, determine the effective dispersers and relate the spatial distribution of palm populations with the dispersion of seeds. To this end, between August 2005-June 2006, observations of the removal of fruits from eight clusters were done, and counting of consumption of fruits beneath 78 palms with mature fruits was undertaken; focal observations of 13 individuals during 90 hours; registration of frugivory with photographic traps during 165 days/nights for a total of 195 photographs and 144 consumption events; experiments with dispersion using 751 perforated fruits/seeds attached to strings and finally, plots to determine spatial distribution all were carried out. In the study area at least five species of mammals ate, dispersed, buried (Sciurus granatensis, Microsciurus mimulus, Dasyprocta punctata y Proechimys sp.), cover (Marmosa robinsoni) and carried the fruits of O. bataua off to caves (Marmosa robinsoni y Proechimys sp.) without damaging the seed. A 21.7% of the fruits were dispersed, 13.2 gnawed or peeled, 5.6% covered, buried and carried to caves. The average distance of removal of seeds and fruits was 3.1m although in a lesser proportion, dispersion events of >50m were recorded. The abundant production of fruits, their size and weight, their intense removal by frugivores, the short dispersion distances, the absence of large size frugivores (reduced by hunting and fragmentation), that might perform long-distance dispersion, and the increase of rodents, especially squirrels, that strongly pressure the fruit resource, generate a spatially restricted seed rain of seeds responsible for the aggregate patterns of distribution of seeds, seedlings and subsequently of juveniles and sub-adults. However the short time and high percentage of seed germination and the robustness of seeds and seedlings give O. bataua the capacity to survive in dense aggregations. Therefore, despite the limitations on dispersion, this is a dominant species in the study area. Populations of O. bataua have been reduced by intense exploitation and by the transformation and reduction of their natural habitat. The over-exploitation of the fruits or the juvenile phases of this palm can affect the age structure and population dynamics. Therefore, the management and exploitation of this palm in the future will depend to large degree on the conservation of forest habitats.

Children's Performance on a False-belief Task Is Impaired by Activation of an Evolutionarily-Canalized Response System.

ERIC Educational Resources Information Center

Keenan, Thomas; Ellis, Bruce J.

2003-01-01

Two studies examined how task content that activates predator-avoidance affects preschool children's performance on a false-belief task. Findings indicated that the proportion of correct answers on the playmate-avoidance task was greater than that for the predator-avoidance task, suggesting that activation of the predator-avoidance system…

Effects of tannins on population dynamics of sympatric seed-eating rodents: the potential role of gut tannin-degrading bacteria.

PubMed

Zhang, Yihao; Bartlow, Andrew W; Wang, Zhenyu; Yi, Xianfeng

2018-05-07

Chemical compounds in seeds exert negative and even lethal effects on seed-consuming animals. Tannin-degrading bacteria in the guts of small mammals have been associated with the ability to digest seeds high in tannins. At the population level, it is not known if tannins influence rodent species differently according to the composition of their gut microbiota. Here, we test the hypothesis that sympatric tree species with different tannins exert contrasting effects on population fluctuations of seed-eating rodents. We collected a 10-year dataset of seed crops and rodent population sizes and sequenced 16S rRNA of gut microbes. The abundance of Apodemus peninsulae was not correlated with seed crop of either high-tannin Quercus mongolica or low-tannin Corylus mandshurica, but positively correlated with their total seed crops. Abundance of Tamias sibiricus was negatively correlated with seed crop of Q. mongolica but positively correlated with C. mandshurica. Body masses of A. peninsulae and T. sibiricus decreased when given high-tannin food; however, only the survival of T. sibiricus was reduced. The abundance of microbial genus Lactobacillus exhibiting potential tannin-degrading activity was significantly higher in A. peninsulae than in T. sibiricus. Our results suggest that masting tree species with different tannin concentrations may differentially influence population fluctuations of seed predators hosting different gut microbial communities. Although the conclusion is based on just correlational analysis of a short time-series, seeds with different chemical composition may influence rodent populations differently. Future work should examine these questions further to understand the complex interactions among seeds, gut microbes, and animal populations.

The diet of a nocturnal pelagic predator, the Bulwer's petrel, across the lunar cycle.

PubMed

Waap, S; Symondson, W O C; Granadeiro, J P; Alonso, H; Serra-Gonçalves, C; Dias, M P; Catry, P

2017-05-03

The lunar cycle is believed to strongly influence the vertical distribution of many oceanic taxa, with implications for the foraging behaviour of nocturnal marine predators. Most studies to date testing lunar effects on foraging have focused on predator activity at-sea, with some birds and marine mammals demonstrating contrasting behavioural patterns, depending on the lunar-phase. However, to date no study has focused on how the lunar cycle might actually affect predator-prey interactions in the upper layers of the ocean. Here, we tested whether the diet of the predominantly nocturnal pelagic predator, the Bulwer's petrel (Bulweria bulwerii) would change throughout the lunar cycle, using molecular analysis to augment detection and taxonomic resolution of prey collected from stomach-contents. We found no evidence of dietary shifts in species composition or diversity, with Bulwer's petrel always consuming a wide range of mesopelagic species. Other co-variables potentially affecting light availability at-sea, such as percentage of cloud cover, did not confound our results. Moreover, many of the species found are thought not to reach the sea-surface. Our findings reveal that nocturnal predators are probably more specialized than previously assumed, irrespective of ambient-light, but also reveal deficiencies in our current understanding of species vertical distribution and predation-dynamics at-sea.

Increased noise levels have different impacts on the anti-predator behaviour of two sympatric fish species.

PubMed

Voellmy, Irene K; Purser, Julia; Simpson, Stephen D; Radford, Andrew N

2014-01-01

Animals must avoid predation to survive and reproduce, and there is increasing evidence that man-made (anthropogenic) factors can influence predator-prey relationships. Anthropogenic noise has been shown to have a variety of effects on many species, but work investigating the impact on anti-predator behaviour is rare. In this laboratory study, we examined how additional noise (playback of field recordings of a ship passing through a harbour), compared with control conditions (playback of recordings from the same harbours without ship noise), affected responses to a visual predatory stimulus. We compared the anti-predator behaviour of two sympatric fish species, the three-spined stickleback (Gasterosteus aculeatus) and the European minnow (Phoxinus phoxinus), which share similar feeding and predator ecologies, but differ in their body armour. Effects of additional-noise playbacks differed between species: sticklebacks responded significantly more quickly to the visual predatory stimulus during additional-noise playbacks than during control conditions, while minnows exhibited no significant change in their response latency. Our results suggest that elevated noise levels have the potential to affect anti-predator behaviour of different species in different ways. Future field-based experiments are needed to confirm whether this effect and the interspecific difference exist in relation to real-world noise sources, and to determine survival and population consequences.

Influence of habitat on behavior of Towndsend's ground squirrels (Spermophilus townsendii)

USGS Publications Warehouse

Sharpe, Peter B.; Van Horne, Beatrice

1998-01-01

Trade-offs between foraging and predator avoidance may affect an animal's survival and reproduction. These trade-offs may be influenced by differences in vegetative cover, especially if foraging profitability and predation risk differ among habitats. We examined above-ground activity of Townsend's ground squirrels (Spermophilus townsendii) in four habitats in the Snake River Birds of Prey National Conservation Area in southwestern Idaho to determine if behavior of ground squirrels varied among habitats, and we assessed factors that might affect perceived predation risk (i. e. predator detectability, predation pressure, population density). The proportion of time spent in vigilance by ground squirrels in winterfat (Krascheninnikovia lanata) and mosaic habitats of winterfat-sagebrush (Artemisia tridentata) was more than twice that of ground squirrels in burned and unburned sagebrush habitats. We found no evidence for the 'many-eyes' hypothesis as an explanation for differences in vigilance among habitats. Instead, environmental heterogeneity, especially vegetation structure, likely influenced activity budgets of ground squirrels. Differences in vigilance may have been caused by differences in predator detectability and refuge availability, because ground squirrels in the winterfat and mosaic habitats also spent more time in upright vigilant postures than ground squirrels in burned-sagebrush or sagebrush habitats. Such postures may enhance predator detection in low-growing winterfat.

Predator experience overrides learned aversion to heterospecifics in stickleback species pairs

PubMed Central

Kozak, Genevieve M.; Boughman, Janette W.

2015-01-01

Predation risk can alter female mating decisions because the costs of mate searching and selecting attractive mates increase when predators are present. In response to predators, females have been found to plastically adjust mate preference within species, but little is known about how predators alter sexual isolation and hybridization among species. We tested the effects of predator exposure on sexual isolation between benthic and limnetic threespine sticklebacks (Gasterosteus spp.). Female discrimination against heterospecific mates was measured before and after females experienced a simulated attack by a trout predator or a control exposure to a harmless object. In the absence of predators, females showed increased aversion to heterospecifics over time. We found that predator exposure made females less discriminating and precluded this learned aversion to heterospecifics. Benthic and limnetic males differ in coloration, and predator exposure also affected sexual isolation by weakening female preferences for colourful males. Predator effects on sexual selection were also tested but predators had few effects on female choosiness among conspecific mates. Our results suggest that predation risk may disrupt the cognitive processes associated with mate choice and lead to fluctuations in the strength of sexual isolation between species. PMID:25808887

Sensitivity of Polygonum aviculare Seeds to Light as Affected by Soil Moisture Conditions

PubMed Central

Batlla, Diego; Nicoletta, Marcelo; Benech-Arnold, Roberto

2007-01-01

Background and Aims It has been hypothesized that soil moisture conditions could affect the dormancy status of buried weed seeds, and, consequently, their sensitivity to light stimuli. In this study, an investigation is made of the effect of different soil moisture conditions during cold-induced dormancy loss on changes in the sensitivity of Polygonum aviculare seeds to light. Methods Seeds buried in pots were stored under different constant and fluctuating soil moisture environments at dormancy-releasing temperatures. Seeds were exhumed at regular intervals during storage and were exposed to different light treatments. Changes in the germination response of seeds to light treatments during storage under the different moisture environments were compared in order to determine the effect of soil moisture on the sensitivity to light of P. aviculare seeds. Key Results Seed acquisition of low-fluence responses during dormancy release was not affected by either soil moisture fluctuations or different constant soil moisture contents. On the contrary, different soil moisture environments affected seed acquisition of very low fluence responses and the capacity of seeds to germinate in the dark. Conclusions The results indicate that under field conditions, the sensitivity to light of buried weed seeds could be affected by the soil moisture environment experienced during the dormancy release season, and this could affect their emergence pattern. PMID:17430979

Fire in the Amazon: impact of experimental fuel addition on responses of ants and their interactions with myrmecochorous seeds.

PubMed

Paolucci, Lucas N; Maia, Maria L B; Solar, Ricardo R C; Campos, Ricardo I; Schoereder, José H; Andersen, Alan N

2016-10-01

The widespread clearing of tropical forests causes lower tree cover, drier microclimate, and higher and drier fuel loads of forest edges, increasing the risk of fire occurrence and its intensity. We used a manipulative field experiment to investigate the influence of fire and fuel loads on ant communities and their interactions with myrmecochorous seeds in the southern Amazon, a region currently undergoing extreme land-use intensification. Experimental fires and fuel addition were applied to 40 × 40-m plots in six replicated blocks, and ants were sampled between 15 and 30 days after fires in four strata: subterranean, litter, epigaeic, and arboreal. Fire had extensive negative effects on ant communities. Highly specialized cryptobiotic and predator species of the litter layer and epigaeic specialist predators were among the most sensitive, but we did not find evidence of overall biotic homogenization following fire. Fire reduced rates of location and transport of myrmecochorous seeds, and therefore the effectiveness of a key ecosystem service provided by ants, which we attribute to lower ant abundance and increased thermal stress. Experimental fuel addition had only minor effects on attributes of fire severity, and limited effects on ant responses to fire. Our findings indicate that enhanced fuel loads will not decrease ant diversity and ecosystem services through increased fire severity, at least in wetter years. However, higher fuel loads can still have a significant effect on ants from Amazonian rainforests because they increase the risk of fire occurrence, which has a detrimental impact on ant communities and a key ecosystem service they provide.

Combined climate- and prey-mediated range expansion of Humboldt squid (Dosidicus gigas), a large marine predator in the California Current System.

PubMed

Stewart, Julia S; Hazen, Elliott L; Bograd, Steven J; Byrnes, Jarrett E K; Foley, David G; Gilly, William F; Robison, Bruce H; Field, John C

2014-06-01

Climate-driven range shifts are ongoing in pelagic marine environments, and ecosystems must respond to combined effects of altered species distributions and environmental drivers. Hypoxic oxygen minimum zones (OMZs) in midwater environments are shoaling globally; this can affect distributions of species both geographically and vertically along with predator-prey dynamics. Humboldt (jumbo) squid (Dosidicus gigas) are highly migratory predators adapted to hypoxic conditions that may be deleterious to their competitors and predators. Consequently, OMZ shoaling may preferentially facilitate foraging opportunities for Humboldt squid. With two separate modeling approaches using unique, long-term data based on in situ observations of predator, prey, and environmental variables, our analyses suggest that Humboldt squid are indirectly affected by OMZ shoaling through effects on a primary food source, myctophid fishes. Our results suggest that this indirect linkage between hypoxia and foraging is an important driver of the ongoing range expansion of Humboldt squid in the northeastern Pacific Ocean. © 2014 John Wiley & Sons Ltd.

No evidence of nonlinear effects of predator density, refuge availability, or body size of prey on prey mortality rates.

PubMed

Simkins, Richard M; Belk, Mark C

2017-08-01

Predator density, refuge availability, and body size of prey can all affect the mortality rate of prey. We assume that more predators will lead to an increase in prey mortality rate, but behavioral interactions between predators and prey, and availability of refuge, may lead to nonlinear effects of increased number of predators on prey mortality rates. We tested for nonlinear effects in prey mortality rates in a mesocosm experiment with different size classes of western mosquitofish ( Gambusia affinis ) as the prey, different numbers of green sunfish ( Lepomis cyanellus ) as the predators, and different levels of refuge. Predator number and size class of prey, but not refuge availability, had significant effects on the mortality rate of prey. Change in mortality rate of prey was linear and equal across the range of predator numbers. Each new predator increased the mortality rate by about 10% overall, and mortality rates were higher for smaller size classes. Predator-prey interactions at the individual level may not scale up to create nonlinearity in prey mortality rates with increasing predator density at the population level.

Native and Non-Native Plants Provide Similar Refuge to Invertebrate Prey, but Less than Artificial Plants

PubMed Central

Grutters, Bart M. C.; Pollux, Bart J. A.; Verberk, Wilco C. E. P.; Bakker, Elisabeth S.

2015-01-01

Non-native species introductions are widespread and can affect ecosystem functioning by altering the structure of food webs. Invading plants often modify habitat structure, which may affect the suitability of vegetation as refuge and could thus impact predator-prey dynamics. Yet little is known about how the replacement of native by non-native vegetation affects predator-prey dynamics. We hypothesize that plant refuge provisioning depends on (1) the plant’s native status, (2) plant structural complexity and morphology, (3) predator identity, and (4) prey identity, as well as that (5) structurally similar living and artificial plants provide similar refuge. We used aquatic communities as a model system and compared the refuge provided by plants to macroinvertebrates (Daphnia pulex, Gammarus pulex and damselfly larvae) in three short-term laboratory predation experiments. Plant refuge provisioning differed between plant species, but was generally similar for native (Myriophyllum spicatum, Ceratophyllum demersum, Potamogeton perfoliatus) and non-native plants (Vallisneria spiralis, Myriophyllum heterophyllum, Cabomba caroliniana). However, plant refuge provisioning to macroinvertebrate prey depended primarily on predator (mirror carp: Cyprinus carpio carpio and dragonfly larvae: Anax imperator) and prey identity, while the effects of plant structural complexity were only minor. Contrary to living plants, artificial plant analogues did improve prey survival, particularly with increasing structural complexity and shoot density. As such, plant rigidity, which was high for artificial plants and one of the living plant species evaluated in this study (Ceratophyllum demersum), may interact with structural complexity to play a key role in refuge provisioning to specific prey (Gammarus pulex). Our results demonstrate that replacement of native by structurally similar non-native vegetation is unlikely to greatly affect predator-prey dynamics. We propose that modification of predator-prey interactions through plant invasions only occurs when invading plants radically differ in growth form, density and rigidity compared to native plants. PMID:25885967

Expression of TaCYP78A3, a gene encoding cytochrome P450 CYP78A3 protein in wheat (Triticum aestivum L.), affects seed size.

PubMed

Ma, Meng; Wang, Qian; Li, Zhanjie; Cheng, Huihui; Li, Zhaojie; Liu, Xiangli; Song, Weining; Appels, Rudi; Zhao, Huixian

2015-07-01

Several studies have described quantitative trait loci (QTL) for seed size in wheat, but the relevant genes and molecular mechanisms remain largely unknown. Here we report the functional characterization of the wheat TaCYP78A3 gene and its effect on seed size. TaCYP78A3 encoded wheat cytochrome P450 CYP78A3, and was specifically expressed in wheat reproductive organs. TaCYP78A3 activity was positively correlated with the final seed size. Its silencing caused a reduction of cell number in the seed coat, resulting in an 11% decrease in wheat seed size, whereas TaCYP78A3 over-expression induced production of more cells in the seed coat, leading to an 11-48% increase in Arabidopsis seed size. In addition, the cell number in the final seed coat was determined by the TaCYP78A3 expression level, which affected the extent of integument cell proliferation in the developing ovule and seed. Unfortunately, TaCYP78A3 over-expression in Arabidopsis caused a reduced seed set due to an ovule developmental defect. Moreover, TaCYP78A3 over-expression affected embryo development by promoting embryo integument cell proliferation during seed development, which also ultimately affected the final seed size in Arabidopsis. In summary, our results indicated that TaCYP78A3 plays critical roles in influencing seed size by affecting the extent of integument cell proliferation. The present study provides direct evidence that TaCYP78A3 affects seed size in wheat, and contributes to an understanding of the cellular basis of the gene influencing seed development. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

Mass enhances speed but diminishes turn capacity in terrestrial pursuit predators.

PubMed

Wilson, Rory P; Griffiths, Iwan W; Mills, Michael G L; Carbone, Chris; Wilson, John W; Scantlebury, David M

2015-08-07

The dynamics of predator-prey pursuit appears complex, making the development of a framework explaining predator and prey strategies problematic. We develop a model for terrestrial, cursorial predators to examine how animal mass modulates predator and prey trajectories and affects best strategies for both parties. We incorporated the maximum speed-mass relationship with an explanation of why larger animals should have greater turn radii; the forces needed to turn scale linearly with mass whereas the maximum forces an animal can exert scale to a 2/3 power law. This clarifies why in a meta-analysis, we found a preponderance of predator/prey mass ratios that minimized the turn radii of predators compared to their prey. It also explained why acceleration data from wild cheetahs pursuing different prey showed different cornering behaviour with prey type. The outcome of predator prey pursuits thus depends critically on mass effects and the ability of animals to time turns precisely.

Do mammalian nest predators follow human scent trails in the shortgrass prairie?

USGS Publications Warehouse

Skagen, S.K.; Stanley, T.R.; Dillon, M.B.

1999-01-01

Nest predation, the major cause of nest failure in passerines, has exerted a strong influence on the evolution of life history traits of birds. Because human disturbance during nest monitoring may alter predation rates, we investigated whether human scent affected the survival of artificial ground nests in shortgrass prairie. Our experiment consisted of two treatments, one in which there was no attempt to mask human scent along travel routes between artificial nests, and one in which we masked human scent with cow manure, a scent familiar to mammalian predators in the study area. We found no evidence that human scent influenced predation rates, nor that mammalian predators followed human trails between nests. We conclude that scent trails made by investigators do not result in lower nesting success of passerines of the shortgrass prairie where vegetation trampling is minimal, mammalian predators predominate, and avian predators are rare.

Plant species composition alters the sign and strength of an emergent multi-predator effect by modifying predator foraging behaviour.

PubMed

Wilby, Andrew; Anglin, Linda Anderson; Nesbit, Christopher M

2013-01-01

The prediction of pest-control functioning by multi-predator communities is hindered by the non-additive nature of species functioning. Such non-additivity, commonly termed an emergent multi-predator effect, is known to be affected by elements of the ecological context, such as the structure and composition of vegetation, in addition to the traits of the predators themselves. Here we report mesocosm experiments designed to test the influence of plant density and species composition (wheat monoculture or wheat and faba bean polyculture) on the emergence of multi-predator effects between Adalia bipunctata and Chrysoperla carnea, in their suppression of populations of the aphid Metopolophium dirhodum. The mesocosm experiments were followed by a series of behavioural observations designed to identify how interactions among predators are modified by plant species composition and whether these effects are consistent with the observed influence of plant species composition on aphid population suppression. Although plant density was shown to have no influence on the multi-predator effect on aphid population growth, plant composition had a marked effect. In wheat monoculture, Adalia and Chrysoperla mixed treatments caused greater suppression of M. dirhodum populations than expected. However this positive emergent effect was reversed to a negative multi-predator effect in wheat and faba bean polyculture. The behavioural observations revealed that although dominant individuals did not respond to the presence of faba bean plants, the behaviour of sub-dominants was affected markedly, consistent with their foraging for extra-floral nectar produced by the faba bean. This interaction between plant composition and predator community composition on the foraging behaviour of sub-dominants is thought to underlie the observed effect of plant composition on the multi-predator effect. Thus, the emergence of multi-predator effects is shown to be strongly influenced by plant species composition, mediated, in this case, by the provision of extra-floral nectar by one of the plant species.

Fish farms, parasites, and predators: implications for salmon population dynamics.

PubMed

Krkosek, Martin; Connors, Brendan M; Ford, Helen; Peacock, Stephanie; Mages, Paul; Ford, Jennifer S; Morton, Alexandra; Volpe, John P; Hilborn, Ray; Dill, Lawrence M; Lewis, Mark A

2011-04-01

For some salmon populations, the individual and population effects of sea lice (Lepeophtheirus salmonis) transmission from sea cage salmon farms is probably mediated by predation, which is a primary natural source of mortality of juvenile salmon. We examined how sea lice infestation affects predation risk and mortality of juvenile pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon, and developed a mathematical model to assess the implications for population dynamics and conservation. A risk-taking experiment indicated that infected juvenile pink salmon accept a higher predation risk in order to obtain foraging opportunities. In a schooling experiment with juvenile chum salmon, infected individuals had increased nearest-neighbor distances and occupied peripheral positions in the school. Prey selection experiments with cutthroat trout (O. clarkii) predators indicated that infection reduces the ability of juvenile pink salmon to evade a predatory strike. Group predation experiments with coho salmon (O. kisutch) feeding on juvenile pink or chum salmon indicated that predators selectively consume infected prey. The experimental results indicate that lice may increase the rate of prey capture but not the handling time of a predator. Based on this result, we developed a mathematical model of sea lice and salmon population dynamics in which parasitism affects the attack rate in a type II functional response. Analysis of the model indicates that: (1) the estimated mortality of wild juvenile salmon due to sea lice infestation is probably higher than previously thought; (2) predation can cause a simultaneous decline in sea louse abundance on wild fish and salmon productivity that could mislead managers and regulators; and (3) compensatory mortality occurs in the saturation region of the type II functional response where prey are abundant because predators increase mortality of parasites but not overall predation rates. These findings indicate that predation is an important component of salmon-louse dynamics and has implications for estimating mortality, reducing infection, and developing conservation policy.

Predator Cue and Prey Density Interactively Influence Indirect Effects on Basal Resources in Intertidal Oyster Reefs

PubMed Central

Hughes, A. Randall; Rooker, Kelly; Murdock, Meagan; Kimbro, David L.

2012-01-01

Predators can influence prey abundance and traits by direct consumption, as well as by non-consumptive effects of visual, olfactory, or tactile cues. The strength of these non-consumptive effects (NCEs) can be influenced by a variety of factors, including predator foraging mode, temporal variation in predator cues, and the density of competing prey. Testing the relative importance of these factors for determining NCEs is critical to our understanding of predator-prey interactions in a variety of settings. We addressed this knowledge gap by conducting two mesocosm experiments in a tri-trophic intertidal oyster reef food web. More specifically, we tested how a predatory fish (hardhead catfish, Ariopsis felis) directly influenced their prey (mud crabs, Panopeus spp.) and indirectly affected basal resources (juvenile oysters, Crassostrea virginica), as well as whether these direct and indirect effects changed across a density gradient of competing prey. Per capita crab foraging rates were inversely influenced by crab density, but they were not affected by water-borne predator cues. As a result, direct consumptive effects on prey foraging rates were stronger than non-consumptive effects. In contrast, predator cue and crab density interactively influenced indirect predator effects on oyster mortality in two experiments, with trait-mediated and density-mediated effects of similar magnitude operating to enhance oyster abundance. Consistent differences between a variable predator cue environment and other predator cue treatments (no cue and constant cue) suggests that an understanding of the natural risk environment experienced by prey is critical to testing and interpreting trait-mediated indirect interactions. Further, the prey response to the risk environment may be highly dependent on prey density, particularly in prey populations with strong intra-specific interactions. PMID:22970316

Species dispersal rates alter diversity and ecosystem stability in pond metacommunities.

PubMed

Howeth, Jennifer G; Leibold, Mathew A

2010-09-01

Metacommunity theory suggests that relationships between diversity and ecosystem stability can be determined by the rate of species dispersal among local communities. The predicted relationships, however, may depend upon the relative strength of local environmental processes and disturbance. Here we evaluate the role of dispersal frequency and local predation perturbations in affecting patterns of diversity and stability in pond plankton metacommunities. Pond metacommunities were composed of three mesocosm communities: one of the three communities maintained constant "press" predation from a selective predator, bluegill sunfish (Lepomis macrochirus); the second community maintained "press" conditions without predation; and the third community experienced recurrent "pulsed" predation from bluegill sunfish. The triads of pond communities were connected at either no, low (0.7%/d), or high (20%/d) planktonic dispersal. Richness and composition of zooplankton and stability of plankton biomass and ecosystem productivity were measured at local and regional spatial scales. Dispersal significantly affected diversity such that local and regional biotas at the low dispersal rate maintained the greatest number of species. The unimodal local dispersal-diversity relationship was predator-dependent, however, as selective press predation excluded species regardless of dispersal. Further, there was no effect of dispersal on beta diversity because predation generated local conditions that selected for distinct community assemblages. Spatial and temporal ecosystem stability responded to dispersal frequency but not predation. Low dispersal destabilized the spatial stability of producer biomass but stabilized temporal ecosystem productivity. The results indicate that selective predation can prevent species augmentation from mass effects but has no apparent influence on stability. Dispersal rates, in contrast, can have significant effects on both species diversity and ecosystem stability at multiple spatial scales in metacommunities.

Turbulence, Temperature, and Turbidity: The Ecomechanics of Predator-Prey Interactions in Fishes.

PubMed

Higham, Timothy E; Stewart, William J; Wainwright, Peter C

2015-07-01

Successful feeding and escape behaviors in fishes emerge from precise integration of locomotion and feeding movements. Fishes inhabit a wide range of habitats, including still ponds, turbulent rivers, and wave-pounded shorelines, and these habitats vary in several physical variables that can strongly impact both predator and prey. Temperature, the conditions of ambient flow, and light regimes all have the potential to affect predator-prey encounters, yet the integration of these factors into our understanding of fish biomechanics is presently limited. We explore existing knowledge of kinematics, muscle function, hydrodynamics, and evolutionary morphology in order to generate a framework for understanding the ecomechanics of predator-prey encounters in fishes. We expect that, in the absence of behavioral compensation, a decrease in temperature below the optimum value will reduce the muscle power available both to predator and prey, thus compromising locomotor performance, suction-feeding mechanics of predators, and the escape responses of prey. Ambient flow, particularly turbulent flow, will also challenge predator and prey, perhaps resulting in faster attacks by predators to minimize mechanical instability, and a reduced responsiveness of prey to predator-generated flow. Reductions in visibility, caused by depth, turbidity, or diel fluctuations in light, will decrease distances at which either predator or prey detect each other, and generally place a greater emphasis on the role of mechanoreception both for predator and prey. We expect attack distances to be shortened when visibility is low. Ultimately, the variation in abiotic features of a fish's environment will affect locomotion and feeding performance of predators, and the ability of the prey to escape. The nature of these effects and how they impact predator-prey encounters stands as a major challenge for future students of the biomechanics of fish during feeding. Just as fishes show adaptations for capturing specific types of prey, we anticipate they are also adapted to the physical features of their preferred habitat and show a myriad of behavioral mechanisms for dealing with abiotic factors during predator-prey encounters. © The Author 2015. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

At Lunch with a Killer: The Effect of Weaver Ants on Host-Parasitoid Interactions on Mango

PubMed Central

Migani, Valentina; Ekesi, Sunday; Merkel, Katharina; Hoffmeister, Thomas

2017-01-01

Predator-prey interactions can affect the behaviour of the species involved, with consequences for population distribution and competitive interactions. Under predation pressure, potential prey may adopt evasive strategies. These responses can be costly and could impact population growth. As some prey species may be more affected than others, predation pressure could also alter the dynamics among species within communities. In field cages and small observation cages, we studied the interactions between a generalist predator, the African weaver ant, Oecophylla longinoda, two species of fruit flies that are primary pests of mango fruits, Ceratitis cosyra and Bactrocera dorsalis, and their two exotic parasitoids, Fopius arisanus and Diachasmimorpha longicaudata. In all experiments, either a single individual (observation cage experiments) or groups of individuals (field cage experiments) of a single species were exposed to foraging in the presence or absence of weaver ants. Weaver ant presence reduced the number of eggs laid by 75 and 50 percent in B. dorsalis and C. cosyra respectively. Similarly, parasitoid reproductive success was negatively affected by ant presence, with success of parasitism reduced by around 50 percent for both F. arisanus and D. longicaudata. The negative effect of weaver ants on both flies and parasitoids was mainly due to indirect predation effects. Encounters with weaver ant workers increased the leaving tendency in flies and parasitoids, thus reduced the time spent foraging on mango fruits. Parasitoids were impacted more strongly than fruit flies. We discuss how weaver ant predation pressure may affect the population dynamics of the fruit flies, and, in turn, how the alteration of host dynamics could impact parasitoid foraging behaviour and success. PMID:28146561

Habitat Selection and Risk of Predation: Re-colonization by Lynx had Limited Impact on Habitat Selection by Roe Deer

PubMed Central

Samelius, Gustaf; Andrén, Henrik; Kjellander, Petter; Liberg, Olof

2013-01-01

Risk of predation is an evolutionary force that affects behaviors of virtually all animals. In this study, we examined how habitat selection by roe deer was affected by risk of predation by Eurasian lynx – the main predator of roe deer in Scandinavia. Specifically, we compared how habitat selection by roe deer varied (1) before and after lynx re-established in the study area and (2) in relation to habitat-specific risk of predation by lynx. All analyses were conducted at the spatial and temporal scales of home ranges and seasons. We did not find any evidence that roe deer avoided habitats in which the risk of predation by lynx was greatest and information-theoretic model selection showed that re-colonization by lynx had limited impact on habitat selection by roe deer despite lynx predation causing 65% of known mortalities after lynx re-colonized the area. Instead we found that habitat selection decreased when habitat availability increased for 2 of 5 habitat types (a pattern referred to as functional response in habitat selection). Limited impact of re-colonization by lynx on habitat selection by roe deer in this study differs from elk in North America altering both daily and seasonal patterns in habitat selection at the spatial scales of habitat patches and home ranges when wolves were reintroduced to Yellowstone National Park. Our study thus provides further evidence of the complexity by which animals respond to risk of predation and suggest that it may vary between ecosystems and predator-prey constellations. PMID:24069419

Habitat selection and risk of predation: re-colonization by lynx had limited impact on habitat selection by roe deer.

PubMed

Samelius, Gustaf; Andrén, Henrik; Kjellander, Petter; Liberg, Olof

2013-01-01

Risk of predation is an evolutionary force that affects behaviors of virtually all animals. In this study, we examined how habitat selection by roe deer was affected by risk of predation by Eurasian lynx - the main predator of roe deer in Scandinavia. Specifically, we compared how habitat selection by roe deer varied (1) before and after lynx re-established in the study area and (2) in relation to habitat-specific risk of predation by lynx. All analyses were conducted at the spatial and temporal scales of home ranges and seasons. We did not find any evidence that roe deer avoided habitats in which the risk of predation by lynx was greatest and information-theoretic model selection showed that re-colonization by lynx had limited impact on habitat selection by roe deer despite lynx predation causing 65% of known mortalities after lynx re-colonized the area. Instead we found that habitat selection decreased when habitat availability increased for 2 of 5 habitat types (a pattern referred to as functional response in habitat selection). Limited impact of re-colonization by lynx on habitat selection by roe deer in this study differs from elk in North America altering both daily and seasonal patterns in habitat selection at the spatial scales of habitat patches and home ranges when wolves were reintroduced to Yellowstone National Park. Our study thus provides further evidence of the complexity by which animals respond to risk of predation and suggest that it may vary between ecosystems and predator-prey constellations.

Large-scale climatic anomalies affect marine predator foraging behaviour and demography.

PubMed

Bost, Charles A; Cotté, Cedric; Terray, Pascal; Barbraud, Christophe; Bon, Cécile; Delord, Karine; Gimenez, Olivier; Handrich, Yves; Naito, Yasuhiko; Guinet, Christophe; Weimerskirch, Henri

2015-10-27

Determining the links between the behavioural and population responses of wild species to environmental variations is critical for understanding the impact of climate variability on ecosystems. Using long-term data sets, we show how large-scale climatic anomalies in the Southern Hemisphere affect the foraging behaviour and population dynamics of a key marine predator, the king penguin. When large-scale subtropical dipole events occur simultaneously in both subtropical Southern Indian and Atlantic Oceans, they generate tropical anomalies that shift the foraging zone southward. Consequently the distances that penguins foraged from the colony and their feeding depths increased and the population size decreased. This represents an example of a robust and fast impact of large-scale climatic anomalies affecting a marine predator through changes in its at-sea behaviour and demography, despite lack of information on prey availability. Our results highlight a possible behavioural mechanism through which climate variability may affect population processes.

Large-scale climatic anomalies affect marine predator foraging behaviour and demography

NASA Astrophysics Data System (ADS)

Bost, Charles A.; Cotté, Cedric; Terray, Pascal; Barbraud, Christophe; Bon, Cécile; Delord, Karine; Gimenez, Olivier; Handrich, Yves; Naito, Yasuhiko; Guinet, Christophe; Weimerskirch, Henri

2015-10-01

Determining the links between the behavioural and population responses of wild species to environmental variations is critical for understanding the impact of climate variability on ecosystems. Using long-term data sets, we show how large-scale climatic anomalies in the Southern Hemisphere affect the foraging behaviour and population dynamics of a key marine predator, the king penguin. When large-scale subtropical dipole events occur simultaneously in both subtropical Southern Indian and Atlantic Oceans, they generate tropical anomalies that shift the foraging zone southward. Consequently the distances that penguins foraged from the colony and their feeding depths increased and the population size decreased. This represents an example of a robust and fast impact of large-scale climatic anomalies affecting a marine predator through changes in its at-sea behaviour and demography, despite lack of information on prey availability. Our results highlight a possible behavioural mechanism through which climate variability may affect population processes.

Intraspecific variation in body size does not alter the effects of mesopredators on prey.

PubMed

Gallagher, Austin J; Brandl, Simon J; Stier, Adrian C

2016-12-01

As humans continue to alter the species composition and size structure of marine food webs, it is critical to understand size-dependent effects of predators on prey. Yet, how shifts in predator body size mediate the effect of predators is understudied in tropical marine ecosystems, where anthropogenic harvest has indirectly increased the density and size of small-bodied predators. Here, we combine field surveys and a laboratory feeding experiment in coral reef fish communities to show that small and large predators of the same species can have similar effects. Specifically, surveys show that the presence of a small predator ( Paracirrhites arcatus ) was correlated with lower chances of prey fish presence, but these correlations were independent of predator size. Experimental trials corroborated the size-independent effect of the predator; attack rates were indistinguishable between small and large predators, suggesting relatively even effects of hawkfish in various size classes on the same type of prey. Our results indicate that the effects of small predators on coral reefs can be size-independent, suggesting that variation in predator size-structure alone may not always affect the functional role of these predators.

Does the shelterwood method to regenerate oak forests affect acorn production and predation?

Treesearch

M.I. Bellocq; C. Jones; D.C. Dey; J.J. Turgeon

2005-01-01

The shelterwood system is one of the primary methods currently used to encourage regeneration of oak forests; yet, little is known about its influence on acorn production and predation. We compared acorn production, and predation by insects and mammals in stands of red oak (Quercus rubra L.) that were regenerated by the shelterwood method (50% canopy...

Predation environment affects boldness temperament of neotropical livebearers.

PubMed

Rasmussen, Josh E; Belk, Mark C

2017-05-01

Behavioral traits of individuals are important phenotypes that potentially interact with many other traits, an understanding of which may illuminate the evolutionary forces affecting populations and species. Among the five axes of temperament is the propensity to behave boldly in the presence of a perceived risk. To determine the effect of different predatorial regimes on boldness and fearfulness, we assessed the behavior of individuals in a novel portable swim chamber (i.e., forced open-field test) by Brachyrhaphis rhabdophora ( n  = 633). We used an information theoretic framework to compare generalized (logistic) linear fixed-effects models of predatorial regime (predator-free [ n  = 6] and predator [ n  = 4] sites), sex, and standard length (SL). Fish from predator sites were much more fearful in the novel arena than fish from nonpredator sites. This varied by length, but not by sex. At 48 mm SL, fish from nonpredator sites were 4.9 times more likely to express bold behavior (ambulation) in the novel swim chamber as fish from predator sites. Probabilities of "ambulating" within the swim chamber increased with size for nonpredator sites and decreased with size for predator sites.

Competition between apex predators? Brown bears decrease wolf kill rate on two continents

PubMed Central

Ordiz, Andrés; Metz, Matthew C.; Milleret, Cyril; Wikenros, Camilla; Smith, Douglas W.; Stahler, Daniel R.; Kindberg, Jonas; MacNulty, Daniel R.; Wabakken, Petter; Swenson, Jon E.; Sand, Håkan

2017-01-01

Trophic interactions are a fundamental topic in ecology, but we know little about how competition between apex predators affects predation, the mechanism driving top-down forcing in ecosystems. We used long-term datasets from Scandinavia (Europe) and Yellowstone National Park (North America) to evaluate how grey wolf (Canis lupus) kill rate was affected by a sympatric apex predator, the brown bear (Ursus arctos). We used kill interval (i.e. the number of days between consecutive ungulate kills) as a proxy of kill rate. Although brown bears can monopolize wolf kills, we found no support in either study system for the common assumption that they cause wolves to kill more often. On the contrary, our results showed the opposite effect. In Scandinavia, wolf packs sympatric with brown bears killed less often than allopatric packs during both spring (after bear den emergence) and summer. Similarly, the presence of bears at wolf-killed ungulates was associated with wolves killing less often during summer in Yellowstone. The consistency in results between the two systems suggests that brown bear presence actually reduces wolf kill rate. Our results suggest that the influence of predation on lower trophic levels may depend on the composition of predator communities. PMID:28179516

State of emergency: behavior of gerbils is affected by the hunger state of their predators.

PubMed

Berger-Tal, Oded; Kotler, Burt P

2010-02-01

Predator-prey interactions are usually composed of behaviorally sophisticated games in which the values of the strategies of foraging prey individuals may depend on those of their predators, and vice versa. Therefore, any change in the behavior of the predator should result in changes to the behavior of the prey. However, this key prediction has rarely been tested. To examine the effects of the predator state on prey behavior, we manipulated the state of captive Barn Owls, Tyto alba, and released them into an enclosure containing Allenby's gerbils, Gerbillus andersoni allenbyi, a common prey of the owls. The owls were significantly more active when hungry. In response, the gerbils altered their behavior according to the state of the owl. When the owl was hungry, the gerbils visited fewer food patches, foraged in fewer patches, and harvested less food from each patch. Moreover, the gerbils kept their foraging bouts closer to their burrow, which reduced the overlap among foraging ranges of individual gerbils. Thus, changes in the state of the predator affect the foraging behavior of its prey and can also mediate competition among prey individuals.

When parasites become prey: ecological and epidemiological significance of eating parasites

USGS Publications Warehouse

Johnson, Pieter T.J.; Dobson, Andrew P.; Lafferty, Kevin D.; Marcogliese, David J.; Memmott, Jane; Orlofske, Sarah A.; Poulin, Robert; Thieltges, David W.

2010-01-01

Recent efforts to include parasites in food webs have drawn attention to a previously ignored facet of foraging ecology: parasites commonly function as prey within ecosystems. Because of the high productivity of parasites, their unique nutritional composition and their pathogenicity in hosts, their consumption affects both food-web topology and disease risk in humans and wildlife. Here, we evaluate the ecological, evolutionary and epidemiological significance of feeding on parasites, including concomitant predation, grooming, predation on free-living stages and intraguild predation. Combining empirical data and theoretical models, we show that consumption of parasites is neither rare nor accidental, and that it can sharply affect parasite transmission and food web properties. Broader consideration of predation on parasites will enhance our understanding of disease control, food web structure and energy transfer, and the evolution of complex life cycles.

Predatory senescence in ageing wolves.

PubMed

MacNulty, Daniel R; Smith, Douglas W; Vucetich, John A; Mech, L David; Stahler, Daniel R; Packer, Craig

2009-12-01

It is well established that ageing handicaps the ability of prey to escape predators, yet surprisingly little is known about how ageing affects the ability of predators to catch prey. Research into long-lived predators has assumed that adults have uniform impacts on prey regardless of age. Here we use longitudinal data from repeated observations of individually-known wolves (Canis lupus) hunting elk (Cervus elaphus) in Yellowstone National Park to demonstrate that adult predatory performance declines with age and that an increasing ratio of senescent individuals in the wolf population depresses the rate of prey offtake. Because this ratio fluctuates independently of population size, predatory senescence may cause wolf populations of equal size but different age structure to have different impacts on prey populations. These findings suggest that predatory senescence is an important, though overlooked, factor affecting predator-prey dynamics.

Predatory senescence in ageing wolves

USGS Publications Warehouse

MacNulty, D.R.; Smith, D.W.; Vucetich, J.A.; Mech, L.D.; Stahler, D.R.; Packer, C.

2009-01-01

It is well established that ageing handicaps the ability of prey to escape predators, yet surprisingly little is known about how ageing affects the ability of predators to catch prey. Research into long-lived predators has assumed that adults have uniform impacts on prey regardless of age. Here we use longitudinal data from repeated observations of individually-known wolves (Canis lupus) hunting elk (Cervus elaphus) in Yellowstone National Park to demonstrate that adult predatory performance declines with age and that an increasing ratio of senescent individuals in the wolf population depresses the rate of prey offtake. Because this ratio fluctuates independently of population size, predatory senescence may cause wolf populations of equal size but different age structure to have different impacts on prey populations. These findings suggest that predatory senescence is an important, though overlooked, factor affecting predator-prey dynamics. ?? 2009 Blackwell Publishing Ltd/CNRS.

Predatory senescence in aging wolves

USGS Publications Warehouse

MacNulty, Daniel R.; Smith, Douglas W.; Vucetich, John A.; Mech, L. David; Stahler, Daniel R.; Packer, Craig

2009-01-01

It is well established that ageing handicaps the ability of prey to escape predators, yet surprisingly little is known about how ageing affects the ability of predators to catch prey. Research into long-lived predators has assumed that adults have uniform impacts on prey regardless of age. Here we use longitudinal data from repeated observations of individually-known wolves (Canis lupus) hunting elk (Cervus elaphus) in Yellowstone National Park to demonstrate that adult predatory performance declines with age and that an increasing ratio of senescent individuals in the wolf population depresses the rate of prey offtake. Because this ratio fluctuates independently of population size, predatory senescence may cause wolf populations of equal size but different age structure to have different impacts on prey populations. These findings suggest that predatory senescence is an important, though overlooked, factor affecting predator-prey dynamics.

Mean fecal glucocorticoid metabolites are associated with vigilance, whereas immediate cortisol levels better reflect acute anti-predator responses in meerkats.

PubMed

Voellmy, Irene K; Goncalves, Ines Braga; Barrette, Marie-France; Monfort, Steven L; Manser, Marta B

2014-11-01

Adrenal hormones likely affect anti-predator behavior in animals. With experimental field studies, we first investigated associations between mean fecal glucocorticoid metabolite (fGC) excretion and vigilance and with behavioral responses to alarm call playbacks in free-ranging meerkats (Suricata suricatta). We then tested how vigilance and behavioral responses to alarm call playbacks were affected in individuals administered exogenous cortisol. We found a positive association between mean fGC concentrations and vigilance behavior, but no relationship with the intensity of behavioral responses to alarm calls. However, in response to alarm call playbacks, individuals administered cortisol took slightly longer to resume foraging than control individuals treated with saline solution. Vigilance behavior, which occurs in the presence and absence of dangerous stimuli, serves to detect and avoid potential dangers, whereas responses to alarm calls serve to avoid immediate predation. Our data show that mean fGC excretion in meerkats was associated with vigilance, as a re-occurring anti-predator behavior over long time periods, and experimentally induced elevations of plasma cortisol affected the response to immediate threats. Together, our results indicate an association between the two types of anti-predator behavior and glucocorticoids, but that the underlying mechanisms may differ. Our study emphasizes the need to consider appropriate measures of adrenal activity specific to different contexts when assessing links between stress physiology and different anti-predator behaviors. Copyright © 2014 Elsevier Inc. All rights reserved.

Individual variation in behavioural plasticity: direct and indirect effects of boldness, exploration and sociability on habituation to predators in lizards.

PubMed

Rodríguez-Prieto, Iñaki; Martín, José; Fernández-Juricic, Esteban

2011-01-22

Little is known about the factors causing variation in behavioural plasticity and the interplay between personality and plasticity. Habituation to predators is a special case of behavioural plasticity. We investigated the direct and indirect effects of boldness, exploration and sociability traits on the habituation ability of Iberian wall lizards, considering exposure and sex effects. Individual boldness was consistent across several non-habituation contexts, but it did not significantly affect habituation. Exploration had a strong direct effect on habituation, with more exploratory individuals being able to habituate faster than less exploratory ones, probably because of their ability to assess risk better. Individual variation in habituation was also affected by sociability, but this was an indirect effect mediated by exposure to the predator. Less social individuals avoided refuges with conspecific cues, increasing exposure to the predator and eventually habituation. Finally, the direct effects of sex (females habituated faster than males) were opposite to its indirect effects through exposure. We conclude that risk assessment, instead of the proactivity-reactivity gradient usually considered in the literature, can affect behavioural plasticity through complex interactions between direct and indirect effects, including exploratory behaviour, degree of exposure to the predator and sex, which represent novel mechanisms generating inter-individual variation in plasticity.

Drivers of seabird population recovery on New Zealand islands after predator eradication.

PubMed

Buxton, Rachel T; Jones, Christopher; Moller, Henrik; Towns, David R

2014-04-01

Eradication of introduced mammalian predators from islands has become increasingly common, with over 800 successful projects around the world. Historically, introduced predators extirpated or reduced the size of many seabird populations, changing the dynamics of entire island ecosystems. Although the primary outcome of many eradication projects is the restoration of affected seabird populations, natural population responses are rarely documented and mechanisms are poorly understood. We used a generic model of seabird colony growth to identify key predictor variables relevant to recovery or recolonization. We used generalized linear mixed models to test the importance of these variables in driving seabird population responses after predator eradication on islands around New Zealand. The most influential variable affecting recolonization of seabirds around New Zealand was the distance to a source population, with few cases of recolonization without a source population ≤25 km away. Colony growth was most affected by metapopulation status; there was little colony growth in species with a declining status. These characteristics may facilitate the prioritization of newly predator-free islands for active management. Although we found some evidence documenting natural recovery, generally this topic was understudied. Our results suggest that in order to guide management strategies, more effort should be allocated to monitoring wildlife response after eradication. © 2014 Society for Conservation Biology.

Trade-offs between larval survival and adult ornament development depend on predator regime in a territorial dragonfly.

PubMed

Moore, Michael P; Martin, Ryan A

2018-05-28

Trade-offs between juvenile survival and the development of sexually selected traits can cause ontogenetic conflict between life stages that constrains adaptive evolution. However, the potential for ecological interactions to alter the presence or strength of these trade-offs remains largely unexplored. Antagonistic selection over the accumulation and storage of resources could be one common cause of environment-specific trade-offs between life stages: higher condition may simultaneously enhance adult ornament development and increase juvenile vulnerability to predators. We tested this hypothesis in an ornamented dragonfly (Pachydiplax longipennis). Higher larval body condition indeed enhanced the initial development of its intrasexually selected wing coloration, but was opposed by viability selection in the presence of large aeshnid predators. In contrast, viability selection did not oppose larval body condition in pools when aeshnids were absent, and was not affected when we manipulated cannibalism risk. Trade-offs between larval survival and ornament development, mediated through the conflicting effects of body condition, therefore occurred only under high predation risk. We additionally characterized how body condition influences several traits associated with predator avoidance. Although body condition did not affect burst distance, it did increase larval abdomen size, potentially making larvae easier targets for aeshnid predators. As high body condition similarly increases vulnerability to predators in many other animals, predator-mediated costs of juvenile resource accumulation could be a common, environment-specific limitation on the elaboration of sexually selected traits.

Global patterns in post-dispersal seed removal by invertebrates and vertebrates.

PubMed

Peco, Begoña; Laffan, Shawn W; Moles, Angela T

2014-01-01

It is commonly accepted that species interactions such as granivory are more intense in the tropics. However, this has rarely been tested. A global dataset of post-dispersal seed removal by invertebrates and vertebrates for 79 native plant species from semi-natural and natural terrestrial habitats ranging from 55° N to 45° S, was compiled from the global literature to test the hypothesis that post-dispersal seed removal by invertebrates and vertebrates is more intense at lower latitudes. We also quantified the relationship between post-dispersal seed removal by vertebrates and by invertebrates to global climatic features including temperature, actual evapotranspiration (AET) and rainfall seasonality. Linear mixed effect models were applied to describe the relationships between seed removal and latitude, hemisphere and climatic variables controlling for the effect of seed mass. Post-dispersal seed removal by invertebrates was negatively related to latitude. In contrast, post-dispersal seed removal by vertebrates was positively but weakly related to latitude. Mean annual temperature and actual evapotranspiration were positively related to post-dispersal seed removal by invertebrates, but not to post-dispersal seed removal by vertebrates, which was only marginally negatively related to rainfall seasonality. The inclusion of seed mass improved the fit of all models, but the term for seed mass was not significant in any model. Although a good climatic model for predicting post-dispersal seed predation by vertebrates at the global level was not found, our results suggest different and opposite latitudinal patterns of post-dispersal seed removal by invertebrates vs vertebrates. This is the first time that a negative relationship between post-dispersal seed removal by invertebrates and latitude, and a positive relationship with temperature and AET have been documented at a global-scale. These results have important implications for understanding global patterns in plant-animal interactions, and the factors that shape plant reproductive ecology, and also for predicting how this plant-animal interaction might respond to climate change.

Global Patterns in Post-Dispersal Seed Removal by Invertebrates and Vertebrates

PubMed Central

Peco, Begoña; Laffan, Shawn W.; Moles, Angela T.

2014-01-01

It is commonly accepted that species interactions such as granivory are more intense in the tropics. However, this has rarely been tested. A global dataset of post-dispersal seed removal by invertebrates and vertebrates for 79 native plant species from semi-natural and natural terrestrial habitats ranging from 55° N to 45° S, was compiled from the global literature to test the hypothesis that post-dispersal seed removal by invertebrates and vertebrates is more intense at lower latitudes. We also quantified the relationship between post-dispersal seed removal by vertebrates and by invertebrates to global climatic features including temperature, actual evapotranspiration (AET) and rainfall seasonality. Linear mixed effect models were applied to describe the relationships between seed removal and latitude, hemisphere and climatic variables controlling for the effect of seed mass. Post-dispersal seed removal by invertebrates was negatively related to latitude. In contrast, post-dispersal seed removal by vertebrates was positively but weakly related to latitude. Mean annual temperature and actual evapotranspiration were positively related to post-dispersal seed removal by invertebrates, but not to post-dispersal seed removal by vertebrates, which was only marginally negatively related to rainfall seasonality. The inclusion of seed mass improved the fit of all models, but the term for seed mass was not significant in any model. Although a good climatic model for predicting post-dispersal seed predation by vertebrates at the global level was not found, our results suggest different and opposite latitudinal patterns of post-dispersal seed removal by invertebrates vs vertebrates. This is the first time that a negative relationship between post-dispersal seed removal by invertebrates and latitude, and a positive relationship with temperature and AET have been documented at a global-scale. These results have important implications for understanding global patterns in plant-animal interactions, and the factors that shape plant reproductive ecology, and also for predicting how this plant-animal interaction might respond to climate change. PMID:24618879

Warming and top predator loss drive ecosystem multifunctionality.

PubMed

Antiqueira, Pablo Augusto P; Petchey, Owen L; Romero, Gustavo Quevedo

2018-01-01

Global change affects ecosystem functioning both directly by modifications in physicochemical processes, and indirectly, via changes in biotic metabolism and interactions. Unclear, however, is how multiple anthropogenic drivers affect different components of community structure and the performance of multiple ecosystem functions (ecosystem multifunctionality). We manipulated small natural freshwater ecosystems to investigate how warming and top predator loss affect seven ecosystem functions representing two major dimensions of ecosystem functioning, productivity and metabolism. We investigated their direct and indirect effects on community diversity and standing stock of multitrophic macro and microorganisms. Warming directly increased multifunctional ecosystem productivity and metabolism. In contrast, top predator loss indirectly affected multifunctional ecosystem productivity via changes in the diversity of detritivorous macroinvertebrates, but did not affect ecosystem metabolism. In addition to demonstrating how multiple anthropogenic drivers have different impacts, via different pathways, on ecosystem multifunctionality components, our work should further spur advances in predicting responses of ecosystems to multiple simultaneous environmental changes. © 2017 John Wiley & Sons Ltd/CNRS.

Panel Discussion: Application of Living Mulch for Spring-Sown Loblolly Pine

Treesearch

Paul Ensminger

2005-01-01

Those who grow hardwood seedlings are familiar with fall sowing seeds and using rye, wheat, or oats to over-winter the crop. Throughout this paper, reference to rye is GRAIN, NOT GRASS (do not use rye grass). The rye stabilizes and insulates the beds while retarding predation and weeds. Normally sown at 2 bushels/ac (5 bushels/ha), the rye is killed with Roundup™...

Nanosecond time-resolved characterization of a pentacene-based room-temperature MASER

PubMed Central

Salvadori, Enrico; Breeze, Jonathan D.; Tan, Ke-Jie; Sathian, Juna; Richards, Benjamin; Fung, Mei Wai; Wolfowicz, Gary; Oxborrow, Mark; Alford, Neil McN.; Kay, Christopher W. M.

2017-01-01

The performance of a room temperature, zero-field MASER operating at 1.45 GHz has been examined. Nanosecond laser pulses, which are essentially instantaneous on the timescale of the spin dynamics, allow the visible-to-microwave conversion efficiency and temporal response of the MASER to be measured as a function of excitation energy. It is observed that the timing and amplitude of the MASER output pulse are correlated with the laser excitation energy: at higher laser energy, the microwave pulses have larger amplitude and appear after shorter delay than those recorded at lower laser energy. Seeding experiments demonstrate that the output variation may be stabilized by an external source and establish the minimum seeding power required. The dynamics of the MASER emission may be modeled by a pair of first order, non-linear differential equations, derived from the Lotka-Volterra model (Predator-Prey), where by the microwave mode of the resonator is the predator and the spin polarization in the triplet state of pentacene is the prey. Simulations allowed the Einstein coefficient of stimulated emission, the spin-lattice relaxation and the number of triplets contributing to the MASER emission to be estimated. These are essential parameters for the rational improvement of a MASER based on a spin-polarized triplet molecule. PMID:28169331

Alkaloid concentration of the invasive plant species Ulex europaeus in relation to geographic origin and herbivory

NASA Astrophysics Data System (ADS)

Hornoy, Benjamin; Atlan, Anne; Tarayre, Michèle; Dugravot, Sébastien; Wink, Michael

2012-11-01

In the study of plant defense evolution, invasive plant species can be very insightful because they are often introduced without their enemies, and traits linked to defense can be released from selective pressures and evolve. Further, studying plant defense evolution in invasive species is important for biological control and use of these species. In this study, we investigated the evolution of the defensive chemicals quinolizidine alkaloids (QAs) in the invasive species gorse, Ulex europaeus. Using a common garden experiment, our goals were to characterize the role of QAs relative to specialist enemies of gorse and to investigate if QA concentration evolved in invaded regions, where gorse was introduced without these enemies. Our results showed that pod infestation rate by the seed predator Exapion ulicis and infestation by the rust pathogen Uromyces genistae-tinctoriae were negatively correlated to concentration of the QA lupanine. Quinolizidine alkaloid concentration was very variable between individuals, both within and among populations, but it was not different between native and invaded regions, suggesting that no evolution of decreased resistance occurred after gorse lost its enemies. Our study also suggests that QA concentrations are traits integrated into seed predation avoidance strategies of gorse, with plants that mass-fruit in spring but do not escape pod infestation in time being richer in QAs.

Alkaloid concentration of the invasive plant species Ulex europaeus in relation to geographic origin and herbivory.

PubMed

Hornoy, Benjamin; Atlan, Anne; Tarayre, Michèle; Dugravot, Sébastien; Wink, Michael

2012-11-01

In the study of plant defense evolution, invasive plant species can be very insightful because they are often introduced without their enemies, and traits linked to defense can be released from selective pressures and evolve. Further, studying plant defense evolution in invasive species is important for biological control and use of these species. In this study, we investigated the evolution of the defensive chemicals quinolizidine alkaloids (QAs) in the invasive species gorse, Ulex europaeus. Using a common garden experiment, our goals were to characterize the role of QAs relative to specialist enemies of gorse and to investigate if QA concentration evolved in invaded regions, where gorse was introduced without these enemies. Our results showed that pod infestation rate by the seed predator Exapion ulicis and infestation by the rust pathogen Uromyces genistae-tinctoriae were negatively correlated to concentration of the QA lupanine. Quinolizidine alkaloid concentration was very variable between individuals, both within and among populations, but it was not different between native and invaded regions, suggesting that no evolution of decreased resistance occurred after gorse lost its enemies. Our study also suggests that QA concentrations are traits integrated into seed predation avoidance strategies of gorse, with plants that mass-fruit in spring but do not escape pod infestation in time being richer in QAs.

Indirect effects of predators control herbivore richness and abundance in a benthic eelgrass (Zostera marina) mesograzer community.

PubMed

Amundrud, Sarah L; Srivastava, Diane S; O'Connor, Mary I

2015-07-01

Herbivore communities can be sensitive to changes in predator pressure (top-down effects) and resource availability (bottom-up effects) in a wide range of systems. However, it remains unclear whether such top-down and bottom-up effects reflect direct impacts of predators and/or resources on herbivores, or are indirect, reflecting altered interactions among herbivore species. We quantified direct and indirect effects of bottom-up and top-down processes on an eelgrass (Zostera marina) herbivore assemblage. In a field experiment, we factorially manipulated water column nutrients (with Osmocote(™) slow-release fertilizer) and predation pressure (with predator exclusion cages) and measured the effects on herbivore abundance, richness and beta diversity. We examined likely mechanisms of community responses by statistically exploring the response of individual herbivore species to trophic manipulations. Predators increased herbivore richness and total abundance, in both cases through indirect shifts in community composition. Increases in richness occurred through predator suppression of common gammarid amphipod species (Monocorophium acherusicum and Photis brevipes), permitting the inclusion of rarer gammarid species (Aoroides columbiae and Pontogeneia rostrata). Increased total herbivore abundance reflected increased abundance of a caprellid amphipod species (Caprella sp.), concurrent with declines in the abundance of other common species. Furthermore, predators decreased beta diversity by decreasing variability in Caprella sp. abundance among habitat patches. Osmocote(™) fertilization increased nutrient concentrations locally, but nutrients dissipated to background levels within 3 m of the fertilizer. Nutrient addition weakly affected the herbivore assemblage, not affecting richness and increasing total abundance by increasing one herbivore species (Caprella sp.). Nutrient addition did not affect beta diversity. We demonstrated that assemblage-level effects of trophic manipulations on community structure are the result of distinct and often indirect responses of herbivore species. These results underscore the importance of understanding herbivore-herbivore interactions in a system commonly subjected to both eutrophication and overfishing. © 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.

What Cues Do Ungulates Use to Assess Predation Risk in Dense Temperate Forests?

PubMed Central

Kuijper, Dries P. J.; Verwijmeren, Mart; Churski, Marcin; Zbyryt, Adam; Schmidt, Krzysztof; Jędrzejewska, Bogumiła; Smit, Chris

2014-01-01

Anti-predator responses by ungulates can be based on habitat features or on the near-imminent threat of predators. In dense forest, cues that ungulates use to assess predation risk likely differ from half-open landscapes, as scent relative to sight is predicted to be more important. We studied, in the Białowieża Primeval Forest (Poland), whether perceived predation risk in red deer (Cervus elaphus) and wild boar (Sus scrofa) is related to habitat visibility or olfactory cues of a predator. We used camera traps in two different set-ups to record undisturbed ungulate behavior and fresh wolf (Canis lupus) scats as olfactory cue. Habitat visibility at fixed locations in deciduous old growth forest affected neither vigilance levels nor visitation rate and cumulative visitation time of both ungulate species. However, red deer showed a more than two-fold increase of vigilance level from 22% of the time present on control plots to 46% on experimental plots containing one wolf scat. Higher vigilance came at the expense of time spent foraging, which decreased from 32% to 12% while exposed to the wolf scat. These behavioral changes were most pronounced during the first week of the experiment but continuous monitoring of the plots suggested that they might last for several weeks. Wild boar did not show behavioral responses indicating higher perceived predation risk. Visitation rate and cumulative visitation time were not affected by the presence of a wolf scat in both ungulate species. The current study showed that perceived predation risk in red deer and wild boar is not related to habitat visibility in a dense forest ecosystem. However, olfactory cues of wolves affected foraging behavior of their preferred prey species red deer. We showed that odor of wolves in an ecologically equivalent dose is sufficient to create fine-scale risk factors for red deer. PMID:24404177

Zinc and selenium accumulation and their effect on iron bioavailability in common bean seeds.

PubMed

de Figueiredo, Marislaine A; Boldrin, Paulo F; Hart, Jonathan J; de Andrade, Messias J B; Guilherme, Luiz R G; Glahn, Raymond P; Li, Li

2017-02-01

Common beans (Phaseolus vulgaris) are the most important legume crops. They represent a major source of micronutrients and a target for essential trace mineral enhancement (i.e. biofortification). To investigate mineral accumulation during seed maturation and to examine whether it is possible to biofortify seeds with multi-micronutrients without affecting mineral bioavailability, three common bean cultivars were treated independently with zinc (Zn) and selenium (Se), the two critical micronutrients that can be effectively enhanced via fertilization. The seed mineral concentrations during seed maturation and the seed Fe bioavailability were analyzed. Common bean seeds were found to respond positively to Zn and Se treatments in accumulating these micronutrients. While the seed pods showed a decrease in Zn and Se along with Fe content during pod development, the seeds maintained relatively constant mineral concentrations during seed maturation. Selenium treatment had minimal effect on the seed accumulation of phytic acid and polyphenols, the compounds affecting Fe bioavailability. Zinc treatment reduced phytic acid level, but did not dramatically affect the concentrations of total polyphenols. Iron bioavailability was found not to be greatly affected in seeds biofortified with Se and Zn. In contrast, the inhibitory polyphenol compounds in the black bean profoundly reduced Fe bioavailability. These results provide valuable information for Se and Zn enhancement in common bean seeds and suggest the possibility to biofortify with these essential nutrients without greatly affecting mineral bioavailability to increase the food quality of common bean seeds. Published by Elsevier Masson SAS.

Predator effects on a detritus-based food web are primarily mediated by non-trophic interactions.

PubMed

Majdi, Nabil; Boiché, Anatole; Traunspurger, Walter; Lecerf, Antoine

2014-07-01

Predator effects on ecosystems can extend far beyond their prey and are often not solely lethally transmitted. Change in prey traits in response to predation risk can have important repercussions on community assembly and key ecosystem processes (i.e. trait-mediated indirect effects). In addition, some predators themselves alter habitat structure or nutrient cycling through ecological engineering effects. Tracking these non-trophic pathways is thus an important, yet challenging task to gain a better grasp of the functional role of predators. Multiple lines of evidence suggest that, in detritus-based food webs, non-trophic interactions may prevail over purely trophic interactions in determining predator effects on plant litter decomposition. This hypothesis was tested in a headwater stream by modulating the density of a flatworm predator (Polycelis felina) in enclosures containing oak (Quercus robur) leaf litter exposed to natural colonization by small invertebrates and microbial decomposers. Causal path modelling was used to infer how predator effects propagated through the food web. Flatworms accelerated litter decomposition through positive effects on microbial decomposers. The biomass of prey and non-prey invertebrates was not negatively affected by flatworms, suggesting that net predator effect on litter decomposition was primarily determined by non-trophic interactions. Flatworms enhanced the deposition and retention of fine sediments on leaf surface, thereby improving leaf colonization by invertebrates - most of which having strong affinities with interstitial habitats. This predator-induced improvement of habitat availability was attributed to the sticky nature of the mucus that flatworms secrete in copious amount while foraging. Results of path analyses further indicated that this bottom-up ecological engineering effect was as powerful as the top-down effect on invertebrate prey. Our findings suggest that predators have the potential to affect substantially carbon flow and nutrient cycling in detritus-based ecosystems and that this impact cannot be fully appreciated without considering non-trophic effects. © 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.

Human shields mediate sexual conflict in a top predator.

PubMed

Steyaert, S M J G; Leclerc, M; Pelletier, F; Kindberg, J; Brunberg, S; Swenson, J E; Zedrosser, A

2016-06-29

Selecting the right habitat in a risky landscape is crucial for an individual's survival and reproduction. In predator-prey systems, prey often can anticipate the habitat use of their main predator and may use protective associates (i.e. typically an apex predator) as shields against predation. Although never tested, such mechanisms should also evolve in systems in which sexual conflict affects offspring survival. Here, we assessed the relationship between offspring survival and habitat selection, as well as the use of protective associates, in a system in which sexually selected infanticide (SSI), rather than interspecific predation, affects offspring survival. We used the Scandinavian brown bear (Ursus arctos) population with SSI in a human-dominated landscape as our model system. Bears, especially adult males, generally avoid humans in our study system. We used resource selection functions to contrast habitat selection of GPS-collared mothers that were successful (i.e. surviving litters, n = 19) and unsuccessful (i.e. complete litter loss, n = 11) in keeping their young during the mating season (2005-2012). Habitat selection was indeed a predictor of litter survival. Successful mothers were more likely to use humans as protective associates, whereas unsuccessful mothers avoided humans. Our results suggest that principles of predator-prey and fear ecology theory (e.g. non-consumptive and cascading effects) can also be applied to the context of sexual conflict. © 2016 The Authors.

Nutrient enrichment differentially affects body sizes of primary consumers and predators in a detritus-based stream

Treesearch

John M. Davis; Amy D. Rosemond; Sue L. Eggert; Wyatt F. Cross; J. Bruce Wallace

2010-01-01

We assessed how a 5-yr nutrient enrichment affected the responses of different size classes of primary consumers and predators in a detritus-based headwater stream. We hypothesized that alterations in detritus availability because of enrichment would decrease the abundance and biomass of large-bodied consumers. In contrast, we found that 2 yr of enrichment increased...

Predator–prey interactions mediated by prey personality and predator hunting mode

PubMed Central

Belgrad, Benjamin A.; Griffen, Blaine D.

2016-01-01

Predator–prey interactions are important drivers in structuring ecological communities. However, despite widespread acknowledgement that individual behaviours and predator species regulate ecological processes, studies have yet to incorporate individual behavioural variations in a multipredator system. We quantified a prevalent predator avoidance behaviour to examine the simultaneous roles of prey personality and predator hunting mode in governing predator–prey interactions. Mud crabs, Panopeus herbstii, reduce their activity levels and increase their refuge use in the presence of predator cues. We measured mud crab mortality and consistent individual variations in the strength of this predator avoidance behaviour in the presence of predatory blue crabs, Callinectes sapidus, and toadfish, Opsanus tau. We found that prey personality and predator species significantly interacted to affect mortality with blue crabs primarily consuming bold mud crabs and toadfish preferentially selecting shy crabs. Additionally, the strength of the predator avoidance behaviour depended upon the predation risk from the predator species. Consequently, the personality composition of populations and predator hunting mode may be valuable predictors of both direct and indirect predator–prey interaction strength. These findings support theories postulating mechanisms for maintaining intraspecies diversity and have broad implications for community dynamics. PMID:27075257

The role of selective predation in harmful algal blooms

NASA Astrophysics Data System (ADS)

Solé, Jordi; Garcia-Ladona, Emilio; Estrada, Marta

2006-08-01

A feature of marine plankton communities is the occurrence of rapid population explosions. When the blooming species are directly or indirectly noxious for humans, these proliferations are denoted as harmful algal blooms (HAB). The importance of biological interactions for the appearance of HABs, in particular when the proliferating microalgae produce toxins that affect other organisms in the food web, remains still poorly understood. Here we analyse the role of toxins produced by a microalgal species and affecting its predators, in determining the success of that species as a bloom former. A three-species predator-prey model is used to define a criterion that determines whether a toxic microalga will be able to initiate a bloom in competition against a non-toxic one with higher growth rate. Dominance of the toxic species depends on a critical parameter that defines the degree of feeding selectivity by grazers. The criterion is applied to a particular simplified model and to numerical simulations of a full marine ecosystem model. The results suggest that the release of toxic compounds affecting predators may be a plausible biological factor in allowing the development of HABs.

Seasonal fecundity and costs to λ are more strongly affected by direct than indirect predation effects across species

USGS Publications Warehouse

LaManna, Joseph A.; Martin, Thomas E.

2017-01-01

Increased perceived predation risk can cause behavioral and physiological responses to reduce direct predation mortality, but these responses can also cause demographic costs through reduced reproductive output. Such indirect costs of predation risk have received increased attention in recent years, but the relative importance of direct vs. indirect predation costs to population growth (λ) across species remains unclear. We measured direct nest predation rates as well as indirect benefits (i.e., reduced predation rates) and costs (i.e., decreased reproductive output) arising from parental responses to perceived offspring predation risk for 10 songbird species breeding along natural gradients in nest predation risk. We show that reductions in seasonal fecundity from behavioral responses to perceived predation risk represent significant demographic costs for six of the 10 species. However, demographic costs from these indirect predation effects on seasonal fecundity comprised only 12% of cumulative predation costs averaged across species. In contrast, costs from direct predation mortality comprised 88% of cumulative predation costs averaged across species. Demographic costs from direct offspring predation were relatively more important for species with higher within-season residual-reproductive value (i.e., multiple-brooded species) than for species with lower residual-reproductive value (i.e., single-brooded species). Costs from indirect predation effects were significant across single- but not multiple-brooded species. Ultimately, demographic costs from behavioral responses to offspring predation risk differed among species as a function of their life-history strategies. Yet direct predation mortality generally wielded a stronger influence than indirect effects on seasonal fecundity and projected λ across species.

Weak trophic links between a crab-spider and the effective pollinators of a rewardless orchid

NASA Astrophysics Data System (ADS)

Quintero, Carolina; Corley, Juan C.; Aizen, Marcelo A.

2015-01-01

Sit and wait predators hunting on flowers are considered to be exploiters of plant-pollinator mutualisms. Several studies have shown that plant-pollinator interactions can be highly susceptible to the impact of a third trophic level, via consumptive (direct) and non-consumptive (indirect) effects that alter pollinator behavior and, ultimately, plant fitness. However, most flowering plants attract a wide array of flower visitors, from which only a subset will be effective pollinators. Hence, a negative effect of an ambush predator on plant fitness should be expected only when: (i) the effective pollinators are part of the predators' diet and/or (ii) the non-consumptive effects of predator presence (e.g. dead prey) alter the behavior of effective pollinators and pollen movement among individual plants. We analyzed the direct and indirect effects of a crab-spider (Misumenops pallidus), on the pollination and reproductive success of Chloraea alpina, a Patagonian rewardless orchid. Our results indicate that most of the flower visitors do not behave as effective pollinators and most effective pollinators were not observed as prey for the crab-spider. In terms of non-consumptive effects, inflorescences with and without spiders and/or dead-prey did not vary the frequency of flower visitors, nor pollinia removal or deposition. Hence, it is not surprising that M. pallidus has a neutral effect on pollinia removal and deposition as well as on fruit and seed set. Similar to other rewardless orchids, the low reproductive success of C. alpina (∼6% fruit set) was associated with the limited number of visits by effective pollinators. Negative top-down effects of a flower-visitor predator on plant pollination may not be anticipated without studying the direct and indirect effects of this predator on the effective pollinators. In pollination systems where effective pollinators visited flowers erratically, such as in deceptive orchids, we expect weak or no effect of predators on plant fitness.

The role of teosinte glume architecture (tga1) in coordinated regulation and evolution of grass glumes and inflorescence axes.

PubMed

Preston, Jill C; Wang, Huai; Kursel, Lisa; Doebley, John; Kellogg, Elizabeth A

2012-01-01

• Hardened floral bracts and modifications to the inflorescence axis of grasses have been hypothesized to protect seeds from predation and/or aid seed dispersal, and have evolved multiple times independently within the family. Previous studies have demonstrated that mutations in the maize (Zea mays ssp. mays) gene teosinte glume architecture (tga1) underlie a reduction in hardened structures, yielding free fruits that are easy to harvest. It remains unclear whether the causative mutation(s) occurred in the cis-regulatory or protein-coding regions of tga1, and whether similar mutations in TGA1-like genes can explain variation in the dispersal unit in related grasses. • To address these questions TGA1-like genes were cloned and sequenced from a number of grasses and analyzed phylogenetically in relation to morphology; protein expression was investigated by immunolocalization. • TGA1-like proteins were expressed throughout the spikelet in the early development of all grasses, and throughout the flower of the grass relative Joinvillea. Later in development, expression patterns differed between Tripsacum dactyloides, maize and teosinte (Z. mays ssp. parviglumis). • These results suggest an ancestral role for TGA1-like genes in early spikelet development, but do not support the hypothesis that TGA1-like genes have been repeatedly modified to affect glume and inflorescence axis diversification. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

Why is seed production so variable among individuals? A ten-year study with oaks reveals the importance of soil environment.

PubMed

Pérez-Ramos, Ignacio M; Aponte, Cristina; García, Luis V; Padilla-Díaz, Carmen M; Marañón, Teodoro

2014-01-01

Mast-seeding species exhibit not only a large inter-annual variability in seed production but also considerable variability among individuals within the same year. However, very little is known about the causes and consequences for population dynamics of this potentially large between-individual variability. Here, we quantified seed production over ten consecutive years in two Mediterranean oak species - the deciduous Quercus canariensis and the evergreen Q. suber - that coexist in forests of southern Spain. First, we calibrated likelihood models to identify which abiotic and biotic variables best explain the magnitude (hereafter seed productivity) and temporal variation of seed production at the individual level (hereafter CVi), and infer whether reproductive effort results from the available soil resources for the plant or is primarily determined by selectively favoured strategies. Second, we explored the contribution of between-individual variability in seed production as a potential mechanism of satiation for predispersal seed predators. We found that Q. canariensis trees inhabiting moister and more fertile soils were more productive than those growing in more resource-limited sites. Regarding temporal variation, individuals of the two studied oak species inhabiting these resource-rich environments also exhibited larger values of CVi. Interestingly, we detected a satiating effect on granivorous insects at the tree level in Q. suber, which was evident in those years where between-individual variability in acorn production was higher. These findings suggest that individual seed production (both in terms of seed productivity and inter-annual variability) is strongly dependent on soil resource heterogeneity (at least for one of the two studied oak species) with potential repercussions for recruitment and population dynamics. However, other external factors (such as soil heterogeneity in pathogen abundance) or certain inherent characteristics of the tree might be also involved in this process.

Beyond Predation: The Zoophytophagous Predator Macrolophus pygmaeus Induces Tomato Resistance against Spider Mites

PubMed Central

Pappas, Maria L.; Steppuhn, Anke; Geuss, Daniel; Topalidou, Nikoleta; Zografou, Aliki; Broufas, George D.

2015-01-01

Many predatory insects that prey on herbivores also feed on the plant, but it is unknown whether plants affect the performance of herbivores by responding to this phytophagy with defence induction. We investigate whether the prior presence of the omnivorous predator Macrolophus pygmaeus (Rambur) on tomato plants affects plant resistance against two different herbivore species. Besides plant-mediated effects of M. pygmaeus on herbivore performance, we examined whether a plant defence trait that is known to be inducible by herbivory, proteinase inhibitors (PI), may also be activated in response to the interactions of this predator with the tomato plant. We show that exposing tomato plants to the omnivorous predator M. pygmaeus reduced performance of a subsequently infesting herbivore, the two-spotted spider mite Tetranychus urticae Koch, but not of the greenhouse whitefly Trialeurodes vaporariorum (Westwood). The spider-mite infested tomato plants experience a lower herbivore load, i.e., number of eggs deposited and individuals present, when previously exposed to the zoophytophagous predator. This effect is not restricted to the exposed leaf and persists on exposed plants for at least two weeks after the removal of the predators. The decreased performance of spider mites as a result of prior exposure of the plant to M. pygmaeus is accompanied by a locally and systemically increased accumulation of transcripts and activity of proteinase inhibitors that are known to be involved in plant defence. Our results demonstrate that zoophytophagous predators can induce plant defence responses and reduce herbivore performance. Hence, the suppression of populations of certain herbivores via consumption may be strengthened by the induction of plant defences by zoophytophagous predators. PMID:25974207

Vulnerability of young white sturgeon, Acipenser transmontanus, to predation in the presence of alternative prey

USGS Publications Warehouse

Gadomski, D.M.; Parsley, M.J.

2005-01-01

We conducted laboratory trials to test the vulnerability of young white sturgeon, Acipenser transmontanus, to predation when an alternative prey was available. In trials with two species of predators, we observed two feeding patterns. When equal numbers of white sturgeon and goldfish, Carassius auratus, were available, prickly sculpins, Cottus asper, ingested more white sturgeon. Conversely, northern pikeminnow, Ptychocheilus oregonensis, ate more juvenile coho salmon, Oncorhynchus kisutch, than white sturgeon in three out of four sets of trials, but ate more white sturgeon in one set of trials. White sturgeon size and the availability of cover did not affect the proportions of prey species ingested. Our results indicate that predation may be affecting survival of white sturgeon larvae and juveniles in the wild and could be one factor limiting recruitment of young-of-the-year white sturgeon in some locations. ?? Springer 2005.

Effects of Microphallus turgidus (Trematoda: Microphallidae) on the predation, behavior, and swimming stamina of the grass shrimp Palaemonetes pugio.

PubMed

Kunz, Alyssa K; Pung, Oscar J

2004-06-01

The effect of the trematode Microphallus turgidus on its second intermediate host, the grass shrimp, Palaemonetes pugio, was tested. To do so, we measured the susceptibility of infected and uninfected shrimp to predation by the mummichog, Fundulus heteroclitus. Shrimp behavior was compared in the presence and absence of a fish predator, and the swimming stamina and backthrust escape responses of infected and uninfected shrimp were measured. Infected shrimp were more likely to be eaten by a predator than uninfected shrimp, had lower swimming stamina, and spent more time swimming and less time motionless in the presence of a predator. There was no difference between backthrust distances traveled in response to a stimulus by either infected or uninfected shrimp. Thus, M. turgidus may increase the predation of P. pugio in the wild, possibly by affecting the swimming stamina and predator avoidance responses of the shrimp.

Mass enhances speed but diminishes turn capacity in terrestrial pursuit predators

PubMed Central

Wilson, Rory P; Griffiths, Iwan W; Mills, Michael GL; Carbone, Chris; Wilson, John W; Scantlebury, David M

2015-01-01

The dynamics of predator-prey pursuit appears complex, making the development of a framework explaining predator and prey strategies problematic. We develop a model for terrestrial, cursorial predators to examine how animal mass modulates predator and prey trajectories and affects best strategies for both parties. We incorporated the maximum speed-mass relationship with an explanation of why larger animals should have greater turn radii; the forces needed to turn scale linearly with mass whereas the maximum forces an animal can exert scale to a 2/3 power law. This clarifies why in a meta-analysis, we found a preponderance of predator/prey mass ratios that minimized the turn radii of predators compared to their prey. It also explained why acceleration data from wild cheetahs pursuing different prey showed different cornering behaviour with prey type. The outcome of predator prey pursuits thus depends critically on mass effects and the ability of animals to time turns precisely. DOI: http://dx.doi.org/10.7554/eLife.06487.001 PMID:26252515

[Effects of sowing date and planting density on the seed yield and oil content of winter oilseed rape].

PubMed

Zhang, Shu-Jie; Li, Ling; Zhang, Chun-Lei

2012-05-01

A field experiment was conducted to investigate the effects of different sowing date and planting density on the seed yield and seed oil content of winter oilseed rape (Brassica napus). Sowing date mainly affected the seed yield of branch raceme, while planting density affected the seed yields of both branch raceme and main raceme. The seed oil content was less affected by sowing date. The proportion of the seed yield of main raceme to the seed yield per plant increased with increasing planting density, and the seed oil content of main raceme was about 1% higher than that of branch raceme. Consequently, the seed oil production per plot increased significantly with increasing planting density. In the experimental region, the sowing date of winter oilseed rape should be earlier than mid-October. When sowing in late October, the seed yield would be decreased significantly. A planting density of 36-48 plants x m(-2) could improve the seed yield and oil content of winter oilseed rape.

Sex- and concentration-dependent effects of predator feces on seasonal regulation of body mass in the bank vole Clethrionomys glareolus.

PubMed

Tidhar, Wendy L; Bonier, Frances; Speakman, John R

2007-11-01

Increased perception of predation risk can cause changes in activity, feeding and reproductive behavior in a wide range of taxa. Many small mammals in the temperate zone exhibit fluctuations in body mass in response to changing photoperiod. Bank voles lose body mass in winter which they regain when photoperiod increases in the spring. To determine if predation risk affects seasonal changes in body mass (BM), bank voles were exposed to two concentrations (low: LC and high: HC) of weasel feces. Food intake (FI) and daily energy expenditure (DEE) were measured to establish if differences in body mass were due to adjustment in energy intake or expenditure. Fecal corticosterone (CORT) was measured to assess whether the voles had detected and responded to predator feces as a physiological stressor. Voles of both sexes had higher levels of fecal CORT in the groups exposed to weasel feces compared to controls. Voles responded to the predator feces in a sex- and concentration-dependent manner. Males responded to LC feces by gaining less mass following the change in photoperiod. This was mediated by reduced FI and higher DEE. Female voles also gained less BM in response to HC feces, but increased both FI and DEE. We hypothesize that males may gain a short-term advantage by lowering BM in response to predation risk, which may be regained without affecting reproductive success. The consequences of mass loss in females may be more significant as this may delay the onset of breeding or reduce the size or number of young, thereby negatively affecting breeding success.

Imidacloprid affects the functional response of predator Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) to strains of Spodoptera frugiperda (J.E. Smith) on Bt cotton.

PubMed

Malaquias, J B; Ramalho, F S; Omoto, C; Godoy, W A C; Silveira, R F

2014-03-01

Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) is one of the most common asopine species in the neotropical region and its occurrence was reported in several countries of South and Central America, as an important biological control agent for many crops. This study was carried out to identify the imidacloprid impacts on the functional response of predator P. nigrispinus fed on Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) strain resistant to lambda-cyhalothrin, on Bt cotton expressing Cry1Ac (Bollgard(®)). Spodoptera frugiperda larvae were used in the following conditions: resistant (1) and susceptible (2) strains to lambda-cyhalothrin fed on Bollgard(®) cotton leaves (DP 404 BG); and resistant (3) and susceptible (4) strains to lambda-cyhalothrin fed on non-genetically modified cotton leaves (cultivar DP4049). The predatory behavior of P. nigrispinus was affected by imidacloprid and the type II asymptotic curve was the one that best described the functional response data. Handling time (T h ) of predator females did not differ among treatments in the presence of imidacloprid. The attack rate did decrease, however, due to an increase in the density of larvae offered. Regardless of the treatment (S. frugiperda strain or cotton cultivar), the predation of P. nigrispinus females on S. frugiperda larvae was significantly lower when exposed to imidacloprid, especially at a density of 16 larvae/predator. The predation behavior of P. nigrispinus on S. frugiperda larvae is affected by the insecticide imidacloprid showing that its applications should be used in cotton crop with caution.

Cryptic biodiversity effects: importance of functional redundancy revealed through addition of food web complexity.

PubMed

Philpott, Stacy M; Pardee, Gabriella L; Gonthier, David J

2012-05-01

Interactions between predators and the degree of functional redundancy among multiple predator species may determine whether herbivores experience increased or decreased predation risk. Specialist parasites can modify predator behavior, yet rarely have cascading effects on multiple predator species and prey been evaluated. We examined influences of specialist phorid parasites (Pseudacteon spp.) on three predatory ant species and herbivores in a coffee agroecosystem. Specifically, we examined whether changes in ant richness affected fruit damage by the coffee berry borer (Hypothenemus hampei) and whether phorids altered multi-predator effects. Each ant species reduced borer damage, and without phorids, increasing predator richness did not further decrease borer damage. However, with phorids, activity of one ant species was reduced, indicating that the presence of multiple ant species was necessary to limit borer damage. In addition, phorid presence revealed synergistic effects of multiple ant species, not observed without the presence of this parasite. Thus, a trait-mediated cascade resulting from a parasite-induced predator behavioral change revealed the importance of functional redundancy, predator diversity, and food web complexity for control of this important pest.

Temperature alters food web body-size structure.

PubMed

Gibert, Jean P; DeLong, John P

2014-08-01

The increased temperature associated with climate change may have important effects on body size and predator-prey interactions. The consequences of these effects for food web structure are unclear because the relationships between temperature and aspects of food web structure such as predator-prey body-size relationships are unknown. Here, we use the largest reported dataset for marine predator-prey interactions to assess how temperature affects predator-prey body-size relationships among different habitats ranging from the tropics to the poles. We found that prey size selection depends on predator body size, temperature and the interaction between the two. Our results indicate that (i) predator-prey body-size ratios decrease with predator size at below-average temperatures and increase with predator size at above-average temperatures, and (ii) that the effect of temperature on predator-prey body-size structure will be stronger at small and large body sizes and relatively weak at intermediate sizes. This systematic interaction may help to simplify forecasting the potentially complex consequences of warming on interaction strengths and food web stability. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Predator-prey interactions in a changing world: humic stress disrupts predator threat evasion in copepods.

PubMed

Santonja, Mathieu; Minguez, Laetitia; Gessner, Mark O; Sperfeld, Erik

2017-03-01

Increasing inputs of colored dissolved organic matter (cDOM), which is mainly composed of humic substances (HS), are a widespread phenomenon of environmental change in aquatic ecosystems. This process of brownification alters the chemical conditions of the environment, but knowledge is lacking of whether elevated cDOM and HS levels interfere with the ability of prey species to evade chemical predator cues and thus affect predator-prey interactions. We assessed the effects of acute and prolonged exposure to HS at increasing concentrations on the ability of freshwater zooplankton to avoid predator threat (imposed by fish kairomones) in laboratory trials with two calanoid copepods (Eudiaptomus gracilis and Heterocope appendiculata). Populations of both species clearly avoided water containing fish kairomones. However, the avoidance behavior weakened with increasing HS concentration, suggesting that HS affected the ability of copepods to perceive or respond to the predator cue. The behavioral responses of the two copepod populations to increasing HS concentrations differed, with H. appendiculata being more sensitive than E. gracilis in an acute exposure scenario, whereas E. gracilis responded more strongly after prolonged exposure. Both showed similar physiological impairment after prolonged exposure, as revealed by their oxidative balance as a stress indicator, but mortality increased more strongly for H. appendiculata when the HS concentration increased. These results indicate that reduced predator threat evasion in the presence of cDOM could make copepods more susceptible to predation in future, with variation in the strength of responses among populations leading to changes in zooplankton communities and lake food-web structure.

Screening Allelochemical-Resistant Species of the Alien Invasive Mikania micrantha for Restoration in South China

PubMed Central

Wu, Ai-Ping; Li, Zi-Li; He, Fei-Fei; Wang, Yan-Hong; Dong, Ming

2015-01-01

To screen allelochemical-resistant species of the alien invasive weed Mikania micrantha, we studied the allelopathic inhibition effects of the leaf aqueous extract (LAE) of Mikania on seed germination and seedling growth of the 26 species native or naturalized in the invaded region in South China. Seed germination was more strongly negatively affected by LAE than seedling growth. Responses of seed germination and seed growth to LAE differed differently among the target species. LAE more strongly negatively affected seed germination, but less strongly negatively affected seedling growth, in non-legume species than in legume species. LAE more strongly negatively affected seed germination and seedling growth in native species than naturalized exotic species. Therefore, naturalized exotic non-legume seedlings are more suitable than seeds of native legume species for restoration of Mikania-invaded habitats. PMID:26177031

Screening Allelochemical-Resistant Species of the Alien Invasive Mikania micrantha for Restoration in South China.

PubMed

Wu, Ai-Ping; Li, Zi-Li; He, Fei-Fei; Wang, Yan-Hong; Dong, Ming

2015-01-01

To screen allelochemical-resistant species of the alien invasive weed Mikania micrantha, we studied the allelopathic inhibition effects of the leaf aqueous extract (LAE) of Mikania on seed germination and seedling growth of the 26 species native or naturalized in the invaded region in South China. Seed germination was more strongly negatively affected by LAE than seedling growth. Responses of seed germination and seed growth to LAE differed differently among the target species. LAE more strongly negatively affected seed germination, but less strongly negatively affected seedling growth, in non-legume species than in legume species. LAE more strongly negatively affected seed germination and seedling growth in native species than naturalized exotic species. Therefore, naturalized exotic non-legume seedlings are more suitable than seeds of native legume species for restoration of Mikania-invaded habitats.

Limiting factors of four rare plant species in `Ōla`A Forest of Hawai'i Volcanoes National Park

USGS Publications Warehouse

VanDeMark, Joshua R.; Pratt, Linda W.; Euaparadorn, Melody

2010-01-01

In conclusion, 2 of the 3 regularly-monitored rare plant species of `Ōla`a Forest appeared to have more than 1 limiting factor inhibiting the natural increase in their populations, while for P. floribunda the most important factor was high seedling mortality. Most plants of the monitored C. giffardii population appeared to be hybrids, probably with the more common species C. lysiosepala. Seed germination rates were low, and natural seedlings were not observed. Pollinators were not seen in many hours of observation, indicating that cross pollination is a rare or uncommon event. The re-introduced population of P. floribunda had relatively low mortality, and reproduction was successful with high rates of fruit formation from abundant flowers. Seed germination rates were high, and a soil seed bank was detected. Natural seedling recruitment was observed, but high seedling mortality indicated that this life stage was the most vulnerable in the species. The population of S. alba was small and the vine life form precluded an accurate estimate of the number of adult plants in `Ōla`a Forest. Natural dormancy was likely a factor in the observed low rate of seed germination. No soil seed bank was detected, and alien rodents were implicated as seed predators. Natural recruitment was observed at multiple sites in `Ōla`a, but seedling mortality was high. The cause of seedling mortality was not identified.

Potential of the Lectin/Inhibitor Isolated from Crataeva tapia Bark (CrataBL) for Controlling Callosobruchus maculatus Larva Development.

PubMed

Nunes, Natalia N S; Ferreira, Rodrigo S; Silva-Lucca, Rosemeire A; de Sá, Leonardo F R; de Oliveira, Antônia Elenir A; Correia, Maria Tereza dos S; Paiva, Patrícia Maria G; Wlodawer, Alexander; Oliva, Maria Luiza V

2015-12-09

Callosobruchus maculatus is an important predator of cowpeas. Due to infestation during storage, this insect affects the quality of seed and crop yield. This study aimed to investigate the effects of CrataBL, a multifunction protein isolated from Crataeva tapia bark, on C. maculatus larva development. The protein, which is stable even in extreme pH conditions, showed toxic activity, reducing the larval mass 45 and 70% at concentrations of 0.25 and 1.0% (w/w), respectively. Acting as an inhibitor, CrataBL decreased by 39% the activity of cysteine proteinases from larval gut. Conversely, the activity of serine proteinases was increased about 8-fold. The toxic properties of CrataBL may also be attributed to its capacity of binding to glycoproteins or glycosaminoglycans. Such binding interferes with larval metabolism, because CrataBL-FITC was found in the fat body, Malpighian tubules, and feces of larvae. These results demonstrate the potential of this protein for controlling larva development.

Responses of predatory invertebrates to seeding density and plant species richness in experimental tallgrass prairie restorations

USGS Publications Warehouse

Nemec, Kristine T.; Allen, Craig R.; Danielson, Stephen D.; Helzer, Christopher J.

2014-01-01

In recent decades, agricultural producers and non-governmental organizations have restored thousands of hectares of former cropland in the central United States with native grasses and forbs. However, the ability of these grassland restorations to attract predatory invertebrates has not been well documented, even though predators provide an important ecosystem service to agricultural producers by naturally regulating herbivores. This study assessed the effects of plant richness and seeding density on the richness and abundance of surface-dwelling (ants, ground beetles, and spiders) and aboveground (ladybird beetles) predatory invertebrates. In the spring of 2006, twenty-four 55 m × 55 m-plots were planted to six replicates in each of four treatments: high richness (97 species typically planted by The Nature Conservancy), at low and high seeding densities, and low richness (15 species representing a typical Natural Resources Conservation Service Conservation Reserve Program mix, CP25), at low and high seeding densities. Ants, ground beetles, and spiders were sampled using pitfall traps and ladybird beetles were sampled using sweep netting in 2007–2009. The abundance of ants, ground beetles, and spiders showed no response to seed mix richness or seeding density but there was a significant positive effect of richness on ladybird beetle abundance. Seeding density had a significant positive effect on ground beetle and spider species richness and Shannon–Weaver diversity. These results may be related to differences in the plant species composition and relative amount of grass basal cover among the treatments rather than richness.

Aggression and feeding of hatchery-reared and naturally reared steelhead (Oncorhynchus mykiss) fry in a laboratory flume and a comparison with observations in natural streams

USGS Publications Warehouse

Riley, S.C.; Tatara, C.P.; Scheurer, J.A.

2005-01-01

We quantified the aggression and feeding of naturally reared steelhead (Oncorhynchus mykiss) fry stocked into a laboratory flume with naturally reared fry or hatchery-reared fry from conventional and enriched rearing environments at three densities in the presence and absence of predators, and compared the aggression and feeding observed in the flume to that observed in two streams. Steelhead fry attack rate increased with density and was reduced in the presence of predators, but was not affected by rearing treatment. Threat rate appeared to increase with density and was significantly affected by rearing treatment combination, but was not significantly affected by predator presence. Feeding rate was not affected by density or rearing treatment, but was reduced in the presence of predators. The rate of aggression by steelhead fry in two streams was lower than that observed in the laboratory and did not increase with density. Rates of aggression and feeding of hatchery-reared and wild steelhead fry were not significantly different in the streams. Overall, we found no evidence that hatchery rearing environments caused higher aggression in steelhead fry. Laboratory observations of salmonid aggression, particularly at high density, may not reflect aggression levels in the wild. ?? 2005 NRC.

Competition between apex predators? Brown bears decrease wolf kill rate on two continents.

PubMed

Tallian, Aimee; Ordiz, Andrés; Metz, Matthew C; Milleret, Cyril; Wikenros, Camilla; Smith, Douglas W; Stahler, Daniel R; Kindberg, Jonas; MacNulty, Daniel R; Wabakken, Petter; Swenson, Jon E; Sand, Håkan

2017-02-08

Trophic interactions are a fundamental topic in ecology, but we know little about how competition between apex predators affects predation, the mechanism driving top-down forcing in ecosystems. We used long-term datasets from Scandinavia (Europe) and Yellowstone National Park (North America) to evaluate how grey wolf ( Canis lupus ) kill rate was affected by a sympatric apex predator, the brown bear ( Ursus arctos ). We used kill interval (i.e. the number of days between consecutive ungulate kills) as a proxy of kill rate. Although brown bears can monopolize wolf kills, we found no support in either study system for the common assumption that they cause wolves to kill more often. On the contrary, our results showed the opposite effect. In Scandinavia, wolf packs sympatric with brown bears killed less often than allopatric packs during both spring (after bear den emergence) and summer. Similarly, the presence of bears at wolf-killed ungulates was associated with wolves killing less often during summer in Yellowstone. The consistency in results between the two systems suggests that brown bear presence actually reduces wolf kill rate. Our results suggest that the influence of predation on lower trophic levels may depend on the composition of predator communities. © 2017 The Authors.

Impact of insecticide exposure on the predation activity of the European earwig Forficula auricularia.

PubMed

Malagnoux, Laure; Capowiez, Yvan; Rault, Magali

2015-09-01

The European earwig Forficula auricularia is an effective predator in apple orchards. It is therefore crucial to study whether insecticides affect this natural pest control agent. Predation activity, i.e., the number of aphids eaten in 24 h, was determined under laboratory conditions after exposure of fourth-instar nymphs and adult earwigs to widely used insecticides (acetamiprid, chlorpyrifos-ethyl, deltamethrin, and spinosad), which were applied at the normal application rates. Inhibition of acetylcholinesterase and carboxylesterase activities were also measured as indicators of pesticide exposure. Predation activity decreased significantly in nymphs exposed to spinosad (62%) and chlorpyrifos-ethyl (98%) compared with controls. A similar response was found for both esterase activities. Spinosad had a stronger effect on AChE (-33%) whereas chlorpyrifos-ethyl affected CbE activity preferentially (-59%). Spinosad (20% of controls), acetamiprid (28%), and chlorpyrifos-ethyl (66%) also significantly decreased the predation behavior of adult male but not female (5 to 40%) earwigs. Adult AChE and CbE activities were also significantly reduced (28 to 67% of controls) in pesticide-exposed earwigs. Our results suggest that earwigs should be included in the environmental risk assessment framework for authorization of newly marketed plant protection products. Their predation behavior appears to be a sensitive and complementary biomarker.

Increased Noise Levels Have Different Impacts on the Anti-Predator Behaviour of Two Sympatric Fish Species

PubMed Central

Voellmy, Irene K.; Purser, Julia; Simpson, Stephen D.; Radford, Andrew N.

2014-01-01

Animals must avoid predation to survive and reproduce, and there is increasing evidence that man-made (anthropogenic) factors can influence predator−prey relationships. Anthropogenic noise has been shown to have a variety of effects on many species, but work investigating the impact on anti-predator behaviour is rare. In this laboratory study, we examined how additional noise (playback of field recordings of a ship passing through a harbour), compared with control conditions (playback of recordings from the same harbours without ship noise), affected responses to a visual predatory stimulus. We compared the anti-predator behaviour of two sympatric fish species, the three-spined stickleback (Gasterosteus aculeatus) and the European minnow (Phoxinus phoxinus), which share similar feeding and predator ecologies, but differ in their body armour. Effects of additional-noise playbacks differed between species: sticklebacks responded significantly more quickly to the visual predatory stimulus during additional-noise playbacks than during control conditions, while minnows exhibited no significant change in their response latency. Our results suggest that elevated noise levels have the potential to affect anti-predator behaviour of different species in different ways. Future field-based experiments are needed to confirm whether this effect and the interspecific difference exist in relation to real-world noise sources, and to determine survival and population consequences. PMID:25058618

Alternative prey use affects helminth parasite infections in grey wolves.

PubMed

Friesen, Olwyn C; Roth, James D

2016-09-01

Predators affect prey populations not only through direct predation, but also by acting as definitive hosts for their parasites and completing parasite life cycles. Understanding the affects of parasitism on prey population dynamics requires knowing how their predators' parasite community is affected by diet and prey availability. Ungulates, such as moose (Alces americanus) and white-tailed deer (Odocoileus virginianus), are often important prey for wolves (Canis lupus), but wolves also consume a variety of alternative prey, including beaver (Castor canadensis) and snowshoe hare (Lepus americanus). The use of alternative prey, which may host different or fewer parasites than ungulates, could potentially reduce overall abundance of ungulate parasites within the ecosystem, benefiting both wolves and ungulate hosts. We examined parasites in wolf carcasses from eastern Manitoba and estimated wolf diet using stable isotope analysis. Taeniidae cestodes were present in most wolves (75%), reflecting a diet primarily comprised of ungulates, but nematodes were unexpectedly rare. Cestode abundance was negatively related to the wolf's δ(13) C value, indicating diet affects parasite abundance. Wolves that consumed a higher proportion of beaver and caribou (Rangifer tarandus), estimated using Bayesian mixing models, had lower cestode abundance, suggesting the use of these alternative prey can reduce parasite loads. Long-term consumption of beavers may lower the abundance of adult parasites in wolves, eventually lowering parasite density in the region and ultimately benefiting ungulates that serve as intermediate hosts. Thus, alternative prey can affect both predator-prey and host-parasite interactions and potentially affect food web dynamics. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

Summer time predation on the obligatory off-host stage of an invasive ectoparasite.

PubMed

Kaunisto, Sirpa; Raunismaa, Ilkka; Kortet, Raine; Ylönen, Hannu

2016-12-01

Predation can regulate populations and strongly affect invasion success of novel prey. The deer ked (Lipoptena cervi; Linnaeus 1758) is an invasive ectoparasite of cervids that spends a long period of its life cycle outside the host. Prior to this study, virtually nothing was known about natural summer time predation on the deer ked. We aimed to evaluate the magnitude of summer time predation on L. cervi pupae in different habitats and to identify potential predators. We conducted a set of field experiments, where we exposed L. cervi pupae to various ground-dwelling vertebrate and invertebrate predators. The loss of pupae was monitored for different predator guilds. Three habitats of the moose, the main host species, were studied: (1) moist heath forest; (2) dry, logged heath forest; and (3) moist meadow. The results indicate notable summer time predation on L. cervi pupae, and the pupal predation varied within and between habitats, being lowest in the meadow habitat. We found a positive correlation between pupal loss and abundance of the common lizard (Zootoca vivipara), harvestmen (Opiliones), ground spiders (Gnaphosidae) and Formicinae-ants. We conclude that summer time predation during the pupal phase can have a notable local importance for the L. cervi abundance.

Reaction of mutualistic and granivorous ants to ulex elaiosome chemicals.

PubMed

Gammans, Nicola; Bullock, James M; Gibbons, Hannah; Schönrogge, Karsten

2006-09-01

It has been proposed that chemicals on plant elaiosomes aid seed detection by seed-dispersing ants. We hypothesized that the chemical interaction between ants and elaiosomes is more intimate than a generic attraction, and that elaiosome chemicals will attract mutualistic but not granivorous ant species. We investigated this by using two gorse species, Ulex minor and U. europaeus, and two associated ant species from European heathlands, the mutualist Myrmica ruginodis and the granivore Tetramorium caespitum. Behavioral studies were conducted with laboratory nests and foraging arenas. Both ants will take Ulex seeds, but while M. ruginodis showed increased antennation toward ether extracts of elaiosome surface chemicals compared with controls, T. caespitum showed no response. Elaiosome extracts were separated into seven lipid fractions. M. ruginodis showed increased antennation only toward the diglyceride fractions of both Ulex species, whereas T. caespitum showed no consistent reaction. This indicates that M. ruginodis can detect the elaiosome by responding to its surface chemicals, but T. caespitum is unresponsive to these chemicals. Responses to surface chemicals could increase the rate of seed detection in the field, and so these results suggest that Ulex elaiosomes produce chemicals that facilitate attraction of mutualistic rather than granivorous ant species. This could reduce seed predation and increase Ulex fitness.

Phenology, seed dispersal and difficulties in natural recruitment of the canopy tree Pachira quinata (Malvaceae).

PubMed

Castellanos, Maria Clara; Stevenson, Pablo R

2011-06-01

Life history and recruitment information of tropical trees in natural populations is scarce even for important commercial species. This study focused on a widely exploited Neotropical canopy species, Pachira quinata (Malvaceae), at the southernmost, wettest limit of its natural distribution, in the Colombian Amazonia. We studied phenological patterns, seed production and natural densities; assessed the importance of seed dispersal and density-dependent effects on recruitment, using field experiments. At this seasonal forest P. quinata was overrepresented by large adult trees and had very low recruitment caused by the combination of low fruit production, high seed predation and very high seedling mortality under continuous canopies mostly due to damping off pathogens. There was no evidence of negative distance or density effects on recruitment, but a clear requirement of canopy gaps for seedling survival and growth, where pathogen incidence was drastically reduced. In spite of the strong dependence on light for survival of seedlings, seeds germinated readily in the dark. At the study site, the population of P. quinata appeared to be declining, likely because recruitment depended on the rare combination of large gap formation with the presence of reproductive trees nearby. The recruitment biology of this species makes it very vulnerable to any type of logging in natural populations.

Spatio-Temporal Variation in Predation by Urban Domestic Cats (Felis catus) and the Acceptability of Possible Management Actions in the UK

PubMed Central

Thomas, Rebecca L.; Fellowes, Mark D. E.; Baker, Philip J.

2012-01-01

Urban domestic cat (Felis catus) populations can attain exceedingly high densities and are not limited by natural prey availability. This has generated concerns that they may negatively affect prey populations, leading to calls for management. We enlisted cat-owners to record prey returned home to estimate patterns of predation by free-roaming pets in different localities within the town of Reading, UK and questionnaire surveys were used to quantify attitudes to different possible management strategies. Prey return rates were highly variable: only 20% of cats returned ≥4 dead prey annually. Consequently, approximately 65% of owners received no prey in a given season, but this declined to 22% after eight seasons. The estimated mean predation rate was 18.3 prey cat−1 year−1 but this varied markedly both spatially and temporally: per capita predation rates declined with increasing cat density. Comparisons with estimates of the density of six common bird prey species indicated that cats killed numbers equivalent to adult density on c. 39% of occasions. Population modeling studies suggest that such predation rates could significantly reduce the size of local bird populations for common urban species. Conversely, most urban residents did not consider cat predation to be a significant problem. Collar-mounted anti-predation devices were the only management action acceptable to the majority of urban residents (65%), but were less acceptable to cat-owners because of perceived risks to their pets; only 24% of cats were fitted with such devices. Overall, cat predation did appear to be of sufficient magnitude to affect some prey populations, although further investigation of some key aspects of cat predation is warranted. Management of the predation behavior of urban cat populations in the UK is likely to be challenging and achieving this would require considerable engagement with cat owners. PMID:23173057

Effect of maternal predator exposure on the ability of stickleback offspring to generalize a learned colour–reward association

PubMed Central

Feng, Sally; McGhee, Katie E.; Bell, Alison M.

2017-01-01

Maternal stress can have long-term negative consequences for offspring learning performance. However, it is unknown whether these maternal effects extend to the ability of offspring to apply previously learned information to new situations. In this study, we first demonstrate that juvenile threespine sticklebacks, Gasterosteus aculeatus, are indeed capable of generalizing an association between a colour and a food reward learned in one foraging context to a new foraging context (i.e. they can apply previously learned knowledge to a new situation). Next, we examined whether this ability to generalize was affected by maternal predator stress. We manipulated whether mothers were repeatedly chased by a model predator while yolking eggs (i.e. before spawning) and then assessed the learning performance of their juvenile offspring in groups and pairs using a colour discrimination task that associated a colour with a food reward. We found that maternal predator exposure affected the tendency of offspring to use social cues: offspring of predator-exposed mothers were faster at copying a leader’s behaviour towards the rewarded colour than offspring of unexposed mothers. However, once the colour–reward association had been learned, offspring of predator-exposed and unexposed mothers were equally able to generalize their learned association to a new foraging task. These results suggest that offspring of predator-exposed mothers might be able to overcome learning deficits caused by maternal stress by relying more on social cues. PMID:29046591

Potential Role of Masting by Introduced Bamboos in Deer Mice (Peromyscus maniculatus) Population Irruptions Holds Public Health Consequences

PubMed Central

Smith, Melissa C.; Gomulkiewicz, Richard; Mack, Richard N.

2015-01-01

We hypothesized that the ongoing naturalization of frost/shade tolerant Asian bamboos in North America could cause environmental consequences involving introduced bamboos, native rodents and ultimately humans. More specifically, we asked whether the eventual masting by an abundant leptomorphic (“running”) bamboo within Pacific Northwest coniferous forests could produce a temporary surfeit of food capable of driving a population irruption of a common native seed predator, the deer mouse (Peromyscus maniculatus), a hantavirus carrier. Single-choice and cafeteria-style feeding trials were conducted for deer mice with seeds of two bamboo species (Bambusa distegia and Yushania brevipaniculata), wheat, Pinus ponderosa, and native mixed diets compared to rodent laboratory feed. Adult deer mice consumed bamboo seeds as readily as they consumed native seeds. In the cafeteria-style feeding trials, Y. brevipaniculata seeds were consumed at the same rate as native seeds but more frequently than wheat seeds or rodent laboratory feed. Females produced a median litter of 4 pups on a bamboo diet. Given the ability of deer mice to reproduce frequently whenever food is abundant, we employed our feeding trial results in a modified Rosenzweig-MacArthur consumer-resource model to project the population-level response of deer mice to a suddenly available/rapidly depleted supply of bamboo seeds. The simulations predict rodent population irruptions and declines similar to reported cycles involving Asian and South American rodents but unprecedented in deer mice. Following depletion of a mast seed supply, the incidence of Sin Nombre Virus (SNV) transmission to humans could subsequently rise with dispersal of the peridomestic deer mice into nearby human settlements seeking food. PMID:25898267

Disentangling the effects of predator hunting mode and habitat domain on the top-down control of insect herbivores.

PubMed

Woodcock, Ben A; Heard, Matthew S

2011-03-01

1. Polyphagous predatory invertebrates play a key role in the top-down control of insect herbivores. However, predicting predation risk for herbivores is not a simple function of predator species richness. Predation risk may be reduced or enhanced depending on the functional characteristics predator species. We predict that where predator species spatially overlap this will reduce predation risk for herbivores by allowing negative inter-specific interaction between predators to occur. Where increased predation risk occurs, we also predict that this will have a cascading effect through the food chain reducing plant growth. 2. We used a substitutive replicated block design to identify the effect of similarity and dissimilarity in predator hunting mode (e.g. 'sit and wait', 'sit and pursue', and 'active') and habitat domain (e.g. canopy or ground) on the top-down control of planthoppers in grasslands. Predators included within the mesocosms were randomly selected from a pool of 17 local species. 3. Predation risk was reduced where predators shared the same habitat domain, independent of whether they shared hunting modes. Where predators shared the same habitat domains, there was some evidence that this had a cascading negative effect on the re-growth of grass biomass. Where predator habitat domains did not overlap, there were substitutable effects on predation risk to planthoppers. Predation risk for planthoppers was affected by taxonomic identity of predator species, i.e. whether they were beetles, spiders or true bugs. 4. Our results indicated that in multi-predator systems, the risk of predation is typically reduced. Consideration of functional characteristics of individual species, in particular aspects of habitat domain and hunting mode, are crucial in predicting the effects of multi-predator systems on the top-down control of herbivores. © 2010 The Authors. Journal of Animal Ecology © 2010 British Ecological Society.

Evolutionary and ecological implications of primate seed dispersal.

PubMed

Lambert, J E; Garber, P A

1998-01-01

In this paper, we evaluate patterns of fruit eating and seed dispersal in monkeys and apes and draw an important distinction between 1) the ecological consequences of primates as seed dispersers and 2) the evolutionary implications of primates on the seed and fruit traits of the plant species they exploit. In many forest communities, primates act as both seed predators and seed dispersers and are likely to have an important ecological impact on patterns of forest regeneration and tree species diversity. Evidence from Kibale National Park, Uganda, and Manu National Park, Peru, as well as several other South American sites indicates that monkeys and apes display a wide range of fruit-processing behaviors, including spitting seeds, dropping seeds, masticating seeds, and swallowing seeds. Differences in consumer body size, diet, ranging patterns, and oral and digestive morphology result in different patterns in the distance and distribution of seeds from the parent plant. In the case of South American monkeys, for example, despite their relatively small body size, platyrrhines were found to exploit larger fruits and swallow larger seeds on average than did Old World monkeys and apes of the Kibale forest. We found little evidence to support the existence of a coevolutionary relationship between a single or set of primate dispersers and the particular plant species they disperse. This is due to variability in the manner in which monkeys and apes select fruits and treat seeds, the fact that many species of primates and nonprimates exploit and disperse the same fruit species, and the fact that extremely high levels of postdispersal seed, seedling, and sapling mortality serve to dilute the influence that any primate species may have on the recruitment of the next generation of adult trees. It is apparent that many primate lineages exhibit dental, digestive, and/or sensory adaptations that aid in the exploitation of particular food types and that many lineages of flowering plants have evolved characteristics of fruits and seeds that facilitate seed dispersal. However, in light of currently available data, we argue that these represent evolutionary rather than more strictly defined coevolutionary relationships.

Your worst enemy could be your best friend: predator contributions to invasion resistance and persistence of natives

PubMed Central

Lounibos, L. Philip; Nishimura, Naoya; Greene, Krystle

2010-01-01

Native predators are postulated to have an important role in biotic resistance of communities to invasion and community resilience. Effects of predators can be complex, and mechanisms by which predators affect invasion success and impact are understood for only a few well-studied communities. We tested experimentally whether a native predator limits an invasive species' success and impact on a native competitor for a community of aquatic insect larvae in water-filled containers. The native mosquito Aedes triseriatus alone had no significant effect on abundance of the invasive mosquito Aedes albopictus. The native predatory midge Corethrella appendiculata, at low or high density, significantly reduced A. albopictus abundance. This effect was not caused by trait-mediated oviposition avoidance of containers with predators, but instead was a density-mediated effect caused by predator-induced mortality. The presence of this predator significantly reduced survivorship of the native species, but high predator density also significantly increased development rate of the native species when the invader was present, consistent with predator-mediated release from interspecific competition with the invader. Thus, a native predator can indirectly benefit its native prey when a superior competitor invades. This shows the importance of native predators as a component of biodiversity for both biotic resistance to invasion and resilience of a community perturbed by successful invasion. PMID:19841945

Effects of behavioral and morphological plasticity on risk of predation in a Neotropical tadpole

USGS Publications Warehouse

McIntyre, P.B.; Baldwin, S.; Flecker, A.S.

2004-01-01

Predator-induced phenotypic plasticity is widespread among aquatic animals, however the relative contributions of behavioral and morphological shifts to reducing risk of predation remain uncertain. We tested the phenotypic plasticity of a Neotropical tadpole (Rana palmipes) in response to chemical cues from predatory Belostoma water bugs, and how phenotype affects risk of predation. Behavior, morphology, and pigmentation all were plastic, resulting in a predator-induced phenotype with lower activity, deeper tail fin and muscle, and darker pigmentation. Tadpoles in the predator cue treatment also grew more rapidly, possibly as a result of the nutrient subsidy from feeding the caged predator. For comparison to phenotypes induced in the experiment, we quantified the phenotype of tadpoles from a natural pool. Wildcaught tadpoles did not match either experimentally induced phenotype; their morphology was more similar to that produced in the control treatment, but their low swimming activity was similar to that induced by predator cues. Exposure of tadpoles from both experimental treatments and the natural pool to a free-ranging predator confirmed that predator-induced phenotypic plasticity reduces risk of predation. Risk of predation was comparable among wild-caught and predator-induced tadpoles, indicating that behavioral shifts can substantially alleviate risk in tadpoles that lack the typical suite of predator-induced morphological traits. The morphology observed in wild-caught tadpoles is associated with rapid growth and high competition in other tadpole species, suggesting that tadpoles may profitably combine a morphology suited to competition for food with behaviors that minimize risk of predation. ?? Springer-Verlag 2004.

Migratory herds of wildebeests and zebras indirectly affect calf survival of giraffes.

PubMed

Lee, Derek E; Kissui, Bernard M; Kiwango, Yustina A; Bond, Monica L

2016-12-01

In long-distance migratory systems, local fluctuations in the predator-prey ratio can exhibit extreme variability within a single year depending upon the seasonal location of migratory species. Such systems offer an opportunity to empirically investigate cyclic population density effects on short-term food web interactions by taking advantage of the large seasonal shifts in migratory prey biomass.We utilized a large-mammal predator-prey savanna food web to evaluate support for hypotheses relating to the indirect effects of "apparent competition" and "apparent mutualism" from migratory ungulate herds on survival of resident megaherbivore calves, mediated by their shared predator. African lions ( Panthera leo ) are generalist predators whose primary, preferred prey are wildebeests ( Connochaetes taurinus ) and zebras ( Equus quagga ), while lion predation on secondary prey such as giraffes ( Giraffa camelopardalis ) may change according to the relative abundance of the primary prey species.We used demographic data from five subpopulations of giraffes in the Tarangire Ecosystem of Tanzania, East Africa, to test hypotheses relating to direct predation and indirect effects of large migratory herds on calf survival of a resident megaherbivore. We examined neonatal survival via apparent reproduction of 860 adult females, and calf survival of 449 giraffe calves, during three precipitation seasons over 3 years, seeking evidence of some effect on neonate and calf survival as a consequence of the movements of large herds of migratory ungulates.We found that local lion predation pressure (lion density divided by primary prey density) was significantly negatively correlated with giraffe neonatal and calf survival probabilities. This supports the apparent mutualism hypothesis that the presence of migratory ungulates reduces lion predation on giraffe calves.Natural predation had a significant effect on giraffe calf and neonate survival, and could significantly affect giraffe population dynamics. If wildebeest and zebra populations in this ecosystem continue to decline as a result of increasingly disrupted migrations and poaching, then giraffe calves will face increased predation pressure as the predator-prey ratio increases. Our results suggest that the widespread population declines observed in many migratory systems are likely to trigger demographic impacts in other species due to indirect effects like those shown here.

Egg-laying environment modulates offspring responses to predation risk in an amphibian.

PubMed

Tóth, Zoltán; Hettyey, Attila

2018-05-01

Predator-induced plasticity has been in the focus of evolutionary ecological research in the last decades, but the consequences of temporal variation in the presence of cues predicting offspring environment have remained controversial. This is partly due to the fact that the role of early environmental effects has scarcely been scrutinized in this context while also controlling for potential maternal effects. In this study, we investigated how past environmental conditions, that is different combinations of risky or safe adult (prenatal) and oviposition (early post-natal) environments, affected offspring's plastic responses in hatching time and locomotor activity to predation risk during development in the smooth newt (Lissotriton vulgaris). We found that females did not adjust their reproductive investment to the perceived level of risk in the adult environment, and this prenatal environment had generally negligible effect on offspring phenotype. However, when predator cues were absent during oviposition, larvae raised in the presence of predator cues delayed their hatching and exhibited a decreased activity compared to control larvae developing without predator cues, which responses are advantageous when predators pose a threat to hatched larvae. In the presence of predator cues during oviposition, the difference in hatching time persisted, but the difference in general locomotor activity disappeared between risk-exposed and control larvae. Our findings provide clear experimental evidence that fine-scale temporal variation in a predictive cue during and after egg-laying interactively affects offspring phenotype, and highlight the importance of the early post-natal environment, which may exert a substantial influence on progeny's phenotype also under natural conditions. © 2018 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2018 European Society For Evolutionary Biology.

Effects of predation stress and food ration on perch gut microbiota.

PubMed

Zha, Yinghua; Eiler, Alexander; Johansson, Frank; Svanbäck, Richard

2018-02-06

Gut microbiota provide functions of importance to influence hosts' food digestion, metabolism, and protection against pathogens. Factors that affect the composition and functions of gut microbial communities are well studied in humans and other animals; however, we have limited knowledge of how natural food web factors such as stress from predators and food resource rations could affect hosts' gut microbiota and how it interacts with host sex. In this study, we designed a two-factorial experiment exposing perch (Perca fluviatilis) to a predator (pike, Esox lucius), and different food ratios, to examine the compositional and functional changes of perch gut microbiota based on 16S rRNA amplicon sequencing. We also investigated if those changes are host sex dependent. We showed that overall gut microbiota composition among individual perch significantly responded to food ration and predator presence. We found that species richness decreased with predator presence, and we identified 23 taxa from a diverse set of phyla that were over-represented when a predator was present. For example, Fusobacteria increased both at the lowest food ration and at predation stress conditions, suggesting that Fusobacteria are favored by stressful situations for the host. In concordance, both food ration and predation stress seemed to influence the metabolic repertoire of the gut microbiota, such as biosynthesis of other secondary metabolites, metabolism of cofactors, and vitamins. In addition, the identified interaction between food ration and sex emphasizes sex-specific responses to diet quantity in gut microbiota. Collectively, our findings emphasize an alternative state in gut microbiota with responses to changes in natural food webs depending on host sex. The obtained knowledge from this study provided us with an important perspective on gut microbiota in a food web context.

Breeding system and pollination of a narrowly endemic herb of the Lower Florida Keys: impacts of the urban-wildland interface.

PubMed

Liu, Hong; Koptur, Suzanne

2003-08-01

We examined the breeding system and pollination of Chamaecrista keyensis Pennell (Fabaceae: Caesalpinioideae) and the effects of urban edge and mosquito control on reproduction of this rare endemic herb of the Lower Florida Keys. Controlled hand-pollination treatments were applied to plants in the field. Although C. keyensis flowers are self-compatible, they are not capable of automatic selfing. Inbreeding depression was observed in both seed set and percentage seed germination. Bees of seven genera were observed visiting C. keyensis flowers during the peak flowering season (June to July). Only Xylocopa micans and Melissodes spp. may be effective pollinators for C. keyensis, as they were the only bees that "buzz pollinate" this species, which has poricidal anther dehiscence. Chamaecrista keyensis received substantially more visits by X. micans, but fewer visits from Melissodes spp. in urban-edge vs. forest sites. Aerial mosquito spraying may exacerbate the existing pollinator limitation suffered by C. keyensis by reducing the number of visits by the buzz-pollinating bees. Individuals of C. keyensis at urban edges produced fewer seeds per fruit than did individuals in a pristine forest mainly because of greater insect seed predation.

The relationship between direct predation and antipredator responses: a test with multiple predators and multiple prey.

PubMed

Creel, Scott; Dröge, Egil; M'soka, Jassiel; Smit, Daan; Becker, Matt; Christianson, Dave; Schuette, Paul

2017-08-01

Most species adjust their behavior to reduce the likelihood of predation. Many experiments have shown that antipredator responses carry energetic costs that can affect growth, survival, and reproduction, so that the total cost of predation depends on a trade-off between direct predation and risk effects. Despite these patterns, few field studies have examined the relationship between direct predation and the strength of antipredator responses, particularly for complete guilds of predators and prey. We used scan sampling in 344 observation periods over a four-year field study to examine behavioral responses to the immediate presence of predators for a complete antelope guild (dominated by wildebeest, zebra, and oribi) in Liuwa Plains National Park, Zambia, testing for differences in response to all large carnivores in the ecosystem (lions, spotted hyenas, cheetahs, and African wild dogs). We quantified the proportion that each prey species contributed to the kills made by each predator (516 total kills), used distance sampling on systematic line transects to determine the abundance of each prey species, and combined these data to quantify the per-capita risk of direct predation for each predator-prey pair. On average, antelopes increased their vigilance by a factor of 2.4 when predators were present. Vigilance varied strongly among prey species, but weakly in response to different predators. Increased vigilance was correlated with reduced foraging in a similar manner for all prey species. The strength of antipredator response was not detectably related to patterns of direct predation (n = 15 predator-prey combinations with sufficient data). This lack of correlation has implications for our understanding of the role of risk effects as part of the limiting effect of predators on prey. © 2017 by the Ecological Society of America.

Predator-induced neophobia in juvenile cichlids.

PubMed

Meuthen, Denis; Baldauf, Sebastian A; Bakker, Theo C M; Thünken, Timo

2016-08-01

Predation is an important but often fluctuating selection factor for prey animals. Accordingly, individuals plastically adopt antipredator strategies in response to current predation risk. Recently, it was proposed that predation risk also plastically induces neophobia (an antipredator response towards novel cues). Previous studies, however, do not allow a differentiation between general neophobia and sensory channel-specific neophobic responses. Therefore, we tested the neophobia hypothesis focusing on adjustment in shoaling behavior in response to a novel cue addressing a different sensory channel than the one from which predation risk was initially perceived. From hatching onwards, juveniles of the cichlid Pelvicachromis taeniatus were exposed to different chemical cues in a split-clutch design: conspecific alarm cues which signal predation risk and heterospecific alarm cues or distilled water as controls. At 2 months of age, their shoaling behavior was examined prior and subsequent to a tactical disturbance cue. We found that fish previously exposed to predation risk formed more compact shoals relative to the control groups in response to the novel disturbance cue. Moreover, the relationship between shoal density and shoal homogeneity was also affected by experienced predation risk. Our findings indicate predator-induced, increased cross-sensory sensitivity towards novel cues making neophobia an effective antipredator mechanism.

What do predators really want? The role of gerbil energetic state in determining prey choice by Barn Owls.

PubMed

Embar, Keren; Mukherjee, Shomen; Kotler, Burt P

2014-02-01

In predator-prey foraging games, predators should respond to variations in prey state. The value of energy for the prey changes depending on season. Prey in a low energetic state and/or in a reproductive state should invest more in foraging and tolerate higher predation risk. This should make the prey more catchable, and thereby, more preferable to predators. We ask, can predators respond to prey state? How does season and state affect the foraging game from the predator's perspective? By letting owls choose between gerbils whose states we experimentally manipulated, we could demonstrate predator sensitivity to prey state and predator selectivity that otherwise may be obscured by the foraging game. During spring, owls invested more time and attacks in the patch with well-fed gerbils. During summer, owls attacked both patches equally, yet allocated more time to the patch with hungry gerbils. Energetic state per se does not seem to be the basis of owl choice. The owls strongly responded to these subtle differences. In summer, gerbils managed their behavior primarily for survival, and the owls equalized capture opportunities by attacking both patches equally.

Predator identity and consumer behavior: differential effects of fish and crayfish on the habitat use of a freshwater snail.

PubMed

Turner, Andrew M; Fetterolf, Shelley A; Bernot, Randall J

1999-02-01

Predators can alter the outcome of ecological interactions among other members of the food web through their effects on prey behavior. While it is well known that animals often alter their behavior with the imposition of predation risk, we know less about how other features of predators may affect prey behavior. For example, relatively few studies have addressed the effects of predator identity on prey behavior, but such knowledge is crucial to understanding food web interactions. This study contrasts the behavioral responses of the freshwater snail Physellagyrina to fish and crayfish predators. Snails were placed in experimental mesocosms containing caged fish and crayfish, so the only communication between experimental snails and their predators was via non-visual cues. The caged fish and crayfish were fed an equal number of snails, thereby simulating equal prey mortality rates. In the presence of fish, the experimental snails moved under cover, which confers safety from fish predators. However, in the presence of crayfish, snails avoided benthic cover and moved to the water surface. Thus, two species of predators, exerting the same level of mortality on prey, induced very different behavioral responses. We predict that these contrasting behavioral responses to predation risk have important consequences for the interactions between snails and their periphyton resources.

Variability in sea ice cover and climate elicit sex specific responses in an Antarctic predator

PubMed Central

Labrousse, Sara; Sallée, Jean-Baptiste; Fraser, Alexander D.; Massom, Rob A.; Reid, Phillip; Hobbs, William; Guinet, Christophe; Harcourt, Robert; McMahon, Clive; Authier, Matthieu; Bailleul, Frédéric; Hindell, Mark A.; Charrassin, Jean-Benoit

2017-01-01

Contrasting regional changes in Southern Ocean sea ice have occurred over the last 30 years with distinct regional effects on ecosystem structure and function. Quantifying how Antarctic predators respond to such changes provides the context for predicting how climate variability/change will affect these assemblages into the future. Over an 11-year time-series, we examine how inter-annual variability in sea ice concentration and advance affect the foraging behaviour of a top Antarctic predator, the southern elephant seal. Females foraged longer in pack ice in years with greatest sea ice concentration and earliest sea ice advance, while males foraged longer in polynyas in years of lowest sea ice concentration. There was a positive relationship between near-surface meridional wind anomalies and female foraging effort, but not for males. This study reveals the complexities of foraging responses to climate forcing by a poleward migratory predator through varying sea ice property and dynamic anomalies. PMID:28233791

Anthropogenic noise compromises the anti-predator behaviour of the European seabass, Dicentrarchus labrax (L.).

PubMed

Spiga, Ilaria; Aldred, Nicholas; Caldwell, Gary S

2017-09-15

Anthropogenic noise is a significant pollutant of the world's oceans, affecting behavioural and physiological traits in a range of species, including anti-predator behaviours. Using the open field test, we investigated the effects of recordings of piling and drilling noise on the anti-predator behaviour of captive juvenile European seabass in response to a visual stimulus (a predatory mimic). The impulsive nature of piling noise triggered a reflexive startle response, which contrasted the behaviour elicited by the continuous drilling noise. When presented with the predatory mimic, fish exposed to both piling and drilling noise explored the experimental arena more extensively than control fish exposed to ambient noise. Fish under drilling and piling conditions also exhibited reduced predator inspection behaviour. Piling and drilling noise induced stress as measured by ventilation rate. This study provides further evidence that the behaviour and physiology of European seabass is significantly affected by exposure to elevated noise levels. Copyright © 2017. Published by Elsevier Ltd.

Variability in sea ice cover and climate elicit sex specific responses in an Antarctic predator.

PubMed

Labrousse, Sara; Sallée, Jean-Baptiste; Fraser, Alexander D; Massom, Rob A; Reid, Phillip; Hobbs, William; Guinet, Christophe; Harcourt, Robert; McMahon, Clive; Authier, Matthieu; Bailleul, Frédéric; Hindell, Mark A; Charrassin, Jean-Benoit

2017-02-24

Contrasting regional changes in Southern Ocean sea ice have occurred over the last 30 years with distinct regional effects on ecosystem structure and function. Quantifying how Antarctic predators respond to such changes provides the context for predicting how climate variability/change will affect these assemblages into the future. Over an 11-year time-series, we examine how inter-annual variability in sea ice concentration and advance affect the foraging behaviour of a top Antarctic predator, the southern elephant seal. Females foraged longer in pack ice in years with greatest sea ice concentration and earliest sea ice advance, while males foraged longer in polynyas in years of lowest sea ice concentration. There was a positive relationship between near-surface meridional wind anomalies and female foraging effort, but not for males. This study reveals the complexities of foraging responses to climate forcing by a poleward migratory predator through varying sea ice property and dynamic anomalies.

Thermal acclimation of interactions: differential responses to temperature change alter predator-prey relationship.

PubMed

Grigaltchik, Veronica S; Ward, Ashley J W; Seebacher, Frank

2012-10-07

Different species respond differently to environmental change so that species interactions cannot be predicted from single-species performance curves. We tested the hypothesis that interspecific difference in the capacity for thermal acclimation modulates predator-prey interactions. Acclimation of locomotor performance in a predator (Australian bass, Macquaria novemaculeata) was qualitatively different to that of its prey (eastern mosquitofish, Gambusia holbrooki). Warm (25°C) acclimated bass made more attacks than cold (15°C) acclimated fish regardless of acute test temperatures (10-30°C), and greater frequency of attacks was associated with increased prey capture success. However, the number of attacks declined at the highest test temperature (30°C). Interestingly, escape speeds of mosquitofish during predation trials were greater than burst speeds measured in a swimming arena, whereas attack speeds of bass were lower than burst speeds. As a result, escape speeds of mosquitofish were greater at warm temperatures (25°C and 30°C) than attack speeds of bass. The decline in the number of attacks and the increase in escape speed of prey means that predation pressure decreases at high temperatures. We show that differential thermal responses affect species interactions even at temperatures that are within thermal tolerance ranges. This thermal sensitivity of predator-prey interactions can be a mechanism by which global warming affects ecological communities.

Termites and large herbivores influence seed removal rates in an African savanna.

PubMed

Acanakwo, Erik Francis; Sheil, Douglas; Moe, Stein R

2017-12-01

Seed removal can influence plant community dynamics, composition, and resulting vegetation characteristics. In the African savanna, termites and large herbivores influence vegetation in various ways, likely including indirect effects on seed predators and secondary dispersers. However, the intensity and variation of seed removal rates in African savannas has seldom been studied. We experimentally investigated whether termites and large herbivores were important factors in the mechanisms contributing to observed patterns in tree species composition on and off mounds, in Lake Mburo National Park, Uganda. Within fenced (excluding large herbivores) and unfenced termite mound and adjacent savanna plots, we placed seeds of nine native tree species within small open "cages," accessed by all animals, roofed cages that only allowed access to small vertebrates and invertebrates, and closed cages that permitted access by smaller invertebrates only (5 mm wire mesh). We found that mean seed removal rate was high (up to 87.3% per 3 d). Mound habitats experienced significantly higher removal rates than off-mound habitats. The mean removal rate of native seeds from closed cages was 11.1% per 3 d compared with 19.4% and 23.3% removed per 3 d in the roofed and open cages, respectively. Smaller seeds experienced higher removal rates than larger seeds. Large herbivore exclusion on mounds reduced native seed removal rates by a mean of 8.8% in the open cages, but increased removal rates by 1.7% in the open cages when off-mound habitats were fenced. While removal rates from open cages were higher on active mounds (30.9%) than on inactive mounds (26.7%), the removal rates from closed cages were lower on active vs. inactive mounds (6.1% vs. 11.6%, respectively). Thus, we conclude that large herbivores and Macrotermes mounds influence seed removal rates, though these effects appear indirect. © 2017 by the Ecological Society of America.

Interaction between parental environment and genotype affects plant and seed performance in Arabidopsis.

PubMed

He, Hanzi; de Souza Vidigal, Deborah; Snoek, L Basten; Schnabel, Sabine; Nijveen, Harm; Hilhorst, Henk; Bentsink, Leónie

2014-12-01

Seed performance after dispersal is highly dependent on parental environmental cues, especially during seed formation and maturation. Here we examine which environmental factors are the most dominant in this respect and whether their effects are dependent on the genotypes under investigation. We studied the influence of light intensity, photoperiod, temperature, nitrate, and phosphate during seed development on five plant attributes and thirteen seed attributes, using 12 Arabidopsis genotypes that have been reported to be affected in seed traits. As expected, the various environments during seed development resulted in changed plant and/or seed performances. Comparative analysis clearly indicated that, overall, temperature plays the most dominant role in both plant and seed performance, whereas light has a prominent impact on plant traits. In comparison to temperature and light, nitrate mildly affected some of the plant and seed traits while phosphate had even less influence on those traits. Moreover, clear genotype-by-environment interactions were identified. This was shown by the fact that individual genotypes responded differentially to the environmental conditions. Low temperature significantly increased seed dormancy and decreased seed longevity of NILDOG1 and cyp707a1-1, whereas low light intensity increased seed dormancy and decreased seed longevity of NILDOG3 and NILDOG6. This also indicates that different genetic and molecular pathways are involved in the plant and seed responses. By identifying environmental conditions that affect the dormancy vs longevity correlation in the same way as previously identified naturally occurring loci, we have identified selective forces that probably shaped evolution for these important seed traits. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Combined effects of predator cues and competition define habitat choice and food consumption of amphipod mesograzers.

PubMed

Beermann, Jan; Boos, Karin; Gutow, Lars; Boersma, Maarten; Peralta, Ana Carolina

2018-03-01

Predation has direct impact on prey populations by reducing prey abundance. In addition, predator presence alone can also have non-consumptive effects on prey species, potentially influencing their interspecific interactions and thus the structure of entire assemblages. The performance of potential prey species may, therefore, depend on both the presence of predators and competitors. We studied habitat use and food consumption of a marine mesograzer, the amphipod Echinogammarus marinus, in the presence/absence of a fish mesopredator and/or an amphipod competitor. The presence of the predator affected both habitat choice and food consumption of the grazer, indicating a trade-off between the use of predator-free space and food acquisition. Without the predator, E. marinus were distributed equally over different microhabitats, whereas in the presence of the predator, most individuals chose a sheltered microhabitat and reduced their food consumption. Furthermore, habitat choice of the amphipods changed in the presence of interspecific competitors, also resulting in reduced feeding rates. The performance of E. marinus is apparently driven by trait-mediated direct and indirect effects caused by the interplay of predator avoidance and competition. This highlights the importance of potential non-consumptive impacts of predators on their prey organisms. The flexible responses of small invertebrate consumers to the combined effects of predation and competition potentially lead to changes in the structure of coastal ecosystems and the multiple species interactions therein.

Fear of feces? Trade-offs between disease risk and foraging drive animal activity around raccoon latrines

USGS Publications Warehouse

Weinstein, Sara B.; Moura, Chad W.; Mendez, Jon Francis; Lafferty, Kevin D.

2017-01-01

Fear of predation alters prey behavior, which can indirectly alter entire landscapes. A parasite-induced ecology of fear might also exist if animals avoid parasite-contaminated resources when infection costs outweigh foraging benefits. To investigate whether animals avoid parasite contaminated sites, and if such avoidance balances disease costs and foraging gains, we monitored animal behavior at raccoon latrines – sites that concentrate both seeds and pathogenic parasite eggs. Using wildlife cameras, we documented over 40 potentially susceptible vertebrate species in latrines and adjacent habitat. Latrine contact rates reflected background activity, diet preferences and disease risk. Disease-tolerant raccoons and rats displayed significant site attraction, while susceptible birds and small mammals avoided these high-risk sites. This suggests that parasites, like predators, might create a landscape of fear for vulnerable hosts. Such non-consumptive parasite effects could alter disease transmission, population dynamics, and even ecosystem structure.

Logging cuts the functional importance of invertebrates in tropical rainforest

PubMed Central

Ewers, Robert M.; Boyle, Michael J. W.; Gleave, Rosalind A.; Plowman, Nichola S.; Benedick, Suzan; Bernard, Henry; Bishop, Tom R.; Bakhtiar, Effendi Y.; Chey, Vun Khen; Chung, Arthur Y. C.; Davies, Richard G.; Edwards, David P.; Eggleton, Paul; Fayle, Tom M.; Hardwick, Stephen R.; Homathevi, Rahman; Kitching, Roger L.; Khoo, Min Sheng; Luke, Sarah H.; March, Joshua J.; Nilus, Reuben; Pfeifer, Marion; Rao, Sri V.; Sharp, Adam C.; Snaddon, Jake L.; Stork, Nigel E.; Struebig, Matthew J.; Wearn, Oliver R.; Yusah, Kalsum M.; Turner, Edgar C.

2015-01-01

Invertebrates are dominant species in primary tropical rainforests, where their abundance and diversity contributes to the functioning and resilience of these globally important ecosystems. However, more than one-third of tropical forests have been logged, with dramatic impacts on rainforest biodiversity that may disrupt key ecosystem processes. We find that the contribution of invertebrates to three ecosystem processes operating at three trophic levels (litter decomposition, seed predation and removal, and invertebrate predation) is reduced by up to one-half following logging. These changes are associated with decreased abundance of key functional groups of termites, ants, beetles and earthworms, and an increase in the abundance of small mammals, amphibians and insectivorous birds in logged relative to primary forest. Our results suggest that ecosystem processes themselves have considerable resilience to logging, but the consistent decline of invertebrate functional importance is indicative of a human-induced shift in how these ecological processes operate in tropical rainforests. PMID:25865801

Logging cuts the functional importance of invertebrates in tropical rainforest.

PubMed

Ewers, Robert M; Boyle, Michael J W; Gleave, Rosalind A; Plowman, Nichola S; Benedick, Suzan; Bernard, Henry; Bishop, Tom R; Bakhtiar, Effendi Y; Chey, Vun Khen; Chung, Arthur Y C; Davies, Richard G; Edwards, David P; Eggleton, Paul; Fayle, Tom M; Hardwick, Stephen R; Homathevi, Rahman; Kitching, Roger L; Khoo, Min Sheng; Luke, Sarah H; March, Joshua J; Nilus, Reuben; Pfeifer, Marion; Rao, Sri V; Sharp, Adam C; Snaddon, Jake L; Stork, Nigel E; Struebig, Matthew J; Wearn, Oliver R; Yusah, Kalsum M; Turner, Edgar C

2015-04-13

Invertebrates are dominant species in primary tropical rainforests, where their abundance and diversity contributes to the functioning and resilience of these globally important ecosystems. However, more than one-third of tropical forests have been logged, with dramatic impacts on rainforest biodiversity that may disrupt key ecosystem processes. We find that the contribution of invertebrates to three ecosystem processes operating at three trophic levels (litter decomposition, seed predation and removal, and invertebrate predation) is reduced by up to one-half following logging. These changes are associated with decreased abundance of key functional groups of termites, ants, beetles and earthworms, and an increase in the abundance of small mammals, amphibians and insectivorous birds in logged relative to primary forest. Our results suggest that ecosystem processes themselves have considerable resilience to logging, but the consistent decline of invertebrate functional importance is indicative of a human-induced shift in how these ecological processes operate in tropical rainforests.

Mesopredator Management: Effects of Red Fox Control on the Abundance, Diet and Use of Space by Feral Cats.

PubMed

Molsher, Robyn; Newsome, Alan E; Newsome, Thomas M; Dickman, Christopher R

2017-01-01

Apex predators are subject to lethal control in many parts of the world to minimize their impacts on human industries and livelihoods. Diverse communities of smaller predators-mesopredators-often remain after apex predator removal. Despite concern that these mesopredators may be 'released' in the absence of the apex predator and exert negative effects on each other and on co-occurring prey, these interactions have been little studied. Here, we investigate the potential effects of competition and intraguild predation between red foxes (Vulpes vulpes) and feral cats (Felis catus) in south-eastern Australia where the apex predator, the dingo (Canis dingo), has been extirpated by humans. We predicted that the larger fox would dominate the cat in encounters, and used a fox-removal experiment to assess whether foxes affect cat abundance, diet, home-range and habitat use. Our results provide little indication that intraguild predation occurred or that cats responded numerically to the fox removal, but suggest that the fox affects some aspects of cat resource use. In particular, where foxes were removed cats increased their consumption of invertebrates and carrion, decreased their home range size and foraged more in open habitats. Fox control takes place over large areas of Australia to protect threatened native species and agricultural interests. Our results suggest that fox control programmes could lead to changes in the way that cats interact with co-occurring prey, and that some prey may become more vulnerable to cat predation in open habitats after foxes have been removed. Moreover, with intensive and more sustained fox control it is possible that cats could respond numerically and alter their behaviour in different ways to those documented herein. Such outcomes need to be considered when estimating the indirect impacts of fox control. We conclude that novel approaches are urgently required to control invasive mesopredators at the same time, especially in areas where apex predators are absent.

Predator-induced changes of female mating preferences: innate and experiential effects

PubMed Central

2011-01-01

Background In many species males face a higher predation risk than females because males display elaborate traits that evolved under sexual selection, which may attract not only females but also predators. Females are, therefore, predicted to avoid such conspicuous males under predation risk. The present study was designed to investigate predator-induced changes of female mating preferences in Atlantic mollies (Poecilia mexicana). Males of this species show a pronounced polymorphism in body size and coloration, and females prefer large, colorful males in the absence of predators. Results In dichotomous choice tests predator-naïve (lab-reared) females altered their initial preference for larger males in the presence of the cichlid Cichlasoma salvini, a natural predator of P. mexicana, and preferred small males instead. This effect was considerably weaker when females were confronted visually with the non-piscivorous cichlid Vieja bifasciata or the introduced non-piscivorous Nile tilapia (Oreochromis niloticus). In contrast, predator experienced (wild-caught) females did not respond to the same extent to the presence of a predator, most likely due to a learned ability to evaluate their predators' motivation to prey. Conclusions Our study highlights that (a) predatory fish can have a profound influence on the expression of mating preferences of their prey (thus potentially affecting the strength of sexual selection), and females may alter their mate choice behavior strategically to reduce their own exposure to predators. (b) Prey species can evolve visual predator recognition mechanisms and alter their mate choice only when a natural predator is present. (c) Finally, experiential effects can play an important role, and prey species may learn to evaluate the motivational state of their predators. PMID:21726456

Landscape-moderated bird nest predation in hedges and forest edges

NASA Astrophysics Data System (ADS)

Ludwig, Martin; Schlinkert, Hella; Holzschuh, Andrea; Fischer, Christina; Scherber, Christoph; Trnka, Alfréd; Tscharntke, Teja; Batáry, Péter

2012-11-01

Landscape-scale agricultural intensification has caused severe declines in biodiversity. Hedges and forest remnants may mitigate biodiversity loss by enhancing landscape heterogeneity and providing habitat to a wide range of species, including birds. However, nest predation, the major cause of reproductive failure of birds, has been shown to be higher in forest edges than in forest interiors. Little is known about how spatial arrangement (configuration) of hedges affects the avian nest predation. We performed an experiment with artificial ground and elevated nests (resembling yellowhammer and whitethroat nests) baited with quail and plasticine eggs. Nests were placed in three habitat types with different degrees of isolation from forests: forest edges, hedges connected to forests and hedges isolated from forests. Nest predation was highest in forest edges, lowest in hedges connected to forests and intermediate in isolated hedges. In the early breeding season, we found similar nest predation on ground and elevated nests, but in the late breeding season nest predation was higher on ground nests than on elevated nests. Small mammals were the main predators of ground nests and appeared to be responsible for the increase in predation from early to late breeding season, whereas the elevated nests were mainly depredated by small birds and small mammals. High predation pressure at forest edges was probably caused by both forest and open-landscape predators. The influence of forest predators may be lower at hedges, leading to lower predation pressure than in forest edges. Higher predation pressure in isolated than connected hedges might be an effect of concentration of predators in these isolated habitats. We conclude that landscape configuration of hedges is important in nest predation, with connected hedges allowing higher survival than isolated hedges and forest edges.

Predation on multiple trophic levels shapes the evolution of pathogen virulence.

PubMed

Friman, Ville-Petri; Lindstedt, Carita; Hiltunen, Teppo; Laakso, Jouni; Mappes, Johanna

2009-08-25

The pathogen virulence is traditionally thought to co-evolve as a result of reciprocal selection with its host organism. In natural communities, pathogens and hosts are typically embedded within a web of interactions with other species, which could affect indirectly the pathogen virulence and host immunity through trade-offs. Here we show that selection by predation can affect both pathogen virulence and host immune defence. Exposing opportunistic bacterial pathogen Serratia marcescens to predation by protozoan Tetrahymena thermophila decreased its virulence when measured as host moth Parasemia plantaginis survival. This was probably because the bacterial anti-predatory traits were traded off with bacterial virulence factors, such as motility or resource use efficiency. However, the host survival depended also on its allocation to warning signal that is used against avian predation. When infected with most virulent ancestral bacterial strain, host larvae with a small warning signal survived better than those with an effective large signal. This suggests that larval immune defence could be traded off with effective defence against bird predators. However, the signal size had no effect on larval survival when less virulent control or evolved strains were used for infection suggesting that anti-predatory defence against avian predators, might be less constrained when the invading pathogen is rather low in virulence. Our results demonstrate that predation can be important indirect driver of the evolution of both pathogen virulence and host immunity in communities with multiple species interactions. Thus, the pathogen virulence should be viewed as a result of both past evolutionary history, and current ecological interactions.

Inconstancy in predator/prey ratios in Quaternary large mammal communities of Italy, with an appraisal of mechanisms

NASA Astrophysics Data System (ADS)

Raia, Pasquale; Meloro, Carlo; Barbera, Carmela

2007-03-01

Constancy in predator/prey ratio (PPR) is a controversial issue in ecological research. Published reports support both constancy and inconstancy of the ratio in animal communities. Only a few studies, however, specifically address its course through time. Here we study the course of predator/prey ratio in communities of large Plio-Pleistocene mammals in Italy. After controlling for taphonomic biases, we find strong support for PPR inconstancy through time. Extinction, dispersal events, and differences in body size trends between predators and their prey were found to affect the ratio, which was distributed almost bimodally. We suggest that this stepwise dynamic in PPR indicates changes in ecosystem functioning. Prey richness was controlled by predation when PPR was high and by resources when PPR was low.

The effects of urbanization on trophic interactions in a desert landscape

USDA-ARS?s Scientific Manuscript database

Background/Question/Methods: Trophic systems can be affected through top-down (predators) and bottom-up (resources) impacts. Human activity can alter trophic systems by causing predators to avoid areas (top-down) or by providing increased resources through irrigation and decorative plants that attra...

Gibbons (Nomascus gabriellae) provide key seed dispersal for the Pacific walnut (Dracontomelon dao), in Asia's lowland tropical forest

NASA Astrophysics Data System (ADS)

Hai, Bach Thanh; Chen, Jin; McConkey, Kim R.; Dayananda, Salindra K.

2018-04-01

Understanding the mutualisms between frugivores and plants is essential for developing successful forest management and conservation strategies, especially in tropical rainforests where the majority of plants are dispersed by animals. Gibbons are among the most effective seed dispersers in South East Asia's tropical forests, but are also one of the highly threatened arboreal mammals in the region. Here we studied the seed dispersal of the Pacific walnut (Dracontomelon dao), a canopy tree which produces fruit that are common in the diet of the endangered southern yellow-cheeked crested gibbon (Nomascus gabriellae). We found that gibbons were the most effective disperser for this species; they consumed approximately 45% of the fruit crop, which was four times more than that consumed by macaques - the only other legitimate disperser. Gibbons tracked the temporal (but not spatial) abundance of ripe fruits, indicating this fruit was a preferred species for the gibbon. Both gibbons and macaques dispersed the majority (>90%) of the seeds at least 20 m away from parent crowns, with mean dispersal distances by gibbons measuring 179.3 ± 98.0 m (range: 4-425 m). Seeds defecated by gibbons germinated quicker and at greater rates than seeds spat by macaques, or in undispersed fruits. Gibbon-dispersed seeds were also more likely to be removed by unknown seed predators or unknown secondary dispersers. Overall, gibbons play a key role in the regeneration of the Pacific walnut. Our findings have significant implications both for the management of the Pacific walnut tree dominating tropical rainforest as well as the reintroduction program of the Southern yellow-cheeked crested gibbon.

Pesticide seed dressings can affect the activity of various soil organisms and reduce decomposition of plant material.

PubMed

Zaller, Johann G; König, Nina; Tiefenbacher, Alexandra; Muraoka, Yoko; Querner, Pascal; Ratzenböck, Andreas; Bonkowski, Michael; Koller, Robert

2016-08-17

Seed dressing with pesticides is widely used to protect crop seeds from pest insects and fungal diseases. While there is mounting evidence that especially neonicotinoid seed dressings detrimentally affect insect pollinators, surprisingly little is known on potential side effects on soil biota. We hypothesized that soil organisms would be particularly susceptible to pesticide seed dressings as they get in direct contact with these chemicals. Using microcosms with field soil we investigated, whether seeds treated either with neonicotinoid insecticides or fungicides influence the activity and interaction of earthworms, collembola, protozoa and microorganisms. The full-factorial design consisted of the factor Seed dressing (control vs. insecticide vs. fungicide), Earthworm (no earthworms vs. addition Lumbricus terrestris L.) and collembola (no collembola vs. addition Sinella curviseta Brook). We used commercially available wheat seed material (Triticum aesticum L. cf. Lukullus) at a recommended seeding density of 367 m(-2). Seed dressings (particularly fungicides) increased collembola surface activity, increased the number of protozoa and reduced plant decomposition rate but did not affect earthworm activity. Seed dressings had no influence on wheat growth. Earthworms interactively affected the influence of seed dressings on collembola activity, whereas collembola increased earthworm surface activity but reduced soil basal respiration. Earthworms also decreased wheat growth, reduced soil basal respiration and microbial biomass but increased soil water content and electrical conductivity. The reported non-target effects of seed dressings and their interactions with soil organisms are remarkable because they were observed after a one-time application of only 18 pesticide treated seeds per experimental pot. Because of the increasing use of seed dressing in agriculture and the fundamental role of soil organisms in agroecosystems these ecological interactions should receive more attention.

Top predators affect the composition of naive protist communities, but only in their early-successional stage.

PubMed

Zander, Axel; Gravel, Dominique; Bersier, Louis-Félix; Gray, Sarah M

2016-02-01

Introduced top predators have the potential to disrupt community dynamics when prey species are naive to predation. The impact of introduced predators may also vary depending on the stage of community development. Early-succession communities are likely to have small-bodied and fast-growing species, but are not necessarily good at defending against predators. In contrast, late-succession communities are typically composed of larger-bodied species that are more predator resistant relative to small-bodied species. Yet, these aspects are greatly neglected in invasion studies. We therefore tested the effect of top predator presence on early- and late-succession communities that were either naive or non-naive to top predators. We used the aquatic community held within the leaves of Sarracenia purpurea. In North America, communities have experienced the S. purpurea top predator and are therefore non-naive. In Europe, this predator is not present and its niche has not been filled, making these communities top-predator naive. We collected early- and late-succession communities from two non-naive and two naive sites, which are climatically similar. We then conducted a common-garden experiment, with and without the presence of the top predator, in which we recorded changes in community composition, body size spectra, bacterial density, and respiration. We found that the top predator had no statistical effect on global measures of community structure and functioning. However, it significantly altered protist composition, but only in naive, early-succession communities, highlighting that the state of community development is important for understanding the impact of invasion.

Limited spatial response to direct predation risk by African herbivores following predator reintroduction.

PubMed

Davies, Andrew B; Tambling, Craig J; Kerley, Graham I H; Asner, Gregory P

2016-08-01

Predators affect ecosystems not only through direct mortality of prey, but also through risk effects on prey behavior, which can exert strong influences on ecosystem function and prey fitness. However, how functionally different prey species respond to predation risk and how prey strategies vary across ecosystems and in response to predator reintroduction are poorly understood. We investigated the spatial distributions of six African herbivores varying in foraging strategy and body size in response to environmental factors and direct predation risk by recently reintroduced lions in the thicket biome of the Addo Elephant National Park, South Africa, using camera trap surveys, GPS telemetry, kill site locations and Light Detection and Ranging. Spatial distributions of all species, apart from buffalo, were driven primarily by environmental factors, with limited responses to direct predation risk. Responses to predation risk were instead indirect, with species distributions driven by environmental factors, and diel patterns being particularly pronounced. Grazers were more responsive to the measured variables than browsers, with more observations in open areas. Terrain ruggedness was a stronger predictor of browser distributions than was vegetation density. Buffalo was the only species to respond to predator encounter risk, avoiding areas with higher lion utilization. Buffalo therefore behaved in similar ways to when lions were absent from the study area. Our results suggest that direct predation risk effects are relatively weak when predator densities are low and the time since reintroduction is short and emphasize the need for robust, long-term monitoring of predator reintroductions to place such events in the broader context of predation risk effects.

Predator Preference for Bt-Fed Spodoptera frugiperda (Lepidoptera: Noctuidae) Prey: Implications for Insect Resistance Management in Bt Maize Seed Blends.

PubMed

Svobodová, Z; Burkness, E C; Skoková Habuštová, O; Hutchison, W D

2017-06-01

Understanding indirect, trophic-level effects of genetically engineered plants, expressing insecticidal proteins derived from the bacterium, Bacillus thuringiensis (Bt), is essential to the ecological risk assessment process. In this study, we examine potential indirect, trophic-level effects of Bt-sensitive prey using the predator, Harmonia axyridis (Pallas), feeding upon Spodoptera frugiperda (J.E. Smith) larvae, which had delayed development (lower body mass) following ingestion of Cry1Ab maize leaves. We found no adverse effects on development and survival when H. axyridis larvae were fed S. frugiperda larvae that had fed on Cry1Ab maize tissue. Presence of Cry1Ab in H. axyridis decreased considerably after switching to another diet within 48 h. In a no-choice assay, H. axyridis larvae consumed more Bt-fed S. frugiperda than non-Bt-fed larvae. Preference for S. frugiperda feeding on Bt maize was confirmed in subsequent choice assays with H. axyridis predation on Bt-fed, 1-5-d-old S. frugiperda larvae. We suggest that H. axyridis preferred prey, not based on whether it had fed on Bt or non-Bt maize, but rather on larval mass, and they compensated for the nutritional deficiency of lighter larvae through increased consumption. Pest larvae with variable levels of resistance developing on Bt diet are often stunted versus sensitive larvae developing on non-Bt diet. It is possible that such larvae may be preferentially removed from local field populations. These results may have implications for insect resistance management and may be played out under field conditions where seed blends of Bt and non-Bt hybrids are planted. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Evolution, Insular Restriction, and Extinction of Oceanic Land Crabs, Exemplified by the Loss of an Endemic Geograpsus in the Hawaiian Islands

PubMed Central

Paulay, Gustav; Starmer, John

2011-01-01

Most oceanic islands harbor unusual and vulnerable biotas as a result of isolation. As many groups, including dominant competitors and predators, have not naturally reached remote islands, others were less constrained to evolve novel adaptations and invade adaptive zones occupied by other taxa on continents. Land crabs are an excellent example of such ecological release, and some crab lineages made the macro-evolutionary transition from sea to land on islands. Numerous land crabs are restricted to, although widespread among, oceanic islands, where they can be keystone species in coastal forests, occupying guilds filled by vertebrates on continents. In the remote Hawaiian Islands, land crabs are strikingly absent. Here we show that absence of land crabs in the Hawaiian Islands is the result of extinction, rather than dispersal limitation. Analysis of fossil remains from all major islands show that an endemic Geograpsus was abundant before human colonization, grew larger than any congener, and extended further inland and to higher elevation than other land crabs in Oceania. Land crabs are major predators of nesting sea birds, invertebrates and plants, affect seed dispersal, control litter decomposition, and are important in nutrient cycling; their removal can lead to large-scale shifts in ecological communities. Although the importance of land crabs is obvious on remote and relatively undisturbed islands, it is less apparent on others, likely because they are decimated by humans and introduced biota. The loss of Geograpsus and potentially other land crabs likely had profound consequences for Hawaiian ecosystems. PMID:21603620

Using Artificial Nests to Study Nest Predation in Birds

ERIC Educational Resources Information Center

Belthoff, James R.

2005-01-01

A simple and effective field exercise that demonstrates factors affecting predation on bird nests is described. With instructor guidance, students in high school biology or college-level biology, ecology, animal behavior, wildlife management or ornithology laboratory courses can collaborate to design field experiments related to nest depredation.

Invasive plant architecture alters trophic interactions by changing predator abundance and behavior

Treesearch

Dean E. Pearson

2009-01-01

As primary producers, plants are known to influence higher trophic interactions by initiating food chains. However, as architects, plants may bypass consumers to directly affect predators with important but underappreciated trophic ramifications. Invasion of western North American grasslands by the perennial forb, spotted knapweed (Centaurea maculosa...

Landscape and regional context differentially affect nest parasitism and nest predation for Wood Thrush in central Virginia, USA (Presentation)

EPA Science Inventory

Many empirical studies have shown that forest-breeding songbirds suffer greater rates of nest predation and nest parasitism in smaller forest patches and in fragmented landscapes. To compare the performance of different metrics of spatial habitat configuration resulting from defo...

Does Noise From Shipping and Boat Traffic Affect Predator Vigilance in the European Common Hermit Crab?

PubMed

Nousek-McGregor, Anna E; Mei, Francesca Tee Liang

2016-01-01

The effect of noise on predator vigilance in Pagurus bernhardus was explored in this study. Latency of the first response, emergence time, and response type were measured from hermit crabs during continuous and variable vessel noise and two controls. The mean (±SE) response latency was longer for the noise treatments (continuous, 18.19 ± 2.78 s; variable, 11.39 ± 1.48 s) than for the controls (ambient, 7.21 ± 0.82 s; silent, 6.66 ± 0.95 s). Response type and emergence time were not significantly affected but were more variable during the noise treatments than during the controls. Noisy conditions may increase predation risk, suggesting potential fitness consequences for invertebrates.

A test of maternal programming of offspring stress response to predation risk in threespine sticklebacks.

PubMed

Mommer, Brett C; Bell, Alison M

2013-10-02

Non-genetic maternal effects are widespread across taxa and challenge our traditional understanding of inheritance. Maternal experience with predators, for example, can have lifelong consequences for offspring traits, including fitness. Previous work in threespine sticklebacks showed that females exposed to simulated predation risk produced eggs with higher cortisol content and offspring with altered anti-predator behavior. However, it is unknown whether this maternal effect is mediated via the offspring glucocorticoid stress response and if it is retained over the entire lifetime of offspring. Therefore, we tested the hypothesis that maternal exposure to simulated predation risk has long-lasting effects on the cortisol response to simulated predation risk in stickleback offspring. We measured circulating concentrations of cortisol before (baseline), 15 min after, and 60 min after exposure to a simulated predation risk. We compared adult offspring of predator-exposed mothers and control mothers in two different social environments (alone or in a group). Relative to baseline, offspring plasma cortisol was highest 15 min after exposure to simulated predation risk and decreased after 60 min. Offspring of predator-exposed mothers differed in the cortisol response to simulated predation risk compared to offspring of control mothers. In general, females had higher cortisol than males, and fish in a group had lower cortisol than fish that were by themselves. The buffering effect of the social environment did not differ between maternal treatments or between males and females. Altogether the results show that while a mother's experience with simulated predation risk might affect the physiological response of her adult offspring to a predator, sex and social isolation have much larger effects on the stress response to predation risk in sticklebacks. Copyright © 2013 Elsevier Inc. All rights reserved.

The roles of large top predators in coastal ecosystems: new insights from long term ecological research

USGS Publications Warehouse

Rosenblatt, Adam E.; Heithaus, Michael R.; Mather, Martha E.; Matich, Philip; Nifong, James C.; Ripple, William J.; Silliman, Brian R.

2013-01-01

During recent human history, human activities such as overhunting and habitat destruction have severely impacted many large top predator populations around the world. Studies from a variety of ecosystems show that loss or diminishment of top predator populations can have serious consequences for population and community dynamics and ecosystem stability. However, there are relatively few studies of the roles of large top predators in coastal ecosystems, so that we do not yet completely understand what could happen to coastal areas if large top predators are extirpated or significantly reduced in number. This lack of knowledge is surprising given that coastal areas around the globe are highly valued and densely populated by humans, and thus coastal large top predator populations frequently come into conflict with coastal human populations. This paper reviews what is known about the ecological roles of large top predators in coastal systems and presents a synthesis of recent work from three coastal eastern US Long Term Ecological Research (LTER) sites where long-term studies reveal what appear to be common themes relating to the roles of large top predators in coastal systems. We discuss three specific themes: (1) large top predators acting as mobile links between disparate habitats, (2) large top predators potentially affecting nutrient and biogeochemical dynamics through localized behaviors, and (3) individual specialization of large top predator behaviors. We also discuss how research within the LTER network has led to enhanced understanding of the ecological roles of coastal large top predators. Highlighting this work is intended to encourage further investigation of the roles of large top predators across diverse coastal aquatic habitats and to better inform researchers and ecosystem managers about the importance of large top predators for coastal ecosystem health and stability.

Impact of cannibalism on predator-prey dynamics: size-structured interactions and apparent mutualism.

PubMed

Rudolf, Volker H W

2008-06-01

Direct and indirect interactions between two prey species can strongly alter the dynamics of predator-prey systems. Most predators are cannibalistic, and as a consequence, even systems with only one predator and one prey include two prey types: conspecifics and heterospecifics. The effects of the complex direct and indirect interactions that emerge in such cannibalistic systems are still poorly understood. This study examined how the indirect interaction between conspecific and heterospecific prey affects cannibalism and predation rates and how the direct interactions between both species indirectly alter the effect of the cannibalistic predator. I tested for these effects using larvae of the stream salamanders Eurycea cirrigera (prey) and Pseudotriton ruber (cannibalistic predator) by manipulating the relative densities of the conspecific and heterospecific prey in the presence and absence of the predator in experimental streams. The rates of cannibalism and heterospecific predation were proportional to the respective densities and negatively correlated, indicating a positive indirect interaction between conspecific and heterospecific prey, similar to "apparent mutualism." Direct interactions between prey species did not alter the effect of the predator. Although both types of prey showed a similar 30% reduction in night activity and switch in microhabitat use in response to the presence of the predator, cannibalism rates were three times higher than heterospecific predation rates irrespective of the relative densities of the two types of prey. Cumulative predation risks differed even more due to the 48% lower growth rate of conspecific prey. Detailed laboratory experiments suggest that the 3:1 difference in cannibalism and predation rate was due to the higher efficiency of heterospecific prey in escaping immediate attacks. However, no difference was observed when the predator was a closely related salamander species, Gyrinophilus porphyriticus, indicating that this difference is species specific. This demonstrates that cannibalism can result in the coupling of predator and prey mortality rates that strongly determines the dynamics of predator-prey systems.

Factors Affecting Tocopherol Concentrations in Soybean Seeds.

PubMed

Carrera, Constanza S; Seguin, Philippe

2016-12-21

Soybean seeds contain several health-beneficial compounds, including tocopherols, which are used by the nutraceutical and functional food industries. Soybean tocopherol concentrations are, however, highly variable. Large differences observed in tocopherol concentrations among soybean genotypes together with the relatively simple biosynthetic pathway involving few genes support the feasibility of selecting for high-tocopherol soybean. Tocopherol concentrations are also highly influenced by environmental factors and field management. Temperature during seed filling and soil moisture appear to be the main factors affecting tocopherol concentrations; other factors such as soil fertility and solar radiation also affect concentrations and composition. Field management decisions including seeding date, row spacing, irrigation, and fertilization also affect tocopherols. Knowledge of factors affecting soybean tocopherols is essential to develop management strategies that will lead to the production of seeds with consistent target concentrations that will meet the needs of the nutraceutical and functional food industries.

Glucocorticoid stress hormones and the effect of predation risk on elk reproduction.

PubMed

Creel, Scott; Winnie, John A; Christianson, David

2009-07-28

Predators affect prey demography through direct predation and through the costs of antipredator behavioral responses, or risk effects. Experiments have shown that risk effects can comprise a substantial proportion of a predator's total effect on prey dynamics, but we know little about their strength in wild populations, or the physiological mechanisms that mediate them. When wolves are present, elk alter their grouping patterns, vigilance, foraging behavior, habitat selection, and diet. These responses are associated with decreased progesterone levels, decreased calf production, and reduced population size [Creel S, Christianson D, Liley S, Winnie JA (2007) Science 315:960]. Two general mechanisms for the effect of predation risk on reproduction have been proposed: the predation stress hypothesis and the predator-sensitive-food hypothesis. Here, we used enzyme immunoassay to measure fecal glucocorticoid metabolite concentrations for 1,205 samples collected from 4 elk populations over 4 winters to test the hypothesis that the effect of predation risk on elk reproduction is mediated by chronic stress. Across populations and years, fecal glucocorticoid concentrations were not related to predator-prey ratios, progesterone concentrations or calf-cow ratios. Overall, the effect of wolf presence on elk reproduction is better explained by changes in foraging patterns that carry nutritional costs than by changes in glucocorticoid concentrations.

Glucocorticoid stress hormones and the effect of predation risk on elk reproduction

PubMed Central

Creel, Scott; Winnie, John A.; Christianson, David

2009-01-01

Predators affect prey demography through direct predation and through the costs of antipredator behavioral responses, or risk effects. Experiments have shown that risk effects can comprise a substantial proportion of a predator's total effect on prey dynamics, but we know little about their strength in wild populations, or the physiological mechanisms that mediate them. When wolves are present, elk alter their grouping patterns, vigilance, foraging behavior, habitat selection, and diet. These responses are associated with decreased progesterone levels, decreased calf production, and reduced population size [Creel S, Christianson D, Liley S, Winnie JA (2007) Science 315:960]. Two general mechanisms for the effect of predation risk on reproduction have been proposed: the predation stress hypothesis and the predator-sensitive-food hypothesis. Here, we used enzyme immunoassay to measure fecal glucocorticoid metabolite concentrations for 1,205 samples collected from 4 elk populations over 4 winters to test the hypothesis that the effect of predation risk on elk reproduction is mediated by chronic stress. Across populations and years, fecal glucocorticoid concentrations were not related to predator-prey ratios, progesterone concentrations or calf-cow ratios. Overall, the effect of wolf presence on elk reproduction is better explained by changes in foraging patterns that carry nutritional costs than by changes in glucocorticoid concentrations. PMID:19617549

Bioinsecticide-predator interactions: azadirachtin behavioral and reproductive impairment of the coconut mite predator Neoseiulus baraki.

PubMed

Lima, Debora B; Melo, José Wagner S; Guedes, Nelsa Maria P; Gontijo, Lessando M; Guedes, Raul Narciso C; Gondim, Manoel Guedes C

2015-01-01

Synthetic pesticide use has been the dominant form of pest control since the 1940s. However, biopesticides are emerging as sustainable pest control alternatives, with prevailing use in organic agricultural production systems. Foremost among botanical biopesticides is the limonoid azadirachtin, whose perceived environmental safety has come under debate and scrutiny in recent years. Coconut production, particularly organic coconut production, is one of the agricultural systems in which azadirachtin is used as a primary method of pest control for the management of the invasive coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae). The management of this mite species also greatly benefits from predation by Neoseiulus baraki (Athias-Henriot) (Acari: Phytoseiidae). Here, we assessed the potential behavioral impacts of azadirachtin on the coconut mite predator, N. baraki. We explored the effects of this biopesticide on overall predator activity, female searching time, and mating behavior and fecundity. Azadirachtin impairs the overall activity of the predator, reducing it to nearly half; however, female searching was not affected. In contrast, mating behavior was compromised by azadirachtin exposure particularly when male predators were exposed to the biopesticide. Consequently, predator fecundity was also compromised by azadirachtin, furthering doubts about its environmental safety and selectivity towards biological control agents.

Incorporating anthropogenic effects into trophic ecology: predator-prey interactions in a human-dominated landscape.

PubMed

Dorresteijn, Ine; Schultner, Jannik; Nimmo, Dale G; Fischer, Joern; Hanspach, Jan; Kuemmerle, Tobias; Kehoe, Laura; Ritchie, Euan G

2015-09-07

Apex predators perform important functions that regulate ecosystems worldwide. However, little is known about how ecosystem regulation by predators is influenced by human activities. In particular, how important are top-down effects of predators relative to direct and indirect human-mediated bottom-up and top-down processes? Combining data on species' occurrence from camera traps and hunting records, we aimed to quantify the relative effects of top-down and bottom-up processes in shaping predator and prey distributions in a human-dominated landscape in Transylvania, Romania. By global standards this system is diverse, including apex predators (brown bear and wolf), mesopredators (red fox) and large herbivores (roe and red deer). Humans and free-ranging dogs represent additional predators in the system. Using structural equation modelling, we found that apex predators suppress lower trophic levels, especially herbivores. However, direct and indirect top-down effects of humans affected the ecosystem more strongly, influencing species at all trophic levels. Our study highlights the need to explicitly embed humans and their influences within trophic cascade theory. This will greatly expand our understanding of species interactions in human-modified landscapes, which compose the majority of the Earth's terrestrial surface. © 2015 The Author(s).

Does fragmentation of Urtica habitats affect phytophagous and predatory insects differentially?

PubMed

Zabel, Jörg; Tscharntke, Teja

1998-09-01

Effects of habitat fragmentation on the insect community of stinging nettle (Urtica dioica L.) were studied, using 32 natural nettle patches of different area and degree of isolation in an agricultural landscape. Habitat fragmentation reduced the species richness of Heteroptera, Auchenorrhyncha, and Coleoptera, and the abundance of populations. Habitat isolation and area reduction did not affect all insect species equally. Monophagous herbivores had a higher probability of absence from small patches than all (monophagous and polyphagous) herbivore species, and the percentage of monophagous herbivores increased with habitat area. Abundance and population variability of species were negatively correlated and could both be used as a predictor of the percentage of occupied habitats. Species richness of herbivores correlated (positively) with habitat area, while species richness of predators correlated (negatively) with habitat isolation. In logistic regressions, the probability of absence of monophagous herbivores from habitat patches could only be explained by habitat area (in 4 out of 10 species) and predator absence probability only by habitat isolation (in 3 out of 14 species). Presumably because of the instability of higher-trophic-level populations and dispersal limitation, predators were more affected by habitat isolation than herbivores, while they did not differ from herbivore populations with respect to abundance or variability. Thus increasing habitat connectivity in the agricultural landscape should primarily promote predator populations.

Interactions of bullfrog tadpole predators and an insecticide: Predation release and facilitation

USGS Publications Warehouse

Boone, M.D.; Semlitsch, R.D.

2003-01-01

The effect of a contaminant on a community may not be easily predicted, given that complex changes in food resources and predator-prey dynamics may result. The objectives of our study were to determine the interactive effects of the insecticide carbaryl and predators on body size, development, survival, and activity of tadpoles of the bullfrog (Rana catesbeiana). We conducted the study in cattle tank mesocosm ponds exposed to 0, 3.5, or 7.0 mg/l carbaryl, and no predators or two red-spotted newts (Notophthalmus viridescens), bluegill sunfish (Lepomis macrochirus), or crayfish (Orconectes sp.). Carbaryl negatively affected predator survival by eliminating crayfish from all ponds, and by eliminating bluegill sunfish from ponds exposed to the highest concentration of carbaryl; carbaryl exposure did not effect survival of red-spotted newts. Because crayfish were eliminated by carbaryl, bullfrogs were released from predation and survival was near that of predator controls at low concentrations of carbaryl exposure. High concentrations of carbaryl reduced tadpole survival regardless of whether predators survived carbaryl exposure or not. Presence of crayfish and newts reduced tadpole survival, while bluegill sunfish appeared to facilitate bullfrog tadpole survival. Presence of carbaryl stimulated bullfrog tadpole mass and development. Our study demonstrates that the presence of a contaminant stress can alter community regulation by releasing prey from predators that are vulnerable to contaminants in some exposure scenarios.

High Arctic lemmings remain reproductively active under predator-induced elevated stress.

PubMed

Fauteux, Dominique; Gauthier, Gilles; Berteaux, Dominique; Palme, Rupert; Boonstra, Rudy

2018-04-12

Non-consumptive effects of predation have rarely been assessed in wildlife populations even though their impact could be as important as lethal effects. Reproduction of individuals is one of the most important demographic parameters that could be affected by predator-induced stress, which in turn can have important consequences on population dynamics. We studied non-consumptive effects of predation on the reproductive activity (i.e., mating and fertilization) of a cyclic population of brown lemmings exposed to intense summer predation in the Canadian High Arctic. Lemmings were live-trapped, their reproductive activity (i.e., testes visible in males, pregnancy/lactation in females) assessed, and predators were monitored during the summers of 2014 and 2015 within a 9 ha predator-reduction exclosure delimited by a fence and covered by a net, and on an 11 ha control area. Stress levels were quantified non-invasively with fecal corticosterone metabolites (FCM). We found that FCM levels of lemmings captured outside the predator exclosure (n = 50) were 1.6 times higher than inside (n = 51). The proportion of pregnant/lactating adult females did not differ between the two areas, nor did the proportion of adult scrotal males. We found that lemmings showed physiological stress reactions due to high predation risk, but had no sign of reduced mating activity or fertility. Thus, our results do not support the hypothesis of reproductive suppression by predator-induced stress.

Ecosystem context and historical contingency in apex predator recoveries.

PubMed

Stier, Adrian C; Samhouri, Jameal F; Novak, Mark; Marshall, Kristin N; Ward, Eric J; Holt, Robert D; Levin, Phillip S

2016-05-01

Habitat loss, overexploitation, and numerous other stressors have caused global declines in apex predators. This "trophic downgrading" has generated widespread concern because of the fundamental role that apex predators can play in ecosystem functioning, disease regulation, and biodiversity maintenance. In attempts to combat declines, managers have conducted reintroductions, imposed stricter harvest regulations, and implemented protected areas. We suggest that full recovery of viable apex predator populations is currently the exception rather than the rule. We argue that, in addition to well-known considerations, such as continued exploitation and slow life histories, there are several underappreciated factors that complicate predator recoveries. These factors include three challenges. First, a priori identification of the suite of trophic interactions, such as resource limitation and competition that will influence recovery can be difficult. Second, defining and accomplishing predator recovery in the context of a dynamic ecosystem requires an appreciation of the timing of recovery, which can determine the relative density of apex predators and other predators and therefore affect competitive outcomes. Third, successful recovery programs require designing adaptive sequences of management strategies that embrace key environmental and species interactions as they emerge. Consideration of recent research on food web modules, alternative stable states, and community assembly offer important insights for predator recovery efforts and restoration ecology more generally. Foremost among these is the importance of a social-ecological perspective in facilitating a long-lasting predator restoration while avoiding unintended consequences.

The relative importance of prey-borne and predator-borne chemical cues for inducible antipredator responses in tadpoles.

PubMed

Hettyey, Attila; Tóth, Zoltán; Thonhauser, Kerstin E; Frommen, Joachim G; Penn, Dustin J; Van Buskirk, Josh

2015-11-01

Chemical cues that evoke anti-predator developmental changes have received considerable attention, but it is not known to what extent prey use information from the smell of predators and from cues released through digestion. We conducted an experiment to determine the importance of various types of cues for the adjustment of anti-predator defences. We exposed tadpoles (common frog, Rana temporaria) to water originating from predators (caged dragonfly larvae, Aeshna cyanea) that were fed different types and quantities of prey outside of tadpole-rearing containers. Variation among treatments in the magnitude of morphological and behavioural responses was highly consistent. Our results demonstrate that tadpoles can assess the threat posed by predators through digestion-released, prey-borne cues and continually released predator-borne cues. These cues may play an important role in the fine-tuning of anti-predator responses and significantly affect the outcome of interactions between predators and prey in aquatic ecosystems. There has been much confusion regards terminology used in the literature, and therefore we also propose a more precise and consistent binomial nomenclature based on the timing of chemical cue release (stress-, attack-, capture-, digestion- or continually released cues) and the origin of cues (prey-borne or predator-borne cues). We hope that this new nomenclature will improve comparisons among studies on this topic.

Ecosystem context and historical contingency in apex predator recoveries

PubMed Central

Stier, Adrian C.; Samhouri, Jameal F.; Novak, Mark; Marshall, Kristin N.; Ward, Eric J.; Holt, Robert D.; Levin, Phillip S.

2016-01-01

Habitat loss, overexploitation, and numerous other stressors have caused global declines in apex predators. This “trophic downgrading” has generated widespread concern because of the fundamental role that apex predators can play in ecosystem functioning, disease regulation, and biodiversity maintenance. In attempts to combat declines, managers have conducted reintroductions, imposed stricter harvest regulations, and implemented protected areas. We suggest that full recovery of viable apex predator populations is currently the exception rather than the rule. We argue that, in addition to well-known considerations, such as continued exploitation and slow life histories, there are several underappreciated factors that complicate predator recoveries. These factors include three challenges. First, a priori identification of the suite of trophic interactions, such as resource limitation and competition that will influence recovery can be difficult. Second, defining and accomplishing predator recovery in the context of a dynamic ecosystem requires an appreciation of the timing of recovery, which can determine the relative density of apex predators and other predators and therefore affect competitive outcomes. Third, successful recovery programs require designing adaptive sequences of management strategies that embrace key environmental and species interactions as they emerge. Consideration of recent research on food web modules, alternative stable states, and community assembly offer important insights for predator recovery efforts and restoration ecology more generally. Foremost among these is the importance of a social-ecological perspective in facilitating a long-lasting predator restoration while avoiding unintended consequences. PMID:27386535

Clever strategists: Australian Magpies vary mobbing strategies, not intensity, relative to different species of predator

PubMed Central

Koboroff, A; Kaplan, G

2013-01-01

Anti-predator behaviour of magpies was investigated, using five species of model predators, at times of raising offspring. We predicted differences in mobbing strategies for each predator presented and also that raising juveniles would affect intensity of the mobbing event. Fourteen permanent resident family groups were tested using 5 different types of predator (avian and reptilian) known to be of varying degrees of risk to magpies and common in their habitat. In all, 210 trials were conducted (across three different stages of juvenile development). We found that the stage of juvenile development did not alter mobbing behaviour significantly, but predator type did. Aerial strategies (such as swooping) were elicited by taxidermic models of raptors, whereas a taxidermic model of a monitor lizard was approached on the ground and a model snake was rarely approached. Swooping patterns also changed according to which of the three raptors was presented. Our results show that, in contrast to findings in other species, magpies vary mobbing strategy depending on the predator rather than varying mobbing intensity. PMID:23638394

Clever strategists: Australian Magpies vary mobbing strategies, not intensity, relative to different species of predator.

PubMed

Koboroff, A; Kaplan, G; Rogers, Lj

2013-01-01

Anti-predator behaviour of magpies was investigated, using five species of model predators, at times of raising offspring. We predicted differences in mobbing strategies for each predator presented and also that raising juveniles would affect intensity of the mobbing event. Fourteen permanent resident family groups were tested using 5 different types of predator (avian and reptilian) known to be of varying degrees of risk to magpies and common in their habitat. In all, 210 trials were conducted (across three different stages of juvenile development). We found that the stage of juvenile development did not alter mobbing behaviour significantly, but predator type did. Aerial strategies (such as swooping) were elicited by taxidermic models of raptors, whereas a taxidermic model of a monitor lizard was approached on the ground and a model snake was rarely approached. Swooping patterns also changed according to which of the three raptors was presented. Our results show that, in contrast to findings in other species, magpies vary mobbing strategy depending on the predator rather than varying mobbing intensity.

Comparison of gamma and electron beam irradiation in reducing populations of E. coli artificially inoculated on Mung Bean, clover and Fenugreek Seeds, and affecting germination and growth of seeds

USDA-ARS?s Scientific Manuscript database

Sprouts have frequently been implicated in outbreaks of foodborne illnesses, mostly due to contaminated seeds. Intervention technologies to decontaminate seeds without affecting sprout yield are needed. In the present study, we compared gamma rays with electron beam in inactivating E. coli artifici...

Landscape features influence postrelease predation on endangered black-footed ferrets

USGS Publications Warehouse

Poessel, S.A.; Breck, S.W.; Biggins, D.E.; Livieri, T.M.; Crooks, K.R.; Angeloni, L.

2011-01-01

Predation can be a critical factor influencing recovery of endangered species. In most recovery efforts lethal and nonlethal influences of predators are not sufficiently understood to allow prediction of predation risk, despite its importance. We investigated whether landscape features could be used to model predation risk from coyotes (Canis latrans) and great horned owls (Bubo virginianus) on the endangered black-footed ferret (Mustela nigripes). We used location data of reintroduced ferrets from 3 sites in South Dakota to determine whether exposure to landscape features typically associated with predators affected survival of ferrets, and whether ferrets considered predation risk when choosing habitat near perches potentially used by owls or near linear features predicted to be used by coyotes. Exposure to areas near likely owl perches reduced ferret survival, but landscape features potentially associated with coyote movements had no appreciable effect on survival. Ferrets were located within 90 m of perches more than expected in 2 study sites that also had higher ferret mortality due to owl predation. Densities of potential coyote travel routes near ferret locations were no different than expected in all 3 sites. Repatriated ferrets might have selected resources based on factors other than predator avoidance. Considering an easily quantified landscape feature (i.e., owl perches) can enhance success of reintroduction efforts for ferrets. Nonetheless, development of predictive models of predation risk and management strategies to mitigate that risk is not necessarily straightforward for more generalist predators such as coyotes. ?? 2011 American Society of Mammalogists.

Effects of subsidized predators, resource variability, and human population density on desert tortoise populations in the Mojave Desert, USA

USGS Publications Warehouse

Esque, Todd C.; Nussear, Kenneth E.; Drake, K. Kristina; Walde, Andrew D.; Berry, Kristin H.; Averill-Murray, Roy C.; Woodman, A. Peter; Boarman, William I.; Medica, Phil A.; Mack, Jeremy S.; Heaton, Jill S.

2010-01-01

Understanding predator–prey relationships can be pivotal in the conservation of species. For 2 decades, desert tortoise Gopherus agassizii populations have declined, yet quantitative evidence regarding the causes of declines is scarce. In 2005, Ft. Irwin National Training Center, California, USA, implemented a translocation project including 2 yr of baseline monitoring of desert tortoises. Unusually high predation on tortoises was observed after translocation occurred. We conducted a retrospective analysis of predation and found that translocation did not affect the probability of predation: translocated, resident, and control tortoises all had similar levels of predation. However, predation rates were higher near human population concentrations, at lower elevation sites, and for smaller tortoises and females. Furthermore, high mortality rates were not limited to the National Training Center. In 2008, elevated mortality (as high as 43%) occurred throughout the listed range of the desert tortoise. Although no temporal prey base data are available for analysis from any of the study sites, we hypothesize that low population levels of typical coyote Canis latrans prey (i.e. jackrabbits Lepus californicus and other small animals) due to drought conditions influenced high predation rates in previous years. Predation may have been exacerbated in areas with high levels of subsidized predators. Many historical reports of increased predation, and our observation of a range-wide pattern, may indicate that high predation rates are more common than generally considered and may impact recovery of the desert tortoise throughout its range.

Sustained disruption of narwhal habitat use and behavior in the presence of Arctic killer whales

PubMed Central

Breed, Greg A.; Matthews, Cory J. D.; Marcoux, Marianne; Higdon, Jeff W.; LeBlanc, Bernard; Petersen, Stephen D.; Orr, Jack; Reinhart, Natalie R.; Ferguson, Steven H.

2017-01-01

Although predators influence behavior of prey, analyses of electronic tracking data in marine environments rarely consider how predators affect the behavior of tracked animals. We collected an unprecedented dataset by synchronously tracking predator (killer whales, N = 1; representing a family group) and prey (narwhal, N = 7) via satellite telemetry in Admiralty Inlet, a large fjord in the Eastern Canadian Arctic. Analyzing the movement data with a switching-state space model and a series of mixed effects models, we show that the presence of killer whales strongly alters the behavior and distribution of narwhal. When killer whales were present (within about 100 km), narwhal moved closer to shore, where they were presumably less vulnerable. Under predation threat, narwhal movement patterns were more likely to be transiting, whereas in the absence of threat, more likely resident. Effects extended beyond discrete predatory events and persisted steadily for 10 d, the duration that killer whales remained in Admiralty Inlet. Our findings have two key consequences. First, given current reductions in sea ice and increases in Arctic killer whale sightings, killer whales have the potential to reshape Arctic marine mammal distributions and behavior. Second and of more general importance, predators have the potential to strongly affect movement behavior of tracked marine animals. Understanding predator effects may be as or more important than relating movement behavior to resource distribution or bottom-up drivers traditionally included in analyses of marine animal tracking data. PMID:28223481

Sustained disruption of narwhal habitat use and behavior in the presence of Arctic killer whales.

PubMed

Breed, Greg A; Matthews, Cory J D; Marcoux, Marianne; Higdon, Jeff W; LeBlanc, Bernard; Petersen, Stephen D; Orr, Jack; Reinhart, Natalie R; Ferguson, Steven H

2017-03-07

Although predators influence behavior of prey, analyses of electronic tracking data in marine environments rarely consider how predators affect the behavior of tracked animals. We collected an unprecedented dataset by synchronously tracking predator (killer whales, [Formula: see text] = 1; representing a family group) and prey (narwhal, [Formula: see text] = 7) via satellite telemetry in Admiralty Inlet, a large fjord in the Eastern Canadian Arctic. Analyzing the movement data with a switching-state space model and a series of mixed effects models, we show that the presence of killer whales strongly alters the behavior and distribution of narwhal. When killer whales were present (within about 100 km), narwhal moved closer to shore, where they were presumably less vulnerable. Under predation threat, narwhal movement patterns were more likely to be transiting, whereas in the absence of threat, more likely resident. Effects extended beyond discrete predatory events and persisted steadily for 10 d, the duration that killer whales remained in Admiralty Inlet. Our findings have two key consequences. First, given current reductions in sea ice and increases in Arctic killer whale sightings, killer whales have the potential to reshape Arctic marine mammal distributions and behavior. Second and of more general importance, predators have the potential to strongly affect movement behavior of tracked marine animals. Understanding predator effects may be as or more important than relating movement behavior to resource distribution or bottom-up drivers traditionally included in analyses of marine animal tracking data.

Direct and indirect effects of different types of microplastics on freshwater prey (Corbicula fluminea) and their predator (Acipenser transmontanus)

PubMed Central

Parnis, J. Mark; Browne, Mark A.; Serrato, Sebastian; Reiner, Eric J.; Robson, Matthew; Young, Thomas; Diamond, Miriam L.; Teh, Swee J.

2017-01-01

We examined whether environmentally relevant concentrations of different types of microplastics, with or without PCBs, directly affect freshwater prey and indirectly affect their predators. Asian clams (Corbicula fluminea) were exposed to environmentally relevant concentrations of polyethylene terephthalate (PET), polyethylene, polyvinylchloride (PVC) or polystyrene with and without polychlorinated biphenyls (PCBs) for 28 days. Their predators, white sturgeon (Acipenser transmontanus), were exposed to clams from each treatment for 28 days. In both species, we examined bioaccumulation of PCBs and effects (i.e., immunohistochemistry, histology, behavior, condition, mortality) across several levels of biological organization. PCBs were not detected in prey or predator, and thus differences in bioaccumulation of PCBs among polymers and biomagnification in predators could not be measured. One of the main objectives of this study was to test the hypothesis that bioaccumulation of PCBs would differ among polymer types. Because we could not answer this question experimentally, a bioaccumulation model was run and predicted that concentrations of PCBs in clams exposed to polyethylene and polystyrene would be greater than PET and PVC. Observed effects, although subtle, seemed to be due to microplastics rather than PCBs alone. For example, histopathology showed tubular dilation in clams exposed to microplastics with PCBs, with only mild effects in clams exposed to PCBs alone. PMID:29108004

Experimental evidence that livestock grazing intensity affects the activity of a generalist predator

NASA Astrophysics Data System (ADS)

Villar, Nacho; Lambin, Xavier; Evans, Darren; Pakeman, Robin; Redpath, Steve

2013-05-01

Grazing by domestic ungulates has substantial impacts on ecosystem structure and composition. In grasslands of the northern hemisphere, livestock grazing limits populations of small mammals, which are a main food source for a variety of vertebrate predators. However, no experimental studies have described the impact of livestock grazing on vertebrate predators. We experimentally manipulated sheep and cattle grazing intensity in the Scottish uplands to test its impact on a relatively abundant small mammal, the field vole (Microtus agrestis), and its archetypal generalist predator, the red fox (Vulpes vulpes). We demonstrate that ungulate grazing had a strong consistent negative impact on both vole densities and indices of fox activity. Ungulate grazing did not substantially affect the relationship between fox activity and vole densities. However, the data suggested that, as grazing intensity increased i) fox activity indices tended to be higher when vole densities were low, and ii) the relationship between fox activity and vole density was weaker. All these patterns are surprising given the relative small scale of our experiment compared to large red fox territories in upland habitats of Britain, and suggest that domestic grazing intensity causes a strong response in the activity of generalist predators important for their conservation in grassland ecosystems.

Restoring lepidopteran diversity in a tropical dry forest: relative importance of restoration treatment, tree identity and predator pressure.

PubMed

Solis-Gabriel, Lizet; Mendoza-Arroyo, Wendy; Boege, Karina; Del-Val, Ek

2017-01-01

Tropical dry forests (TDFs) have been widely transformed by human activities worldwide and the ecosystem services they provide are diminishing. There has been an urgent call for conservation and restoration of the degraded lands previously occupied by TDFs. Restoration experiences aim to recover species diversity and ecological functions. Different restoration strategies have been used to maximize plant performance including weeding, planting or using artificial mulching. In this investigation, we evaluated whether different restoration practices influence animal arrival and the reestablishment of biotic interactions. We particularly evaluated lepidopteran larvae diversity and caterpillar predation on plants established under different restoration treatments (mulching, weeding and control) in the Pacific West Coast of México. This study corroborated the importance of plant host identity for lepidopteran presence in a particular area. Lepidopteran diversity and herbivory rates were not affected by the restoration treatment but they were related to tree species. In contrast, caterpillar predation marks were affected by restoration treatment, with a greater number of predation marks in control plots, while caterpillar predation marks among plant species were not significantly different. This study highlights the importance of considering the introduction of high plant species diversity when planning TDF restoration to maximize lepidopteran diversity and ecosystem functioning.

Growth history and intrinsic factors influence risk assessment at a critical life transition for a fish

NASA Astrophysics Data System (ADS)

Lönnstedt, O. M.; McCormick, M. I.

2011-09-01

Making the appropriate decision in the face of predation risk dictates the fate of prey, and predation risk is highest at life history boundaries such as settlement. At the end of the larval phase, most coral reef fishes enter patches of reef containing novel predators. Since vision is often obscured in the complex surroundings, chemical information released from damaged conspecific is used to forewarn prey of an active predator. However, larvae enter the reef environment with their own feeding and growth histories, which will influence their motivation to feed and take risks. The present study explored the link between recent growth, feeding history, current performance and behavioural risk taking in newly settling stages of a coral reef damselfish ( Pomacentrus amboinensis). Older and larger juveniles in good body condition had a stronger response to chemical alarm cues of injured conspecifics; these fish spent a longer time in shelter and displayed a more dramatic decrease in foraging behaviour than fish in lower body condition. Feeding experiments supported these findings and emphasized the importance of body condition in affecting risk assessment. Evidently, larval growth history and body condition influences the likelihood of taking risks under the threat of predation immediately after settlement, thereby affecting the probability of survival in P. amboinensis.

Restoring lepidopteran diversity in a tropical dry forest: relative importance of restoration treatment, tree identity and predator pressure

PubMed Central

Solis-Gabriel, Lizet; Mendoza-Arroyo, Wendy

2017-01-01

Tropical dry forests (TDFs) have been widely transformed by human activities worldwide and the ecosystem services they provide are diminishing. There has been an urgent call for conservation and restoration of the degraded lands previously occupied by TDFs. Restoration experiences aim to recover species diversity and ecological functions. Different restoration strategies have been used to maximize plant performance including weeding, planting or using artificial mulching. In this investigation, we evaluated whether different restoration practices influence animal arrival and the reestablishment of biotic interactions. We particularly evaluated lepidopteran larvae diversity and caterpillar predation on plants established under different restoration treatments (mulching, weeding and control) in the Pacific West Coast of México. This study corroborated the importance of plant host identity for lepidopteran presence in a particular area. Lepidopteran diversity and herbivory rates were not affected by the restoration treatment but they were related to tree species. In contrast, caterpillar predation marks were affected by restoration treatment, with a greater number of predation marks in control plots, while caterpillar predation marks among plant species were not significantly different. This study highlights the importance of considering the introduction of high plant species diversity when planning TDF restoration to maximize lepidopteran diversity and ecosystem functioning. PMID:28560101

In a warmer Arctic, mosquitoes avoid increased mortality from predators by growing faster.

PubMed

Culler, Lauren E; Ayres, Matthew P; Virginia, Ross A

2015-09-22

Climate change is altering environmental temperature, a factor that influences ectothermic organisms by controlling rates of physiological processes. Demographic effects of warming, however, are determined by the expression of these physiological effects through predator-prey and other species interactions. Using field observations and controlled experiments, we measured how increasing temperatures in the Arctic affected development rates and mortality rates (from predation) of immature Arctic mosquitoes in western Greenland. We then developed and parametrized a demographic model to evaluate how temperature affects survival of mosquitoes from the immature to the adult stage. Our studies showed that warming increased development rate of immature mosquitoes (Q10 = 2.8) but also increased daily mortality from increased predation rates by a dytiscid beetle (Q10 = 1.2-1.5). Despite increased daily mortality, the model indicated that faster development and fewer days exposed to predators resulted in an increased probability of mosquito survival to the adult stage. Warming also advanced mosquito phenology, bringing mosquitoes into phenological synchrony with caribou. Increases in biting pests will have negative consequences for caribou and their role as a subsistence resource for local communities. Generalizable frameworks that account for multiple effects of temperature are needed to understand how climate change impacts coupled human-natural systems. © 2015 The Author(s).

Differential effects of plant species on a mite pest (Tetranychus utricae) and its predator (Phytoseiulus persimilis): implications for biological control.

PubMed

Skirvin, D J; de Courcy Williams, M

1999-06-01

The influence of plant species on the population dynamics of the spider mite pest, Tetranychus urticae, and its predator, Phytoseiulus persimilis, was examined as a prerequisite to effective biological control on ornamental nursery stock. Experiments have been done to investigate how the development, fecundity and movement of T. urticae, and the movement of P. persimilis were affected by plant species. A novel experimental method, which incorporates plant structure, was used to investigate the functional response of P. persimilis. Development times for T. urticae were consistent with published data and did not differ with plant species in a biologically meaningful way. Plant species was shown to have a major influence on fecundity (P < 0.001) and movement of the pest mite (P < 0.01), but no influence on the movement of the predator. The movement of both pest and predator was shown to be related to the density of the adult pest mites on the plant (P < 0.001). Plant structure affected the functional response, particularly in relation to the ability of the predator to locate prey at low densities. The impact of these findings on the effective use of biological control on ornamental nursery stock is discussed.

Dispersal ecology of lodgepole pine (Pinus contorta Dougl.) in its native environment as related to Swedish forestry

USGS Publications Warehouse

Despain, Don G.

2001-01-01

Lodgepole pine (Pinus contorta Dougl.) covers extensive areas of the mountains of western North America. It has evolved into four subspecies, each adapted to slightly different environmental conditions. All are adapted to reproduce following fire. Subspecies latifolia is the most extensive and economically important in North America. Serotiny is common in this subspecies, but trees bearing nonserotinous cones can be found in most stands, sometimes constituting more that 70% of the trees. Cone crops are produced yearly and seed loss to seed predators, insects and diseases are minimal. Germination and establishment occurs across a broad range of conditions allowing lodgepole pine to grow on poor sites as well as highly productive sites. These characteristics give lodgepole pine the ability to be highly invasive in new areas of suitable habitat.

Body size and the division of niche space: food and predation differentially shape the distribution of Serengeti grazers.

PubMed

Hopcraft, J Grant C; Anderson, T Michael; Pérez-Vila, Saleta; Mayemba, Emilian; Olff, Han

2012-01-01

1. Theory predicts that small grazers are regulated by the digestive quality of grass, while large grazers extract sufficient nutrients from low-quality forage and are regulated by its abundance instead. In addition, predation potentially affects populations of small grazers more than large grazers, because predators have difficulty capturing and handling large prey. 2. We analyse the spatial distribution of five grazer species of different body size in relation to gradients of food availability and predation risk. Specifically, we investigate how the quality of grass, the abundance of grass biomass and the associated risks of predation affect the habitat use of small, intermediate and large savanna grazers at a landscape level. 3. Resource selection functions of five mammalian grazer species surveyed over a 21-year period in Serengeti are calculated using logistic regressions. Variables included in the analyses are grass nitrogen, rainfall, topographic wetness index, woody cover, drainage lines, landscape curvature, water and human habitation. Structural equation modelling (SEM) is used to aggregate predictor variables into 'composites' representing food quality, food abundance and predation risk. Subsequently, SEM is used to investigate species' habitat use, defined as their recurrence in 5 × 5 km cells across repeated censuses. 4. The distribution of small grazers is constrained by predation and food quality, whereas the distribution of large grazers is relatively unconstrained. The distribution of the largest grazer (African buffalo) is primarily associated with forage abundance but not predation risk, while the distributions of the smallest grazers (Thomson's gazelle and Grant's gazelle) are associated with high grass quality and negatively with the risk of predation. The distributions of intermediate sized grazers (Coke's hartebeest and topi) suggest they optimize access to grass biomass of sufficient quality in relatively predator-safe areas. 5. The results illustrate how top-down (vegetation-mediated predation risk) and bottom-up factors (biomass and nutrient content of vegetation) predictably contribute to the division of niche space for herbivores that vary in body size. Furthermore, diverse grazing assemblages are composed of herbivores of many body sizes (rather than similar body sizes), because these herbivores best exploit the resources of different habitat types. © 2011 The Authors. Journal of Animal Ecology © 2011 British Ecological Society.

Vulnerability of age-0 pallid sturgeon Scaphirhynchus albus to predation; effects of predator type, turbidity, body size, and prey density

USGS Publications Warehouse

French, William E.; Graeb, Brian D. S.; Chipps, Steven R.; Klumb, Robert A.

2014-01-01

Predation can play an important role in the recruitment dynamics of fishes with intensity regulated by behavioral (i.e., prey selectivity) and/or environmental conditions that may be especially important for rare or endangered fishes. We conducted laboratory experiments to quantify prey selection and capture efficiency by three predators employing distinct foraging strategies: pelagic piscivore (walleye Sander vitreus); benthic piscivore (flathead catfish Pylodictis olivaris) and generalist predator (smallmouth bass Micropterus dolomieu) foraging on two size classes of age-0 pallid sturgeon: large (75–100 mm fork length [FL]) and small (40–50 mm FL). Experiments at high (> 70 nephalometric turbidity units [NTU]) and low (< 5 NTU) turbidity for each predator were conducted with high and low densities of pallid sturgeon and contrasting densities of an alternative prey, fathead minnow Pimephales promelas. Predator behaviors (strikes, captures, and consumed prey) were also quantified for each prey type. Walleye and smallmouth bass negatively selected pallid sturgeon (Chesson’s α = 0.04–0.1) across all treatments, indicating low relative vulnerability to predation. Relative vulnerability to predation by flathead catfish was moderate for small pallid sturgeon (α = 0.44, neutral selection), but low for large pallid sturgeon (α = 0.11, negative selection). Turbidity (up to 100 NTU) did not affect pallid sturgeon vulnerability, even at low density of alternative prey. Age-0 pallid sturgeon were easily captured by all predators, but were rarely consumed, suggesting mechanisms other than predator capture efficiency govern sturgeon predation vulnerability.

Threat-sensitive anti-predator defence in precocial wader, the northern lapwing Vanellus vanellus.

PubMed

Królikowska, Natalia; Szymkowiak, Jakub; Laidlaw, Rebecca Anne; Kuczyński, Lechosław

2016-01-01

Birds exhibit various forms of anti-predator behaviours to avoid reproductive failure, with mobbing-observation, approach and usually harassment of a predator-being one of the most commonly observed. Here, we investigate patterns of temporal variation in the mobbing response exhibited by a precocial species, the northern lapwing ( Vanellus vanellus ). We test whether brood age and self-reliance, or the perceived risk posed by various predators, affect mobbing response of lapwings. We quantified aggressive interactions between lapwings and their natural avian predators and used generalized additive models to test how timing and predator species identity are related to the mobbing response of lapwings. Lapwings diversified mobbing response within the breeding season and depending on predator species. Raven Corvus corax , hooded crow Corvus cornix and harriers evoked the strongest response, while common buzzard Buteo buteo , white stork Ciconia ciconia , black-headed gull Chroicocephalus ridibundus and rook Corvus frugilegus were less frequently attacked. Lapwings increased their mobbing response against raven, common buzzard, white stork and rook throughout the breeding season, while defence against hooded crow, harriers and black-headed gull did not exhibit clear temporal patterns. Mobbing behaviour of lapwings apparently constitutes a flexible anti-predator strategy. The anti-predator response depends on predator species, which may suggest that lapwings distinguish between predator types and match mobbing response to the perceived hazard at different stages of the breeding cycle. We conclude that a single species may exhibit various patterns of temporal variation in anti-predator defence, which may correspond with various hypotheses derived from parental investment theory.

Modelling the fear effect in predator-prey interactions.

PubMed

Wang, Xiaoying; Zanette, Liana; Zou, Xingfu

2016-11-01

A recent field manipulation on a terrestrial vertebrate showed that the fear of predators alone altered anti-predator defences to such an extent that it greatly reduced the reproduction of prey. Because fear can evidently affect the populations of terrestrial vertebrates, we proposed a predator-prey model incorporating the cost of fear into prey reproduction. Our mathematical analyses show that high levels of fear (or equivalently strong anti-predator responses) can stabilize the predator-prey system by excluding the existence of periodic solutions. However, relatively low levels of fear can induce multiple limit cycles via subcritical Hopf bifurcations, leading to a bi-stability phenomenon. Compared to classic predator-prey models which ignore the cost of fear where Hopf bifurcations are typically supercritical, Hopf bifurcations in our model can be both supercritical and subcritical by choosing different sets of parameters. We conducted numerical simulations to explore the relationships between fear effects and other biologically related parameters (e.g. birth/death rate of adult prey), which further demonstrate the impact that fear can have in predator-prey interactions. For example, we found that under the conditions of a Hopf bifurcation, an increase in the level of fear may alter the direction of Hopf bifurcation from supercritical to subcritical when the birth rate of prey increases accordingly. Our simulations also show that the prey is less sensitive in perceiving predation risk with increasing birth rate of prey or increasing death rate of predators, but demonstrate that animals will mount stronger anti-predator defences as the attack rate of predators increases.