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Sample records for affects seed predation

  1. Corridors cause differential seed predation.

    SciTech Connect

    Orrock, John L.; Damschen, Ellen I.

    2005-06-01

    Orrock, John, L., and Ellen I. Damschen. 2005. Corridors cause differential seed predation. Ecol. Apps. 15(3):793-798. Abstract. Corridors that connect disjunct populations are heavily debated in conservation, largely because the effects of corridors have rarely been evaluated by replicated, large-scale studies. Using large-scale experimental landscapes, we found that, in addition to documented positive effects, corridors also have negative impacts on bird-dispersed plants by affecting seed predation, and that overall predation is a function of the seeds primary consumer (rodents or arthropods). Both large-seeded Prunus serotina and small-seeded Rubus allegheniensis experienced greater predation in connected patches. However, P. serotina experienced significantly less seed predation compared to R. allegheniensis in unconnected patches, due to decreased impacts of rodent seed predators on this large-seeded species. Viewed in light of previous evidence that corridors have beneficial impacts by increasing pollination and seed dispersal, this work demonstrates that corridors may have both positive and negative effects for the same plant species at different life stages. Moreover, these effects may differentially affect plant species within the same community: seeds primarily consumed by rodents suffer less predation in unconnected patches. By shifting the impact of rodent and arthropod seed predators, corridors constructed for plant conservation could lead to shifts in the seed bank.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  3. Habitat area and structure affect the impact of seed predators and the potential for coevolutionary arms races.

    PubMed

    Mezquida, Eduardo T; Benkman, Craig W

    2010-03-01

    Both habitat patch size and structure affect the abundance and occurrence of species and thereby can affect the ecology and evolution of species interactions. Here we contrast the level of seed predation and selection exerted by Common Crossbills (Loxia curvirostra complex) and red squirrels (Sciurus vulgaris) in the extensive mountain pine (Pinus uncinata) forests in the Pyrenees with their level of seed predation in two small, isolated forests. Crossbills consumed 5.1 times more seeds in the Pyrenees than in the isolated forests, and six of seven cone traits under selection by crossbills were enhanced in the Pyrenees. In contrast, red squirrels tend to be uncommon in the open mountain pine forests, consuming relatively few seeds in both regions and having limited impact on both mountain pine and the interaction between crossbills and mountain pine. Resident crossbills in mountain pine forests in the Pyrenees have larger bills than in nearby forests, consistent with local adaptation by crossbills and a coevolutionary arms race between crossbills and mountain pine. The mechanisms leading to variation in the interaction between crossbills and mountain pine should be general to many systems because habitat patch size and structure often vary across the range of a species.

  4. Differential predation of forage seed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  5. Pre-dispersal predation effect on seed packaging strategies and seed viability.

    PubMed

    DeSoto, Lucía; Tutor, David; Torices, Rubén; Rodríguez-Echeverría, Susana; Nabais, Cristina

    2016-01-01

    An increased understanding of intraspecific seed packaging (i.e. seed size/number strategy) variation across different environments may improve current knowledge of the ecological forces that drive seed evolution in plants. In particular, pre-dispersal seed predation may influence seed packaging strategies, triggering a reduction of the resources allocated to undamaged seeds within the preyed fruits. Assessing plant reactions to pre-dispersal seed predation is crucial to a better understanding of predation effects, but the response of plants to arthropod attacks remains unexplored. We have assessed the effect of cone predation on the size and viability of undamaged seeds in populations of Juniperus thurifera with contrasting seed packaging strategies, namely, North African populations with single-large-seeded cones and South European populations with multi-small-seeded cones. Our results show that the incidence of predation was lower on the single-large-seeded African cones than on the multi-small-seeded European ones. Seeds from non-preyed cones were also larger and had a higher germination success than uneaten seeds from preyed cones, but only in populations with multi-seeded cones and in cones attacked by Trisetacus sp., suggesting a differential plastic response to predation. It is possible that pre-dispersal seed predation has been a strong selective pressure in European populations with high cone predation rates, being a process which maintains multi-small-seeded cones and empty seeds as a strategy to save some seeds from predation. Conversely, pre-dispersal predation might not have a strong effect in the African populations with single-large-seeded cones characterized by seed germination and filling rates higher than those in the European populations. Our results indicate that differences in pre-dispersal seed predators and predation levels may affect both selection on and intraspecific variation in seed packaging.

  6. Spatial ecology of predator-prey interactions: corridors and patch shape influence seed predation.

    SciTech Connect

    J. L . Orrock; B. J. Danielson; M. J. Burns; D. J. Levey

    2003-02-03

    J.L. Orrock, B.J. Danielson, M.J. Burns, and D.J. Levey. 2003. Spatial ecology of predator-prey interactions: corridors and patch shape influence seed predation. Ecology, 84(10):2589-2599. Abstract: Corridors that connect patches of disjunct habitat may be promising tools for mediating the negative impacts of habitat fragmentation, but little is known about how corridors affect ecological interactions. In eight 12-ha experimental landscapes, we examined how corridors affect the impact of invertebrate, rodent, and avian seed predators on pokeweed, Phytolacca americana. Over 13 months in 2000 and 2001, we quantified the effects of patch shape, connectivity, and predator type on the number of seeds germinating in the field (germinants), seed removal, and the viability of remaining seeds. Corridors did not affect the number of P. americana germinants in experimental exclosures or the viability of seeds remaining in exclosures. However, corridors affected the removal of seeds in a predator-specific manner: invertebrates removed more seeds in unconnected patches, whereas rodents removed more seeds in connected patches. Seed removal by birds was similar in connected and unconnected patches. Total seed removal by all seed predators was not affected by corridors, because invertebrates removed more seeds where rodents removed fewer seeds, and vice versa. Overall, seed predation signi®cantly reduced the number and viability of remaining seeds, and reduced the number of germinants in 2000 but not in 2001. The abundance of naturally occurring P. americana plants in our experimental patches in 2000 decreased with increasing seed removal from exclosures but was not related to viability or germinants in 2000, suggesting that seed removal may shape the distribution and abundance of this species. Complementary patterns of seed removal by rodents and invertebrates suggest that corridors alter the effects of these predator taxa by changing the relative amounts of edge and core

  7. Seed size variation and predation of seeds produced by wild and crop-wild sunflowers.

    PubMed

    Alexander, H M; Cummings, C L; Kahn, L; Snow, A A

    2001-04-01

    The movement of pollen between crop and wild sunflowers (both Helianthus annuus) has led to concerns about the possible introduction of crop transgenes into wild populations. The persistence of crop traits in wild populations will depend in part on the relative fitness of crop-wild hybrid vs. wild plants. Using seeds from two large experimental field plots, we found that seeds produced by crop-wild plants were twice the size of wild seeds and differed in coloration. Head diameter, date of flowering, identity of mother plant, and levels of predispersal predation explained some variation in mean seed size. We hypothesized that postdispersal vertebrate seed predation would be affected by seed size, with hybrid seeds preferentially eaten. In each of three field trials, significantly more hybrid seeds were eaten (62% of hybrid seed; 42% of wild seed). Within the category of wild seeds, larger seeds were preferentially eaten; however among hybrid seeds, predation was not significantly related to seed size. In this study, differential predation thus reduces hybrid fitness and would presumably slow the spread of transgenes into wild populations.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. Empty seeds are not always bad: simultaneous effect of seed emptiness and masting on animal seed predation.

    PubMed

    Perea, Ramón; Venturas, Martin; Gil, Luis

    2013-01-01

    Seed masting and production of empty seeds have often been considered independently as different strategies to reduce seed predation by animals. Here, we integrate both phenomena within the whole assemblage of seed predators (both pre and post-dispersal) and in two contrasting microsites (open vs. sheltered) to improve our understanding of the factors controlling seed predation in a wind-dispersed tree (Ulmus laevis). In years with larger crop sizes more avian seed predators were attracted with an increase in the proportion of full seeds predated on the ground. However, for abundant crops, the presence of empty seeds decreased the proportion of full seeds predated. Empty seeds remained for a very long period in the tree, making location of full seeds more difficult for pre-dispersal predators and expanding the overall seed drop period at a very low cost (in dry biomass and allocation of C, N and P). Parthenocarpy (non-fertilized seeds) was the main cause of seed emptiness whereas seed abortion was produced in low quantity. These aborted seeds fell prematurely and, thus, could not work as deceptive seeds. A proportion of 50% empty seeds significantly reduced ground seed predation by 26%. However, a high rate of parthenocarpy (beyond 50% empty seeds) did not significantly reduce seed predation in comparison to 50% empty seeds. We also found a high variability and unpredictability in the production of empty seeds, both at tree and population level, making predator deception more effective. Open areas were especially important to facilitate seed survival since rodents (the main post-dispersal predators) consumed seeds mostly under shrub cover. In elm trees parthenocarpy is a common event that might work as an adaptive strategy to reduce seed predation. Masting per se did not apparently reduce the overall proportion of seeds predated in this wind-dispersed tree, but kept great numbers of seeds unconsumed.

  13. Empty Seeds Are Not Always Bad: Simultaneous Effect of Seed Emptiness and Masting on Animal Seed Predation

    PubMed Central

    Perea, Ramón; Venturas, Martin; Gil, Luis

    2013-01-01

    Seed masting and production of empty seeds have often been considered independently as different strategies to reduce seed predation by animals. Here, we integrate both phenomena within the whole assemblage of seed predators (both pre and post-dispersal) and in two contrasting microsites (open vs. sheltered) to improve our understanding of the factors controlling seed predation in a wind-dispersed tree (Ulmus laevis). In years with larger crop sizes more avian seed predators were attracted with an increase in the proportion of full seeds predated on the ground. However, for abundant crops, the presence of empty seeds decreased the proportion of full seeds predated. Empty seeds remained for a very long period in the tree, making location of full seeds more difficult for pre-dispersal predators and expanding the overall seed drop period at a very low cost (in dry biomass and allocation of C, N and P). Parthenocarpy (non-fertilized seeds) was the main cause of seed emptiness whereas seed abortion was produced in low quantity. These aborted seeds fell prematurely and, thus, could not work as deceptive seeds. A proportion of 50% empty seeds significantly reduced ground seed predation by 26%. However, a high rate of parthenocarpy (beyond 50% empty seeds) did not significantly reduce seed predation in comparison to 50% empty seeds. We also found a high variability and unpredictability in the production of empty seeds, both at tree and population level, making predator deception more effective. Open areas were especially important to facilitate seed survival since rodents (the main post-dispersal predators) consumed seeds mostly under shrub cover. In elm trees parthenocarpy is a common event that might work as an adaptive strategy to reduce seed predation. Masting per se did not apparently reduce the overall proportion of seeds predated in this wind-dispersed tree, but kept great numbers of seeds unconsumed. PMID:23776503

  14. Hierarchical levels of seed predation variation by introduced beetles on an endemic Mediterranean palm.

    PubMed

    Rodríguez, Marta; Delibes, Miguel; Fedriani, José M

    2014-01-01

    Seed predators can limit plant recruitment and thus profoundly impinge the dynamics of plant populations, especially when diverse seed predators (e.g., native and introduced) attack particular plant populations. Surprisingly, however, we know little concerning the potential hierarchy of spatial scales (e.g., region, population, patch) and coupled ecological correlates governing variation in the overall impact that native and introduced seed predators have on plant populations. We investigated several spatial scales and ecological correlates of pre-dispersal seed predation by invasive borer beetles in Chamaerops humilis (Arecaceae), a charismatic endemic palm of the Mediteranean basin. To this end, we considered 13 palm populations (115 palms) within four geographical regions of the Iberian Peninsula. The observed interregional differences in percentages of seed predation by invasive beetles were not significant likely because of considerable variation among populations within regions. Among population variation in seed predation was largely related to level of human impact. In general, levels of seed predation were several folds higher in human-altered populations than in natural populations. Within populations, seed predation declined significantly with the increase in amount of persisting fruit pulp, which acted as a barrier against seed predators. Our results revealed that a native species (a palm) is affected by the introduction of related species because of the concurrent introduction of seed predators that feed on both the introduced and native palms. We also show how the impact of invasive seed predators on plants can vary across a hierarchy of levels ranging from variation among individuals within local populations to large scale regional divergences.

  15. Assessing ant seed predation in threatened plants: a case study

    NASA Astrophysics Data System (ADS)

    Albert, María José; Escudero, Adrián; Iriondo, José María

    2005-11-01

    Erodium paularense is a threatened plant species that is subject to seed predation by the granivorous ant Messor capitatus. In this paper we assessed the intensity and pattern of ant seed predation and looked for possible adaptive strategies at the seed and plant levels to cope with this predation. Seed predation was estimated in 1997 and 1998 at the population level by comparing total seed production and ant consumption, assessed by counting seed hulls in refuse piles. According to this method, ant seed predation ranged between 18% and 28%. A more detailed and direct assessment conducted in 1997 raised this estimate to 43%. In this assessment spatial and temporal patterns of seed predation by ants were studied by mapping all nest entrances in the studied area and marking the mature fruits of 109 reproductive plants with a specific colour code throughout the seed dispersal period. Intact fruit coats were later recovered from the refuse piles, and their mother plants and time of dispersal were identified. Seeds dispersed at the end of the dispersal period had a greater probability of escaping from ant seed predation. Similarly, in plants with late dispersal a greater percentage of seeds escaped from ant predation. Optimum dispersal time coincided with the maximum activity of granivorous ants because, at this time, ants focused their harvest on other plant species of the community. It was also observed that within-individual seed dispersal asynchrony minimised seed predation. From a conservation perspective, results show that the granivorous ant-plant interaction cannot be assessed in isolation and that the intensity of its effects basically depends on the seed dispersal pattern of the other members of the plant community. Furthermore, this threat must be assessed by considering the overall situation of the target population. Thus, in E. paularense, the strong limitation of safe-sites for seedling establishment reduces the importance of seed predation.

  16. Trait-mediated seed predation, dispersal and survival among frugivore-dispersed plants in a fragmented subtropical forest, Southwest China.

    PubMed

    Lai, Xin; Guo, Cong; Xiao, Zhishu

    2014-06-01

    By tracking the fate of individual seeds from 6 frugivore-dispersed plants with contrasting seed traits in a fragmented subtropical forest in Southwest China, we explored how rodent seed predation and hoarding were influenced by seed traits such as seed size, seed coat hardness and seed profitability. Post-dispersal seed fates varied significantly among the 6 seed species and 3 patterns were witnessed: large-seeded species with a hard seed coat (i.e. Choerospoadias axillaries and Diospyros kaki var. silvestris) had more seeds removed, cached and then surviving at caches, and they also had fewer seeds predated but a higher proportion of seeds surviving at the source; medium-sized species with higher profitability and thinner seed coat (i.e. Phoebe zhennan and Padus braohypoda) were first harvested and had the lowest probability of seeds surviving either at the source or at caches due to higher predation before or after removal; and small-seeded species with lower profitability (i.e. Elaeocarpus japonicas and Cornus controversa) had the highest probability of seeds surviving at the source but the lowest probability of seeds surviving at caches due to lower predation at the source and lower hoarding at caches. Our study indicates that patterns of seed predation, dispersal and survival among frugivore-dispersed plants are highly determined by seed traits such as seed size, seed defense and seed profitability due to selective predation and hoarding by seed-eating rodents. Therefore, trait-mediated seed predation, dispersal and survival via seed-eating rodents can largely affect population and community dynamics of frugivore-dispersed plants in fragmented forests.

  17. Spatial dynamics of specialist seed predators on synchronized and intermittent seed production of host plants.

    PubMed

    Satake, Akiko; Bjørnstad, Ottar N

    2004-04-01

    Masting, the synchronized and intermittent seed production by plant populations, provides highly variable food resources for specialist seed predators. Such a reproductive mode helps minimize seed losses through predator satiation and extinction of seed predator populations. The seed predators can buffer the resource variation through dispersal or extended diapause. We developed a spatially explicit resource-consumer model to understand the effect of masting on specialist seed predators. The masting dynamics were assumed to follow a resource-based model for plant reproduction, and the population dynamics of the predator were represented by a spatially extended Nicholson-Bailey model. The resultant model demonstrated that when host plants reproduce intermittently, seed predator populations go locally extinct, but global persistence of the predator is facilitated by dispersal or extended diapause. Global extinction of the predator resulted when the intermittent reproduction is highly synchronized among plants. An approximate invasion criterion for the predators showed that negative lag-1 autocorrelation in seeding reduces invasibility, and positive lag-1 cross-correlation enhances invasibility. Spatial synchronization in seeding at local scale caused by pollen coupling (or climate forcing) further prevented invasion of the predators. If the predators employed extended diapause, extremely high temporal variability in reproduction was required for plants to evade the predators.

  18. Seed predation and selection exerted by a seed predator influence subalpine tree densities.

    PubMed

    Siepielski, Adam M; Benkman, Craig W

    2008-10-01

    Strongly interacting species often have pronounced direct and indirect effects on other species. Here we focus of the effects of pine squirrels (Tamiasciurus spp.), which are a dominant pre-dispersal seed predator of many conifers including limber pines (Pinus flexilis) and whitebark pines (P. albicaulis). Pine squirrels depress seed abundance by harvesting most limber and whitebark pine cones on their territories. Pine squirrels further reduce seed availability for Clark's Nutcrackers (Nucifraga columbiana), the primary seed disperser of these pines, because selection exerted by pine squirrels has reduced the number of seeds per cone and causes seeds to be less accessible. We predicted that, if fewer seeds were available for dispersal by nutcrackers, pine recruitment should be suppressed in areas with pine squirrels. In support of this prediction, stand densities were about two times greater in areas where pine squirrels are absent than in areas where they are present. Alternative explanations that we considered do not account for these differences; however, precipitation may limit stand densities in the absence of seed limitation by pine squirrels. In sum, pine squirrels apparently depress limber and whitebark pine stand densities, with the potential for ecosystem impacts because these pines are foundation species within Western subalpine ecosystems.

  19. Edge effect on post-dispersal artificial seed predation in the southeastern Amazonia, Brazil.

    PubMed

    Penido, G; Ribeiro, V; Fortunato, D S

    2015-05-01

    This paper evaluates the post-dispersal artificial seed predation rates in two areas of the southeastern Amazon forest-savanna boundary, central Brazil. We conducted the survey in a disturbance regime controlled research site to verify if exists an edge effect in these rates and if the disturbance (in this case annual fire and no fire) affects seed predation. We placed 800 peanuts seeds in each area at regular distance intervals from the fragment`s edge. Data were analyzed by a likelihood ratio model selection in generalized linear models (GLM). The complete model (with effects from edge distance and site and its interaction) was significative (F3=4.43; p=0.005). Seeds had a larger predation rates in fragment's interior in both areas, but in the controlled area (no disturbance) this effect was less linear. This suggests an edge effect for post-dispersal seed predation, and that disturbances might alter these effects. Even if we exclude the site effect (grouping both areas together) there is still a strong edge effect on seed predation rates (F3=32.679; p>0.001). We did not verify predator's species in this study; however, the presence of several species of ants was extremely common in the seeds. The detection of an edge effect in only a short survey time suggests that there is heterogeneity in predation rates and that this variation might affect plant recruitment in fragmented areas of the Amazon forest. Henceforth, this seed predation should be taken in consideration in reforestation projects, where the main source of plants species is from seed distribution.

  20. 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.

  1. 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.

  2. 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.

  3. Linking fruit traits to variation in predispersal vertebrate seed predation, insect seed predation, and pathogen attack.

    PubMed

    Beckman, Noelle G; Muller-Landau, Helene C

    2011-11-01

    The importance of vertebrates, invertebrates, and pathogens for plant communities has long been recognized, but their absolute and relative importance in early recruitment of multiple coexisting tropical plant species has not been quantified. Further, little is known about the relationship of fruit traits to seed mortality due to natural enemies in tropical plants. To investigate the influences of vertebrates, invertebrates, and pathogens on reproduction of seven canopy plant species varying in fruit traits, we quantified reductions in fruit development and seed germination due to vertebrates, invertebrates, and fungal pathogens through experimental removal of these enemies using canopy exclosures, insecticide, and fungicide, respectively. We also measured morphological fruit traits hypothesized to mediate interactions of plants with natural enemies of seeds. Vertebrates, invertebrates, and fungi differentially affected predispersal seed mortality depending on the plant species. Fruit morphology explained some variation among species; species with larger fruit and less physical protection surrounding seeds exhibited greater negative effects of fungi on fruit development and germination and experienced reduced seed survival integrated over fruit development and germination in response to vertebrates. Within species, variation in seed size also contributed to variation in natural enemy effects on seed viability. Further, seedling growth was higher for seeds that developed in vertebrate exclosures for Anacardium excelsum and under the fungicide treatment for Castilla elastica, suggesting that predispersal effects of natural enemies may carry through to the seedling stage. This is the first experimental test of the relative effects of vertebrates, invertebrates, and pathogens on seed survival in the canopy. This study motivates further investigation to determine the generality of our results for plant communities. If there is strong variation in natural enemy attack

  4. Seed predation, not seed dispersal, explains the landscape-level abundance of an early-successional plant.

    SciTech Connect

    Orrock, John, L.; Douglas J. Levey; Brent J. Danielson; Ellen I Damschen.

    2006-01-01

    Plants may not occur in a given area if there are no suitable sites for seeds to establish (microsite limitation), if seeds fail to arrive in suitable microsites (dispersal limitation) or if seeds in suitable microsites are destroyed by predators (predator limitation). When dispersal and microsites are not limiting, the role of local seed predators can be important for generating emergent, large-scale patterns of plant abundance across landscapes. Moreover, because predators may generate large-scale patterns that resemble other forms of limitation and predators may target specific species, predator impacts should be more frequently incorporated into experiments on the role of seed limitation and plant community composition.

  5. Effects of carbaryl-bran bait on trap catch and seed predation by ground beetles (Coleoptera: Carabidae).

    PubMed

    Fielding, Dennis J; DeFoliart, Linda S; Hagerty, Aaron M

    2013-04-01

    Carbaryl-bran bait is effective against grasshoppers without many impacts on nontarget organisms, but ground beetles (Coleoptera: Carabidae) may be susceptible to these baits. Carabids are beneficial in agricultural settings as predators of insect pests and weed seeds. Carabid species and their consumption of weed seeds have not been previously studied in agricultural settings in Alaska. This study examined the effect of grasshopper bran bait on carabid activity-density, as measured by pitfall trap catches, and subsequent predation by invertebrates of seeds of three species of weed. Data were collected in fallow fields in agricultural landscape in the interior of Alaska, near Delta Junction, in 2008 and 2010. Bait applications reduced ground beetle activity-density by over half in each of 2 yr of bait applications. Seed predation was generally low overall (1-10%/wk) and not strongly affected by the bait application, but predation of lambsquarters (Chenopodium album L.) seed was lower on treated plots in 1 yr (340 seeds recovered versus 317 seeds, on treated versus untreated plots, respectively). Predation of dandelion (Taraxacum officinale G. H. Weber ex Wiggers) seeds was correlated with ground beetle activity-density in 1 yr, and predation of dragonhead mint (Dracocephalum parvifolium Nutt.) seed in the other year. We conclude that applications of carbaryl-bran bait for control of grasshoppers will have only a small, temporary effect on weed seed populations in high-latitude agricultural ecosystems.

  6. Parthenocarpy and Seed Predation by Insects in Bursera morelensis

    PubMed Central

    Ramos-Ordoñez, María F.; Márquez-Guzmán, Judith; Del Coro Arizmendi, Ma.

    2008-01-01

    Background and Aims While parthenocarpy (meaning the production of fruits without seeds) may limit fecundity in many plants, its function is not clear; it has been proposed, however, that it might be associated with a strategy to avoid seed predation. Bursera morelensis is a dioecious endemic plant that produces fruits with and without seeds, and its fruits are parasitized by insects. Its reproductive system is not well described and no published evidence of parthenocarpy exists for the species. The purpose of this work was to describe the breeding system of B. morelensis and its relationship to seed predation by insects. Methods The breeding system was described using pollination experiments, verifying the presence of parthenocarpic fruits and apomictic seeds. Reproductive structures from flower buds to mature fruits were quantified. For fruits, an anatomical and histological characterization was made. The number of fruits in which seeds had been predated by insects was correlated with parthenocarpic fruit production. Key Results The major abortion of reproductive structures occurred during fruit set. The results discard the formation of apomictic seeds. Flowers that were not pollinated formed parthenocarpic fruits and these could be distinguished during early developmental stages. In parthenocarpic fruits in the first stages of development, an unusual spread of internal walls of the ovary occurred invading the locule and preventing ovule development. Unlike fruits with seeds, parthenocarpic fruits do not have calcium oxalate crystals in the ovary wall. Both fruit types can be separated in the field at fruit maturity by the presence of dehiscence, complete in seeded and partial in parthenocarpic fruits. Trees with more parthenocarpic fruits had more parasitized fruits. Conclusions This is the first time the anatomy of parthenocarpic fruits in Burseraceae has been described. Parthenocarpic fruits in B. morelensis might function as a deceit strategy for insect seed

  7. 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

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

    PubMed

    Bell, David M; Clark, James S

    2016-04-01

    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 interannual climate variation on seed abortion rates, (2) assess the impact of seed density on predation rates, and (3) examine the degree to which density-dependent seed predation would amplify or dampen interannual variation in fecundity associated with seed abortion. We used a 19-year study of seed abortion and pre-dispersal predation rates by insects and vertebrates (birds and rodents) for five temperate tree species across forest plots from the North Carolina Piedmont to the Southern Appalachian Mountains in the southeastern USA. We found that rates of seed abortion and predation increased reproductive variation for oaks (Quercus species). Probability of seed abortion was greatest during years with cool, dry springs. Responses of seed predation on Quercus species to current year's seed density varied by species, but exhibited positive density-dependence to previous year's seed density consistent with numerical responses of seed predators. Seed abortion and predation rates for two drupe species responded little to variation in climate or seed density, respectively. Given that predation increased interannual variation in seed availability and the negative density-dependence to previous year's seed density, our results indicate that consistent numerical responses of oak seed predators may amplify interannual variation due to climate-mediated processes like seed abortion.

  9. 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.

  10. The functional response of a hoarding seed predator to mast seeding.

    PubMed

    Fletcher, Quinn E; Boutin, Stan; Lane, Jeffrey E; LaMontagne, Jalene M; McAdam, Andrew G; Krebs, Charles J; Humphries, Murray M

    2010-09-01

    Mast seeding involves the episodic and synchronous production of large seed crops by perennial plants. The predator satiation hypothesis proposes that mast seeding maximizes seed escape because seed predators consume a decreasing proportion of available seeds with increasing seed production. However, the seed escape benefits of masting depend not only on whether predators are satiated at high levels of seed production, but also on the shape of their functional response (type II vs. type III), and the actual proportion of available seeds that they consume at different levels of seed production. North American red squirrels (Tamiasciurus hudsonicus) are the primary vertebrate predator of white spruce (Picea glauca) mast seed crops in many boreal regions because they hoard unopened cones in underground locations, preempting the normal sequence of cone opening, seed dispersal, and seed germination. We document the functional response of cone-hoarding by red squirrels across three non-mast years and one mast year by estimating the number of cones present in the territories of individual red squirrels and the proportion of these cones that they hoarded each autumn. Even though red squirrels are not constrained by the ingestive and on-body (fat reserves) energy reserve limitations experienced by animals that consume seeds directly, most squirrels hoarded < 10% of the cones present on their territories under mast conditions. Cone availability during non-mast years also reached levels that satiated the hoarding activity of red squirrels; however, this occurred only on the highest-quality territories. Squirrels switched to mushroom-hoarding when cone production was low and mushrooms were abundant. This resulted in type III functional response whereby the proportional harvest of cones was highest at levels of cone availability that were intermediate within non-mast years. Overall, more cones escaped squirrel cone-hoarding during a mast event than when cone production was low

  11. Predator diversity and density affect levels of predation upon strongly interactive species in temperate rocky reefs.

    PubMed

    Guidetti, Paolo

    2007-12-01

    Indirect effects of predators in the classic trophic cascade theory involve the effects of basal species (e.g. primary producers) mediated by predation upon strongly interactive consumers (e.g. grazers). The diversity and density of predators, and the way in which they interact, determine whether and how the effects of different predators on prey combine. Intraguild predation, for instance, was observed to dampen the effects of predators on prey in many ecosystems. In marine systems, species at high trophic levels are particularly susceptible to extinction (at least functionally). The loss of such species, which is mainly attributed to human activities (mostly fishing), is presently decreasing the diversity of marine predators in many areas of the world. Experimental studies that manipulate predator diversity and investigate the effects of this on strongly interactive consumers (i.e. those potentially capable of causing community-wide effects) in marine systems are scant, especially in the rocky sublittoral. I established an experiment that utilised cage enclosures to test whether the diversity and density of fish predators (two sea breams and two wrasses) would affect predation upon juvenile and adult sea urchins, the most important grazers in Mediterranean sublittoral rocky reefs. Changes in species identity (with sea breams producing major effects) and density of predators affected predation upon sea urchins more than changes in species richness per se. Predation upon adult sea urchins decreased in the presence of multiple predators, probably due to interference competition between sea breams and wrasses. This study suggests that factors that influence both fish predator diversity and density in Mediterranean rocky reefs (e.g. fishing and climate change) may have the potential to affect the predators' ability to control sea urchin population density, with possible repercussions for the whole benthic community structure.

  12. [Predation and removal of rodents on the seeds with different size and pericarp traits].

    PubMed

    Zhou, Li-biao; Yan, Xing-fu; Wang, Jian-li; Zhou, Yun-feng

    2013-08-01

    A field survey was conducted in the Quercus wutaishanica shrubs in Liupan Mountains of Ningxia, Northwest China to study the predation and removal of rodents on the seeds of Q. wutaishanica, Prunus salicina and Pinus armandii, aimed to explore the effects of seed size and pericarp traits on the predation and removal behaviors of rodents. The in situ seed predation rates of smaller Q. wutaishanica seeds and P. armandii seeds were significantly higher than those of larger Q. wutaishanica seeds and P. salicina seeds. The P. salicina seeds with hard and thick pericarp (endocarp) had the highest predation rate and hoarding rate after the removal by rodents. The movement distance of larger Q. wutaishanica seeds during predation events was the longest (3.10 m), and the seed hoarding distance of this species (6.48 m) was significantly longer than that of the three other types of seeds. Over 80% of sites were used as the predation sites by rodents for the seeds, except that the P. salicina seeds contained only a single seed and the cache sites contained a single seed accounted for over 90% for all types of seeds. Few predation and cache sites containing over two seeds were detected. Higher proportion of P. armandii seeds were predated in microhabitats except at the base of shrubs and in the holes after removal by rodent, while the seeds of other three types were predated mainly at the base of shrubs and in the holes after removal by rodents. The seed hoarding patterns after removal by rodents were primarily determined by pericarp traits, and higher proportion of soil burial that the rodents hoarded seeds with hard pericarp (endocarp) was detected.

  13. 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.

  14. 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

  15. 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.

  16. Effects of a disease affecting a predator on the dynamics of a predator-prey system.

    PubMed

    Auger, Pierre; McHich, Rachid; Chowdhury, Tanmay; Sallet, Gauthier; Tchuente, Maurice; Chattopadhyay, Joydev

    2009-06-07

    We study the effects of a disease affecting a predator on the dynamics of a predator-prey system. We couple an SIRS model applied to the predator population, to a Lotka-Volterra model. The SIRS model describes the spread of the disease in a predator population subdivided into susceptible, infected and removed individuals. The Lotka-Volterra model describes the predator-prey interactions. We consider two time scales, a fast one for the disease and a comparatively slow one for predator-prey interactions and for predator mortality. We use the classical "aggregation method" in order to obtain a reduced equivalent model. We show that there are two possible asymptotic behaviors: either the predator population dies out and the prey tends to its carrying capacity, or the predator and prey coexist. In this latter case, the predator population tends either to a "disease-free" or to a "disease-endemic" state. Moreover, the total predator density in the disease-endemic state is greater than the predator density in the "disease-free" equilibrium (DFE).

  17. Evaluating the interacting influences of pollination, seed predation, invasive species and isolation on reproductive success in a threatened alpine plant.

    PubMed

    Krushelnycky, Paul D

    2014-01-01

    Reproduction in rare plants may be influenced and limited by a complex combination of factors. External threats such as invasive species and landscape characteristics such as isolation may impinge on both pollination and seed predation dynamics, which in turn can strongly affect reproduction. I assessed how patterns in floral visitation, seed predation, invasive ant presence, and plant isolation influenced one another and ultimately affected viable seed production in Haleakalā silverswords (Argyroxiphium sandwicense subsp. macrocephalum) of Hawai'i. Floral visitation was dominated by endemic Hylaeus bees, and patterns of visitation were influenced by floral display size and number of plants clustered together, but not by floral herbivory or nearest flowering neighbor distance. There was also some indication that Argentine ant presence impacted floral visitation, but contradictory evidence and limitations of the study design make this result uncertain. Degree of seed predation was associated only with plant isolation, with the two main herbivores partitioning resources such that one preferentially attacked isolated plants while the other attacked clumped plants; total seed predation was greater in more isolated plants. Net viable seed production was highly variable among individuals (0-55% seed set), and was affected mainly by nearest neighbor distance, apparently owing to low cross-pollination among plants separated by even short distances (>10-20 m). This isolation effect dominated net seed set, with no apparent influence from floral visitation rates, percent seed predation, or invasive ant presence. The measured steep decline in seed set with isolation distance may not be typical of the entire silversword range, and may indicate that pollinators in addition to Hylaeus bees could be important for greater gene flow. Management aimed at maintaining or maximizing silversword reproduction should focus on the spatial context of field populations and outplanting

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

    PubMed

    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.

  19. 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.

  20. Seed Predation by the Shore Crab Carcinus maenas: A Positive Feedback Preventing Eelgrass Recovery?

    PubMed Central

    2016-01-01

    There is an increasing interest to restore the ecosystem services that eelgrass provides, after their continuous worldwide decline. Most attempts to restore eelgrass using seeds are challenged by very high seed losses and the reasons for these losses are not all clear. We assess the impact of predation on seed loss and eelgrass establishment, and explore methods to decrease seed loss during restoration in the Swedish northwest coast. In a laboratory study we identified three previously undescribed seed predators, the shore crab Carcinus maenas, the hermit crab Pagurus bernhardus and the sea urchin Strongylocentrotus droebachiensis, of which shore crabs consumed 2–7 times more seeds than the other two species. The importance of shore crabs as seed predators was supported in field cage experiments where one enclosed crab caused 73% loss of seeds over a 1-week period on average (~ 21 seeds per day). Seedling establishment was significantly higher (14%) in cages that excluded predators over an 8-month period than in uncaged plots and cages that allowed predators but prevented seed-transport (0.5%), suggesting that seed predation constitutes a major source of seed loss in the study area. Burying the seeds 2 cm below the sediment surface prevented seed predation in the laboratory and decreased predation in the field, constituting a way to decrease seed loss during restoration. Shore crabs may act as a key feedback mechanism that prevent the return of eelgrass both by direct consumption of eelgrass seeds and as a predator of algal mesograzers, allowing algal mats to overgrow eelgrass beds. This shore crab feedback mechanism could become self-generating by promoting the growth of its own nursery habitat (algal mats) and by decreasing the nursery habitat (seagrass meadow) of its dominant predator (cod). This double feedback-loop is supported by a strong increase of shore crab abundance in the last decades and may partly explain the regime shift in vegetation observed

  1. Quinolizidine alkaloids in Ormosia arborea seeds inhibit predation but not hoarding by agoutis (Dasyprocta leporina).

    PubMed

    Guimarães, Paulo Roberto; José, Juliana; Galetti, Mauro; Trigo, José Roberto

    2003-05-01

    Quinolizidine alkaloids (QAs) are secondary compounds found in seeds of many species of plants, possibly protecting them against pathogens and seed predators. QAs were isolated from Ormosia arborea seeds and bioassayed against red-rumped agoutis (Dasyprocta leporina, Rodentia: Caviomorpha) to verify if they inhibit seed predation and food hoarding (seed dispersal). Three treatments were used: (1) seeds of O. arborea, (2) palatable seeds of Mimusops coriacea (Sapotaceae) treated with MeOH, and (3) seeds of M. coriacea treated with QAs dissolved in MeOH in similar concentration to that present in O. arborea. Palatable seeds were significantly more preyed upon than seeds treated with QAs and Ormosia seeds, but QAs did not influence hoarding behavior. QAs in O. arborea may have a strong effect in avoiding seed predation by rodents, without reducing dispersal.

  2. Multiple infestation by seed predators: the effect of loculate fruits on intraspecific insect larval competition

    NASA Astrophysics Data System (ADS)

    Serrano, José M.; Delgado, Juan A.; López, Francisco; Acosta, Francisco J.; Fungairiño, Sara G.

    2001-06-01

    Many morphological features of fruits are important factors affecting predispersal seed predation by insects. This paper analyses the predispersal seed predation process of a major predator (a Noctuidae lepidopteran larvae) in loculate fruits of a bushy perennial plant, Cistus ladanifer. The main aim of the study is to assess the potential effect of internal valvae (which partition groups of seeds) in the intraspecific competition between larvae in multiple-infested fruits. Our results show that larvae do not reject already infested fruits, but they avoid the proximity of other larvae within the fruit, keeping an average minimum distance of one locule. In multiple-infested fruits, larval mortality increases and the proportion of seeds consumed by each larvae decreases. In those situations in which valvae keep apart larvae within a fruit, these only suffer the cost of exploitation competition with a low acquisition of resources. However, when all valvae between them are pierced by the larvae, competition switches to an interference component and larval mortality increases markedly. The existence of valvae within a fruit allows larvae to diminish the cost of intraspecific competition, obtaining high life expectancies (70%), even in triple-infested fruits.

  3. Cues of intraguild predators affect the distribution of intraguild prey.

    PubMed

    Choh, Yasuyuki; van der Hammen, Tessa; Sabelis, Maurice W; Janssen, Arne

    2010-06-01

    Theory on intraguild (IG) predation predicts that coexistence of IG-predators and IG-prey is only possible for a limited set of parameter values, suggesting that IG-predation would not be common in nature. This is in conflict with the observation that IG-predation occurs in many natural systems. One possible explanation for this difference might be antipredator behaviour of the IG-prey, resulting in decreased strength of IG-predation. We studied the distribution of an IG-prey, the predatory mite Neoseiulus cucumeris (Acari: Phytoseiidae), in response to cues of its IG-predator, the predatory mite Iphiseius degenerans. Shortly after release, the majority of IG-prey was found on the patch without cues of IG-predators, suggesting that they can rapidly assess predation risk. IG-prey also avoided patches where conspecific juveniles had been killed by IG-predators. Because it is well known that antipredator behaviour in prey is affected by the diet of the predator, we also tested whether IG-prey change their distribution in response to the food of the IG-predators (pollen or conspecific juveniles), but found no evidence for this. The IG-prey laid fewer eggs on patches with cues of IG-predators than on patches without cues. Hence, IG-prey changed their distribution and oviposition in response to cues of IG-predators. This might weaken the strength of IG-predation, possibly providing more opportunities for IG-prey and IG-predators to co-exist.

  4. Getting out alive: how predators affect the decision to metamorphose.

    PubMed

    Relyea, Rick A

    2007-06-01

    Metamorphosis has intrigued biologists for a long time as an extreme form of complex life cycles that are ubiquitous in animals. While investigated from a variety of perspectives, the ecological focus has been on identifying and understanding the ecological factors that affect an individual's decision on when, and at what size, to metamorphose. Predation is a major factor that affects metamorphic decisions and a recent review by Benard (Annu Rev Ecol Evol Syst 35:651-673, 2004)) documented how predator cues induce metamorphic changes relative to model predictions. Importantly, however, real predators affect larval prey via several mechanisms beyond simple induction. In this paper, I contrast the leading models of metamorphosis, provide an overview of the multiple ways that predators can directly and indirectly affect larval growth and development (via induction, thinning, and selection), and identify how each process should affect the time to and size at metamorphosis. With this mechanistic foundation established, I then turn to the well-studied model system of larval amphibians to synthesize studies on: (1) caged predators (which cause only induction), and (2) lethal predators (which cause induction, thinning, and selection). Among the caged-predator studies, the chemical cues emitted by predators rarely induce a smaller size at metamorphosis or a shorter time to metamorphosis, which is in direct contrast to theoretical predictions but in agreement with Benard's (Annu Rev Ecol Evol Syst 35:651-673, 2004) review based on a considerably smaller dataset. Among the lethal-predator studies, there is a diversity of outcomes depending upon the relative importance of induction versus thinning with the relative importance of the two processes appearing to change with larval density. Finally, I review the persistent effects of larval predators after metamorphosis including both phenotypic and fitness effects. At the end, I outline a number of future directions to allow

  5. 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

  6. 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.

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

    SciTech Connect

    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.

  8. Corridors and olfactory predator cues affect small mammal behavior.

    SciTech Connect

    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 connected 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.

  9. Taste and Physiological Responses to Glucosinolates: Seed Predator versus Seed Disperser

    PubMed Central

    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. PMID:25383693

  10. 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.

  11. Conflicting selection from fire and seed predation drives fine-scaled phenotypic variation in a widespread North American conifer

    PubMed Central

    Talluto, Matthew V.; Benkman, Craig W.

    2014-01-01

    Recent work has demonstrated that evolutionary processes shape ecological dynamics on relatively short timescales (eco-evolutionary dynamics), but demonstrating these effects at large spatial scales in natural landscapes has proven difficult. We used empirical studies and modeling to investigate how selective pressures from fire and predispersal seed predation affect the evolution of serotiny, an ecologically important trait. Serotiny is a highly heritable key reproductive trait in Rocky Mountain lodgepole pine (Pinus contorta subsp. latifolia), a conifer that dominates millions of hectares in western North America. In these forests, the frequency of serotiny determines postfire seedling density with corresponding community- and ecosystem-level effects. We found that serotinous individuals have a selective advantage at high fire frequencies and low predation pressure; however, very high seed predation shifted the selective advantage to nonserotinous individuals even at high fire frequencies. Simulation modeling suggests that spatial variation in the frequency of serotiny results from heterogeneity in these two selective agents. These results, combined with previous findings showing a negative association between the density of seed predators and the frequency of serotiny at both landscape and continental scales, demonstrate that contemporary patterns in serotiny reflect an evolutionary response to conflicting selection pressures from fire and seed predation. Thus, we show that variation in the frequency of a heritable polygenic trait depends on spatial variation in two dominant selective agents, and, importantly, the effects of the local trait variation propagate with profound consequences to the structure and function of communities and ecosystems across a large landscape. PMID:24979772

  12. Conflicting selection from fire and seed predation drives fine-scaled phenotypic variation in a widespread North American conifer.

    PubMed

    Talluto, Matthew V; Benkman, Craig W

    2014-07-01

    Recent work has demonstrated that evolutionary processes shape ecological dynamics on relatively short timescales (eco-evolutionary dynamics), but demonstrating these effects at large spatial scales in natural landscapes has proven difficult. We used empirical studies and modeling to investigate how selective pressures from fire and predispersal seed predation affect the evolution of serotiny, an ecologically important trait. Serotiny is a highly heritable key reproductive trait in Rocky Mountain lodgepole pine (Pinus contorta subsp. latifolia), a conifer that dominates millions of hectares in western North America. In these forests, the frequency of serotiny determines postfire seedling density with corresponding community- and ecosystem-level effects. We found that serotinous individuals have a selective advantage at high fire frequencies and low predation pressure; however, very high seed predation shifted the selective advantage to nonserotinous individuals even at high fire frequencies. Simulation modeling suggests that spatial variation in the frequency of serotiny results from heterogeneity in these two selective agents. These results, combined with previous findings showing a negative association between the density of seed predators and the frequency of serotiny at both landscape and continental scales, demonstrate that contemporary patterns in serotiny reflect an evolutionary response to conflicting selection pressures from fire and seed predation. Thus, we show that variation in the frequency of a heritable polygenic trait depends on spatial variation in two dominant selective agents, and, importantly, the effects of the local trait variation propagate with profound consequences to the structure and function of communities and ecosystems across a large landscape.

  13. Reciprocity in predator-prey interactions: exposure to defended prey and predation risk affects intermediate predator life history and morphology.

    PubMed

    Hammill, Edd; Beckerman, Andrew P

    2010-05-01

    A vast body of literature exists documenting the morphological, behavioural and life history changes that predators induce in prey. However, little attention has been paid to how these induced changes feed back and affect the predators' life history and morphology. Larvae of the phantom midge Chaoborus flavicans are intermediate predators in a food web with Daphnia pulex as the basal resource and planktivorous fish as the top predator. C. flavicans prey on D. pulex and are themselves prey for fish; as D. pulex induce morphological defences in the presence of C. flavicans this is an ideal system in which to evaluate the effects of defended prey and top predators on an intermediate consumer. We assessed the impact on C. flavicans life history and morphology of foraging on defended prey while also being exposed to the non-lethal presence of a top fish predator. We tested the basic hypothesis that the effects of defended prey will depend on the presence or absence of top predator predation risk. Feeding rate was significantly reduced and time to pupation was significantly increased by defended morph prey. Gut size, development time, fecundity, egg size and reproductive effort respond to fish chemical cues directly or significantly alter the relationship between a trait and body size. We found no significant interactions between prey morph and the non-lethal presence of a top predator, suggesting that the effects of these two biological factors were additive or singularly independent. Overall it appears that C. flavicans is able to substantially modify several aspects of its biology, and while some changes appear mere consequences of resource limitation others appear facultative in nature.

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

    PubMed

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

    2007-10-22

    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.

  15. 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

  16. Direct effects of tillage on the activity density of ground beetle (Coleoptera: Carabidae) weed seed predators.

    PubMed

    Shearin, A F; Reberg-Horton, S C; Gallandt, E R

    2007-10-01

    Ground beetles are well known as beneficial organisms in agroecosystems, contributing to the predation of a wide range of animal pests and weed seeds. Tillage has generally been shown to have a negative effect on ground beetles, but it is not known whether this is because of direct mortality or the result of indirect losses resulting from dispersal caused by habitat deterioration. In 2005, field experiments measured direct, tillage-induced mortality, of four carabid weed seed predators, Harpalus rufipes DeGeer, Agonum muelleri Herbst, Anisodactylus merula Germar, and Amara cupreolata Putzeys, and one arthropod predator, Pterostichus melanarius Illiger, common to agroecosystems in the northeastern United States. Three tillage treatments (moldboard plow, chisel plow, and rotary tillage) were compared with undisturbed controls at two sites (Stillwater and Presque Isle) and at two dates (July and August) in Maine. Carabid activity density after disturbance was measured using fenced pitfall traps installed immediately after tillage to remove any effects of dispersal. Rotary tillage and moldboard plowing reduced weed seed predator activity density 52 and 54%, respectively. Carabid activity density after chisel plowing was similar to the undisturbed control. This trend was true for each of the weed seed predator species studied. However, activity density of the arthropod predator P. melanarius was reduced by all tillage types, indicating a greater sensitivity to tillage than the four weed seed predator species. These results confirm the need to consider both direct and indirect effects of management in studies of invertebrate seed predators.

  17. Spatial and temporal effects on seed dispersal and seed predation of Musa acuminata in southern Yunnan, China.

    PubMed

    Meng, Lingzeng; Gao, Xiuxia; Chen, Jin; Martin, Konrad

    2012-03-01

    Wild bananas are abundant in tropical areas and many ecologists have observed that the succession process is quicker following increased disturbance. This study was conducted to analyze animal-seed interactions and their effects on the seed fate of a wild banana species (Musa acuminata) in tropical southern Yunnan (China) through experiments considering spatial (site and habitat) and temporal (seasons) variation. The largest proportion of fruits (81%) was removed by frugivorous seed dispersers, especially by bats at nighttime. Only 13% of the fruits were removed by climbing seed predators (different species of rats). In the exclosure treatment, rodents accounted for a significantly higher total artificially exposed seed removal number than ants, but with spatial and temporal differences. The highest seed predation rate by rodents (70%) was found in forest with wild banana stands, corresponding with the highest rodent diversity (species numbers and abundance) among the habitat types. In contrast, the seed removal number by ants (57%) was highest in the open land habitats, but there was no close correlation with ant diversity. Seed removal numbers by ants were significantly higher in the dry compared to the rainy season, but rodent activity showed no differences between seasons. The overall results suggest that the largest proportion of seeds produced by wild banana are primarily dispersed by bats. Primary seed dispersal by bats at nighttime is essential for wild banana seeds to escape seed predation.

  18. Effects of pollination limitation and seed predation on female reproductive success of a deceptive orchid.

    PubMed

    Walsh, Ryan P; Arnold, Paige M; Michaels, Helen J

    2014-06-09

    For many species of conservation significance, multiple factors limit reproduction. This research examines the contributions of plant height, number of flowers, number of stems, pollen limitation and seed predation to female reproductive success in the deceit-pollinated orchid, Cypripedium candidum. The deceptive pollination strategy employed by many orchids often results in high levels of pollen limitation. While increased floral display size may attract pollinators, C. candidum's multiple, synchronously flowering stems could promote selfing and also increase attack by weevil seed predators. To understand the joint impacts of mutualists and antagonists, we examined pollen limitation, seed predation and the effects of pollen source over two flowering seasons (2009 and 2011) in Ohio. In 2009, 36 pairs of plants size-matched by flower number, receiving either supplemental hand or open pollination, were scored for fruit maturation, mass of seeds and seed predation. Pollen supplementation increased proportion of flowers maturing into fruit, with 87 % fruit set when hand pollinated compared with 46 % for naturally pollinated flowers. Inflorescence height had a strong effect, as taller inflorescences had higher initial fruit set, while shorter stems had higher predation. Seed predation was seen in 73 % of all fruits. A parallel 2011 experiment that included a self-pollination treatment and excluded seed predators found initial and final fruit set were higher in the self and outcross pollination treatments than in the open-pollinated treatment. However, seed mass was higher in both open pollinated and outcross pollination treatments compared with hand self-pollinated. We found greater female reproductive success for taller flowering stems that simultaneously benefited from increased pollination and reduced seed predation. These studies suggest that this species is under strong reinforcing selection to increase allocation to flowering stem height. Our results may help

  19. Effects of pollination limitation and seed predation on female reproductive success of a deceptive orchid

    PubMed Central

    Walsh, Ryan P.; Arnold, Paige M.; Michaels, Helen J.

    2014-01-01

    For many species of conservation significance, multiple factors limit reproduction. This research examines the contributions of plant height, number of flowers, number of stems, pollen limitation and seed predation to female reproductive success in the deceit-pollinated orchid, Cypripedium candidum. The deceptive pollination strategy employed by many orchids often results in high levels of pollen limitation. While increased floral display size may attract pollinators, C. candidum's multiple, synchronously flowering stems could promote selfing and also increase attack by weevil seed predators. To understand the joint impacts of mutualists and antagonists, we examined pollen limitation, seed predation and the effects of pollen source over two flowering seasons (2009 and 2011) in Ohio. In 2009, 36 pairs of plants size-matched by flower number, receiving either supplemental hand or open pollination, were scored for fruit maturation, mass of seeds and seed predation. Pollen supplementation increased proportion of flowers maturing into fruit, with 87 % fruit set when hand pollinated compared with 46 % for naturally pollinated flowers. Inflorescence height had a strong effect, as taller inflorescences had higher initial fruit set, while shorter stems had higher predation. Seed predation was seen in 73 % of all fruits. A parallel 2011 experiment that included a self-pollination treatment and excluded seed predators found initial and final fruit set were higher in the self and outcross pollination treatments than in the open-pollinated treatment. However, seed mass was higher in both open pollinated and outcross pollination treatments compared with hand self-pollinated. We found greater female reproductive success for taller flowering stems that simultaneously benefited from increased pollination and reduced seed predation. These studies suggest that this species is under strong reinforcing selection to increase allocation to flowering stem height. Our results may help

  20. Escaping peril: perceived predation risk affects migratory propensity

    PubMed Central

    Hulthén, Kaj; Chapman, Ben B.; Nilsson, P. Anders; Vinterstare, Jerker; Hansson, Lars-Anders; Skov, Christian; Brodersen, Jakob; Baktoft, Henrik; Brönmark, Christer

    2015-01-01

    Although migratory plasticity is increasingly documented, the ecological drivers of plasticity are not well understood. Predation risk can influence migratory dynamics, but whether seasonal migrants can adjust their migratory behaviour according to perceived risk is unknown. We used electronic tags to record the migration of individual roach (Rutilus rutilus), a partially migratory fish, in the wild following exposure to manipulation of direct (predator presence/absence) and indirect (high/low roach density) perceived predation risk in experimental mesocosms. Following exposure, we released fish in their lake summer habitat and monitored individual migration to connected streams over an entire season. Individuals exposed to increased perceived direct predation risk (i.e. a live predator) showed a higher migratory propensity but no change in migratory timing, while indirect risk (i.e. roach density) affected timing but not propensity showing that elevated risk carried over to alter migratory behaviour in the wild. Our key finding demonstrates predator-driven migratory plasticity, highlighting the powerful role of predation risk for migratory decision-making and dynamics. PMID:26311158

  1. 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.

  2. Consistency and variation in phenotypic selection exerted by a community of seed predators.

    PubMed

    Benkman, Craig W; Smith, Julie W; Maier, Monika; Hansen, Leif; Talluto, Matt V

    2013-01-01

    Phenotypic selection that is sustained over time underlies both anagenesis and cladogenesis, but the conditions that lead to such selection and what causes variation in selection are not well known. We measured the selection exerted by three species of predispersal seed predators of lodgepole pine (Pinus contorta latifolia) in the South Hills, Idaho, and found that net selection on different cone and seed traits exerted by red crossbills (Loxia curvirostra) and cone borer moths (Eucosma recissoriana) over 10 years of seed crops was similar to that measured in another mountain range. We also found that the strength of selection increased as seed predation increased, which provides a mechanism for the correlation between the escalation of seed defenses and the density of seed predators. Red crossbills consume the most seeds and selection they exert accounts for much of the selection experienced by lodgepole pine, providing additional support for a coevolutionary arms race between crossbills and lodgepole pine in the South Hills. The third seed predator, hairy woodpeckers (Picoides villosus), consumed less than one-sixth as many seeds as crossbills. Across the northern Rocky Mountains, woodpecker abundance and therefore selective impact appears limited by the elevated seed defenses of lodgepole pine.

  3. Annual post-dispersal weed seed predation in contrasting field environments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  4. 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

  5. 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

  6. Simulated predator extinctions: predator identity affects survival and recruitment of oysters.

    PubMed

    O'Connor, Nessa E; Grabowski, Jonathan H; Ladwig, Laura M; Bruno, John F

    2008-02-01

    The rate of species loss is increasing at a global scale, and human-induced extinctions are biased toward predator species. We examined the effects of predator extinctions on a foundation species, the eastern oyster (Crassostrea virginica). We performed a factorial experiment manipulating the presence and abundance of three of the most common predatory crabs, the blue crab (Callinectes sapidus), stone crab (Menippe mercenaria), and mud crab (Panopeus herbstii) in estuaries in the eastern United States. We tested the effects of species richness and identity of predators on juvenile oyster survival, oyster recruitment, and organic matter content of sediment. We also manipulated the density of each of the predators and controlled for the loss of biomass of species by maintaining a constant mass of predators in one set of treatments and simultaneously using an additive design. This design allowed us to test the density dependence of our results and test for functional compensation by other species. The identity of predator species, but not richness, affected oyster populations. The loss of blue crabs, alone or in combination with either of the other species, affected the survival rate of juvenile oysters. Blue crabs and stone crabs both affected oyster recruitment and sediment organic matter negatively. Mud crabs at higher than ambient densities, however, could fulfill some of the functions of blue and stone crabs, suggesting a level of ecological redundancy. Importantly, the strong effects of blue crabs in all processes measured no longer occurred when individuals were present at higher-than-ambient densities. Their role as dominant predator is, therefore, dependent on their density within the system and the density of other species within their guild (e.g., mud crabs). Our findings support the hypothesis that the effects of species loss at higher trophic levels are determined by predator identity and are subject to complex intraguild interactions that are largely

  7. Ecological patterns and genetic analysis of post-dispersal seed predation in sunflower (Helianthus annuus) crop-wild hybrids.

    PubMed

    Dechaine, Jennifer M; Burger, Jutta C; Burke, John M

    2010-08-01

    Crop-wild hybridization has been documented in many cultivated species, but the ecological and genetic factors that influence the likelihood or rate that cultivar alleles will introgress into wild populations are poorly understood. Seed predation is one factor that could mitigate the spread of otherwise advantageous cultivar alleles into the wild by reducing seedling recruitment of crop-like individuals in hybrid populations. Seed predation has previously been linked to several seed characters that differ between cultivated and wild sunflower, such as seed size and oil content. In this study, seed morphological and nutritional characters were measured in a segregating population of sunflower crop-wild hybrids and wild and cultivated lines. Seed predation rates among lines were then assessed in the field. The relationship between seed predation and seed characters was investigated and quantitative trait loci (QTL) were mapped for all traits. There was no effect of seed type (hybrid vs. parents) on seed predation, although a trend toward more early predation of wild seeds was observed. Within the hybrids, seed predators preferred seeds that contained more oil and energy but were lower in fibre. The relationship between seed predation and oil content was supported by co-localized QTL for these traits on one linkage group. These results suggest that oil content may be a more important determinant of seed predation than seed size and provide molecular genetic evidence for this relationship. The cultivar allele was also found to increase predation at all QTL, indicating that post-dispersal seed predation may mitigate the spread of cultivar alleles into wild populations.

  8. 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.

  9. 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

    2016-10-15

    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.

  10. 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.

  11. 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

  12. 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.

  13. Seed dispersal and predation of Buchenavia tomentosa Eichler (Combretaceae) in a Cerrado sensu stricto, midwest Brazil.

    PubMed

    Farias, J; Sanchez, M; Abreu, M F; Pedroni, F

    2015-11-01

    The ecology of seed dispersal is critical to understand the patterns of distribution and abundance of plant species. We investigated seed dispersal aspects associated with the high abundance of Buchenavia tomentosa in the Serra Azul State Park (PESA). We estimated fruit production and conducted fruit removal experiments. We carried out diurnal and nocturnal observations on frugivory as well as germination tests. Fruiting occurred in the dry season and totaled 1,365,015 ± 762,670 fruits.ha-1. B. tomentosa fruits were utilized by eight animal species. The lowland tapir (Tapirus terrestris) was considered the main seed disperser. Leafcutter ants (Atta laevigata and Atta sexdens) participated in the seed cleaning and occasionally dispersed seeds. The beetle Amblycerus insuturatus, blue-and-yellow macaw (Ara ararauna) and red-and-green macaw (Ara chloropterus) were considered pre-dispersal seed predators. The seeds manually cleaned presented higher germination rate (100%) and speed index (4.2 seeds.d-1) than that of seeds with pulp. Germination of seeds found in tapirs'feces was 40%, while for the seeds without pulp it was 25%. The high abundance of B. tomentosa in the cerrado of PESA may be due to massive fruit production, low rates of seed predation, and efficient seed dispersal by tapirs, occurring before the rains which promote germination and recruitment of this species.

  14. 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.

  15. 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.

  16. Additive effects of herbivory, nectar robbing and seed predation on male and female fitness estimates of the host plant Ipomopsis aggregata.

    PubMed

    Irwin, Rebecca E; Brody, Alison K

    2011-07-01

    Many antagonistic species attack plants and consume specific plant parts. Understanding how these antagonists affect plant fitness individually and in combination is an important research focus in ecology and evolution. We examined the individual and combined effects of herbivory, nectar robbing, and pre-dispersal seed predation on male and female estimates of fitness in the host plant Ipomopsis aggregata. By examining the effects of antagonists on plant traits, we were able to tease apart the direct consumptive effects of antagonists versus the indirect effects mediated through changes in traits important to pollination. In a three-way factorial field experiment, we manipulated herbivory, nectar robbing, and seed predation. Herbivory and seed predation reduced some male and female fitness estimates, whereas plants tolerated the effects of robbing. The effects of herbivory, robbing, and seed predation were primarily additive, and we found little evidence for non-additive effects of multiple antagonists on plant reproduction. Herbivory affected plant reproduction through both direct consumptive effects and indirectly through changes in traits important to pollination (i.e., nectar and phenological traits). Conversely, seed predators primarily had direct consumptive effects on plants. Our results suggest that the effects of multiple antagonists on estimates of plant fitness can be additive, and investigating which traits respond to damage can provide insight into how antagonists shape plant performance.

  17. 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.

  18. 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.

  19. Scatterhoarding rodents favor higher predation risks for cache sites: The potential for predators to influence the seed dispersal process.

    PubMed

    Steele, Michael A; Rompré, Ghislain; Stratford, Jeffrey A; Zhang, Hongmao; Suchocki, Matthew; Marino, Shealyn

    2015-05-01

    Scatterhoarding rodents often place caches in the open where pilferage rates are reduced, suggesting that they tradeoff higher risks of predation for more secure cache sites. We tested this hypothesis in two study systems by measuring predation risks inferred from measures of giving-up densities (GUDs) at known cache sites and other sites for comparison. Rodent GUDs were measured with small trays containing 3 L of fine sand mixed with sunflower seeds. In the first experiment, we relied on a 2-year seed dispersal study in a natural forest to identify caches of eastern gray squirrels (Sciurus carolinensis) and then measured GUDs at: (i) these caches; (ii) comparable points along logs and rocks where rodent activity was assumed highest; and (iii) a set of random points. We found that GUDs and, presumably, predation risks, were higher at both cache and random points than those with cover. At the second site, we measured GUDs of eastern gray squirrels in an open park system and found that GUDs were consistently lowest at the base of the tree compared to more open sites, where previous studies show caching by squirrels to be highest and pilferage rates by naïve competitors to be lowest. These results confirm that predation risks can influence scatterhoarding decisions but that they are also highly context dependent, and that the landscape of fear, now so well documented in the literature, could potentially shape the temporal and spatial patterns of seedling establishment and forest regeneration in systems where scatterhoarding is common.

  20. Contrasting Foraging Patterns: Testing Resource-Concentration and Dilution Effects with Pollinators and Seed Predators

    PubMed Central

    Wenninger, Alexandria; Kim, Tania N.; Spiesman, Brian J.; Gratton, Claudio

    2016-01-01

    Resource concentration effects occur when high resource density patches attract and support more foragers than low density patches. In contrast, resource dilution effects can occur if high density patches support fewer consumers. In this study, we examined the foraging rates of pollinators and seed predators on two perennial plant species (Rudbeckia triloba and Verbena stricta) as functions of resource density. Specifically, we examined whether resource-dense patches (densities of flower and seeds on individual plants) resulted in greater visitation and seed removal rates, respectively. We also examined whether foraging rates were context-dependent by conducting the study in two sites that varied in resource densities. For pollinators, we found negative relationships between the density of flowers per plant and visitation rates, suggesting dilution effects. For seed predators, we found positive relationships consistent with concentration effects. Saturation effects and differences in foraging behaviors might explain the opposite relationships; most of the seed predators were ants (recruitment-based foragers), and pollinators were mostly solitary foragers. We also found that foraging rates were site-dependent, possibly due to site-level differences in resource abundance and consumer densities. These results suggest that these two plant species may benefit from producing as many flowers as possible, given high levels of pollination and low seed predation. PMID:27271673

  1. Contrasting Foraging Patterns: Testing Resource-Concentration and Dilution Effects with Pollinators and Seed Predators.

    PubMed

    Wenninger, Alexandria; Kim, Tania N; Spiesman, Brian J; Gratton, Claudio

    2016-06-03

    Resource concentration effects occur when high resource density patches attract and support more foragers than low density patches. In contrast, resource dilution effects can occur if high density patches support fewer consumers. In this study, we examined the foraging rates of pollinators and seed predators on two perennial plant species (Rudbeckia triloba and Verbena stricta) as functions of resource density. Specifically, we examined whether resource-dense patches (densities of flower and seeds on individual plants) resulted in greater visitation and seed removal rates, respectively. We also examined whether foraging rates were context-dependent by conducting the study in two sites that varied in resource densities. For pollinators, we found negative relationships between the density of flowers per plant and visitation rates, suggesting dilution effects. For seed predators, we found positive relationships consistent with concentration effects. Saturation effects and differences in foraging behaviors might explain the opposite relationships; most of the seed predators were ants (recruitment-based foragers), and pollinators were mostly solitary foragers. We also found that foraging rates were site-dependent, possibly due to site-level differences in resource abundance and consumer densities. These results suggest that these two plant species may benefit from producing as many flowers as possible, given high levels of pollination and low seed predation.

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

    PubMed

    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.

  3. 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

  4. Physical properties of fruit and seeds ingested by primate seed predators with emphasis on sakis and bearded sakis.

    PubMed

    Norconk, Marilyn A; Veres, Michael

    2011-12-01

    Several primate radiations exhibit dental adaptations that enable them to gain access to seeds embedded in well-protected fruit. To a database drawn from published sources in which hardness of fruit and seeds were tested in the field, we added an additional 100+ species of plants used as resources by pitheciin primates (specifically, South American white-faced sakis (Pithecia pithecia) and bearded sakis (Chiropotes spp.). This sample allowed us to compare hardness of fruit and seeds and deduce the relative incisive and masticatory capability of several primate taxa (New World monkeys, Old World monkeys, prosimians and chimpanzees). Pitheciins have very well developed and highly modified anterior dentition that they use in gaining access to mechanically-protected fruit. In addition, their molars bear thin, but decussated enamel that protects the tooth enamel from crack proliferation. The ability of sakis (Chiropotes spp. and Pithecia pithecia) to open fruit orally was comparable to larger-bodied Old World seed predators-Lophocebus and Cercocebus. But, baboons and chimpanzees masticate seeds that are two to three orders of magnitude harder than sakis or mangabeys. In spite of their puncture abilities, ∼40% of foods ingested by pitheciins were in the range of a ripe fruit eater (Ateles paniscus). This raises the possibility that pitheciins exemplify Liem's paradox, that is, "that phenotypic specialization [is] not accompanied by ecological specialization" (Robinson and Wilson, 1998:224). Last, we examined the possibility that seeds may serve as fallback resources for primate seed predators. While pericarp hardness may vary seasonally for some seed predators (e.g., mangabeys), our data on bearded sakis and white-faced sakis suggest that seeds are their primary resources year round and pericarp hardness is unrelated to seasonal variation in rainfall. Pitheciins evolved specialized dentition that affords them access to relatively abundant and high-quality resources, a

  5. Spatial and temporal patterns of carabid activity-density in cereals do not explain levels of predation on weed seeds.

    PubMed

    Saska, P; van der Werf, W; de Vries, E; Westerman, P R

    2008-04-01

    Seed predation is an important component of seed mortality of weeds in agro-ecosystems, but the agronomic use and management of this natural weed suppression is hampered by a lack of insight in the underlying ecological processes. In this paper, we investigate whether and how spatial and temporal variation in activity-density of granivorous ground beetles (Coleoptera: Carabidae) results in a corresponding pattern of seed predation. Activity-density of carabids was measured by using pitfall traps in two organic winter wheat fields from March to July 2004. Predation of seeds (Capsella bursa-pastoris, Lamium amplexicaule, Poa annua and Stellaria media) was assessed using seed cards at the same sites and times. As measured by pitfall traps, carabids were the dominant group of insects that had access to the seed cards. In the field, predation of the four different species of seed was in the order: C. bursa-pastoris>P. annua>S. media>L. amplexicaule; and this order of preference was confirmed in the laboratory using the dominant species of carabid. On average, seed predation was higher in the field interior compared to the edge, whereas catches of carabids were highest near the edge. Weeks with elevated seed predation did not concur with high activity-density of carabids. Thus, patterns of spatial and temporal variation in seed predation were not matched by similar patterns in the abundance of granivorous carabid beetles. The lack of correspondence is ascribed to effects of confounding factors, such as weather, the background density of seeds, the composition of the carabid community, and the phenology and physiological state of the beetles. Our results show that differences in seed loss among weed species may be predicted from laboratory trials on preference. However, predator activity-density, as measured in pitfall traps, is an insufficient predictor of seed predation over time and space within a field.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  7. Evidence of a component Allee effect driven by predispersal seed predation in a plant (Pedicularis rex, Orobanchaceae)

    PubMed Central

    Xia, Jing; Sun, ShiGuo; Liu, GuiHua

    2013-01-01

    A small or sparse population may suffer a reduction in fitness owing to Allee effects. Here, we explored effects of plant density on pollination, reproduction and predation in the alpine herb Pedicularis rex over two years. We did not detect a significant difference in the pollination rate or fecundity (fruit set and the initial seed set) before predation between sparse and dense patches in either year, indicating no pollination-driven Allee effect. However, dense patches experienced significantly fewer attacks by predispersal seed predators in both years, resulting in a significantly decreased realized fecundity (final seed set), suggesting a component Allee effect driven by predispersal seed predation. Predation-driven Allee effects have been predicted by many models and demonstrated for a range of animals, but there is scant evidence for such effects in plants. Our study provides strong evidence of a component Allee effect driven by predation in a plant species. PMID:23925832

  8. 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.

  9. Negative impacts of a vertebrate predator on insect pollinator visitation and seed output in Chuquiraga oppositifolia, a high Andean shrub.

    PubMed

    Muñoz, Alejandro A; Arroyo, Mary T K

    2004-01-01

    Studies on plant-pollinator interactions have largely neglected the potential negative effects of the predators of pollinators on seed output, even though anti-predatory behaviour of pollinators may affect visitation patterns, pollen transfer, and therefore potentially, plant reproductive output. We tested the hypothesis that the presence of lizards and insectivorous birds, by reducing pollinator visitation, can have significant negative effects on seed output in the insect-pollinated, genetically self-incompatible lower alpine Andean shrub, Chuquiraga oppositifolia (Asteraceae). The lower alpine belt supports a high density of territorial Liolaemus (Tropiduridae) lizards and low shrubs interspersed among rocks of varying sizes, the latter inhabited by lizards and commonly used by flycatchers Muscisaxicola (Tyrannidae) as perching sites. In a 2x2 factorial predator-exclusion experiment, visitation rates of the most frequent pollinators of C. oppositifolia (the satyrid butterfly Cosmosatyrus chilensis and the syrphid fly Scaeva melanostoma), the duration of pollinator visits, and seed output, were 2-4 times greater when lizards were excluded, while birds had no effect. In a natural experiment, visits by S. melanostoma were 9 times shorter, and pollinator visitation rates of C. chilensis and S. melanostoma, and C. oppositifolia seed output were 2-3 times lower on shrubs growing adjacent to lizard-occupied rocks compared to those growing distant from rocks. Our results, verified for additional Andean sites, suggest that lizard predators can alter the behaviour of pollinators and elicit strong top-down indirect negative effects on seed output. Such effects may be especially important in high alpine plant communities, where pollinator activity can be low and erratic, and pollen limitation has been reported.

  10. Sex-biased seed predation and the maintenance of females in a gynodioecious plant.

    PubMed

    Marshall, M; Ganders, F R

    2001-08-01

    We investigated genetic and ecological factors contributing to the maintenance of females in populations of the gynodioecious plant, Sidalcea hendersonii (Malvaceae). Our crossing experiments indicated that male sterility is controlled by a dominant nuclear allele. Nuclear determination of sex theoretically requires much higher female fitness to account for the high frequency of female plants often observed during surveys of S. hendersonii populations. Females were, in fact, shown to have higher fitness in an experimental population, producing more viable seed and surviving offspring than hermaphrodite plants. In natural populations, however, differences in viable seed production were not evident unless seed predation was considered. Sex-biased seed predation appears to play an important role in the maintenance of gynodioecy in S. hendersonii. In populations with high female frequencies, weevil larvae destroyed significantly more seeds from hermaphrodite plants than females, substantially reducing their seed production. To our knowledge, this study provides the first evidence that sex-biased predation may be responsible for high female frequencies in natural populations of a gynodioecious species.

  11. 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.

  12. Predation risk affects reproductive physiology and demography of elk.

    PubMed

    Creel, Scott; Christianson, David; Liley, Stewart; Winnie, John A

    2007-02-16

    Elk (Cervus elaphus) in the Greater Yellowstone Ecosystem alter patterns of aggregation, habitat selection, vigilance, and foraging in the presence of wolves (Canis lupus). Antipredator behaviors like these can reduce predation risk but are also likely to carry costs. Data from five elk populations studied for 16 site years showed that progesterone concentrations (from 1489 fecal samples) declined with the ratio of elk to wolves. In turn, progesterone concentrations were a good predictor of calf recruitment in the subsequent year. Together, these data suggest that wolves indirectly affect the reproductive physiology and the demography of elk through the costs of antipredator behavior.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  14. Population-level compensation by an invasive thistle thwarts biological control from seed predators

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Predispersal seed predators are often chosen as biocontrol agents because of their high impacts on plant fitness; however, they have a mixed record in realizing decreased plant population growth. Few studies have experimentally removed agents to explore their impact on weed population growth. Here...

  15. Effects of carbaryl-bran bait on trap-catch and seed predation by ground beetles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Carbaryl-bran bait is effective against grasshoppers without many impacts on non-target organisms, but ground beetles (Coleoptera: Carabidae) may be susceptible to these baits. Carabids are beneficial in agricultural settings as predators of insect pests and weed seeds. Carabid species composition a...

  16. [Predation, removal and seed dispersal in a wetland dominated by palms (Arecaceae)].

    PubMed

    Myers, Ronald L

    2013-09-01

    In the Tortuguero floodplains, Costa Rica, a significant number of trees such as Carapa guianensis, Pentaclethra mnacroloba and the palm Manicaria saccifera have floating seeds adapted to hydrocory, while others, such as the almendro Dipteryx oleifera and the raffia palm Raphia taedigera have heavy seeds that do not float. These species have differential distributions, and while C. guianensis, P macroloba and D. oleifera also grow on slopes away from the flood, the palms M saccifera and R. taedigera hardly occur outside the swamps, where they stand as the dominant species. To understand the differences in the micro-distribution of these tree species in waterlogged environments and differences in their seed adaptations, I did a series of experiments to compare the loss and germination of their seeds in the slope forest and in palm swamps in the region. Overall, seeds in the forest slope have higher removal rates than those in the M. saccifera and R. taedigera swamps. This last one exhibits the lowest seed loss of all three habitats. Also, differences in seed predation/removal were noticed between the two species of palms studied. Thus, seeds of M saccifera disappeared rapidly, regardless of density aggregation and location in the swamp. Removal rates in R. taedigera seeds were low in the raffia dominated swamp, where apparently, seed losses are slightly higher in the mounds of palm clumps than in the swamp floor. These observations suggest that both: flooding and microtopography determine, directly or indirectly, the fate of tree species within these wetlands. Restrictions on seed dispersal and the slow germination confine R. taedigera marshes and flooded places, whereas flooding and predators mediate in the distribution of the other tree species.

  17. When condition trumps location: seed consumption by fruit-eating birds removes pathogens and predator attractants

    PubMed Central

    Fricke, Evan C; Simon, Melissa J; Reagan, Karen M; Levey, Douglas J; Riffell, Jeffrey A; Carlo, Tomás A; Tewksbury, Joshua J

    2013-01-01

    Seed ingestion by frugivorous vertebrates commonly benefits plants by moving seeds to locations with fewer predators and pathogens than under the parent. For plants with high local population densities, however, movement from the parent plant is unlikely to result in ‘escape’ from predators and pathogens. Changes to seed condition caused by gut passage may also provide benefits, yet are rarely evaluated as an alternative. Here, we use a common bird-dispersed chilli pepper (Capsicum chacoense) to conduct the first experimental comparison of escape-related benefits to condition-related benefits of animal-mediated seed dispersal. Within chilli populations, seeds dispersed far from parent plants gained no advantage from escape alone, but seed consumption by birds increased seed survival by 370% – regardless of dispersal distance – due to removal during gut passage of fungal pathogens and chemical attractants to granivores. These results call into question the pre-eminence of escape as the primary advantage of dispersal within populations and document two overlooked mechanisms by which frugivores can benefit fruiting plants. PMID:23786453

  18. Rodent foraging is affected by indirect, but not by direct, cues of predation risk.

    SciTech Connect

    Orrock, John, L.; Danielson, Brent, J.; Brinkerhoff, R., Jory

    2004-01-01

    Behavioral Ecology Vol. 15 No. 3: 433 - 437 We used foraging trays to determine whether old field mice, Peromyscus polionotus , altered foraging in response to direct cues of predation risk (urine of native and nonnative predators) and indirect cues of predation risk (foraging microhabitat, precipitation, and moon illumination). The proportion of seeds remaining in each tray (a measure of the giving-up density [GUD]) was used to measure risk perceived by mice. Mice did not alter their GUD when presented with cues of native predators (bobcats, Lynx r ufus , and red foxes, Vulpes vulpes), recently introduced predators (coyotes, Canis latrans ), nonnative predators (ocelots, Leopardus pardalis ), a native herbivore (white-tailed deer, Odocoileus virginianus), or a water control. Rather, GUD was related to microhabitat: rodents removed more seeds from foraging trays sheltered beneath vegetative cover compared with exposed trays outside of cover. Rodents also removed more seeds during nights with precipitation and when moon illumination was low. Our results suggest that P. polionotus used indirect cues rather than direct cues to assess risk of vertebrate predation. Indirect cues may be more reliable than are direct scent cues for estimating risk from multiple vertebrate predators that present the most risk in open environments.

  19. 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.

  20. Gut passage and secondary metabolites alter the source of post-dispersal predation for bird-dispersed chili seeds.

    PubMed

    Fricke, Evan C; Haak, David C; Levey, Douglas J; Tewksbury, Joshua J

    2016-07-01

    Plants can influence the source and severity of seed predation through various mechanisms; the use of secondary metabolites for chemical defense, for example, is well documented. Gut passage by frugivores can also reduce mortality of animal-dispersed seeds, although this mechanism has gained far less attention than secondary metabolites. Apart from influencing the severity of seed predation, gut passage may also influence the source of seed predation. In Bolivia, we compared impacts of these two mechanisms, gut passage and secondary metabolites, on the source of seed predation in Capsicum chacoense, a wild chili species that is polymorphic for pungency (individual plants either produce fruits and seeds containing or lacking capsaicinoids). Using physical exclosures, we isolated seed removal by insects, mammals, and birds; seeds in the trials were from either pungent or non-pungent fruits and were either passed or not passed by seed-dispersing birds. Pungency had little influence on total short-term seed removal by animals, although prior work on this species indicates that capsaicin reduces mortality caused by fungi at longer time scales. Gut passage strongly reduced removal by insects, altering the relative impact of the three predator types. The weak impact of pungency on short-term predation contrasts with previous studies, highlighting the context dependence of secondary metabolites. The strong impact of gut passage demonstrates that this mechanism alone can influence which seed predators consume seeds, and that impacts of gut passage can be larger than those of secondary metabolites, which are more commonly acknowledged as a defense mechanism.

  1. Seed harvester ants (Polonomyrmex rugosus) as "pulse" predators

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seed harvesting ants, Pogonomyrmex rugosus, collected grass cicadas at a high rate (>5 min-1 taken into the nest) at one location where cicada emergence exceeded 3m-2. Dry conditions in the winter-spring resulted in no annual plants in the northern Chihuahuan Desert. P. rugosus colonies were inactiv...

  2. A Multi-species Assessment of Post-dispersal Seed Predation in the Central Chilean Andes

    PubMed Central

    MUÑOZ, ALEJANDRO A.; CAVIERES, LOHENGRIN A.

    2006-01-01

    • Background and Aims Post-dispersal seed predation in alpine communities has received little attention despite evidence that seeds removed by granivores can decrease plant recruitment into ecosystems. Moreover, few studies have assessed the effects of removal of seeds of a range of species after dispersal on the seeds remaining in ecosystems. A comparison was made of the magnitude of seed removal by ants and birds of nine different shrubby-, herbaceous- and cushion-plant species in the central Chilean Andes in order to assess the interactions between birds, ants and wind, and the types of seeds. • Methods A total of 324 soil-covered plates, each containing 50 seeds of one species, were placed in the field at an altitude of 2700 m and assigned to one of four treatments: control, exclusion of ants, birds, and both. The design also allowed the effects of wind to be assessed. Seed removal from plates was monitored over 20 d. • Key Results Mean accumulative seed removal by granivores averaged over all nine species combined was 25 %. However, large differences between species were evident, with limited seed removal (3–11 %) in three herbaceous species (Alstroemeria pallida, Sisyrinchium arenarium, Pozoa coriacea), moderate (18–33 %) in five species, including a shrub (Chuquiraga oppositifolia), two herbs (Taraxacum officinale, Rhodophiala rhodolirion), and two cushion-plants (Laretia acaulis, Azorella monantha), and substantial (78 %) in the shrub Anarthrophyllum cumingii. The magnitudes of losses caused by birds compared with ants did not differ for the majority of species, although removal by birds was greater than by ants in A. cumingii, and smaller for C. oppositifolia. • Conclusions Post-dispersal seed removal is shown to be an important cause of decreased potential plant species recruitment into alpine ecosystems. The substantial differences in the magnitude of seed losses to ants and birds demonstrate the need for evaluation of seed removal

  3. Beach almond (Terminalia catappa, Combretaceae) seed production and predation by scarlet macaws (Ara macao) and variegated squirrels (Sciurus variegatoides).

    PubMed

    Henn, Jonathan J; McCoy, Michael B; Vaughan, Christopher S

    2014-09-01

    Knowledge of ecological impacts of exotic beach almond (Terminalia catappa) in the central Pacific of Costa Rica are little known, but studies have found this species to be a potentially important food source for endangered scarlet macaws (Ara macao). In this study, reproductive phenology and seed predation by variegated squirrels (Sciurus variegatoides) and scarlet macaws were measured during March and April 2011 on beaches of central Pacific coastal Costa Rica. Seed productivity and predation levels were quantified on a weekly basis for 111 beach almond trees to assess the importance of beach almond as a food source for scarlet macaws and the extent of resource partitioning between seed predators. Seed production of the trees was great (about 194 272 seeds) and approximately 67% of seeds were predated by seed predators. Macaws consumed an estimated 49% of seeds while squirrels consumed 18%. Additionally, evidence of resource partitioning between squirrels and macaws was found. Scarlet macaws preferred to feed on the northern side and edge of the canopy while squirrels preferred to feed on the southern and inside parts of the canopy. Both species ate most seeds on the ocean side of the tree. Despite the status of this tree as an exotic species, the beach almond appears to be an important resource for scarlet macaw population recovery. The resource produced by this tree should be taken into account as reforestation efforts continue in Costa Rica.

  4. Herbivore and predator diversity interactively affect ecosystem properties in an experimental marine community.

    PubMed

    Douglass, James G; Duffy, J Emmett; Bruno, John F

    2008-06-01

    Interacting changes in predator and prey diversity likely influence ecosystem properties but have rarely been experimentally tested. We manipulated the species richness of herbivores and predators in an experimental benthic marine community and measured their effects on predator, herbivore and primary producer performance. Predator composition and richness strongly affected several community and population responses, mostly via sampling effects. However, some predators survived better in polycultures than in monocultures, suggesting complementarity due to stronger intra- than interspecific interactions. Predator effects also differed between additive and substitutive designs, emphasizing that the relationship between diversity and abundance in an assemblage can strongly influence whether and how diversity effects are realized. Changing herbivore richness and predator richness interacted to influence both total herbivore abundance and predatory crab growth, but these interactive diversity effects were weak. Overall, the presence and richness of predators dominated biotic effects on community and ecosystem properties.

  5. Climate affects predator control of an herbivore outbreak.

    PubMed

    Preisser, Evan L; Strong, Donald R

    2004-05-01

    Herbivore outbreaks and the accompanying devastation of plant biomass can have enormous ecological effects. Climate directly affects such outbreaks through plant stress or alterations in herbivore life-history traits. Large-scale variation in climate can indirectly affect outbreaks through trophic interactions, but the magnitude of such effects is unknown. On the California coast, rainfall in years during and immediately previous to mass lupine mortality was two-thirds that of years without such mortality. However, neither mature lupines nor their root-feeding herbivores are directly affected by annual variation in rainfall. By increasing soil moisture to levels characteristic of summers following El Niño/Southern Oscillation (ENSO) events, we increased persistence of a predator (the entomopathogenic nematode Heterorhabditis marelatus). This led to suppression of an outbreak of the herbivorous moth Hepialus californicus, indirectly protecting bush lupine (Lupinus arboreus). Our results are consistent with the marine-oriented Menge-Sutherland hypothesis (Menge and Sutherland 1987) that abiotic stress has greater effects on higher than on lower trophic levels. The mechanisms producing these results differ from those proposed by Menge-Sutherland, however, highlighting differences between trophic processes in underground and terrestrial/marine food webs. Our evidence suggests that herbivore outbreaks and mass lupine mortality are indirectly affected by ENSO's facilitation of top-down control in this food web.

  6. It's a predator-eat-parasite world: how characteristics of predator, parasite and environment affect consumption.

    PubMed

    Orlofske, Sarah A; Jadin, Robert C; Johnson, Pieter T J

    2015-06-01

    Understanding the effects of predation on disease dynamics is increasingly important in light of the role ecological communities can play in host-parasite interactions. Surprisingly, however, few studies have characterized direct predation of parasites. Here we used an experimental approach to show that consumption of free-living parasite stages is highly context dependent, with significant influences of parasite size, predator size and foraging mode, as well as environmental condition. Among the four species of larval trematodes and two types of predators (fish and larval damselflies) studied here, parasites with larger infective stages (size >1,000 μm) were most vulnerable to predation by fish, while small-bodied fish and damselflies (size <10 mm) consumed the most infectious stages. Small parasite species (size approx. 500 μm) were less frequently consumed by both fish and larval damselflies. However, these results depended strongly on light availability; trials conducted in the dark led to significantly fewer parasites consumed overall, especially those with a size of <1,000 μm, emphasizing the importance of circadian shedding times of parasite free-living stages for predation risk. Intriguingly, active predation functioned to help limit fishes' infection by directly penetrating parasite species. Our results are consistent with established theory developed for predation on zooplankton that emphasizes the roles of body size, visibility and predation modes and further suggest that consumer-resource theory may provide a predictive framework for when predators should significantly influence parasite transmission. These results contribute to our understanding of transmission in natural systems, the role of predator-parasite links in food webs and the evolution of parasite morphology and behavior.

  7. 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

  8. Seed predation by mammals and forest dominance by Quercus oleoides, a tropical lowland oak.

    PubMed

    Boucher, Douglas H

    1981-07-01

    Quercus oleoides Cham. and Schlecht is an unusual tree in several respects: it is an oak found in neotropical lowland forests, its distribution is not continuous but ratherdivided into many patches of various sizes, and it is a dominant in all the forests in which it occurs, attaining densities far higher than most species of tropical trees. This density pattern is related to the vulnerability of Q. oleoides acorns to predation by mammals. Observations of agoutis, deer, peccaries, squirrels, pocket mice and other seed consumers in Santa Rosa National Park, Costa Rica, showed that these mammals act only as predators, not dispersers, of Q. oleoides acorns. Experiments which involved placing acorns in deciduous forest where Q. oleoides does not occur, demonstrated that, due to high predation rates, the number of acorns produced by an isolated tree is far too low for adults to replace themselves.In oak forest, on the other hand, where the combined acorn crops of many oaks satiate the seed predators, acorn survivorship until germination is high enough to maintain the population. Furthermore, acorn survivorship in oak forest areas is inversely proportional to the apparent mammal density in those areas. Thus the pattern of forest dominance and patchy distribution is related to positively density-dependent acorn survivorship: where Q. oleoides is the forest dominant, it will survive, but if its density falls to the level typical of tropical trees, it will go locally extinct.

  9. Seed Predators, not Herbivores, Exert Natural Selection on Solidago spp. in an Urban Archipelago.

    PubMed

    Bode, R F; Gilbert, A B

    2016-02-01

    The effects of urbanization on biodiversity are well established, as a growing city will reduce the size and diversity of patches of native plants. Recolonization of old patches and discovery of new ones by arthropod herbivores should occur as predicted by island biogeography theory. Although colonization represents an increase in biodiversity, such arrivals may exert new forms of natural selection on plants through herbivory and seed predation. Using a single species of old-field aster (Solidago altissima L.), we found that the level of natural selection by seed predators and herbivores follows patterns of island biogeography, with lower amounts of damage on smaller islands, where there are fewer species, and hypothetically smaller populations of arthropods. We also found that in an urban system, levels of herbivory are far below the tolerance levels of Solidago, and that seed predators are likely to be the only arthropod to cause reduced fitness. The pattern seen also implies that as a patch of Solidago grows through clonal expansion, it will come under higher selective pressure.

  10. Fruit production and predispersal seed fall and predation in Rhamnus alaternus (Rhamnaceae)

    NASA Astrophysics Data System (ADS)

    Bas, Josep M.; Gómez, Crisanto; Pons, Pere

    2005-03-01

    In the reproductive cycle of fleshy-fruited plants, and before the seeds are dispersed, some fruits fall down or are predated on the branches. Here, we study the predispersal biology of Rhamnus alaternus in the north-east of the Iberian Peninsula over a 4-year period. Specifically, we examined fruit production, fructification and the phenology of ripening, together with the causes and the consequences of the predispersal loss in female plants. In addition, we evaluated the influence of the biometric traits and the spatial distribution of plants with regard to these aspects. The total estimated fruit production and fruiting phenology varied between localities and years, and there was no relation either to the plant biometry or to the spatial situation. The ripening period was between April and August, with a mean period of fruit permanence on the branches of 102 days. The maximum presence of ripe fruits was from early June to July, 54 days in average after fruit ripening began. The interaction of animals with the fruits has four important consequences: (a) losses in the initial production due to depredation of seeds, mainly by rodents; (b) direct fall of fruit and seeds under the cover of the female plants due to invertebrate predators of pulp; (c) reduction of the period of fruit availability on the branches; and (d) reduction of the proportion of ripe fruits on branches. In summary, the number of seeds available to be dispersed by frugivorous vertebrates is considerably reduced as a consequence of predispersal effects.

  11. Cascading effects of defaunation on the coexistence of two specialized insect seed predators.

    PubMed

    Peguero, Guille; Muller-Landau, Helene C; Jansen, Patrick A; Wright, S Joseph

    2017-01-01

    Identification of the mechanisms enabling stable coexistence of species with similar resource requirements is a central challenge in ecology. Such coexistence can be facilitated by species at higher trophic levels through complex multi-trophic interactions, a mechanism that could be compromised by ongoing defaunation. We investigated cascading effects of defaunation on Pachymerus cardo and Speciomerus giganteus, the specialized insect seed predators of the Neotropical palm Attalea butyracea, testing the hypothesis that vertebrate frugivores and granivores facilitate their coexistence. Laboratory experiments showed that the two seed parasitoid species differed strongly in their reproductive ecology. Pachymerus produced many small eggs that it deposited exclusively on the fruit exocarp (exterior). Speciomerus produced few large eggs that it deposited exclusively on the endocarp, which is normally exposed only after a vertebrate handles the fruit. When eggs of the two species were deposited on the same fruit, Pachymerus triumphed only when it had a long head start, and the loser always succumbed to intraguild predation. We collected field data on the fates of 6569 Attalea seeds across sites in central Panama with contrasting degrees of defaunation and wide variation in the abundance of vertebrate frugivores and granivores. Speciomerus dominated where vertebrate communities were intact, whereas Pachymerus dominated in defaunated sites. Variation in the relative abundance of Speciomerus across all 84 sampling sites was strongly positively related to the proportion of seeds attacked by rodents, an indicator of local vertebrate abundance.

  12. Social deprivation affects cooperative predator inspection in a cichlid fish

    PubMed Central

    Hesse, Saskia; Anaya-Rojas, Jaime M.; Frommen, Joachim G.; Thünken, Timo

    2015-01-01

    The social environment individuals are exposed to during ontogeny shapes social skills and social competence in group-living animals. Consequently, social deprivation has serious effects on behaviour and development in animals but little is known about its impact on cooperation. In this study, we examined the effect of social environment on cooperative predator inspection. Predator inspection behaviour is a complex behaviour, which is present in a variety of shoaling fish species. Often, two fish leave the safety of the group and inspect a potentially dangerous predator in order to gather information about the current predation risk. As predator inspection is highly risky, it is prone to conflicts and cheating. However, cooperation among individuals may reduce the individual predation risk. We investigated this complex social behaviour in juveniles of the cichlid fish Pelvicachromis taeniatus that were reared in two different social environments throughout development. Fish reared in a group inspected more often than isolation-reared fish and were more likely to cooperate, i.e. they conducted conjoint inspection of a predator. By contrast, isolation-reared fish were more likely to perform a single inspection without a companion. These results suggest an impairment of cooperative behaviour in isolation-reared fish most probably due to lack of social experience and resulting in lowered social skills needed in coordinated behaviour. PMID:26064616

  13. 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

  14. 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.

  15. Seasonally Varying Predation Behavior and Climate Shifts Are Predicted to Affect Predator-Prey Cycles.

    PubMed

    Tyson, Rebecca; Lutscher, Frithjof

    2016-11-01

    The functional response of some predator species changes from a pattern characteristic for a generalist to that for a specialist according to seasonally varying prey availability. Current theory does not address the dynamic consequences of this phenomenon. Since season length correlates strongly with altitude and latitude and is predicted to change under future climate scenarios, including this phenomenon in theoretical models seems essential for correct prediction of future ecosystem dynamics. We develop and analyze a two-season model for the great horned owl (Bubo virginialis) and snowshoe hare (Lepus americanus). These species form a predator-prey system in which the generalist to specialist shift in predation pattern has been documented empirically. We study the qualitative behavior of this predator-prey model community as summer season length changes. We find that relatively small changes in summer season length can have a profound impact on the system. In particular, when the predator has sufficient alternative resources available during the summer season, it can drive the prey to extinction, there can be coexisting stable states, and there can be stable large-amplitude limit cycles coexisting with a stable steady state. Our results illustrate that the impacts of global change on local ecosystems can be driven by internal system dynamics and can potentially have catastrophic consequences.

  16. Prey community structure affects how predators select for Mullerian mimicry.

    PubMed

    Ihalainen, Eira; Rowland, Hannah M; Speed, Michael P; Ruxton, Graeme D; Mappes, Johanna

    2012-06-07

    Müllerian mimicry describes the close resemblance between aposematic prey species; it is thought to be beneficial because sharing a warning signal decreases the mortality caused by sampling by inexperienced predators learning to avoid the signal. It has been hypothesized that selection for mimicry is strongest in multi-species prey communities where predators are more prone to misidentify the prey than in simple communities. In this study, wild great tits (Parus major) foraged from either simple (few prey appearances) or complex (several prey appearances) artificial prey communities where a specific model prey was always present. Owing to slower learning, the model did suffer higher mortality in complex communities when the birds were inexperienced. However, in a subsequent generalization test to potential mimics of the model prey (a continuum of signal accuracy), only birds that had foraged from simple communities selected against inaccurate mimics. Therefore, accurate mimicry is more likely to evolve in simple communities even though predator avoidance learning is slower in complex communities. For mimicry to evolve, prey species must have a common predator; the effective community consists of the predator's diet. In diverse environments, the limited diets of specialist predators could create 'simple community pockets' where accurate mimicry is selected for.

  17. Predator-induced morphological changes in an amphibian: predation by dragonflies affects tadpole shape and color.

    PubMed

    McCollum, S A; Leimberger, J D

    1997-02-01

    Predator-induced defenses are well studied in plants and invertebrate animals, but have only recently been recognized in vertebrates. Gray treefrog (Hylachrysoscelis) tadpoles reared with predatory dragonfly (Aeshnaumbrosa) larvae differ in shape and color from tadpoles reared in the absence of dragonflies. By exposing tadpoles to tail damage and the non-lethal presence of starved and fed dragonflies, we determined that these phenotypic differences are induced by non-contact cues present when dragonflies prey on Hyla. The induced changes in shape are in the direction that tends to increase swimming speed; thus, the induced morphology may help tadpoles evade predators. Altering morphology in response to predators is likely to influence interactions with other species in the community as well.

  18. Predation.

    ERIC Educational Resources Information Center

    Spain, James D.; Soldan, Theodore

    1983-01-01

    Describes two computer simulations of the predator-prey interaction in which students explore theories and mathematical equations involved in this biological process. The programs (for Apple II), designed for college level ecology, may be used in lecture/demonstrations or as a basis for laboratory assignments. A list of student objectives is…

  19. Coexistence of annual plants: generalist seed predation weakens the storage effect.

    PubMed

    Kuang, Jessica J; Chesson, Peter

    2009-01-01

    We investigate the effect of seed predation on the coexistence of competing annual plants. We demonstrate a role for predation that is opposite to the conventional wisdom that predation promotes coexistence by reducing the intensity of competition. In the common situation where competitive coexistence involves intraspecific competition exceeding interspecific competition, predation can undermine coexistence by reducing the overall magnitude of competition, replacing competition with "apparent competition" in a way that does not lead to differential intraspecific and interspecific effects. We demonstrate this outcome in the case where coexistence occurs by "the storage effect" in a variable environment. The storage effect arises when the environment interacts with competition to create opportunities for species to increase from low density. Critical to the storage effect is positive covariance between the response of population growth to the environment and its response to competition, when a species is at high density. This outcome prevents species at high density from taking advantage of favorable environmental conditions. A species at low density has lower covariance and can take advantage of favorable environmental conditions, giving it an advantage over a high-density species, fostering its recovery from low density. Hence, species coexistence is promoted. Here we find that density-dependent predation lowers population densities, and so weakens competition, replacing competition with apparent competition, which does not covary with the environment. As a consequence, covariance between environment and competition is weakened, reducing the advantage to a species at low density. The species still strongly interact through the combination of competition and apparent competition, but the reduced low-density advantage reduces their ability to coexist. Although this result is demonstrated specifically for the storage effect with a focus on annual plant communities

  20. 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.

  1. Predator density and timing of arrival affect reef fish community assembly.

    PubMed

    Stier, Adrian C; Geange, Shane W; Hanson, Kate M; Bolker, Benjamin M

    2013-05-01

    Most empirical studies of predation use simple experimental approaches to quantify the effects of predators on prey (e.g., using constant densities of predators, such as ambient vs. zero). However, predator densities vary in time, and these effects may not be well represented by studies that use constant predator densities. Although studies have independently examined the importance of predator density, temporal variability, and timing of arrival (i.e., early or late relative to prey), the relative contribution of these different predator regimes on prey abundance, diversity, and composition remains poorly understood. The hawkfish (Paracirrhites arcatus), a carnivorous coral reef fish, exhibits substantial variability in patch occupancy, density, and timing of arrival to natural reefs. Our field experiments demonstrated that effects of hawkfish on prey abundance depended on both hawkfish density and the timing of their arrival, but not on variability in hawkfish density. Relative to treatments without hawkfish, hawkfish presence reduced prey abundance by 50%. This effect increased with a doubling of hawkfish density (an additional 33% reduction), and when hawkfish arrived later during community development (a 34% reduction). Hawkfish did not affect within-patch diversity (species richness), but they increased between-patch diversity (beta) based on species incidence (22%), and caused shifts in species composition. Our results suggest that the timing of predator arrival can be as important as predator density in modifying prey abundance and community composition.

  2. Predation and landscape characteristics independently affect reef fish community organization.

    PubMed

    Stier, Adrian C; Hanson, Katharine M; Holbrook, Sally J; Schmitt, Russell J; Brooks, Andrew J

    2014-05-01

    Trophic island biogeography theory predicts that the effects of predators on prey diversity are context dependent in heterogeneous landscapes. Specifically, models predict that the positive effect of habitat area on prey diversity should decline in the presence of predators, and that predators should modify the partitioning of alpha and beta diversity across patchy landscapes. However, experimental tests of the predicted context dependency in top-down control remain limited. Using a factorial field experiment we quantify the effects of a focal predatory fish species (grouper) and habitat characteristics (patch size, fragmentation) on the partitioning of diversity and assembly of coral reef fish communities. We found independent effects of groupers and patch characteristics on prey communities. Groupers reduced prey abundance by 50% and gamma diversity by 45%, with a disproportionate removal of rare species relative to common species (64% and 36% reduction, respectively; an oddity effect). Further, there was a 77% reduction in beta diversity. Null model analysis demonstrated that groupers increased the importance of stochastic community assembly relative to patches without groupers. With regard to patch size, larger patches contained more fishes, but a doubling of patch size led to a modest (36%) increase in prey abundance. Patch size had no effect on prey diversity; however, fragmented patches had 50% higher species richness and modified species composition relative to unfragmented patches. Our findings suggest two different pathways (i.e., habitat or predator shifts) by which natural and/or anthropogenic processes can drive variation in fish biodiversity and community assembly.

  3. 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.

  4. 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.

  5. Reduced seed predation after invasion supports enemy release in a broad biogeographical survey.

    PubMed

    Castells, Eva; Morante, Maria; Blanco-Moreno, José M; Sans, F Xavier; Vilatersana, Roser; Blasco-Moreno, Anabel

    2013-12-01

    The Enemy Release (ER) hypothesis predicts an increase in the plant invasive capacity after being released from their associated herbivores or pathogens in their area of origin. Despite the large number of studies on biological invasions addressing this hypothesis, tests evaluating changes in herbivory on native and introduced populations and their effects on plant reproductive potential at a biogeographical level are relatively rare. Here, we tested the ER hypothesis on the South African species Senecio pterophorus (Asteraceae), which is native to the Eastern Cape, has expanded into the Western Cape, and was introduced into Australia (>70-100 years ago) and Europe (>30 years ago). Insect seed predation was evaluated to determine whether plants in the introduced areas were released from herbivores compared to plants from the native range. In South Africa, 25 % of the seedheads of sampled plants were damaged. Plants from the introduced populations suffered lower seed predation compared to those from the native populations, as expected under the ER hypothesis, and this release was more pronounced in the region with the most recent introduction (Europe 0.2 % vs. Australia 15 %). The insect communities feeding on S. pterophorus in Australia and Europe differed from those found in South Africa, suggesting that the plants were released from their associated fauna after invasion and later established new associations with local herbivore communities in the novel habitats. Our study is the first to provide strong evidence of enemy release in a biogeographical survey across the entire known distribution of a species.

  6. Inducible offences affect predator-prey interactions and life-history plasticity in both predators and prey.

    PubMed

    Kishida, Osamu; Costa, Zacharia; Tezuka, Ayumi; Michimae, Hirofumi

    2014-07-01

    Phenotypic plasticity can have strong impacts on predator-prey interactions. Although much work has examined the effects of inducible defences, less understood is how inducible offences in predators affect predator-prey interactions and predator and prey phenotypes. Here, we examine the impacts of an inducible offence on the interactions and life histories of a cohort of predatory Hynobius retardatus salamander larvae and their prey, Rana pirica tadpoles. We examined larval (duration, survival) and post-metamorphic (size) traits of both species after manipulating the presence/absence of tadpoles and salamanders with offensive (broadened gape width) or non-offensive phenotypes in pond enclosures. Offensive phenotype salamanders reduced tadpole survival and metamorph emergence by 58% compared to tadpole-only treatments, and by over 30% compared to non-offensive phenotypes. Average time to metamorphosis of frogs was delayed by 30% in the presence of salamanders, although this was independent of salamander phenotype. Thus, offensive phenotype salamanders reduced the number of tadpoles remaining in the pond over time by reducing tadpole survival, not by altering patterns of metamorph emergence. Offensive phenotypes also caused tadpoles to metamorphose 19% larger than no salamander treatments and 6% larger than non-offensive phenotype treatments. Pooled across salamander treatments, tadpoles caused salamanders to reach metamorphosis faster and larger. Moreover, in the presence of tadpoles, offensive phenotype salamanders metamorphosed 25% faster and 5% larger than non-offensive phenotype salamanders, but in their absence, neither their size nor larval period differed from non-offensive phenotype individuals. To our knowledge, this study is the first to demonstrate that inducible offences in predators can have strong impacts on predator and prey phenotypes across multiple life stages. Since early metamorphosis at a larger size has potential fitness advantages, the impacts

  7. Habitat stability and predation pressure affect temperament behaviours in populations of three-spined sticklebacks.

    PubMed

    Brydges, Nichola M; Colegrave, Nick; Heathcote, Robert J P; Braithwaite, Victoria A

    2008-03-01

    1. There is growing interest in the causes and consequences of animal temperaments. Temperament behaviours often have heritable components, but ecological variables can also affect them. Numerous variables are likely to differ between habitats, and these may interact to influence temperament behaviours. 2. Temperament behaviours may be correlated within populations (behavioural syndromes), although the underlying causes of such correlations are currently unclear. 3. We analysed three different temperament behaviours and learning ability in three-spined sticklebacks, Gasterosteus aculeatus, to determine how different ecological variables influence them both within and between populations. We selected populations from four ponds and four rivers that varied naturally in their exposure to predators. 4. High-predation river populations were significantly less bold than a high-predation pond and low-predation river populations, and low-predation pond populations were significantly less bold than a high-predation pond population. Within populations, temperament behaviours were correlated in one high-predation river population only. 5. These results suggest that multiple ecological factors can interact to affect temperament behaviours between populations, and also correlations in those behaviours within populations.

  8. 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

  9. Individual experience and evolutionary history of predation affect expression of heritable variation in fish personality and morphology.

    PubMed

    Dingemanse, Niels J; Van der Plas, Fons; Wright, Jonathan; Réale, Denis; Schrama, Maarten; Roff, Derek A; Van der Zee, Els; Barber, Iain

    2009-04-07

    Predation plays a central role in evolutionary processes, but little is known about how predators affect the expression of heritable variation, restricting our ability to predict evolutionary effects of predation. We reared families of three-spined stickleback Gasterosteus aculeatus from two populations-one with a history of fish predation (predator sympatric) and one without (predator naive)-and experimentally manipulated experience of predators during ontogeny. For a suite of ecologically relevant behavioural ('personality') and morphological traits, we then estimated two key variance components, additive genetic variance (VA) and residual variance (VR), that jointly shape narrow-sense heritability (h2=VA/(VA+VR)). Both population and treatment differentially affected VA versus VR, hence h2, but only for certain traits. The predator-naive population generally had lower VA and h2 values than the predator-sympatric population for personality behaviours, but not morphological traits. Values of VR and h2 were increased for some, but decreased for other personality traits in the predator-exposed treatment. For some personality traits, VA and h2 values were affected by treatment in the predator-naive population, but not in the predator-sympatric population, implying that the latter harboured less genetic variation for behavioural plasticity. Replication and experimental manipulation of predation regime are now needed to confirm that these population differences were related to variation in predator-induced selection. Cross-environment genetic correlations (rA) were tight for most traits, suggesting that predator-induced selection can affect the evolution of the same trait expressed in the absence of predators. The treatment effects on variance components imply that predators can affect evolution, not only by acting directly as selective agents, but also by influencing the expression of heritable variation.

  10. Plastic Hatching Timing by Red-Eyed Treefrog Embryos Interacts with Larval Predator Identity and Sublethal Predation to Affect Prey Morphology but Not Performance

    PubMed Central

    Touchon, Justin C.; Wojdak, Jeremy M.

    2014-01-01

    Many animals respond to predation risk by altering their morphology, behavior, or life-history. We know a great deal about the cues prey respond to and the changes to prey that can be induced by predation risk, but less is known about how plastic responses to predators may be affected by separate plastic responses occurring earlier in life, particularly during the embryonic period. Embryos of a broad array of taxa can respond to egg- or larval-stage risks by altering hatching timing, which may alter the way organisms respond to future predators. Using the red-eyed treefrog (Agalychnis callidryas), a model for understanding the effects of plasticity across life-stages, we assessed how the combined effects of induced variation in the timing of embryo hatching and variation in the larval predator community impacted tadpole morphology, pigmentation and swimming performance. We found that A. callidryas tadpoles developed deeper tail muscles and fins and darker pigmentation in response to fish predators, either when alone or in diverse community with other predators. Tadpoles altered morphology much less so to dragonfly naiads or water bugs. Interestingly, morphological responses to predators were also affected by induced differences in hatching age, with early and late-hatched tadpoles exhibiting different allometric relationships between tail height and body length in different predator environments. Beyond induced morphological changes, fish predators often damaged tadpoles’ tails without killing them (i.e., sublethal predation), but these tadpoles swam equally quickly to those with fully intact tails. This was due to the fact that tadpoles with more damaged tails increased tail beats to achieve equal swimming speed. This study demonstrates that plastic phenotypic responses to predation risk can be influenced by a complex combination of responses to both the embryo and larval environments, but also that prey performance can be highly resilient to sublethal predation

  11. 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  13. Seed predation and fruit damage of Solanum lycocarpum (Solanaceae) by rodents in the cerrado of central Brazil

    NASA Astrophysics Data System (ADS)

    Briani and, Denis C., Jr.; Guimarães, Paulo R.

    2007-01-01

    Although neotropical savannas and grasslands, collectively referred to as cerrado, are rich in seed-eating species of rodents, little is known about seed predation and its determinants in this habitat. In this study, we investigated seed predation and damage to fruits of the widespread shrub Solanum lycocarpum. In addition, the influence of two possible determinants (distance from the parental plant and total crop size) on the feeding behaviour of Oryzomys scotti (Rodentia, Sigmodontinae) was also examined. O. scotti were captured more frequently close to the shrubs or on shrub crops, indicating that these rodents were attracted to the shrubs and that seed predation was probably distance-dependent. Moreover, the proportion of damaged fruit on the plant decreased as the total crop size increased; consequently, more productive plants were attacked proportionally less by rodents. This pattern of fruit damage may reflect predator satiation caused by the consumption of a large amount of pulp. Alternatively, secondary metabolites in S. lycocarpum fruits may reduce the pulp consumption per feeding event, thereby limiting the number of fruits damaged.

  14. Elevated CO2 affects predator-prey interactions through altered performance.

    PubMed

    Allan, Bridie J M; Domenici, Paolo; McCormick, Mark I; Watson, Sue-Ann; Munday, Philip L

    2013-01-01

    Recent research has shown that exposure to elevated carbon dioxide (CO2) affects how fishes perceive their environment, affecting behavioral and cognitive processes leading to increased prey mortality. However, it is unclear if increased mortality results from changes in the dynamics of predator-prey interactions or due to prey increasing activity levels. Here we demonstrate that ocean pCO2 projected to occur by 2100 significantly effects the interactions of a predator-prey pair of common reef fish: the planktivorous damselfish Pomacentrus amboinensis and the piscivorous dottyback Pseudochromis fuscus. Prey exposed to elevated CO2 (880 µatm) or a present-day control (440 µatm) interacted with similarly exposed predators in a cross-factored design. Predators had the lowest capture success when exposed to elevated CO2 and interacting with prey exposed to present-day CO2. Prey exposed to elevated CO2 had reduced escape distances and longer reaction distances compared to prey exposed to present-day CO2 conditions, but this was dependent on whether the prey was paired with a CO2 exposed predator or not. This suggests that the dynamics of predator-prey interactions under future CO2 environments will depend on the extent to which the interacting species are affected and can adapt to the adverse effects of elevated CO2.

  15. Elevated CO2 Affects Predator-Prey Interactions through Altered Performance

    PubMed Central

    Allan, Bridie J. M.; Domenici, Paolo; McCormick, Mark I.; Watson, Sue-Ann; Munday, Philip L.

    2013-01-01

    Recent research has shown that exposure to elevated carbon dioxide (CO2) affects how fishes perceive their environment, affecting behavioral and cognitive processes leading to increased prey mortality. However, it is unclear if increased mortality results from changes in the dynamics of predator-prey interactions or due to prey increasing activity levels. Here we demonstrate that ocean pCO2 projected to occur by 2100 significantly effects the interactions of a predator-prey pair of common reef fish: the planktivorous damselfish Pomacentrus amboinensis and the piscivorous dottyback Pseudochromis fuscus. Prey exposed to elevated CO2 (880 µatm) or a present-day control (440 µatm) interacted with similarly exposed predators in a cross-factored design. Predators had the lowest capture success when exposed to elevated CO2 and interacting with prey exposed to present-day CO2. Prey exposed to elevated CO2 had reduced escape distances and longer reaction distances compared to prey exposed to present-day CO2 conditions, but this was dependent on whether the prey was paired with a CO2 exposed predator or not. This suggests that the dynamics of predator-prey interactions under future CO2 environments will depend on the extent to which the interacting species are affected and can adapt to the adverse effects of elevated CO2. PMID:23484032

  16. 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.

  17. 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.

  18. Interactions between benthic predators and zooplanktonic prey are affected by turbulent waves.

    PubMed

    Robinson, H E; Finelli, C M; Koehl, M A R

    2013-11-01

    Predators capture prey in complex and variable environments. In the ocean, bottom-dwelling (benthic) organisms are subjected to water currents, waves, and turbulent eddies. For benthic predators that feed on small animals carried in the water (zooplankton), flow not only delivers prey, but can also shape predator-prey interactions. Benthic passive suspension feeders collect prey delivered by movement of ambient water onto capture-surfaces, whereas motile benthic predators, such as burrow-dwelling fish, dart out to catch passing zooplankton. How does the flow of ambient water affect these contrasting modes of predation by benthic zooplanktivores? We studied the effects of turbulent, wavy flow on the encounter, capture, and retention of motile zooplanktonic prey (copepods, Acartia spp.) by passive benthic suspension feeders (sea anemones, Anthopleura elegantissima). Predator-prey interactions were video-recorded in a wave-generating flume under two regimes of oscillating flow with different peak wave velocities and levels of turbulent kinetic energy ("weak" and "strong" waves). Rates of encounter (number of prey passing through a sea anemone's capture zone per time), capture (prey contacting and sticking to tentacles per time), and retention (prey retained on tentacles, without struggling free or washing off, per time) were measured at both strengths of waves. Strong waves enhanced encounter rates both for dead copepods and for actively swimming copepods, but there was so much variability in the behavior of the live prey that the effect of wave strength on encounter rates was not significant. Trapping efficiency (number of prey retained per number encountered) was the same in both flow regimes because, although fewer prey executed maneuvers to escape capture in strong waves, more of the captured prey was washed off the predators' tentacles. Although peak water velocities and turbulence of waves did not affect feeding rates of passive suspension-feeding sea anemones

  19. Predator cues and an herbicide affect activity and emigration in an agrobiont wolf spider.

    PubMed

    Wrinn, Kerri M; Evans, Samuel C; Rypstra, Ann L

    2012-04-01

    Animals use chemical cues for signaling between species. However, anthropogenic chemicals might interrupt this natural chemical information flow, with potential impacts on predator-prey interactions. Our goal was to explore how Buccaneer® Plus, a common herbicide similar to Round-up® (active ingredient glyphosate), affected the interactions between intraguild predators. The wolf spider Pardosa milvina (Hentz, 1844) is numerically dominant in agricultural systems across the eastern United States, and often falls prey to or competes with the larger wolf spider, Hogna helluo (Walckenaer, 1837) and/or the carabid beetle, Scarites quadriceps (Chaudoir, 1843). We tested the effects of chemical cues from these intraguild predators and exposure to herbicide on the activity, emigration, and survival of P. milvina using a full-factorial laboratory experiment. Both predator cues and herbicide led to a decrease in movement by P. milvina. However, although H. helluo cues alone decreased movement, S. quadriceps cues only decreased movement when combined with herbicide. These results indicate that predation risk and herbicide application likely interact in complex ways to affect the movement of a major arthropod predator in agricultural systems, and thus may have complex effects on the food web.

  20. Zebra mussels affect benthic predator foraging success and habitat choice on soft sediments.

    PubMed

    Beekey, M A; McCabe, D J; Marsden, J E

    2004-09-01

    The introduction of zebra mussels ( Dreissena spp.) to North America has resulted in dramatic changes to the complexity of benthic habitats. Changes in habitat complexity may have profound effects on predator-prey interactions in aquatic communities. Increased habitat complexity may affect prey and predator dynamics by reducing encounter rates and foraging success. Zebra mussels form thick contiguous colonies on both hard and soft substrates. While the colonization of substrata by zebra mussels has generally resulted in an increase in both the abundance and diversity of benthic invertebrate communities, it is not well known how these changes affect the foraging efficiencies of predators that prey on benthic invertebrates. We examined the effect of zebra mussels on the foraging success of four benthic predators with diverse prey-detection modalities that commonly forage in soft substrates: slimy sculpin ( Cottus cognatus), brown bullhead ( Ameirus nebulosus), log perch ( Percina caprodes), and crayfish ( Orconectes propinquus). We conducted laboratory experiments to assess the impact of zebra mussels on the foraging success of predators using a variety of prey species. We also examined habitat use by each predator over different time periods. Zebra mussel colonization of soft sediments significantly reduced the foraging efficiencies of all predators. However, the effect was dependent upon prey type. All four predators spent more time in zebra mussel habitat than in either gravel or bare sand. The overall effect of zebra mussels on benthic-feeding fishes is likely to involve a trade-off between the advantages of increased density of some prey types balanced against the reduction in foraging success resulting from potential refugia offered in the complex habitat created by zebra mussels.

  1. Small but powerful: top predator local extinction affects ecosystem structure and function in an intermittent stream.

    PubMed

    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

  2. The mechanical defence advantage of small seeds.

    PubMed

    Fricke, Evan C; Wright, S Joseph

    2016-08-01

    Seed size and toughness affect seed predators, and size-dependent investment in mechanical defence could affect relationships between seed size and predation. We tested how seed toughness and mechanical defence traits (tissue density and protective tissue content) are related to seed size among tropical forest species. Absolute toughness increased with seed size. However, smaller seeds had higher specific toughness both within and among species, with the smallest seeds requiring over 2000 times more energy per gram to break than the largest seeds. Investment in mechanical defence traits varied widely but independently of the toughness-mass allometry. Instead, a physical scaling relationship confers a toughness advantage on small seeds independent of selection on defence traits and without a direct cost. This scaling relationship may contribute to seed size diversity by decreasing fitness differences among large and small seeds. Allometric scaling of toughness reconciles predictions and conflicting empirical relationships between seed size and predation.

  3. 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

  4. 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.

  5. Interspecific and annual variation in pre-dispersal seed predation by a granivorous bird in two East Asian hackberries, Celtis biondii and Celtis sinensis.

    PubMed

    Yoshikawa, T; Masaki, T; Isagi, Y; Kikuzawa, K

    2012-05-01

    Pre-dispersal seed predation by granivorous birds has potential to limit fruit removal and subsequent seed dispersal by legitimate avian seed dispersers in bird-dispersed plants, especially when the birds form flocks. We monitored pre-dispersal seed predation by the Japanese grosbeak, Eophona personata, of two bird-dispersed hackberry species (Cannabaceae), Celtis biondii (four trees) and Celtis sinensis (10 trees), for 3 years (2005, 2007 and 2008) in a fragmented forest in temperate Japan. Throughout the 3 years, predation was more intense on C. biondii, which, as a consequence, lost a larger part of its fruit crop. Grosbeaks preferred C. biondii seeds that had a comparatively lower energy content and lower hardness than C. sinensis, suggesting an association between seed hardness and selective foraging by grosbeaks. In C. biondii, intensive predation markedly reduced fruit duration and strongly limited fruit removal by seed dispersers, especially in 2007 and 2008. In C. sinensis, seed dispersers consumed fruits throughout the fruiting seasons in all 3 years. In C. biondii, variation in the timing of grosbeak migration among years was associated with annual variation in this bird's effects on fruit removal. Our results demonstrate that seed predation by flocks of granivorous birds can dramatically disrupt seed dispersal in fleshy-fruited plants and suggest the importance of understanding their flocking behaviour.

  6. Interactions between a pollinating seed predator and its host plant: the role of environmental context within a population

    PubMed Central

    Kula, Abigail A R; Castillo, Dean M; Dudash, Michele R; Fenster, Charles B

    2014-01-01

    Plant–insect interactions often are important for plant reproduction, but the outcome of these interactions may vary with environmental context. Pollinating seed predators have positive and negative effects on host plant reproduction, and the interaction outcome is predicted to vary with density or abundance of the partners. We studied the interaction between Silene stellata, an herbaceous perennial, and Hadena ectypa, its specialized pollinating seed predator. Silene stellata is only facultatively dependent upon H. ectypa for pollination because other nocturnal moth co-pollinators are equally effective at pollen transfer. We hypothesized that for plants without conspecific neighbors, H. ectypa would have higher visitation rates compared to co-pollinators, and the plants would experience lower levels of H. ectypa pollen deposition. We predicted similar oviposition throughout the study site but greater H. ectypa predation in the area without conspecific neighbors compared to plants embedded in a naturally high density area. We found that H. ectypa had consistently higher visitation than moth co-pollinators in all host plant contexts. However, H. ectypa pollinator importance declined in areas with low conspecific density because of reduced pollen deposition, resulting in lower seed set. Conversely, oviposition was similar across the study site independent of host plant density. Greater likelihood of very high fruit predation combined with lower pollination by H. ectypa resulted in reduced S. stellata female reproductive success in areas with low conspecific density. Our results demonstrate local context dependency of the outcomes of pollinating seed predator interactions with conspecific host plant density within a population. PMID:25165527

  7. 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

  8. Distribution and abundance of predators that affect duck production--prairie pothole region

    USGS Publications Warehouse

    Sargeant, A.B.; Greenwood, R.J.; Sovada, M.A.; Shaffer, T.L.

    1993-01-01

    During 1983-88, the relative abundance of 18 species and species-groups of mammalian and avian predators affecting duck production in the prairie pothole region was determined in 33 widely scattered study areas ranging in size from 23-26 km2. Accounts of each studied species and species-group include habitat and history, population structure and reported densities, and information on distribution and abundance from the present study. Index values of undetected, scarce, uncommon, common, or numerous were used to rate abundance of nearly all species in each study area. Principal survey methods were livetrapping of striped skunks (Mephitis mephitis) and Franklin's ground squirrels (Spermophilus franklinii), systematic searches for carnivore tracks in quarter sections (0.65 km2), daily records of sightings of individual predator species, and systematic searches for occupied nests of tree-nesting avian predators. Abundances of predators in individual areas were studied 1-3 years.The distribution and abundance of predator species throughout the prairie pothole region have undergone continual change since settlement of the region by Europeans in the late 1800's. Predator populations in areas we studied differed markedly from those of pristine times. The changes occurred from habitat alterations, human-inflicted mortality of predators, and interspecific relations among predator species. Indices from surveys of tracks revealed a decline in the abundance of red foxes (Vulpes vulpes) and an albeit less consistent decline in the abundance of raccoons (Procyon lotor) with an increase in the abundance of coyotes (Canis latrans). Records of locations of occupied nests revealed great horned owls (Bubo virginianus) and red-tailed hawks (Buteo jamaicensis) tended to nest 0.5 km apart, and American crows (Corvus brachyrhynchos) tended to avoid nesting 0.5 km of nests of red-tailed hawks. Excluding large gulls, for which no measurements of abundance were obtained, the number of

  9. Phenotypic Selection Exerted by a Seed Predator Is Replicated in Space and Time and among Prey Species.

    PubMed

    Benkman, Craig W; Mezquida, Eduardo T

    2015-11-01

    Although consistent phenotypic selection arising from biotic interactions is thought to be the primary cause of adaptive diversification, studies documenting such selection are relatively few. Here we analyze 12 episodes of phenotypic selection exerted by a predispersal seed predator, the red crossbill (Loxia curvirostra complex), on five species of pines (Pinus). We find that even though the intensity of selection for some traits increased with the strength of the interaction (i.e., proportion of seeds eaten), the relative strength of selection exerted by crossbills on cone and seed traits is replicated across space and time and among species. Such selection (1) can account for repeated patterns of conifer cone evolution and escalation in seed defenses with time and (2) suggests that variation in selection is less the result of variation intrinsic to pairwise biotic interactions than, for example, variation in relative densities of the interacting species, community context, and abiotic factors.

  10. The impact of specialist and generalist pre-dispersal seed predators on the reproductive output of a common and a rare Euphorbia species

    NASA Astrophysics Data System (ADS)

    Boieiro, Mário; Rego, Carla; Serrano, Artur R. M.; Espadaler, Xavier

    2010-03-01

    Pre-dispersal seed predators can have a severe impact on the reproductive output of their hosts, which can translate into negative effects on population dynamics. Here we compared the losses due to specialist and generalist insect seed predators in two Euphorbia species, a rare ( Euphorbia welwitschii) and a common one ( Euphorbia characias). Pre-dispersal losses to specialist seed-wasps ( Eurytoma jaltica) and generalist hemipterans ( Cydnus aterrimus and Dicranocephalus agilis) were on average higher for the rare E. welwitschii than for its widespread congener. In both Euphorbia species, the variation in losses to specialist and generalist seed predators was not related with traits indicative of plant size, fecundity, or isolation. Nevertheless, the temporal variation in losses to seed-wasps seemed to be intimately associated with the magnitude of yearly variation in fruit production. The impact of seed-wasps and hemipterans on the reproductive output of both Euphorbia species was additive, though there was evidence for infochemical-mediated interference at the fruit level. The moderate levels of seed predation in E. welwitschii, together with the results from the comparative analysis with its widespread congener, suggest that insect seed predation is not a causal effect of plant rarity.

  11. Reproduction, pollination and seed predation of Senna multijuga (Fabaceae) in two protected areas in the Brazilian Atlantic forest.

    PubMed

    Wolowski, Marina; Freitas, Leandro

    2011-12-01

    One important subject is to determine the effectiveness of conservation areas, where different management categories are being applied, to maintain effective sexual reproduction in plants and their interactions with animal groups. To evaluate this issue, we compared the phenology, reproductive success, pollination and pre-dispersal seed predation of the legume tree Senna multijuga in two differently managed protected areas in Southeastern Brazil: the Itatiaia National Park and the Environmental Protection Area of Serrinha do Alambari, from December 2007 to December 2008. Vegetative and reproductive phenodinamycs were registered monthly in 80 individuals; other evaluations included 104 observation hours for pollination (March-May 2008) in 51 inflorescences; besides, fruit counts, fecundity and seed predation. Sexual reproduction of S. multijuga depends on the transfer of pollen by large bees (Bombus, Centris, Epicharis and Xylocopa), as the species is self-incompatible. Bruchidae species of the genus Acanthoscelides and Sennius predate seeds. Vegetative and reproductive phenodynamics differed among sites. Our results indicated that ecological interactions were lower at the protected area, but the reproductive processes in S. multijuga were not ruptured or critically degraded. This reinforces the idea that landscape areas with intermediate levels of protection, such as environmental protection areas, are suitable as buffer zones, and thus, relevant to the conservation of ecological processes when associated with more strictly protected areas.

  12. Phylogeography of specialist weevil Trichobaris soror: a seed predator of Datura stramonium.

    PubMed

    De-la-Mora, Marisol; Piñero, Daniel; Núñez-Farfán, Juan

    2015-12-01

    Can the genetic structure of a specialist weevil be explained by the geological history of their distribution zone? We analyze the genetic variation of the weevil Trichobaris soror, a specialist seed predator of Datura stramonium, in order to address this question. For the phylogeographic analysis we used the COI gene, and assessed species identity in weevil populations through geometric morphometric approach. In total, we found 53 haplotypes in 413 samples, whose genetic variation supports the formation of three groups: (1) the Transmexican Volcanic Belt (TVB group), (2) the Sierra Madre Sur (SMS group) and (3) the Balsas Basin (BB group). The morphometric analysis suggests that BB group is probably not T. soror. Our results have two implications: first, the phylogeographic pattern of T. soror is explained by both the formation of the geological provinces where it is currently distributed and the coevolution with its host plant, because the TVB and SMS groups could be separated due to the discontinuity of altitude between the geological provinces, but the recent population expansion of TVB group and the high frequency of only one haplotype can be due to specialization to the host plant. Second, we report a new record of a different species of weevil in BB group parasitizing D. stramonium fruits.

  13. Caterpillar seed predators mediate shifts in selection on flowering phenology in their host plant.

    PubMed

    Valdés, Alicia; Ehrlén, Johan

    2017-01-01

    Variation in selection among populations and years has important implications for evolutionary trajectories of populations. Yet, the agents of selection causing this variation have rarely been identified. Selection on the time of reproduction within a season in plants might differ both among populations and among years, and selection can be mediated by both mutualists and antagonists. We investigated if differences in the direction of phenotypic selection on flowering phenology among 20 populations of Gentiana pneumonanthe during 2 yr were related to the presence of the butterfly seed predator Phengaris alcon, and if butterfly incidence was associated with the abundance of the butterfly's second host, Myrmica ants. In plant populations without the butterfly, phenotypic selection favored earlier flowering. In populations where the butterfly was present, caterpillars preferentially attacked early-flowering individuals, shifting the direction of selection to favoring later flowering. Butterfly incidence in plant populations increased with ant abundance. Our results demonstrate that antagonistic interactions can shift the direction of selection on flowering phenology, and suggest that such shifts might be associated with differences in the community context.

  14. Bird predation affects diurnal and nocturnal web-building spiders in a Mediterranean citrus grove

    NASA Astrophysics Data System (ADS)

    Mestre, L.; Garcia, N.; Barrientos, J. A.; Espadaler, X.; Piñol, J.

    2013-02-01

    Spiders and birds can greatly decrease insect populations, but birds also limit spider densities in some habitats. Bird predation is thought to be one of the causes behind nocturnal activity in spiders, so night-active spiders that hide in retreats during the day should be less affected by bird foraging than day-active spiders. However, this hypothesis has not yet been tested. We investigated the importance of bird predation on the spider community of a Mediterranean organic citrus grove. We excluded birds by placing net cages over the trees and we conducted visual searches in the canopies to sample web-building spiders. As there are many nocturnal species in the family Araneidae, we conducted searches both by day and by night to compare the abundance of active araneids in these two time periods. We sampled the tree trunks with cardboard bands to collect hunting spiders. In bird-excluded canopies there were more spiders of the families Araneidae and Theridiidae. There were higher numbers of active Araneidae at night, but these were just as negatively affected by bird predation as day-active Araneidae, so there was no evidence of nocturnal activity serving as an anti-predator strategy. We did not find any negative impact of birds on hunting spiders. Our results contrast with other studies reporting a negative effect of birds on hunting but not on web-building spiders.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. Perceived risk of predation affects reproductive life-history traits in Gambusia holbrooki, but not in Heterandria formosa.

    PubMed

    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.

  1. Feeding behaviour of an intertidal snail: Does past environmental stress affect predator choices and prey vulnerability?

    NASA Astrophysics Data System (ADS)

    Gestoso, Ignacio; Arenas, Francisco; Olabarria, Celia

    2015-03-01

    Predation is one of the most important factors in determining structure and dynamics of communities on intertidal rocky shores. Such regulatory role may be of special relevance in novel communities resulting from biological invasions. Non-indigenous species frequently escape natural predators that limit their distribution and abundance in the native range. However, biological interactions also can limit the establishment and spread of non-native populations. There is a growing concern that climate change might affect predator-prey interactions exacerbating the ecological impacts of non-indigenous species. However, mechanisms underlying such interactions are poorly understood in marine ecosystems. Here, we explored if past environmental stress, i.e., increasing temperature and decreasing pH, could affect the vulnerability of two mussel prey, the native Mytilus galloprovincialis and the non-indigenous Xenostrobus securis, to predation by the native dogwhelk Nucella lapillus. In addition, we evaluated the consequences on the feeding behaviour of N. lapillus. First, we exposed monospecific assemblages of each mussel species to combined experimental conditions of increasing temperature and decreasing pH in mesocosms for 3 weeks. Then assemblages were placed on a rocky shore and were enclosed in cages with dogwhelks where they remained for 3 weeks. Despite the lack of preference, consumption was much greater on the native than on the invasive mussels, which barely were consumed by dogwhelks. However, this trend was diverted when temperature increased. Thus, under a coastal warming scenario shifts in dogwhelks feeding behaviour may help to contain invader's populations, especially in estuarine areas where these predators are abundant.

  2. Negative synergism of rainfall patterns and predators affects frog egg survival.

    PubMed

    Touchon, Justin Charles; Warkentin, Karen Michelle

    2009-07-01

    1. The importance of rainfall is recognized in arid habitats, but has rarely been explored in ecosystems not viewed as rainfall limited. In addition, most attempts to study how rainfall affects organismal survival have focused on long-term rainfall metrics (e.g. monthly or seasonal patterns) instead of short-term measures. For organisms that are short lived or are sensitive to desiccation, short-term patterns of rainfall may provide insight to understanding what determines survival in particular habitats. 2. We monitored daily rainfall and survival of arboreal eggs of the treefrog Dendropsophus ebraccatus at two ponds during the rainy season in central Panama. Desiccation and predation were the primary sources of egg mortality and their effects were not independent. Rainfall directly reduced desiccation mortality by hydrating and thickening the jelly surrounding eggs. In addition, rainfall reduced predation on egg clutches. 3. To elucidate the mechanism by which rainfall alters predation, we exposed experimentally hydrated and dehydrated egg clutches to the two D. ebraccatus egg predators most common at our site, ants and social wasps. Ants and wasps preferentially preyed on dehydrated clutches and ants consumed dehydrated eggs three times faster than hydrated eggs. 4. Rainfall patterns are expected to change and the responses of organisms that use rainfall as a reliable cue to reproduce may prove maladaptive. If rainfall becomes more sporadic, as is predicted to happen during this century, it may have negative consequences for desiccation-sensitive organisms.

  3. 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.

  4. Short-term exposure to predation affects body elemental composition, climbing speed and survival ability in Drosophila melanogaster

    PubMed Central

    Eichler Inwood, Sarah; Trakimas, Giedrius; Krams, Ronalds; Burghardt, Gordon M.; Butler, David M.; Luoto, Severi; Krama, Tatjana

    2016-01-01

    Factors such as temperature, habitat, larval density, food availability and food quality substantially affect organismal development. In addition, risk of predation has a complex impact on the behavioural and morphological life history responses of prey. Responses to predation risk seem to be mediated by physiological stress, which is an adaptation for maintaining homeostasis and improving survivorship during life-threatening situations. We tested whether predator exposure during the larval phase of development has any influence on body elemental composition, energy reserves, body size, climbing speed and survival ability of adult Drosophila melanogaster. Fruit fly larvae were exposed to predation by jumping spiders (Phidippus apacheanus), and the percentage of carbon (C) and nitrogen (N) content, extracted lipids, escape response and survival were measured from predator-exposed and control adult flies. The results revealed predation as an important determinant of adult phenotype formation and survival ability. D. melanogaster reared together with spiders had a higher concentration of body N (but equal body C), a lower body mass and lipid reserves, a higher climbing speed and improved adult survival ability. The results suggest that the potential of predators to affect the development and the adult phenotype of D. melanogaster is high enough to use predators as a more natural stimulus in laboratory experiments when testing, for example, fruit fly memory and learning ability, or when comparing natural populations living under different predation pressures. PMID:27602281

  5. Short-term exposure to predation affects body elemental composition, climbing speed and survival ability in Drosophila melanogaster.

    PubMed

    Krams, Indrikis; Eichler Inwood, Sarah; Trakimas, Giedrius; Krams, Ronalds; Burghardt, Gordon M; Butler, David M; Luoto, Severi; Krama, Tatjana

    2016-01-01

    Factors such as temperature, habitat, larval density, food availability and food quality substantially affect organismal development. In addition, risk of predation has a complex impact on the behavioural and morphological life history responses of prey. Responses to predation risk seem to be mediated by physiological stress, which is an adaptation for maintaining homeostasis and improving survivorship during life-threatening situations. We tested whether predator exposure during the larval phase of development has any influence on body elemental composition, energy reserves, body size, climbing speed and survival ability of adult Drosophila melanogaster. Fruit fly larvae were exposed to predation by jumping spiders (Phidippus apacheanus), and the percentage of carbon (C) and nitrogen (N) content, extracted lipids, escape response and survival were measured from predator-exposed and control adult flies. The results revealed predation as an important determinant of adult phenotype formation and survival ability. D. melanogaster reared together with spiders had a higher concentration of body N (but equal body C), a lower body mass and lipid reserves, a higher climbing speed and improved adult survival ability. The results suggest that the potential of predators to affect the development and the adult phenotype of D. melanogaster is high enough to use predators as a more natural stimulus in laboratory experiments when testing, for example, fruit fly memory and learning ability, or when comparing natural populations living under different predation pressures.

  6. Brain size affects female but not male survival under predation threat

    PubMed Central

    Kotrschal, Alexander; Buechel, Séverine D; Zala, Sarah M; Corral-Lopez, Alberto; Penn, Dustin J; Kolm, Niclas; Sorci, Gabriele

    2015-01-01

    There is remarkable diversity in brain size among vertebrates, but surprisingly little is known about how ecological species interactions impact the evolution of brain size. Using guppies, artificially selected for large and small brains, we determined how brain size affects survival under predation threat in a naturalistic environment. We cohoused mixed groups of small- and large-brained individuals in six semi-natural streams with their natural predator, the pike cichlid, and monitored survival in weekly censuses over 5 months. We found that large-brained females had 13.5% higher survival compared to small-brained females, whereas the brain size had no discernible effect on male survival. We suggest that large-brained females have a cognitive advantage that allows them to better evade predation, whereas large-brained males are more colourful, which may counteract any potential benefits of brain size. Our study provides the first experimental evidence that trophic interactions can affect the evolution of brain size. PMID:25960088

  7. 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.

  8. Along came a spider who sat down beside her: Perceived predation risk, but not female age, affects female mate choosiness.

    PubMed

    Atwell, Ashley; Wagner, William E

    2015-06-01

    Organisms often exhibit behavioral plasticity in response to changes in factors, such as predation risk, mate density, and age. Particularly, female mate choosiness (the strength of female's attraction to male traits as they deviate from preferred trait values) has repeatedly been shown to be plastic. This is due to the costs associated with searching for preferred males fluctuating with changes in such factors. Because these factors can interact naturally, it is important to understand how female mate choosiness responds to these interactions. We studied the interaction between perceived predation risk and female age on the variable field cricket, Gryllus lineaticeps. Females were either exposed or not exposed to predation cues from a sympatric, cursorial, wolf spider predator, Hogna sp. We then tested the females at one of three adult ages and measured their choosiness by recording their responsiveness to a low quality male song. We found female choosiness plasticity was affected by neither age nor the interaction between age and perceived predation risk. Perceived predation risk was the only factor to significantly affect the plasticity of female mate choosiness: females were less choosy when they perceived predation risk and were more choosy when they did not. Predation may be such a strong source of selection that, regardless of differences in other factors, most individuals respond similarly.

  9. A female's past experience with predators affects male courtship and the care her offspring will receive from their father.

    PubMed

    McGhee, Katie E; Feng, Sally; Leasure, Sagan; Bell, Alison M

    2015-11-22

    Differential allocation occurs when individuals adjust their reproductive investment based on their partner's traits. However, it remains unknown whether animals differentially allocate based on their partner's past experiences with predation risk. If animals can detect a potential mate's experience with predators, this might inform them about the stress level of their potential mate, the likelihood of parental effects in offspring and/or the dangers present in the environment. Using threespined stickleback (Gasterosteus aculeatus), we examined whether a female's previous experience with being chased by a model predator while yolking eggs affects male mating effort and offspring care. Males displayed fewer conspicuous courtship behaviours towards females that had experienced predation risk in the past compared with unexposed females. This differential allocation extended to how males cared for the resulting offspring of these matings: fathers provided less parental care to offspring of females that had experienced predation risk in the past. Our results show for the first time, to our knowledge, that variation among females in their predator encounters can contribute to behavioural variation among males in courtship and parental care, even when males themselves do not encounter a predator. These results, together with previous findings, suggest that maternal predator exposure can influence offspring development both directly and indirectly, through how it affects father care.

  10. Do predator-prey relationships on the river bed affect fine sediment ingress?

    NASA Astrophysics Data System (ADS)

    Mathers, Kate; Rice, Stephen; Wood, Paul

    2016-04-01

    Ecosystem engineers are organisms that alter their physical environment and thereby influence the flow of resources through ecosystems. In rivers, several ecosystem engineers are also important geomorphological agents that modify fluvial sediment dynamics. By altering channel morphology and bed material characteristics, such modifications can affect the availability of habitats for other organisms, with implications for ecosystem health and wider community composition. In this way geomorphological and ecological systems are intimately interconnected. This paper focuses on one element of this intricate abiotic-biotic coupling: the interaction between fine sediment ingress into the river bed and the predator-prey relationships of aquatic organisms living on and in the river bed. Signal crayfish (Pacifastacus leniusculus) have been shown to modify fine sediment fluxes in rivers, but their effect on fine sediment ingress into riverbeds remains unclear. Many macroinvertebrate taxa have adapted avoidance strategies to avoid predation by crayfish, with one example being the freshwater shrimp (Gammarus pulex) which relies on open interstitial spaces within subsurface sediments as a refuge from crayfish predation. Fine sedimentation that fills gravelly frameworks may preclude access to those spaces, therefore leaving freshwater shrimp susceptible to predation. Ex-situ experiments were conducted which sought to examine: i) if freshwater shrimps and signal crayfish, alone and in combination, influenced fine sediment infiltration rates; and ii) whether modifications to substratum composition, specifically the introduction of fine sediment, modified predator-prey interactions. The results demonstrate that crayfish are significant geomorphic agents and that fine sediment ingress rates were significantly enhanced in their presence compared to control conditions or the presence of only freshwater shrimps. The combination of both organisms (i.e. allowing the interaction between

  11. Tri-trophic interactions affect density dependence of seed fate in a tropical forest palm.

    PubMed

    Visser, Marco D; Muller-Landau, Helene C; Wright, S Joseph; Rutten, Gemma; Jansen, Patrick A

    2011-11-01

    Natural enemies, especially host-specific enemies, are hypothesised to facilitate the coexistence of plant species by disproportionately inflicting more damage at increasing host abundance. However, few studies have assessed such Janzen-Connell mechanisms on a scale relevant for coexistence and no study has evaluated potential top-down influences on the specialized pests. We quantified seed predation by specialist invertebrates and generalist vertebrates, as well as larval predation on these invertebrates, for the Neotropical palm Attalea butyracea across ten 4-ha plots spanning 20-fold variation in palm density. As palm density increased, seed attack by bruchid beetles increased, whereas seed predation by rodents held constant. But because rodent predation on bruchid larvae increased disproportionately with increasing palm density, bruchid emergence rates and total seed predation by rodents and bruchids combined were both density-independent. Our results demonstrate that top-down effects can limit the potential of host-specific insects to induce negative-density dependence in plant populations.

  12. Livestock guardian dogs as surrogate top predators? How Maremma sheepdogs affect a wildlife community.

    PubMed

    van Bommel, Linda; Johnson, Chris N

    2016-09-01

    Use of livestock guardian dogs (LGDs) to reduce predation on livestock is increasing. However, how these dogs influence the activity of wildlife, including predators, is not well understood. We used pellet counts and remote cameras to investigate the effects of free ranging LGDs on four large herbivores (eastern gray kangaroo, common wombat, swamp wallaby, and sambar deer) and one mesopredator (red fox) in Victoria, Australia. Generalized mixed models and one- and two-species detection models were used to assess the influence of the presence of LGDs on detection of the other species. We found avoidance of LGDs in four species. Swamp wallabies and sambar deer were excluded from areas occupied by LGDs; gray kangaroos showed strong spatial and temporal avoidance of LGD areas; foxes showed moderately strong spatial and temporal avoidance of LGD areas. The effect of LGDs on wombats was unclear. Avoidance of areas with LGDs by large herbivores can benefit livestock production by reducing competition for pasture and disease transmission from wildlife to livestock, and providing managers with better control over grazing pressure. Suppression of mesopredators could benefit the small prey of those species. Synthesis and applications: In pastoral areas, LGDs can function as a surrogate top-order predator, controlling the local distribution and affecting behavior of large herbivores and mesopredators. LGDs may provide similar ecological functions to those that in many areas have been lost with the extirpation of native large carnivores.

  13. Density-dependent dispersal and relative dispersal affect the stability of predator-prey metacommunities.

    PubMed

    Hauzy, Céline; Gauduchon, Mathias; Hulot, Florence D; Loreau, Michel

    2010-10-07

    Although density-dependent dispersal and relative dispersal (the difference in dispersal rates between species) have been documented in natural systems, their effects on the stability of metacommunities are poorly understood. Here we investigate the effects of intra- and interspecific density-dependent dispersal on the regional stability in a predator-prey metacommunity model. We show that, when the dynamics of the populations reach equilibrium, the stability of the metacommunity is not affected by density-dependent dispersal. However, the regional stability, measured as the regional variability or the persistence, can be modified by density-dependent dispersal when local populations fluctuate over time. Moreover these effects depend on the relative dispersal of the predator and the prey. Regional stability is modified through changes in spatial synchrony. Interspecific density-dependent dispersal always desynchronizses local dynamics, whereas intraspecific density-dependent dispersal may either synchronize or desynchronize it depending on dispersal rates. Moreover, intra- and interspecific density-dependent dispersal strengthen the top-down control of the prey by the predator at intermediate dispersal rates. As a consequence the regional stability of the metacommunity is increased at intermediate dispersal rates. Our results show that density-dependent dispersal and relative dispersal of species are keys to understanding the response of ecosystems to fragmentation.

  14. Habitat restoration affects immature stages of a wetland butterfly through indirect effects on predation.

    PubMed

    Aschehoug, Erik T; Sivakoff, F S; Cayton, H L; Morris, W F; Haddad, N M

    2015-07-01

    Habitat loss worldwide has led to the widespread use of restoration practices for the recovery of imperiled species. However, recovery success may be hampered by focusing on plant communities, rather than the complex suite of direct and indirect interactions among trophic levels that occur in natural systems. Through a factorial field experiment, we tested the effects of wetland restoration on egg and juvenile survival of a locally rare butterfly, Satyrodes appalachia, via tree removal and damming. Tree removal more than tripled S. appalachia host plant abundance, but neither restoration action directly affected S. appalachia egg and juvenile survival. Instead, we found strong indirect effects of habitat manipulation on S. appalachia egg and juvenile survival that were mediated through predation. The interaction of tree removal and damming significantly decreased predation of S. appalachia eggs relative to each treatment alone. Damming alone had a significant positive indirect effect on the survival of S. appalachia juveniles, likely because increases in standing water reduced predator access. Our results emphasize the need for experiments that evaluate the demographic responses of imperiled species to habitat restoration prior to management action and quantify potential indirect effects mediated through higher trophic levels.

  15. The Nutritional Content of Prey Affects the Foraging of a Generalist Arthropod Predator

    PubMed Central

    Schmidt, Jason M.; Sebastian, Peter; Wilder, Shawn M.; Rypstra, Ann L.

    2012-01-01

    While foraging theory predicts that predatory responses should be determined by the energy content and size of prey, it is becoming increasingly clear that carnivores regulate their intake of specific nutrients. We tested the hypothesis that prey nutrient composition and predator nutritional history affects foraging intensity, consumption, and prey selection by the wolf spider, Pardosa milvina. By altering the rearing environment for fruit flies, Drosophila melanogaster, we produced high quality flies containing more nitrogen and protein and less lipid than low quality fruit flies. In one experiment, we quantified the proportion of flies taken and consumption across a range of densities of either high or low quality flies and, in a second experiment, we determined the prey capture and consumption of spiders that had been maintained on contrasting diets prior to testing. In both cases, the proportion of prey captured declined with increasing prey density, which characterizes the Type II functional response that is typical of wolf spiders. Spiders with similar nutritional histories killed similar numbers of each prey type but consumed more of the low quality prey. Spiders provided high quality prey in the weeks prior to testing killed more prey than those on the low quality diet but there was no effect of prior diet on consumption. In the third experiment, spiders were maintained on contrasting diets for three weeks and then allowed to select from a mixture of high and low quality prey. Interestingly, feeding history affected prey preferences: spiders that had been on a low quality diet showed no preference but those on the high quality diet selected high quality flies from the mixture. Our results suggest that, even when prey size and species identity are controlled, the nutritional experience of the predator as well as the specific content of the prey shapes predator-prey interactions. PMID:23145130

  16. Management intensity at field and landscape levels affects the structure of generalist predator communities.

    PubMed

    Rusch, Adrien; Birkhofer, Klaus; Bommarco, Riccardo; Smith, Henrik G; Ekbom, Barbara

    2014-07-01

    Agricultural intensification is recognised as a major driver of biodiversity loss in human-modified landscapes. Several agro-environmental measures at different spatial scales have been suggested to mitigate the negative impact of intensification on biodiversity and ecosystem services. The effect of these measures on the functional structure of service-providing communities remains, however, largely unexplored. Using two distinct landscape designs, we examined how the management options of organic farming at the field scale and crop diversification at the landscape level affect the taxonomic and functional structure of generalist predator communities and how these effects vary along a landscape complexity gradient. Organic farming as well as landscapes with longer and more diversified crop rotations enhanced the activity-density of spiders and rove beetles, but not the species richness or evenness. Our results indicate that the two management options affected the functional composition of communities, as they primarily enhanced the activity-density of functionally similar species. The two management options increased the functional similarity between spider species in regards to hunting mode and habitat preference. Organic farming enhanced the functional similarity of rove beetles. Management options at field and landscape levels were generally more important predictors of community structure when compared to landscape complexity. Our study highlights the importance of considering the functional composition of generalist predators in order to understand how agro-environmental measures at various scales shape community assemblages and ecosystem functioning in agricultural landscapes.

  17. 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.

  18. Disturbance frequency and vertical distribution of seeds affect long-term population dynamics: a mechanistic seed bank model.

    PubMed

    Eager, Eric Alan; Haridas, Chirakkal V; Pilson, Diana; Rebarber, Richard; Tenhumberg, Brigitte

    2013-08-01

    Seed banks are critically important for disturbance specialist plants because seeds of these species germinate only in disturbed soil. Disturbance and seed depth affect the survival and germination probability of seeds in the seed bank, which in turn affect population dynamics. We develop a density-dependent stochastic integral projection model to evaluate the effect of stochastic soil disturbances on plant population dynamics with an emphasis on mimicking how disturbances vertically redistribute seeds within the seed bank. We perform a simulation analysis of the effect of the frequency and mean depth of disturbances on the population's quasi-extinction probability, as well as the long-term mean and variance of the total density of seeds in the seed bank. We show that increasing the frequency of disturbances increases the long-term viability of the population, but the relationship between the mean depth of disturbance and the long-term viability of the population are not necessarily monotonic for all parameter combinations. Specifically, an increase in the probability of disturbance increases the long-term viability of the total seed bank population. However, if the probability of disturbance is too low, a shallower mean depth of disturbance can increase long-term viability, a relationship that switches as the probability of disturbance increases. However, a shallow disturbance depth is beneficial only in scenarios with low survival in the seed bank.

  19. Radish (Raphanus sativus) seed size affects germination response to coumarin

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The inhibition of seed germination by an allelochemical is generally greater in small seeds than in large seeds. Studies reporting these results used a large number of plant species that varied in seed size, which might have introduced differences in germination characteristics or various parameter...

  20. Seed chemistry of Sophora chrysophylla (mamane) in relation to diet of specialist avian seed predator Loxioides bailleui (palila) in Hawaii

    USGS Publications Warehouse

    Banko, P.C.; Cipollini, M.L.; Breton, G.W.; Paulk, E.; Wink, M.; Izhaki, I.

    2002-01-01

    This study describes the chemical ecology of a tritrophic interaction among species endemic to the island of Hawaii, USA: a tree (Sophora chrysophylla: mamane), an endangered bird (Loxioides bailleui; palila), and moth larvae (Cydia spp.). Palila and Cydia both specialize on the seed embryos of mamane but avoid eating the seed coats. Palila actively seek out and feed mamane embryos and Cydia larvae to their nestlings. Because mamane embryos contain potentially toxic levels of alkaloids, including broadly toxic quinolizidine alkaloids, and because insects often sequester alkaloids from their food plants, we focus on the questions of why palila forage upon mamane embryos and why they supplement their diet with Cydia larvae. Our data show that mamane embryos contain high amounts of potentially toxic alkaloids, but are well balanced nutritionally and contain lipids, carbohydrates, proteins, amino acids, and minerals at levels that are likely to be sufficient for maintenance and breeding. Mamane seed coats contain lower levels of alkaloids and nutrients, somewhat higher levels of phenolics, and much higher levels of nondigestible fiber. Taken together, these results suggest that palila have evolved tolerance to high levels of alkaloids and that they forage upon embryos primarily because of their availability in the habitat and high nutritional reward. Our data also suggest that Cydia are used by palila because they are readily accessible, nontoxic, and nutritious; the larvae apparently do not sequester alkaloids while feeding upon mamane seeds. Our results are interpreted with respect to the likelihood of current and historical coadaptive responses in this ecologically isolated and simplified island setting.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  2. Seed viability and functional properties of broccoli sprouts during germination and postharvest storage as affected by irradiation of seeds.

    PubMed

    Waje, Catherine K; Jun, So-Yun; Lee, Yeon-Kyung; Moon, Kwang-Deog; Choi, Yong Hee; Kwon, Joong-Ho

    2009-06-01

    The viability of broccoli seeds and functional properties, such as ascorbic acid, carotenoid, chlorophyll, and total phenol contents, of broccoli sprouts grown from irradiated seeds were evaluated. The seeds were irradiated using electron beam and gamma ray at doses up to 8 kGy. High germination percentages (>90%) were observed in seeds irradiated at < or =4 kGy, but the yield ratio and sprout length decreased with increased irradiation dose. Irradiation at > or =6 kGy resulted in curling of the sprout roots. Germinated seeds contained higher amounts of nutrients than raw seeds but the nutritional quality of sprouts decreased during postharvest storage. Radiation treatment hampered the growth of irradiated seeds resulting in underdeveloped sprouts with decreased ascorbic acid, carotenoid, and chlorophyll contents. In addition, the decrease in functional content of sprouts was more substantial in samples grown from high-dose (5 kGy) irradiated seeds than that of the low-dose (1 kGy) treated ones. Seed irradiation did not negatively affect the total phenol content of sprouts. In general, electron beam and gamma irradiation of broccoli seeds showed similar effects on the viability and functional properties of sprouts.

  3. 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.

  4. Ecological conditions affect evolutionary trajectory in a predator-prey system.

    PubMed

    Gallet, Romain; Tully, Thomas; Evans, Margaret E K

    2009-03-01

    The arms race of adaptation and counter adaptation in predator-prey interactions is a fascinating evolutionary dynamic with many consequences, including local adaptation and the promotion or maintenance of diversity. Although such antagonistic coevolution is suspected to be widespread in nature, experimental documentation of the process remains scant, and we have little understanding of the impact of ecological conditions. Here, we present evidence of predator-prey coevolution in a long-term experiment involving the predatory bacterium Bdellovibrio bacteriovorus and the prey Pseudomonas fluorescens, which has three morphs (SM, FS, and WS). Depending on experimentally applied disturbance regimes, the predator-prey system followed two distinct evolutionary trajectories, where the prey evolved to be either super-resistant to predation (SM morph) without counter-adaptation by the predator, or moderately resistant (FS morph), specialized to and coevolving with the predator. Although predation-resistant FS morphs suffer a cost of resistance, the evolution of extreme resistance to predation by the SM morph was apparently unconstrained by other traits (carrying capacity, growth rate). Thus we demonstrate empirically that ecological conditions can shape the evolutionary trajectory of a predator-prey system.

  5. Tracking Seed Fates of Tropical Tree Species: Evidence for Seed Caching in a Tropical Forest in North-East India.

    PubMed

    Sidhu, Swati; Datta, Aparajita

    2015-01-01

    Rodents affect the post-dispersal fate of seeds by acting either as on-site seed predators or as secondary dispersers when they scatter-hoard seeds. The tropical forests of north-east India harbour a high diversity of little-studied terrestrial murid and hystricid rodents. We examined the role played by these rodents in determining the seed fates of tropical evergreen tree species in a forest site in north-east India. We selected ten tree species (3 mammal-dispersed and 7 bird-dispersed) that varied in seed size and followed the fates of 10,777 tagged seeds. We used camera traps to determine the identity of rodent visitors, visitation rates and their seed-handling behavior. Seeds of all tree species were handled by at least one rodent taxon. Overall rates of seed removal (44.5%) were much higher than direct on-site seed predation (9.9%), but seed-handling behavior differed between the terrestrial rodent groups: two species of murid rodents removed and cached seeds, and two species of porcupines were on-site seed predators. In addition, a true cricket, Brachytrupes sp., cached seeds of three species underground. We found 309 caches formed by the rodents and the cricket; most were single-seeded (79%) and seeds were moved up to 19 m. Over 40% of seeds were re-cached from primary cache locations, while about 12% germinated in the primary caches. Seed removal rates varied widely amongst tree species, from 3% in Beilschmiedia assamica to 97% in Actinodaphne obovata. Seed predation was observed in nine species. Chisocheton cumingianus (57%) and Prunus ceylanica (25%) had moderate levels of seed predation while the remaining species had less than 10% seed predation. We hypothesized that seed traits that provide information on resource quantity would influence rodent choice of a seed, while traits that determine resource accessibility would influence whether seeds are removed or eaten. Removal rates significantly decreased (p < 0.001) while predation rates increased (p = 0

  6. Tracking Seed Fates of Tropical Tree Species: Evidence for Seed Caching in a Tropical Forest in North-East India

    PubMed Central

    Sidhu, Swati; Datta, Aparajita

    2015-01-01

    Rodents affect the post-dispersal fate of seeds by acting either as on-site seed predators or as secondary dispersers when they scatter-hoard seeds. The tropical forests of north-east India harbour a high diversity of little-studied terrestrial murid and hystricid rodents. We examined the role played by these rodents in determining the seed fates of tropical evergreen tree species in a forest site in north-east India. We selected ten tree species (3 mammal-dispersed and 7 bird-dispersed) that varied in seed size and followed the fates of 10,777 tagged seeds. We used camera traps to determine the identity of rodent visitors, visitation rates and their seed-handling behavior. Seeds of all tree species were handled by at least one rodent taxon. Overall rates of seed removal (44.5%) were much higher than direct on-site seed predation (9.9%), but seed-handling behavior differed between the terrestrial rodent groups: two species of murid rodents removed and cached seeds, and two species of porcupines were on-site seed predators. In addition, a true cricket, Brachytrupes sp., cached seeds of three species underground. We found 309 caches formed by the rodents and the cricket; most were single-seeded (79%) and seeds were moved up to 19 m. Over 40% of seeds were re-cached from primary cache locations, while about 12% germinated in the primary caches. Seed removal rates varied widely amongst tree species, from 3% in Beilschmiedia assamica to 97% in Actinodaphne obovata. Seed predation was observed in nine species. Chisocheton cumingianus (57%) and Prunus ceylanica (25%) had moderate levels of seed predation while the remaining species had less than 10% seed predation. We hypothesized that seed traits that provide information on resource quantity would influence rodent choice of a seed, while traits that determine resource accessibility would influence whether seeds are removed or eaten. Removal rates significantly decreased (p < 0.001) while predation rates increased (p = 0

  7. Antidepressants at environmentally relevant concentrations affect predator avoidance behavior of larval fathead minnows (Pimephales promelas).

    USGS Publications Warehouse

    Furlong, Edward T.; Barber, Larry B.; Meghan R. McGee,; Megan A. Buerkley,; Matthew L. Julius,; Vajda, Alan M.; Heiko L. Schoenfuss,; Schultz, Melissa M.; Norris, David O.

    2009-01-01

    The effects of embryonic and larval exposure to environmentally relevant (ng/L) concentrations of common antidepressants, fluoxetine, sertraline, venlafaxine, and bupropion (singularly and in mixture) on C-start escape behavior were evaluated in fathead minnows (Pimephales promelas). Embryos (postfertilization until hatching) were exposed for 5 d and, after hatching, were allowed to grow in control well water until 12 d old. Similarly, posthatch fathead minnows were exposed for 12 d to these compounds. High-speed (1,000 frames/s) video recordings of escape behavior were collected and transferred to National Institutes of Health Image for frame-by- frame analysis of latency periods, escape velocities, and total escape response (combination of latency period and escape velocity). When tested 12 d posthatch, fluoxetine and venlafaxine adversely affected C-start performance of larvae exposed as embryos. Conversely, larvae exposed for 12 d posthatch did not exhibit altered escape responses when exposed to fluoxetine but were affected by venlafaxine and bupropion exposure. Mixtures of these four antidepressant pharmaceuticals slowed predator avoidance behaviors in larval fathead minnows regardless of the exposure window. The direct impact of reduced C-start performance on survival and, ultimately, reproductive fitness provides an avenue to assess the ecological relevance of exposure in an assay of relatively short duration.

  8. Antidepressants at environmentally relevant concentrations affect predator avoidance behavior of larval fathead minnows (Pimephales promelas)

    USGS Publications Warehouse

    Painter, M.M.; Buerkley, M.A.; Julius, M.L.; Vajda, A.M.; Norris, D.O.; Barber, L.B.; Furlong, E.T.; Schultz, M.M.; Schoenfuss, H.L.

    2009-01-01

    The effects of embryonic and larval exposure to environmentally relevant (ng/L) concentrations of common antidepressants, fluoxetine, sertraline, venlafaxine, and bupropion (singularly and in mixture) on C-start escape behavior were evaluated in fathead minnows (Pimephales promelas). Embryos (postfertilization until hatching) were exposed for 5 d and, after hatching, were allowed to grow in control well water until 12 d old. Similarly, posthatch fathead minnows were exposed for 12 d to these compounds. High-speed (1,000 frames/s) video recordings of escape behavior were collected and transferred to National Institutes of Health Image for frame-by-frame analysis of latency periods, escape velocities, and total escape response (combination of latency period and escape velocity). When tested 12 d posthatch, fluoxetine and venlafaxine adversely affected C-start performance of larvae exposed as embryos. Conversely, larvae exposed for 12 d posthatch did not exhibit altered escape responses when exposed to fluoxetine but were affected by venlafaxine and bupropion exposure. Mixtures of these four antidepressant pharmaceuticals slowed predator avoidance behaviors in larval fathead minnows regardless of the exposure window. The direct impact of reduced C-start performance on survival and, ultimately, reproductive fitness provides an avenue to assess the ecological relevance of exposure in an assay of relatively short duration. ?? 2009 SETAC.

  9. Form of an evolutionary tradeoff affects eco-evolutionary dynamics in a predator-prey system.

    PubMed

    Kasada, Minoru; Yamamichi, Masato; Yoshida, Takehito

    2014-11-11

    Evolution on a time scale similar to ecological dynamics has been increasingly recognized for the last three decades. Selection mediated by ecological interactions can change heritable phenotypic variation (i.e., evolution), and evolution of traits, in turn, can affect ecological interactions. Hence, ecological and evolutionary dynamics can be tightly linked and important to predict future dynamics, but our understanding of eco-evolutionary dynamics is still in its infancy and there is a significant gap between theoretical predictions and empirical tests. Empirical studies have demonstrated that the presence of genetic variation can dramatically change ecological dynamics, whereas theoretical studies predict that eco-evolutionary dynamics depend on the details of the genetic variation, such as the form of a tradeoff among genotypes, which can be more important than the presence or absence of the genetic variation. Using a predator-prey (rotifer-algal) experimental system in laboratory microcosms, we studied how different forms of a tradeoff between prey defense and growth affect eco-evolutionary dynamics. Our experimental results show for the first time to our knowledge that different forms of the tradeoff produce remarkably divergent eco-evolutionary dynamics, including near fixation, near extinction, and coexistence of algal genotypes, with quantitatively different population dynamics. A mathematical model, parameterized from completely independent experiments, explains the observed dynamics. The results suggest that knowing the details of heritable trait variation and covariation within a population is essential for understanding how evolution and ecology will interact and what form of eco-evolutionary dynamics will result.

  10. Predator functional response and prey survival: Direct and indirect interactions affecting a marked prey population

    USGS Publications Warehouse

    Miller, David A.; Grand, J.B.; Fondell, T.F.; Anthony, M.

    2006-01-01

    1. Predation plays an integral role in many community interactions, with the number of predators and the rate at which they consume prey (i.e. their functional response) determining interaction strengths. Owing to the difficulty of directly observing predation events, attempts to determine the functional response of predators in natural systems are limited. Determining the forms that predator functional responses take in complex systems is important in advancing understanding of community interactions. 2. Prey survival has a direct relationship to the functional response of their predators. We employed this relationship to estimate the functional response for bald eagle Haliaeetus leucocepalus predation of Canada goose Branta canadensis nests. We compared models that incorporated eagle abundance, nest abundance and alternative prey presence to determine the form of the functional response that best predicted intra-annual variation in survival of goose nests. 3. Eagle abundance, nest abundance and the availability of alternative prey were all related to predation rates of goose nests by eagles. There was a sigmoidal relationship between predation rate and prey abundance and prey switching occurred when alternative prey was present. In addition, predation by individual eagles increased as eagle abundance increased. 4. A complex set of interactions among the three species examined in this study determined survival rates of goose nests. Results show that eagle predation had both prey- and predator-dependent components with no support for ratio dependence. In addition, indirect interactions resulting from the availability of alternative prey had an important role in mediating the rate at which eagles depredated nests. As a result, much of the within-season variation in nest survival was due to changing availability of alternative prey consumed by eagles. 5. Empirical relationships drawn from ecological theory can be directly integrated into the estimation process to

  11. Predator functional response and prey survival: direct and indirect interactions affecting a marked prey population.

    PubMed

    Miller, David A; Grand, James B; Fondell, Thomas F; Anthony, Michael

    2006-01-01

    1. Predation plays an integral role in many community interactions, with the number of predators and the rate at which they consume prey (i.e. their functional response) determining interaction strengths. Owing to the difficulty of directly observing predation events, attempts to determine the functional response of predators in natural systems are limited. Determining the forms that predator functional responses take in complex systems is important in advancing understanding of community interactions. 2. Prey survival has a direct relationship to the functional response of their predators. We employed this relationship to estimate the functional response for bald eagle Haliaeetus leucocepalus predation of Canada goose Branta canadensis nests. We compared models that incorporated eagle abundance, nest abundance and alternative prey presence to determine the form of the functional response that best predicted intra-annual variation in survival of goose nests. 3. Eagle abundance, nest abundance and the availability of alternative prey were all related to predation rates of goose nests by eagles. There was a sigmoidal relationship between predation rate and prey abundance and prey switching occurred when alternative prey was present. In addition, predation by individual eagles increased as eagle abundance increased. 4. A complex set of interactions among the three species examined in this study determined survival rates of goose nests. Results show that eagle predation had both prey- and predator-dependent components with no support for ratio dependence. In addition, indirect interactions resulting from the availability of alternative prey had an important role in mediating the rate at which eagles depredated nests. As a result, much of the within-season variation in nest survival was due to changing availability of alternative prey consumed by eagles. 5. Empirical relationships drawn from ecological theory can be directly integrated into the estimation process to

  12. UV wavelengths experienced during development affect larval newt visual sensitivity and predation efficiency.

    PubMed

    Martin, Mélissa; Théry, Marc; Rodgers, Gwendolen; Goven, Delphine; Sourice, Stéphane; Mège, Pascal; Secondi, Jean

    2016-02-01

    We experimentally investigated the influence of developmental plasticity of ultraviolet (UV) visual sensitivity on predation efficiency of the larval smooth newt, Lissotriton vulgaris. We quantified expression of SWS1 opsin gene (UV-sensitive protein of photoreceptor cells) in the retinas of individuals who had developed in the presence (UV+) or absence (UV-) of UV light (developmental treatments), and tested their predation efficiency under UV+ and UV- light (testing treatments). We found that both SWS1 opsin expression and predation efficiency were significantly reduced in the UV- developmental group. Larvae in the UV- testing environment displayed consistently lower predation efficiency regardless of their developmental treatment. These results prove for the first time, we believe, functional UV vision and developmental plasticity of UV sensitivity in an amphibian at the larval stage. They also demonstrate that UV wavelengths enhance predation efficiency and suggest that the magnitude of the behavioural response depends on retinal properties induced by the developmental lighting environment.

  13. An Analysis of Predator Selection to Affect Aposematic Coloration in a Poison Frog Species.

    PubMed

    Dreher, Corinna E; Cummings, Molly E; Pröhl, Heike

    2015-01-01

    Natural selection is widely noted to drive divergence of phenotypic traits. Predation pressure can facilitate morphological divergence, for example the evolution of both cryptic and conspicuous coloration in animals. In this context Dendrobatid frogs have been used to study evolutionary forces inducing diversity in protective coloration. The polytypic strawberry poison frog (Oophaga pumilio) shows strong divergence in aposematic coloration among populations. To investigate whether predation pressure is important for color divergence among populations of O. pumilio we selected four mainland populations and two island populations from Costa Rica and Panama. Spectrometric measurements of body coloration were used to calculate color and brightness contrasts of frogs as an indicator of conspicuousness for the visual systems of several potential predators (avian, crab and snake) and a conspecific observer. Additionally, we conducted experiments using clay model frogs of different coloration to investigate whether the local coloration of frogs is better protected than non-local color morphs, and if predator communities vary among populations. Overall predation risk differed strongly among populations and interestingly was higher on the two island populations. Imprints on clay models indicated that birds are the main predators while attacks of other predators were rare. Furthermore, clay models of local coloration were equally likely to be attacked as those of non-local coloration. Overall conspicuousness (and brightness contrast) of local frogs was positively correlated with attack rates by birds across populations. Together with results from earlier studies we conclude that conspicuousness honestly indicates toxicity to avian predators. The different coloration patterns among populations of strawberry poison frogs in combination with behavior and toxicity might integrate into equally efficient anti-predator strategies depending on local predation and other ecological

  14. An Analysis of Predator Selection to Affect Aposematic Coloration in a Poison Frog Species

    PubMed Central

    Dreher, Corinna E.; Cummings, Molly E.; Pröhl, Heike

    2015-01-01

    Natural selection is widely noted to drive divergence of phenotypic traits. Predation pressure can facilitate morphological divergence, for example the evolution of both cryptic and conspicuous coloration in animals. In this context Dendrobatid frogs have been used to study evolutionary forces inducing diversity in protective coloration. The polytypic strawberry poison frog (Oophaga pumilio) shows strong divergence in aposematic coloration among populations. To investigate whether predation pressure is important for color divergence among populations of O. pumilio we selected four mainland populations and two island populations from Costa Rica and Panama. Spectrometric measurements of body coloration were used to calculate color and brightness contrasts of frogs as an indicator of conspicuousness for the visual systems of several potential predators (avian, crab and snake) and a conspecific observer. Additionally, we conducted experiments using clay model frogs of different coloration to investigate whether the local coloration of frogs is better protected than non-local color morphs, and if predator communities vary among populations. Overall predation risk differed strongly among populations and interestingly was higher on the two island populations. Imprints on clay models indicated that birds are the main predators while attacks of other predators were rare. Furthermore, clay models of local coloration were equally likely to be attacked as those of non-local coloration. Overall conspicuousness (and brightness contrast) of local frogs was positively correlated with attack rates by birds across populations. Together with results from earlier studies we conclude that conspicuousness honestly indicates toxicity to avian predators. The different coloration patterns among populations of strawberry poison frogs in combination with behavior and toxicity might integrate into equally efficient anti-predator strategies depending on local predation and other ecological

  15. Alterations in seed development gene expression affect size and oil content of Arabidopsis seeds.

    PubMed

    Fatihi, Abdelhak; Zbierzak, Anna Maria; Dörmann, Peter

    2013-10-01

    Seed endosperm development in Arabidopsis (Arabidopsis thaliana) is under control of the polycomb group complex, which includes Fertilization Independent Endosperm (FIE). The polycomb group complex regulates downstream factors, e.g. Pheres1 (PHE1), by genomic imprinting. In heterozygous fie mutants, an endosperm develops in ovules carrying a maternal fie allele without fertilization, finally leading to abortion. Another endosperm development pathway depends on MINISEED3 (a WRKY10 transcription factor) and HAIKU2 (a leucine-rich repeat kinase). While the role of seed development genes in the embryo and endosperm establishment has been studied in detail, their impact on metabolism and oil accumulation remained unclear. Analysis of oil, protein, and sucrose accumulation in mutants and overexpression plants of the four seed development genes revealed that (1) seeds carrying a maternal fie allele accumulate low oil with an altered composition of triacylglycerol molecular species; (2) homozygous mutant seeds of phe1, mini3, and iku2, which are smaller, accumulate less oil and slightly less protein, and starch, which accumulates early during seed development, remains elevated in mutant seeds; (3) embryo-specific overexpression of FIE, PHE1, and MINI3 has no influence on seed size and weight, nor on oil, protein, or sucrose content; and (4) overexpression of IKU2 results in seeds with increased size and weight, and oil content of overexpressed IKU2 seeds is increased by 35%. Thus, IKU2 overexpression represents a novel strategy for the genetic manipulation of the oil content in seeds.

  16. Species-abundance--seed-size patterns within a plant community affected by grazing disturbance.

    PubMed

    Wu, Gao-lin; Shang, Zhan-huan; Zhu, Yuan-jun; Ding, Lu-ming; Wang, Dong

    2015-04-01

    Seed size has been advanced as a key factor that influences the dynamics of plant communities, but there are few empirical or theoretical predictions of how community dynamics progress based on seed size patterns. Information on the abundance of adults, seedlings, soil seed banks, seed rains, and the seed mass of 96 species was collected in alpine meadows of the Qinghai-Tibetan Plateau (China), which had different levels of grazing disturbance. The relationships between seed-mass-abundance patterns for adults, seedlings, the soil seed bank, and seed rain in the plant community were evaluated using regression models. Results showed that grazing levels affected the relationship between seed size and abundance properties of adult species, seedlings, and the soil seed bank, suggesting that there is a shift in seed-size--species-abundance relationships as a response to the grazing gradient. Grazing had no effect on the pattern of seed-size-seed-rain-abundance at four grazing levels. Grazing also had little effect on the pattern of seed-size--species-abundance and pattern of seed-size--soil-seed-bank-abundance in meadows with no grazing, light grazing, and moderate grazing), but there was a significant negative effect in meadows with heavy grazing. Grazing had little effect on the pattern of seed-size--seedling-abundance with no grazing, but had significant negative effects with light, moderate, and heavy grazing, and the |r| values increased with grazing levels. This indicated that increasing grazing pressure enhanced the advantage of smaller-seeded species in terms of the abundances of adult species, seedlings, and soil seed banks, whereas only the light grazing level promoted the seed rain abundance of larger-seeded species in the plant communities. This study suggests that grazing disturbances are favorable for increasing the species abundance for smaller-seeded species but not for the larger-seeded species in an alpine meadow community. Hence, there is a clear

  17. [Effects of rodents and litter coverage on the seed fate of wild Prunus divaricata in wild fruit forest of Tianshan Mountain, Northwest China].

    PubMed

    Zhao, Yu; Liu, Ying; Wang, Jian-Ming; Zhang, Yong-Heng; Yang, Yun-Fei

    2014-09-01

    The dynamic variation characteristics of seed bank and the main factors influencing the fate of Prunus divaricata seeds under the pressure of rodent predation and litter coverage were investigated with artificial soil seed banks from September, 2010 to April, 2013. It was found that there was about 48.3% of seeds germinated under the rodent predation disturbance conditions, 50% of the seeds was predated in situ or removed, and only about 4% decayed. The artificial seed bank formed a short-term persistent soil seed bank without any rodent predation disturbance, and the seeds could germinate even though they had been stored in the seed bank for three years. Soil burial provided a lower predation pressure and promoted the recruitment of wild P. divaricata seedlings, removal and predation in situ by animals was an important factor affecting the fate of seeds. At the same time, seeds removed and foraged in situ in the control and litter coverage samples were significantly less than that in the bare soil samples. Ground coverage reduced the removal and predation of seeds by rodents, but the effect was not enough to result in more seedlings. Rodent predation and removal were the main factors that could affect the seed fate and dynamics of seed bank.

  18. Interaction between parental environment and genotype affects plant and seed performance in Arabidopsis

    PubMed Central

    He, Hanzi; de Souza Vidigal, Deborah; Snoek, L. Basten; Schnabel, Sabine; Nijveen, Harm; Hilhorst, Henk; Bentsink, Leónie

    2014-01-01

    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. PMID:25240065

  19. 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.

  20. How does predation affect the bioaccumulation of hydrophobic organic compounds in aquatic organisms?

    PubMed

    Xia, Xinghui; Li, Husheng; Yang, Zhifeng; Zhang, Xiaotian; Wang, Haotian

    2015-04-21

    It is well-known that the body burden of hydrophobic organic compounds (HOCs) increases with the trophic level of aquatic organisms. However, the mechanism of HOC biomagnification is not fully understood. To fill this gap, this study investigated the effect of predation on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs), one type of HOC, in low-to-high aquatic trophic levels under constant freely dissolved PAH concentrations (1, 5, or 10 μg L(-1)) maintained by passive dosing systems. The tested PAHs included phenanthrene, anthracene, fluoranthene, and pyrene. The test organisms included zebrafish, which prey on Daphnia magna, and cichlids, which prey on zebrafish. The results revealed that for both zebrafish and cichlids, predation elevated the uptake and elimination rates of PAHs. The increase of uptake rate constant ranged from 20.8% to 39.4% in zebrafish with the amount of predation of 5 daphnids per fish per day, and the PAH uptake rate constant increased with the amount of predation. However, predation did not change the final bioaccumulation equilibrium; the equilibrium concentrations of PAHs in fish only depended on the freely dissolved concentration in water. Furthermore, the lipid-normalized water-based bioaccumulation factor of each PAH was constant for fish at different trophic levels. These findings infer that the final bioaccumulation equilibrium of PAHs is related to a partition between water and lipids in aquatic organisms, and predation between trophic levels does not change bioaccumulation equilibrium but bioaccumulation kinetics at stable freely dissolved PAH concentrations. This study suggests that if HOCs have not reached bioaccumulation equilibrium, biomagnification occurs due to enhanced uptake rates caused by predation in addition to higher lipid contents in higher trophic organisms. Otherwise, it is only due to the higher lipid contents in higher trophic organisms.

  1. Stress in the wild: chronic predator pressure and acute restraint affect plasma DHEA and corticosterone levels in a songbird.

    PubMed

    Newman, A E M; Zanette, L Y; Clinchy, M; Goodenough, N; Soma, K K

    2013-05-01

    The effects of chronic stressors on glucocorticoid levels are well described in laboratory rodents, but far less is known about the effects of chronic stressors on wild animals or on dehydroepiandrosterone (DHEA) levels. DHEA can be produced by the adrenal cortex and has prominent antiglucocorticoid properties. Here, we examined wild songbirds to elucidate the relationship between chronic predator pressure and plasma DHEA and corticosterone levels. We measured circulating steroid levels at baseline and after acute restraint in the breeding and nonbreeding seasons. During the breeding season, males in low predator pressure (LPP) environments had higher baseline DHEA levels than males in high predator pressure (HPP) environments. Also, acute restraint decreased DHEA levels in LPP males only but increased corticosterone levels in HPP and LPP males similarly. During the nonbreeding season, DHEA and corticosterone levels were lower than during the breeding season, and acute restraint decreased DHEA levels in both HPP and LPP males. Unlike males, breeding females showed no effect of predator pressure on baseline DHEA or corticosterone levels. These data suggest that naturalistic chronic and acute stressors affect circulating DHEA and corticosterone levels in wild animals and highlight the importance of using multiple endpoints when studying the physiological effects of chronic stress.

  2. Soybean seed phenol, lignin, and isoflavones partitioning as affected by seed node position and genotype differences

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Factors controlling the production and partitioning of seed phenolics within soybean are not understood. Understanding these factors may justify selection for higher levels of seed phenolics because of their beneficial impact on human health and soybean defense against diseases. The objective of thi...

  3. Macroalgal assemblage type affects predation pressure on sea urchins by altering adhesion strength.

    PubMed

    Gianguzza, P; Bonaviri, C; Milisenda, G; Barcellona, A; Agnetta, D; Vega Fernández, T; Badalamenti, F

    2010-07-01

    In the Mediterranean, sea breams are the most effective Paracentrotus lividus and Arbacia lixula predators. Generally, seabreams dislodge adult urchins from the rocky substrate, turn them upside down and crush their tests. Sea urchins may respond to fish attacks clinging tenaciously to the substratum. This study is the first attempt to investigate sea urchin adhesion strength in two alternative algal assemblages of the rocky infralittoral and valuated its possible implication for fish predation. We hypothesized that (1) sea urchin adhesion strength is higher in rocky shores dominated by encrusting macroalgae (ECA) than in erected macroalgae (EMA); (2) predation rates upon sea urchins are lower in ECA than in EMA; and (3) predation rate on A. lixula is lower than that on P. lividus. We observed that attachment tenacity of both sea urchins was higher in ECA than EMA and that A. lixula exhibited a stronger attachment tenacity than P. lividus in ECA. Results supported the importance of adhesion strength, as efficient defence against sea bream attacks, only for, P. lividus. A. lixula adhesion strength does not seem to be an important factor in avoiding fish predation, possibly because of the low palatability of the species. These patterns may deserve particular interest in understanding the processes responsible for the maintenance of sea urchin barrens that are dominated by ECA assemblage.

  4. Does small mammal prey guild affect the exposure of predators to anticoagulant rodenticides?

    PubMed

    Tosh, D G; McDonald, R A; Bearhop, S; Lllewellyn, N R; Fee, S; Sharp, E A; Barnett, E A; Shore, R F

    2011-10-01

    Ireland has a restricted small mammal prey guild but still includes species most likely to consume anticoagulant rodenticide (AR) baits. This may enhance secondary exposure of predators to ARs. We compared liver AR residues in foxes (Vulpes vulpes) in Northern Ireland (NI) with those in foxes from Great Britain which has a more diverse prey guild but similar agricultural use of ARs. Liver ARs were detected in 84% of NI foxes, more than in a comparable sample of foxes from Scotland and similar to that of suspected AR poisoned animals from England and Wales. High exposure in NI foxes is probably due to greater predation of commensal rodents and non-target species most likely to take AR baits, and may also partly reflect greater exposure to highly persistent brodifacoum and flocoumafen. High exposure is likely to enhance risk and Ireland may be a sentinel for potential effects on predator populations.

  5. Increased temperatures negatively affect Juniperus communis seeds: evidence from transplant experiments along a latitudinal gradient.

    PubMed

    Gruwez, R; De Frenne, P; Vander Mijnsbrugge, K; Vangansbeke, P; Verheyen, K

    2016-05-01

    With a distribution range that covers most of the Northern hemisphere, common juniper (Juniperus communis) has one of the largest ranges of all vascular plant species. In several regions in Europe, however, populations are decreasing in size and number due to failing recruitment. One of the main causes for this failure is low seed viability. Observational evidence suggests that this is partly induced by climate warming, but our mechanistic understanding of this effect remains incomplete. Here, we experimentally assess the influence of temperature on two key developmental phases during sexual reproduction, i.e. gametogenesis and fertilisation (seed phase two, SP2) and embryo development (seed phase three, SP3). Along a latitudinal gradient from southern France to central Sweden, we installed a transplant experiment with shrubs originating from Belgium, a region with unusually low juniper seed viability. Seeds of both seed phases were sampled during three consecutive years, and seed viability assessed. Warming temperatures negatively affected the seed viability of both SP2 and SP3 seeds along the latitudinal gradient. Interestingly, the effect on embryo development (SP3) only occurred in the third year, i.e. when the gametogenesis and fertilisation also took place in warmer conditions. We found strong indications that this negative influence mostly acts via disrupting growth of the pollen tube, the development of the female gametophyte and fertilisation (SP2). This, in turn, can lead to failing embryo development, for example, due to nutritional problems. Our results confirm that climate warming can negatively affect seed viability of juniper.

  6. 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.

  7. Swimming with Predators and Pesticides: How Environmental Stressors Affect the Thermal Physiology of Tadpoles

    PubMed Central

    Katzenberger, Marco; Hammond, John; Duarte, Helder; Tejedo, Miguel; Calabuig, Cecilia; Relyea, Rick A.

    2014-01-01

    To forecast biological responses to changing environments, we need to understand how a species's physiology varies through space and time and assess how changes in physiological function due to environmental changes may interact with phenotypic changes caused by other types of environmental variation. Amphibian larvae are well known for expressing environmentally induced phenotypes, but relatively little is known about how these responses might interact with changing temperatures and their thermal physiology. To address this question, we studied the thermal physiology of grey treefrog tadpoles (Hyla versicolor) by determining whether exposures to predator cues and an herbicide (Roundup) can alter their critical maximum temperature (CTmax) and their swimming speed across a range of temperatures, which provides estimates of optimal temperature (Topt) for swimming speed and the shape of the thermal performance curve (TPC). We discovered that predator cues induced a 0.4°C higher CTmax value, whereas the herbicide had no effect. Tadpoles exposed to predator cues or the herbicide swam faster than control tadpoles and the increase in burst speed was higher near Topt. In regard to the shape of the TPC, exposure to predator cues increased Topt by 1.5°C, while exposure to the herbicide marginally lowered Topt by 0.4°C. Combining predator cues and the herbicide produced an intermediate Topt that was 0.5°C higher than the control. To our knowledge this is the first study to demonstrate a predator altering the thermal physiology of amphibian larvae (prey) by increasing CTmax, increasing the optimum temperature, and producing changes in the thermal performance curves. Furthermore, these plastic responses of CTmax and TPC to different inducing environments should be considered when forecasting biological responses to global warming. PMID:24869960

  8. Seasonal Variation in the Fate of Seeds under Contrasting Logging Regimes

    PubMed Central

    Fleury, Marina; Rodrigues, Ricardo R.; do Couto, Hilton T. Z.; Galetti, Mauro

    2014-01-01

    Seed predators and dispersers may drive the speed and structure of forest regeneration in natural ecosystems. Rodents and ants prey upon and disperse seeds, yet empirical studies on the magnitude of these effects are lacking. Here, we examined the role of ants and rodents on seed predation in 4 plant species in a successional gradient on a tropical rainforest island. We found that (1) seeds are mostly consumed rather than dispersed; (2) rates of seed predation vary by habitat, season, and species; (3) seed size, shape, and hardness do not affect the probability of being depredated. Rodents were responsible for 70% of seed predation and were negligible (0.14%) seed dispersers, whereas ants were responsible for only 2% of seed predation and for no dispersal. We detected seasonal and habitat effects on seed loss, with higher seed predation occurring during the wet season and in old-growth forests. In the absence of predators regulating seed-consumer populations, the densities of these resilient animals explode to the detriment of natural regeneration and may reduce diversity and carrying capacity for consumers and eventually lead to ecological meltdown. PMID:24614500

  9. Does predation contribute to tree diversity?

    PubMed

    Beckage, Brian; Clark, James S

    2005-04-01

    Seed and seedling predation may differentially affect competitively superior tree species to increase the relative recruitment success of poor competitors and contribute to the coexistence of tree species. We examined the effect of seed and seedling predation on the seedling recruitment of three tree species, Acer rubrum (red maple), Liriodendron tulipifera (yellow poplar), and Quercus rubra (northern red oak), over three years by manipulating seed and seedling exposure to predators under contrasting microsite conditions of shrub cover, leaf litter, and overstory canopy. Species rankings of seedling emergence were constant across microsites, regardless of exposure to seed predators, but varied across years. A. rubrum had the highest emergence probabilities across microsites in 1997, but Q. rubra had the highest emergence probabilities in 1999. Predators decreased seedling survival uniformly across species, but did not affect relative growth rates (RGRs). Q. rubra had the highest seedling survivorship across microsites, while L. tulipifera had the highest RGRs. Our results suggest that annual variability in recruitment success contributes more to seedling diversity than differential predation across microsites. We synthesized our results from separate seedling emergence and survival experiments to project seedling bank composition. With equal fecundity assumed across species, Q. rubra dominated the seedling bank, capturing 90% of the regeneration sites on average, followed by A. rubrum (8% of sites) and L. tulipifera (2% of sites). When seed abundance was weighted by species-specific fecundity, seedling bank composition was more diverse; L. tulipifera captured 62% of the regeneration sites, followed by A. rubrum (21% of sites) and Q. rubra (17% of sites). Tradeoffs between seedling performance and fecundity may promote the diversity of seedling regeneration by increasing the probability of inferior competitors capturing regeneration sites.

  10. Water-triacylglycerol interactions affect oil body structure and seed viability

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We are investigating interactions between water and triacylglycerols (TAG) that appear to affect oil body stability and viability of seeds. Dried seeds are usually stored at freezer temperatures (-20oC) for long-term conservation of genetic resources. This globally accepted genebanking practice is...

  11. Seed coating with a neonicotinoid insecticide negatively affects wild bees.

    PubMed

    Rundlöf, Maj; Andersson, Georg K S; Bommarco, Riccardo; Fries, Ingemar; Hederström, Veronica; Herbertsson, Lina; Jonsson, Ove; Klatt, Björn K; Pedersen, Thorsten R; Yourstone, Johanna; Smith, Henrik G

    2015-05-07

    Understanding the effects of neonicotinoid insecticides on bees is vital because of reported declines in bee diversity and distribution and the crucial role bees have as pollinators in ecosystems and agriculture. Neonicotinoids are suspected to pose an unacceptable risk to bees, partly because of their systemic uptake in plants, and the European Union has therefore introduced a moratorium on three neonicotinoids as seed coatings in flowering crops that attract bees. The moratorium has been criticized for being based on weak evidence, particularly because effects have mostly been measured on bees that have been artificially fed neonicotinoids. Thus, the key question is how neonicotinoids influence bees, and wild bees in particular, in real-world agricultural landscapes. Here we show that a commonly used insecticide seed coating in a flowering crop can have serious consequences for wild bees. In a study with replicated and matched landscapes, we found that seed coating with Elado, an insecticide containing a combination of the neonicotinoid clothianidin and the non-systemic pyrethroid β-cyfluthrin, applied to oilseed rape seeds, reduced wild bee density, solitary bee nesting, and bumblebee colony growth and reproduction under field conditions. Hence, such insecticidal use can pose a substantial risk to wild bees in agricultural landscapes, and the contribution of pesticides to the global decline of wild bees may have been underestimated. The lack of a significant response in honeybee colonies suggests that reported pesticide effects on honeybees cannot always be extrapolated to wild bees.

  12. Tillage and residue burning affects weed populations and seed banks.

    PubMed

    Narwal, S; Sindel, B M; Jessop, R S

    2006-01-01

    An integrated weed management approach requires alternative management practices to herbicide use such as tillage, crop rotations and cultural controls to reduce soil weed seed banks. The objective of this study was to examine the value of different tillage practices and stubble burning to exhaust the seed bank of common weeds from the northern grain region of Australia. Five tillage and burning treatments were incorporated in a field experiment, at Armidale (30 degrees 30'S, 151 degrees 40'E), New South Wales, Australia in July 2004 in a randomized block design replicated four times. The trial was continued and treatments repeated in July 2005 with all the mature plants from the first year being allowed to shed seed in their respective treatment plots. The treatments were (i) no tillage (NT), (ii) chisel ploughing (CP), (iii) mould board ploughing (MBP), (iv) wheat straw burning with no tillage (SBNT) and (v) wheat straw burning with chisel ploughing (SBC). Soil samples were collected before applying treatments and before the weeds flowered to establish the seed bank status of the various weeds in the soil. Wheat was sown after the tillage treatments. Burning treatments were only initiated in the second year, one month prior to tillage treatments. The major weeds present in the seed bank before initiating the trial were Polygonum aviculare, Sonchus oleraceus and Avena fatua. Tillage promoted the germination of other weeds like Hibiscus trionum, Medicago sativa, Vicia sp. and Phalaris paradoxa later in the season in 2004 and Convolvulus erubescens emerged as a new weed in 2005. The MBP treatment in 2004 reduced the weed biomass to a significantly lower level of 55 g/m2 than the other treatments of CP (118 g/m2) and NT plots (196 g/m2) (P < 0.05). However, in 2005 SBC and MBP treatments were similar in reducing the weed biomass. In 2004, the grain yield trend of wheat was significantly different between CP and NT, and MBP and NT (P < 0.05) with maximum yield of 5898

  13. Oviposition choices by a pre-dispersal seed predator (Hylemya sp.) : I. Correspondence with hummingbird pollinators, and the role of plant size, density and floral morphology.

    PubMed

    Brody, Alison K

    1992-08-01

    Although the importance of pollinators has most often been examined in the evolution of floral characters, seed predators may also play a role in shaping floral evolution. In this study, I examined the role of interplant distance, plant size, and flower morphology on Ipomopsis aggregatás (Polemoniaceae) attractiveness to a pre-dispersal seed predator, Hylemya sp. (Anthomyiidae) and to hummingbird pollinators. The attractiveness of I. aggregata individuals to Hylemya was nonlinearly related to interplant distance in experimental arrays. Clumped and highly dispersed plants were preyed upon more frequently than those at intermediate distances. I found no relationship between interplant distance and visitation rates by hummingbird pollinators in these experimental arrays. However, in natural populations studied, clumped plants were more frequently approached by hummingbirds than those growing more widely dispersed. Display size was unrelated to visitation by Hylemya on inflorescences I clipped and maintained as "large", "small" and "control". Display size was also unrelated to the total number of visits by hummingbird pollinators to each of these experimental plants, however "large" display plants were more likely to be visited first in any given visitation sequence. Of various morphological measurements, corolla length showed the strongest positive correlation with Hylemya egg presence. To the extent that plant spacing and morphology is correlated with pollinator visits and ultimate seed set, Hylemya could be choosing flowers optimally, and playing a role in the evolution of floral traits.

  14. 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.

  15. 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

  16. Factors affecting individual foraging specialization and temporal diet stability across the range of a large “generalist” apex predator

    USGS Publications Warehouse

    Rosenblatt, Adam E.; Nifong, James C.; Heithaus, Michael R.; Mazzotti, Frank J.; Cherkiss, Michael S.; Jeffery, Brian M.; Elsey, Ruth M.; Decker, Rachel A.; Silliman, Brian R.; Guillette, Louis J.; Lowers, Russell H.; Larson, Justin C.

    2015-01-01

    Individual niche specialization (INS) is increasingly recognized as an important component of ecological and evolutionary dynamics. However, most studies that have investigated INS have focused on the effects of niche width and inter- and intraspecific competition on INS in small-bodied species for short time periods, with less attention paid to INS in large-bodied reptilian predators and the effects of available prey types on INS. We investigated the prevalence, causes, and consequences of INS in foraging behaviors across different populations of American alligators (Alligator mississippiensis), the dominant aquatic apex predator across the southeast US, using stomach contents and stable isotopes. Gut contents revealed that, over the short term, although alligator populations occupied wide ranges of the INS spectrum, general patterns were apparent. Alligator populations inhabiting lakes exhibited lower INS than coastal populations, likely driven by variation in habitat type and available prey types. Stable isotopes revealed that over longer time spans alligators exhibited remarkably consistent use of variable mixtures of carbon pools (e.g., marine and freshwater food webs). We conclude that INS in large-bodied reptilian predator populations is likely affected by variation in available prey types and habitat heterogeneity, and that INS should be incorporated into management strategies to efficiently meet intended goals. Also, ecological models, which typically do not consider behavioral variability, should include INS to increase model realism and applicability.

  17. Waves affect predator-prey interactions between fish and benthic invertebrates.

    PubMed

    Gabel, Friederike; Stoll, Stefan; Fischer, Philipp; Pusch, Martin T; Garcia, Xavier-François

    2011-01-01

    Little is known about the effects of waves on predator-prey interactions in the littoral zones of freshwaters. We conducted a set of mesocosm experiments to study the differential effects of ship- and wind-induced waves on the foraging success of littoral fish on benthic invertebrates. Experiments were conducted in a wave tank with amphipods (Gammarus roeseli) as prey, and age-0 bream (Abramis brama, B0), age-0 and age-1 dace (Leuciscus leuciscus, D0 and D1) as predators. The number of gammarids suspended in the water column was higher in the wave treatments compared to a no-wave control treatment, especially during pulse waves mimicking ship-induced waves in comparison to continuous waves mimicking wind-induced waves. The resulting higher prey accessibility in the water column was differently exploited by the three types of predatory fish. D0 and D1 showed significantly higher foraging success in the pulse wave treatment than in the continuous and control treatments. The foraging success of D0 appears to be achieved more easily, since significantly higher swimming activity and more foraging attempts were recorded only for D1 under the wave treatments. In contrast, B0 consumed significantly fewer gammarids in both wave treatments than in the control. Hence, waves influenced predator-prey interactions differently depending on wave type and fish type. It is expected that regular exposure to ship-induced waves can alter littoral invertebrate and fish assemblages by increasing the predation risk for benthic invertebrates that are suspended in the water column, and by shifting fish community compositions towards species that benefit from waves.

  18. 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.

  19. Glyphosate affects seed composition in glyphosate-resistant soybean.

    PubMed

    Zobiole, Luiz H S; Oliveira, Rubem S; Visentainer, Jesui V; Kremer, Robert J; Bellaloui, Nacer; Yamada, Tsuioshi

    2010-04-14

    The cultivation of glyphosate-resistant (GR) soybeans has continuously increased worldwide in recent years mainly due to the importance of glyphosate in current weed management systems. However, not much has been done to understand eventual effects of glyphosate application on GR soybean physiology, especially those related to seed composition with potential effects on human health. Two experiments were conducted to evaluate the effects of glyphosate application on GR soybeans compared with its near-isogenic non-GR parental lines. Results of the first experiment showed that glyphosate application resulted in significant decreases in shoot nutrient concentrations, photosynthetic parameters, and biomass production. Similar trends were observed for the second experiment, although glyphosate application significantly altered seed nutrient concentrations and polyunsaturated fatty acid percentages. Glyphosate resulted in significant decreases in polyunsaturated linoleic acid (18:2n-6) (2.3% decrease) and linolenic acid (18:3n-3) (9.6% decrease) and a significant increase in monounsaturated fatty acids 17:1n-7 (30.3% increase) and 18:1n-7 (25% increase). The combined observations of decreased photosynthetic parameters and low nutrient availability in glyphosate-treated plants may explain potential adverse effects of glyphosate in GR soybeans.

  20. Maternal environment affects the genetic basis of seed dormancy in Arabidopsis thaliana.

    PubMed

    Postma, Froukje M; Ågren, Jon

    2015-02-01

    The genetic basis of seed dormancy, a key life history trait important for adaptive evolution in plant populations, has yet been studied only using seeds produced under controlled conditions in greenhouse environments. However, dormancy is strongly affected by maternal environmental conditions, and interactions between seed genotype and maternal environment have been reported. Consequently, the genetic basis of dormancy of seeds produced under natural field conditions remains unclear. We examined the effect of maternal environment on the genetic architecture of seed dormancy using a recombinant inbred line (RIL) population derived from a cross between two locally adapted populations of Arabidopsis thaliana from Italy and Sweden. We mapped quantitative trait loci (QTL) for dormancy of seeds produced in the greenhouse and at the native field sites of the parental genotypes. The Italian genotype produced seeds with stronger dormancy at fruit maturation than did the Swedish genotype in all three environments, and the maternal field environments induced higher dormancy levels compared to the greenhouse environment in both genotypes. Across the three maternal environments, a total of nine dormancy QTL were detected, three of which were only detected among seeds matured in the field, and six of which showed significant QTL × maternal environment interactions. One QTL had a large effect on dormancy across all three environments and colocalized with the candidate gene DOG1. Our results demonstrate the importance of studying the genetic basis of putatively adaptive traits under relevant conditions.

  1. A decrease in phytic acid content substantially affects the distribution of mineral elements within rice seeds.

    PubMed

    Sakai, Hiroaki; Iwai, Toru; Matsubara, Chie; Usui, Yuto; Okamura, Masaki; Yatou, Osamu; Terada, Yasuko; Aoki, Naohiro; Nishida, Sho; Yoshida, Kaoru T

    2015-09-01

    Phytic acid (myo-inositol hexakisphosphate; InsP6) is the storage compound of phosphorus and many mineral elements in seeds. To determine the role of InsP6 in the accumulation and distribution of mineral elements in seeds, we performed fine mappings of mineral elements through synchrotron-based X-ray microfluorescence analysis using developing seeds from two independent low phytic acid (lpa) mutants of rice (Oryza sativa L.). The reduced InsP6 in lpa seeds did not affect the translocation of mineral elements from vegetative organs into seeds, because the total amounts of phosphorus and the other mineral elements in lpa seeds were identical to those in the wild type (WT). However, the reduced InsP6 caused large changes in mineral localization within lpa seeds. Phosphorus and potassium in the aleurone layer of lpa greatly decreased and diffused into the endosperm. Zinc and copper, which were broadly distributed from the aleurone layer to the inner endosperm in the WT, were localized in the narrower space around the aleurone layer in lpa mutants. We also confirmed that similar distribution changes occurred in transgenic rice with the lpa phenotype. Using these results, we discussed the role of InsP6 in the dynamic accumulation and distribution patterns of mineral elements during seed development.

  2. Richness and species composition of arboreal arthropods affected by nutrients and predators: a press experiment.

    PubMed

    Gruner, Daniel S; Taylor, Andrew D

    2006-04-01

    A longstanding goal for ecologists is to understand the processes that maintain biological diversity in communities, yet few studies have investigated the combined effects of predators and resources on biodiversity in natural ecosystems. We fertilized nutrient limited plots and excluded insectivorous birds in a randomized block design, and examined the impacts on arthropods associated with the dominant tree in the Hawaiian Islands, Metrosideros polymorpha (Myrtaceae). After 33 months, the species load (per foliage mass) of herbivores and carnivores increased with fertilization, but rarified richness (standardized to abundance) did not change. Fertilization depressed species richness of arboreal detritivores, and carnivore richness dropped in caged, unfertilized plots, both because of the increased dominance of common, introduced species with treatments. Herbivore species abundance distributions were more equitable than other trophic levels following treatments, and fertilization added specialized native species without changing relativized species richness. Overall, bird removal and nutrient addition treatments on arthropod richness acted largely independently, but with countervailing influences that obscured distinct top-down and bottom-up effects on different trophic levels. This study demonstrates that species composition, biological invasions, and the individuality of species traits may complicate efforts to predict the interactive effects of resources and predation on species diversity in food webs.

  3. Scatter Hoarding of Seeds Confers Survival Advantages and Disadvantages to Large-Seeded Tropical Plants at Different Life Stages

    PubMed Central

    Kuprewicz, Erin K.

    2015-01-01

    Scatter hoarding of seeds by animals contributes significantly to forest-level processes, including plant recruitment and forest community composition. However, the potential positive and negative effects of caching on seed survival, germination success, and seedling survival have rarely been assessed through experimental studies. Here, I tested the hypothesis that seed burial mimicking caches made by scatter hoarding Central American agoutis (Dasyprocta punctate) enhances seed survival, germination, and growth by protecting seeds from seed predators and providing favorable microhabitats for germination. In a series of experiments, I used simulated agouti seed caches to assess how hoarding affects seed predation by ground-dwelling invertebrates and vertebrates for four plant species. I tracked germination and seedling growth of intact and beetle-infested seeds and, using exclosures, monitored the effects of mammals on seedling survival through time. All experiments were conducted over three years in a lowland wet forest in Costa Rica. The majority of hoarded palm seeds escaped predation by both invertebrates and vertebrates while exposed seeds suffered high levels of infestation and removal. Hoarding had no effect on infestation rates of D. panamensis, but burial negatively affected germination success by preventing endocarp dehiscence. Non-infested palm seeds had higher germination success and produced larger seedlings than infested seeds. Seedlings of A. alatum and I. deltoidea suffered high mortality by seed-eating mammals. Hoarding protected most seeds from predators and enhanced germination success (except for D. panamensis) and seedling growth, although mammals killed many seedlings of two plant species; all seedling deaths were due to seed removal from the plant base. Using experimental caches, this study shows that scatter hoarding is beneficial to most seeds and may positively affect plant propagation in tropical forests, although tradeoffs in seed

  4. Scatter hoarding of seeds confers survival advantages and disadvantages to large-seeded tropical plants at different life stages.

    PubMed

    Kuprewicz, Erin K

    2015-01-01

    Scatter hoarding of seeds by animals contributes significantly to forest-level processes, including plant recruitment and forest community composition. However, the potential positive and negative effects of caching on seed survival, germination success, and seedling survival have rarely been assessed through experimental studies. Here, I tested the hypothesis that seed burial mimicking caches made by scatter hoarding Central American agoutis (Dasyprocta punctate) enhances seed survival, germination, and growth by protecting seeds from seed predators and providing favorable microhabitats for germination. In a series of experiments, I used simulated agouti seed caches to assess how hoarding affects seed predation by ground-dwelling invertebrates and vertebrates for four plant species. I tracked germination and seedling growth of intact and beetle-infested seeds and, using exclosures, monitored the effects of mammals on seedling survival through time. All experiments were conducted over three years in a lowland wet forest in Costa Rica. The majority of hoarded palm seeds escaped predation by both invertebrates and vertebrates while exposed seeds suffered high levels of infestation and removal. Hoarding had no effect on infestation rates of D. panamensis, but burial negatively affected germination success by preventing endocarp dehiscence. Non-infested palm seeds had higher germination success and produced larger seedlings than infested seeds. Seedlings of A. alatum and I. deltoidea suffered high mortality by seed-eating mammals. Hoarding protected most seeds from predators and enhanced germination success (except for D. panamensis) and seedling growth, although mammals killed many seedlings of two plant species; all seedling deaths were due to seed removal from the plant base. Using experimental caches, this study shows that scatter hoarding is beneficial to most seeds and may positively affect plant propagation in tropical forests, although tradeoffs in seed

  5. Plant genetic identity of foundation tree species and their hybrids affects a litter-dwelling generalist predator.

    PubMed

    Wojtowicz, Todd; Compson, Zacchaeus G; Lamit, Louis J; Whitham, Thomas G; Gehring, Catherine A

    2014-11-01

    The effects of plant genetics on predators, especially those not living on the plant itself, are rarely studied and poorly understood. Therefore, we investigated the effect of plant hybridization and genotype on litter-dwelling spiders. Using an 18-year-old cottonwood common garden, we recorded agelenid sheet-web density associated with the litter layers of replicated genotypes of three tree cross types: Populus fremontii, Populus angustifolia, and their F1 hybrids. We surveyed 118 trees for agelenid litter webs at two distances from the trees (0-100 and 100-200 cm from trunk) and measured litter depth as a potential mechanism of web density patterns. Five major results emerged: web density within a 1-m radius of P. angustifolia was approximately three times higher than within a 1-m radius of P. fremontii, with F1 hybrids having intermediate densities; web density responded to P. angustifolia and F1 hybrid genotypes as indicated by a significant genotype × distance interaction, with some genotypes exhibiting a strong decline in web density with distance, while others did not; P. angustifolia litter layers were deeper than those of P. fremontii at both distance classes, and litter depth among P. angustifolia genotypes differed up to 300%; cross type and genotype influenced web density via their effects on litter depth, and these effects were influenced by distance; web density was more sensitive to the effects of tree cross type than genotype. By influencing generalist predators, plant hybridization and genotype may indirectly impact trophic interactions such as intraguild predation, possibly affecting trophic cascades and ecosystem processes.

  6. Intraspecific variation in a predator affects community structure and cascading trophic interactions.

    PubMed

    Post, David M; Palkovacs, Eric P; Schielke, Erika G; Dodson, Stanley I

    2008-07-01

    Intraspecific phenotypic variation in ecologically important traits is widespread and important for evolutionary processes, but its effects on community and ecosystem processes are poorly understood. We use life history differences among populations of alewives, Alosa pseudoharengus, to test the effects of intraspecific phenotypic variation in a predator on pelagic zooplankton community structure and the strength of cascading trophic interactions. We focus on the effects of differences in (1) the duration of residence in fresh water (either seasonal or year-round) and (2) differences in foraging morphology, both of which may strongly influence interactions between alewives and their prey. We measured zooplankton community structure, algal biomass, and spring total phosphorus in lakes that contained landlocked, anadromous, or no alewives. Both the duration of residence and the intraspecific variation in foraging morphology strongly influenced zooplankton community structure. Lakes with landlocked alewives had small-bodied zooplankton year-round, and lakes with no alewives had large-bodied zooplankton year-round. In contrast, zooplankton communities in lakes with anadromous alewives cycled between large-bodied zooplankton in the winter and spring and small-bodied zooplankton in the summer. In summer, differences in feeding morphology of alewives caused zooplankton biomass to be lower and body size to be smaller in lakes with anadromous alewives than in lakes with landlocked alewives. Furthermore, intraspecific variation altered the strength of the trophic cascade caused by alewives. Our results demonstrate that intraspecific phenotypic variation of predators can regulate community structure and ecosystem processes by modifying the form and strength of complex trophic interactions.

  7. Vulnerability of black grouse hens to goshawk predation: result of food supply or predation facilitation?

    PubMed

    Tornberg, Risto; Helle, Pekka; Korpimäki, Erkki

    2011-07-01

    The plant cycle hypothesis says that poor-quality food affects both herbivorous voles (Microtinae spp.) and grouse (Tetraonidae spp.) in vole decline years, leading to increased foraging effort in female grouse and thus a higher risk of predation by the goshawk Accipiter gentilis. Poor-quality food (mainly the bilberry Vaccinium myrtillus) for these herbivores is induced by seed masting failure in the previous year, when the bilberry is able to allocate resources for chemical defence (the mast depression hypothesis; MDH). The predation facilitation hypothesis (PFH) in turn states that increased searching activity of vole-eating predators during or after the decline year of voles disturbs incubating and brooding grouse females. The behaviours used by grouse to avoid these terrestrial predators make them more vulnerable to predation by goshawks. We tested the main predictions of the MDH and PFH by collecting long-term (21-year) data from black grouse Tetrao tetrix hens and cocks killed by breeding goshawks supplemented with indices of bilberry crop, vole abundance and small carnivores in the vicinity of Oulu, northern Finland. We did not find obvious support for the prediction of the MDH that there is a negative correlation of bilberry crop in year t with vole abundance and with predation index of black grouse hens in year t + 1. We did find obvious support for the prediction of the PFH that there is a positive correlation between predator abundance and predation index of grouse hens, because the stoat Mustela erminea abundance index was positively related to the predation index of black grouse hens. We suggest that changes in vulnerability of grouse hens may mainly be caused by the guild of vole-eating predators, who shift to alternative prey in the decline phase of the vole cycle, and thus chase grouse hens and chicks to the talons of goshawks and other avian predators.

  8. Volumetric Abnormalities Predating the Onset of Schizophrenia and Affective Psychoses: An MRI Study in Subjects at Ultrahigh Risk of Psychosis

    PubMed Central

    Dazzan, Paola; Soulsby, Bridget; Mechelli, Andrea; Wood, Stephen J.; Velakoulis, Dennis; Phillips, Lisa J.; Yung, Alison R.; Chitnis, Xavier; Lin, Ashleigh; Murray, Robin M.; McGorry, Patrick D.; McGuire, Philip K.; Pantelis, Christos

    2012-01-01

    It remains unclear whether brain structural abnormalities observed before the onset of psychosis are specific to schizophrenia or are common to all psychotic disorders. This study aimed to measure regional gray matter volume prior to the onset of schizophreniform and of affective psychoses. We investigated 102 subjects at ultrahigh risk (UHR) of developing psychosis recruited from the Personal Assessment and Crisis Evaluation Clinic in Melbourne, Australia. Twenty-eight of these subjects developed psychosis subsequent to scanning: 19 schizophrenia, 7 affective psychoses, and 2 other psychoses. We examined regional gray matter volume using 1.5 mm thick, coronal, 1.5 Tesla magnetic resonance imaging and voxel-based morphometry methods of image analysis. Subjects were scanned at presentation and were followed up clinically for a minimum of 12 months, to detect later transition to psychosis. We found that both groups of subjects who subsequently developed psychosis (schizophrenia and affective psychosis) showed reductions in the frontal cortex relative to UHR subjects who did not develop psychosis. The subgroup that subsequently developed schizophrenia also showed smaller volumes in the parietal cortex and, at trend level, in the temporal cortex, whereas those who developed an affective psychosis had significantly smaller subgenual cingulate volumes. These preliminary findings suggest that volumetric abnormalities in UHR individuals developing schizophrenia vs affective psychoses comprise a combination of features that predate both disorders and others that may be specific to the nature of the subsequent disorder. PMID:21518921

  9. Biotic structure indirectly affects associated prey in a predator-specific manner via changes in the sensory environment.

    PubMed

    Wilson, Miranda L; Weissburg, Marc J

    2013-02-01

    Indirect effects, which can be either positive or negative, may be important in areas containing biotic structure, because such structure can provide refuge and habitat, produce additional sensory cues that may attract predators, and modify the sensory landscape in which predator-prey interactions occur. To determine the indirect effects of biotic structure on prey populations, we assessed predation on patches of hard clams (Mercenaria mercenaria) by large odor-mediated blue crab (Callinectes sapidus) and knobbed whelk (Busycon carica) predators at 0, 5, and 10 m from oyster reefs in intertidal salt marshes. Oyster reefs had an overall indirect negative effect on hard clams, with higher predation rates closer to the reef than farther away. Predator-specific patterns of predation showed that blue crabs consumed more clams very close to the reef, whereas whelks consumed more clams at intermediate distances. Laboratory flume experiments suggest that the oyster reef structure creates turbulence that diminishes predator foraging efficiency, particularly in rapidly mobile predators such as blue crabs, but that oyster reef chemicals ameliorate the negative impact of turbulence on foraging success for both predators. Changes in the sensory landscape, in combination with predator perceptual ability, will determine the positive and/or negative impacts of biotic structure on associated prey. Gaining an understanding of the context specificity of positive and negative sensory effects of biotic structure provides insights that are important for developing a predictive framework to assess the magnitude and distribution of indirect interactions in natural communities.

  10. Factors affecting methylmercury biomagnification by a widespread aquatic invertebrate predator, the phantom midge larvae Chaoborus.

    PubMed

    Le Jeune, Anne-Hélène; Bourdiol, Floriane; Aldamman, Lama; Perron, Tania; Amyot, Marc; Pinel-Alloul, Bernadette

    2012-06-01

    MeHg biomagnification by the phantom midge Chaoborus in relation to MeHg concentrations in their prey and its migratory behavior was investigated in two Canadian Precambrian Shield lakes. Three Chaoborus species with contrasted migratory behavior were collected in a fishless and a fish-inhabited lake. All species accumulated MeHg through their ontogenic development. In the lake inhabited by fish, all instars of Chaoborus punctipennis displayed a marked migratory behavior and were unable to biomagnify MeHg, whereas in the fishless lake, Chaoborus americanus and Chaoborus trivittatus biomagnified MeHg. Reduced biomagnification capacity of C. trivittatus, the coexisting species living with C. americanus, was also ascribed to a progressive vertical segregation with age. Growth dilution, amount and type of prey items or trophic position could not explain the different patterns of biomagnification. Our findings demonstrate that the most common invertebrate predator of temperate planktonic food webs can biomagnify mercury, contrarily to previous reports.

  11. Defaunation affects Astrocaryum gratum (Arecales: Arecaceae) seed survivorship in a sub-montane tropical forest.

    PubMed

    Aliaga-Rossel, Enzo; Manuel Fragoso, Jos

    2015-03-01

    initial 400 seeds left for each control exclosure in each type of forest, there was a significant difference between the seed removal; 1.75% seeds in the unhunted forest remained; 43.5% in the moderately hunted forest, and 48.5% in hunted forest. The main cause of seed mortality was white lipped peccaries; while in the forests without them, the main removal was caused by rodents and a higher insect infection was observed in the heavily hunted forest. Our results indicated that defaunation affects seed survivorship.

  12. Pollination and seed predation by moths on Silene and allied Caryophyllaceae: evaluating a model system to study the evolution of mutualisms.

    PubMed

    Kephart, Susan; Reynolds, Richard J; Rutter, Matthew T; Fenster, Charles B; Dudash, Michele R

    2006-01-01

    Nursery pollinators, and the plants they use as hosts for offspring development, function as exemplary models of coevolutionary mutualism. The two pre-eminent examples--fig wasps and yucca moths--show little variation in the interaction: the primary pollinator is an obligate mutualist. By contrast, nursery pollination of certain Caryophyllaceae, including Silene spp., by two nocturnal moth genera, Hadena and Perizoma, ranges from antagonistic to potentially mutualistic, offering an opportunity to test hypotheses about the factors that promote or discourage the evolution of mutualism. Here, we review nursery pollination and host-plant interactions in over 30 caryophyllaceous plants, based on published studies and a survey of researchers investigating pollination, seed predation, and moth morphology and behavior. We detected little direct evidence of mutualism in these moth-plant interactions, but found traits and patterns in both that are nonetheless consistent with the evolution of mutualism and merit further attention.

  13. Linkage between isozyme markers and a locus affecting seed size in Phaseolus vulgaris L.

    PubMed

    Vallejos, C E; Chase, C D

    1991-03-01

    Backcross and F2 progenies were produced between two bean genotypes, 'XR-235' and 'Calima,' which differ in seed weight by a factor of two. The small-seeded 'XR-235' was used as the pistillate and recurrent parent. These genotypes showed polymorphisms at nine isozyme loci and at the phaseolin locus. Seed size parameters (weight, length, width, and thickness) were determined for each BC1 and F2 individual, i.e., for seeds harvested from 'XR-235' after pollination with F1 and from the F1 after selfing, respectively. A combination of starch gel electrophoresis and enzyme activity staining was used to determine the genotype of each BC1 and F2 individual at the segregating loci. SDS-PAGE and Coomassie blue staining were used to determine geno-type at the phaseolin locus. Tests for independent assortment using two-way contingency and maximum likelihood tables revealed three linkage pairs: Aco-1 - 20 cM - Dia-1; Adh-1 - 2 cM - Got-2; and Est-2 - 11 cM - Pha. Statistical comparisons were made between the means of genotype classes at each segregating locus for all seed size parameters. The results from two independently obtained BC1s and the F2 consistently indicated that the Adh-1-Got-2 segment was linked to a locus that affected seed size and overcame maternal control over seed size. This locus has been designated Ssz-1. This gene exhibited additive gene action and accounted for 30-50% of the seed size difference between the parents.

  14. 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.

  15. The effect of burial depth on removal of seeds of Phytolacca americana.

    SciTech Connect

    Orrock, John, L.: Damschen, Ellen, I.

    2007-04-01

    Abstract - Although burial is known to have important effects on seed predation in a variety of habitats, the role of burial depth in affecting the removal of seeds in early successional systems is poorly known. Phytolacca American (pokeweed) is a model species to examine the role of burial depth in affecting seed removal because it is common in early-successional habitats, studies suggest that seed removal is indicative of seed predation, and seed predation is related to the recruitment of mature plants. To determine how burial depth affects P. americana seed removal, 20 seeds of P. americana were buried at depths of 0, 1, or 3 cm in early-successional habitats at the Savannah River Site in South Carolina for over 6 weeks. The frequency with which seeds were encountered (as measured by the removal of at least one seed) and the proportion of seeds removed was significantly greater when seeds were on the soil surface (0 cm depth) compared to seeds that were buried 1 cm or 3 cm; there was no difference in encounter or removal between seeds at 1 cm or 3 cm. Our findings suggest that burial may have important consequences for P. americana population dynamics, because seed survival depends upon whether or not the seed is buried, and relatively shallow burial can yield large increases in seed survival. Because seed limitation is known to be an important determinant of plant community composition in early successional systems, our work suggests that burial may play an unappreciated role in the dynamics of these communities by reducing predator-mediated seed limitation.

  16. Seed germination of medicinal plant, fennel (Foeniculum vulgare Mill), as affected by different priming techniques.

    PubMed

    Tahaei, Amirreza; Soleymani, Ali; Shams, Majid

    2016-09-01

    Reduced seed germination is among the most important factors adversely affecting crop stand and subsequent plant growth. Fennel (Foeniculum vulgare Mill) is an important medicinal plant with poor seed germination rate, occasionally. It is accordingly pertinent to find methods which can enhance fennel seed germination and remove the barriers of dormancy breaking. The present experiments studied the effects of two different priming (cold moist stratification and osmopriming) and 14 dormancy breaking techniques (hormonal, osmopriming, biopriming, chemical priming, and hydropriming) on the seed germination and seedling growth of two different fennel genotypes under growth chamber conditions. In the first and second experiment, the priming techniques including the time lengths of cold moist stratification (0, 15, 30, and 45 days) and the concentrations of polyethylene glycol 6000 (PEG6000, osmopriming at -0.99, -1.35, and -2.33 MPa) were used as the main plots. However, in both experiments, the dormancy breaking techniques and fennel genotypes were factorially combined and used as the subplots. Different seed- and seedling-related parameters including germination (%), plumule, radicle and seedling length, average germination time, rate and homogeneity of germination, and seed vigor index were determined. Both priming techniques were efficient on the enhancement of seed germination and seedling growth. Among the dormancy breaking techniques, Aminol Forte (biopriming), kadostim (biopriming), benzyl adenine + kinetin (biopriming), distilled water (hydropriming), gibberellin + kinetin (hormonal priming), and benzyl adenine + kinetin + gibberellin (biopriming) were the most effective ones. The related concentrations were equal to 100 mg/l, 10(-5) M, and 0.4 %. The fennel genotypes reacted significantly different under priming conditions. It is possible to enhance seed germination and seedling growth of fennel using priming and dormancy breaking

  17. Rapid and Quantitative Assay of Amyloid-Seeding Activity in Human Brains Affected with Prion Diseases

    PubMed Central

    Takatsuki, Hanae; Satoh, Katsuya; Sano, Kazunori; Fuse, Takayuki; Nakagaki, Takehiro; Mori, Tsuyoshi; Ishibashi, Daisuke; Mihara, Ban; Takao, Masaki; Iwasaki, Yasushi; Yoshida, Mari; Atarashi, Ryuichiro; Nishida, Noriyuki

    2015-01-01

    The infectious agents of the transmissible spongiform encephalopathies are composed of amyloidogenic prion protein, PrPSc. Real-time quaking-induced conversion can amplify very small amounts of PrPSc seeds in tissues/body fluids of patients or animals. Using this in vitro PrP-amyloid amplification assay, we quantitated the seeding activity of affected human brains. End-point assay using serially diluted brain homogenates of sporadic Creutzfeldt–Jakob disease patients demonstrated that 50% seeding dose (SD50) is reached approximately 1010/g brain (values varies 108.79–10.63/g). A genetic case (GSS-P102L) yielded a similar level of seeding activity in an autopsy brain sample. The range of PrPSc concentrations in the samples, determined by dot-blot assay, was 0.6–5.4 μg/g brain; therefore, we estimated that 1 SD50 unit was equivalent to 0.06–0.27 fg of PrPSc. The SD50 values of the affected brains dropped more than three orders of magnitude after autoclaving at 121°C. This new method for quantitation of human prion activity provides a new way to reduce the risk of iatrogenic prion transmission. PMID:26070208

  18. How optimally foraging predators promote prey coexistence in a variable environment.

    PubMed

    Stump, Simon Maccracken; Chesson, Peter

    2017-04-01

    Optimal foraging is one of the major predictive theories of predator foraging behavior. However, how an optimally foraging predator affects the coexistence of competing prey is not well understood either in a constant or variable environment, especially for multiple prey species. We study the impact of optimal foraging on prey coexistence using an annual plant model, with and without annual variation in seed germination. Seed predators are modeled using Charnov's model of adaptive diet choice. Our results reveal that multiple prey species can coexist because of this type of predator, and that their effect is not greatly modified by environmental variation. However, in diverse communities, the requirements for coexistence by optimal foraging alone are very restrictive. Optimally foraging predators can have a strong equalizing effect on their prey by creating a competition-predation trade-off. Thus, their main role in promoting diversity may be to reduce species-average fitness differences, making it easier for other mechanisms, such as the storage effect, to allow multiple species to coexist. Like previous models, our model showed that when germination rates vary, the storage effect from competition promotes coexistence. Our results also show that optimally foraging predators can generate a negative storage effect from predation, undermining coexistence, but that this effect will be minor whenever predators commonly differentiate their prey.

  19. Diurnal Temperature Variations Affect Development of a Herbivorous Arthropod Pest and its Predators

    PubMed Central

    Vangansbeke, Dominiek; Audenaert, Joachim; Nguyen, Duc Tung; Verhoeven, Ruth; Gobin, Bruno; Tirry, Luc; De Clercq, Patrick

    2015-01-01

    The impact of daily temperature variations on arthropod life history remains woefully understudied compared to the large body of research that has been carried out on the effects of constant temperatures. However, diurnal varying temperature regimes more commonly represent the environment in which most organisms thrive. Such varying temperature regimes have been demonstrated to substantially affect development and reproduction of ectothermic organisms, generally in accordance with Jensen’s inequality. In the present study we evaluated the impact of temperature alternations at 4 amplitudes (DTR0, +5, +10 and +15°C) on the developmental rate of the predatory mites Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus McGregor (Acari: Phytoseiidae) and their natural prey, the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae). We have modelled their developmental rates as a function of temperature using both linear and nonlinear models. Diurnally alternating temperatures resulted in a faster development in the lower temperature range as compared to their corresponding mean constant temperatures, whereas the opposite was observed in the higher temperature range. Our results indicate that Jensen’s inequality does not suffice to fully explain the differences in developmental rates at constant and alternating temperatures, suggesting additional physiological responses play a role. It is concluded that diurnal temperature range should not be ignored and should be incorporated in predictive models on the phenology of arthropod pests and their natural enemies and their performance in biological control programmes. PMID:25874697

  20. Diurnal temperature variations affect development of a herbivorous arthropod pest and its predators.

    PubMed

    Vangansbeke, Dominiek; Audenaert, Joachim; Nguyen, Duc Tung; Verhoeven, Ruth; Gobin, Bruno; Tirry, Luc; De Clercq, Patrick

    2015-01-01

    The impact of daily temperature variations on arthropod life history remains woefully understudied compared to the large body of research that has been carried out on the effects of constant temperatures. However, diurnal varying temperature regimes more commonly represent the environment in which most organisms thrive. Such varying temperature regimes have been demonstrated to substantially affect development and reproduction of ectothermic organisms, generally in accordance with Jensen's inequality. In the present study we evaluated the impact of temperature alternations at 4 amplitudes (DTR0, +5, +10 and +15°C) on the developmental rate of the predatory mites Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus McGregor (Acari: Phytoseiidae) and their natural prey, the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae). We have modelled their developmental rates as a function of temperature using both linear and nonlinear models. Diurnally alternating temperatures resulted in a faster development in the lower temperature range as compared to their corresponding mean constant temperatures, whereas the opposite was observed in the higher temperature range. Our results indicate that Jensen's inequality does not suffice to fully explain the differences in developmental rates at constant and alternating temperatures, suggesting additional physiological responses play a role. It is concluded that diurnal temperature range should not be ignored and should be incorporated in predictive models on the phenology of arthropod pests and their natural enemies and their performance in biological control programmes.

  1. Alterations in Seed Development Gene Expression Affect Size and Oil Content of Arabidopsis Seeds1[C][W][OPEN

    PubMed Central

    Fatihi, Abdelhak; Zbierzak, Anna Maria; Dörmann, Peter

    2013-01-01

    Seed endosperm development in Arabidopsis (Arabidopsis thaliana) is under control of the polycomb group complex, which includes Fertilization Independent Endosperm (FIE). The polycomb group complex regulates downstream factors, e.g. Pheres1 (PHE1), by genomic imprinting. In heterozygous fie mutants, an endosperm develops in ovules carrying a maternal fie allele without fertilization, finally leading to abortion. Another endosperm development pathway depends on MINISEED3 (a WRKY10 transcription factor) and HAIKU2 (a leucine-rich repeat kinase). While the role of seed development genes in the embryo and endosperm establishment has been studied in detail, their impact on metabolism and oil accumulation remained unclear. Analysis of oil, protein, and sucrose accumulation in mutants and overexpression plants of the four seed development genes revealed that (1) seeds carrying a maternal fie allele accumulate low oil with an altered composition of triacylglycerol molecular species; (2) homozygous mutant seeds of phe1, mini3, and iku2, which are smaller, accumulate less oil and slightly less protein, and starch, which accumulates early during seed development, remains elevated in mutant seeds; (3) embryo-specific overexpression of FIE, PHE1, and MINI3 has no influence on seed size and weight, nor on oil, protein, or sucrose content; and (4) overexpression of IKU2 results in seeds with increased size and weight, and oil content of overexpressed IKU2 seeds is increased by 35%. Thus, IKU2 overexpression represents a novel strategy for the genetic manipulation of the oil content in seeds. PMID:24014578

  2. Arabidopsis thaliana DOF6 negatively affects germination in non-after-ripened seeds and interacts with TCP14

    PubMed Central

    Rueda-Romero, Paloma; Barrero-Sicilia, Cristina; Gómez-Cadenas, Aurelio; Carbonero, Pilar; Oñate-Sánchez, Luis

    2012-01-01

    Seed dormancy prevents seeds from germinating under environmental conditions unfavourable for plant growth and development and constitutes an evolutionary advantage. Dry storage, also known as after-ripening, gradually decreases seed dormancy by mechanisms not well understood. An Arabidopsis thaliana DOF transcription factor gene (DOF6) affecting seed germination has been characterized. The transcript levels of this gene accumulate in dry seeds and decay gradually during after-ripening and also upon seed imbibition. While constitutive over-expression of DOF6 produced aberrant growth and sterility in the plant, its over-expression induced upon seed imbibition triggered delayed germination, abscisic acid (ABA)-hypersensitive phenotypes and increased expression of the ABA biosynthetic gene ABA1 and ABA-related stress genes. Wild-type germination and gene expression were gradually restored during seed after-ripening, despite of DOF6-induced over-expression. DOF6 was found to interact in a yeast two-hybrid system and in planta with TCP14, a previously described positive regulator of seed germination. The expression of ABA1 and ABA-related stress genes was also enhanced in tcp14 knock-out mutants. Taken together, these results indicate that DOF6 negatively affects seed germination and opposes TCP14 function in the regulation of a specific set of ABA-related genes. PMID:22155632

  3. Arabidopsis thaliana DOF6 negatively affects germination in non-after-ripened seeds and interacts with TCP14.

    PubMed

    Rueda-Romero, Paloma; Barrero-Sicilia, Cristina; Gómez-Cadenas, Aurelio; Carbonero, Pilar; Oñate-Sánchez, Luis

    2012-03-01

    Seed dormancy prevents seeds from germinating under environmental conditions unfavourable for plant growth and development and constitutes an evolutionary advantage. Dry storage, also known as after-ripening, gradually decreases seed dormancy by mechanisms not well understood. An Arabidopsis thaliana DOF transcription factor gene (DOF6) affecting seed germination has been characterized. The transcript levels of this gene accumulate in dry seeds and decay gradually during after-ripening and also upon seed imbibition. While constitutive over-expression of DOF6 produced aberrant growth and sterility in the plant, its over-expression induced upon seed imbibition triggered delayed germination, abscisic acid (ABA)-hypersensitive phenotypes and increased expression of the ABA biosynthetic gene ABA1 and ABA-related stress genes. Wild-type germination and gene expression were gradually restored during seed after-ripening, despite of DOF6-induced over-expression. DOF6 was found to interact in a yeast two-hybrid system and in planta with TCP14, a previously described positive regulator of seed germination. The expression of ABA1 and ABA-related stress genes was also enhanced in tcp14 knock-out mutants. Taken together, these results indicate that DOF6 negatively affects seed germination and opposes TCP14 function in the regulation of a specific set of ABA-related genes.

  4. Seed trait-mediated selection by rodents affects mutualistic interactions and seedling recruitment of co-occurring tree species.

    PubMed

    Zhang, Hongmao; Yan, Chuan; Chang, Gang; Zhang, Zhibin

    2016-02-01

    As mutualists, seed dispersers may significantly affect mutualistic interactions and seedling recruitment of sympatric plants that share similar seed dispersers, but studies are rare. Here, we compared seed dispersal fitness in two co-occurring plant species (Armeniaca sibirica and Amygdalus davidiana) that inhabit warm temperate deciduous forest in northern China. We tested the hypothesis that seed trait-mediated selection by rodents may influence mutualistic interactions with rodents and then seedling establishment of co-occurring plant species. A. davidiana seeds are larger and harder (thick endocarps) than A. sibirica seeds, but they have similar levels of nutrients (crude fat, crude protein), caloric value and tannin. More A. sibirica seedlings are found in the field. Semi-natural enclosure tests indicated that the two seed species were both harvested by the same six rodent species, but that A. sibirica had mutualistic interactions (scatter hoarding) with four rodent species (Apodemus peninsulae, A. agrarius, Sciurotamias davidianus, Tamias sibiricus), and A. davidiana with only one (S. davidianus). Tagged seed dispersal experiments in the field indicated that more A. sibirica seeds were scatter-hoarded by rodents, and more A. sibirica seeds survived to the next spring and became seedlings. A. sibirica seeds derive more benefit from seed dispersal by rodents than A. davidiana seeds, particularly in years with limited seed dispersers, which well explained the higher seedling recruitment of A. sibirica compared with that of A. davidiana under natural conditions. Our results suggest that seed dispersers may play a significant role in seedling recruitment and indirect competition between co-occurring plant species.

  5. 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

  6. Seed protein, oil, fatty acids, and minerals concentration as affected by foliar K-glyphosate application in soybean cultivars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Previous studies showed that glyphosate (Gly) may chelate cation nutrients, including potassium (K), which might affect the nutritional status of soybean seed. The objective of this study was to evaluate seed composition (protein, oil, fatty acids, and minerals) as influenced by foliar applications ...

  7. Effects of Fruit Toxins on Intestinal and Microbial β-Glucosidase Activities of Seed-Predating and Seed-Dispersing Rodents (Acomys spp.).

    PubMed

    Kohl, Kevin D; Samuni-Blank, Michal; Lymberakis, Petros; Kurnath, Patrice; Izhaki, Ido; Arad, Zeev; Karasov, William H; Dearing, M Denise

    2016-01-01

    Plant secondary compounds (PSCs) have profound influence on the ecological interaction between plants and their consumers. Glycosides, a class of PSC, are inert in their intact form and become toxic on activation by either plant β-glucosidase enzymes or endogenous β-glucosidases produced by the intestine of the plant-predator or its microbiota. Many insect herbivores decrease activities of endogenous β-glucosidases to limit toxin exposure. However, such an adaptation has never been investigated in nonmodel mammals. We studied three species of spiny mice (Acomys spp.) that vary in their feeding behavior of the glycoside-rich fruit of Ochradenus baccatus. Two species, the common (Acomys cahirinus) and Crete (Acomys minous) spiny mice, behaviorally avoid activating glycosides, while the golden spiny mouse (Acomys russatus) regularly consumes activated glycosides. We fed each species a nontoxic diet of inert glycosides or a toxic diet of activated fruit toxins and investigated the responses of intestinal and microbial β-glucosidase activities. We found that individuals feeding on activated toxins had lower intestinal β-glucosidase activity and that the species that behaviorally avoid activating glycosides also had lower intestinal β-glucosidase activity regardless of treatment. The microbiota represented a larger source of toxin liberation, and the toxin-adapted species (golden spiny mouse) exhibited almost a fivefold increase in microbial β-glucosidase when fed activated toxins, while other species showed slight decreases. These results are contrary to those in insects, where glycoside-adapted species have lower β-glucosidase activity. The glycoside-adapted golden spiny mouse may have evolved tolerance mechanisms such as enhanced detoxification rather than avoidance mechanisms.

  8. 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.

  9. Mutant alleles at the rugosus loci in pea affect seed moisture sorption isotherms and the relations between seed longevity and moisture content.

    PubMed

    Lyall, T W; Ellis, R H; John, P; Hedley, C L; Wang, T L

    2003-01-01

    Pea (Pisum sativum L.) mutant near-isogenic lines (RRrbrb, rrRbRb, rrrbrb) with lower starch but higher lipid contents, brought about by lesions in the starch biosynthetic pathway, had seed moisture sorption isotherms displaced below that of the wild type (RRRbRb). The negative logarithmic relationship between seed longevity and seed storage moisture content (%, f.wt basis), determined in hermetic storage at 65 degrees C, also differed: longevity in the mutant near-isogenic lines was poorer and less sensitive to moisture content than in the wild type (i.e. C(W) was lower). The low-moisture-content limit (m(c)) to this relation also differed, being lower in the mutant near-isogenic lines (5.4-5.9%) than in the wild type (6.1%). In contrast, all four near-isogenic lines showed no difference (P >0.25) in the negative semi-logarithmic relationship between equilibrium relative humidity (ERH) and seed longevity. It is concluded that the effect of these alleles at the r and rb loci on seed longevity was largely indirect; a consequence of their effect on seed composition and hence on moisture sorption isotherms. However, this explanation could not be invoked at moisture contents below m(c) where differences in longevity remained substantial (RRRbRb double that of rrrbrb). Hence, these mutant alleles affected seed longevity directly at very low moisture contents.

  10. Hairy vetch (Vicia villosa) seed size affects germination response to coumarin

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The inhibition of seed germination by an allelochemical is generally greater in small seeds than in large seeds. This response may have significant impact on weed control by allelopathic cover crops where the small-seeded weeds would be more effectively controlled than large-seeded species. The stu...

  11. Contagious seed dispersal beneath heterospecific fruiting trees and its consequences.

    SciTech Connect

    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 by 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.

  12. How predator functional responses and Allee effects in prey affect the paradox of enrichment and population collapses.

    PubMed

    Boukal, David S; Sabelis, Maurice W; Berec, Ludek

    2007-08-01

    In Rosenzweig-MacArthur models of predator-prey dynamics, Allee effects in prey usually destabilize interior equilibria and can suppress or enhance limit cycles typical of the paradox of enrichment. We re-evaluate these conclusions through a complete classification of a wide range of Allee effects in prey and predator's functional response shapes. We show that abrupt and deterministic system collapses not preceded by fluctuating predator-prey dynamics occur for sufficiently steep type III functional responses and strong Allee effects (with unstable lower equilibrium in prey dynamics). This phenomenon arises as type III functional responses greatly reduce cyclic dynamics and strong Allee effects promote deterministic collapses. These collapses occur with decreasing predator mortality and/or increasing susceptibility of the prey to fall below the threshold Allee density (e.g. due to increased carrying capacity or the Allee threshold itself). On the other hand, weak Allee effects (without unstable equilibrium in prey dynamics) enlarge the range of carrying capacities for which the cycles occur if predators exhibit decelerating functional responses. We discuss the results in the light of conservation strategies, eradication of alien species, and successful introduction of biocontrol agents.

  13. Fenugreek seed affects intestinal microbiota and immunological variables in piglets after weaning.

    PubMed

    Zentek, Jürgen; Gärtner, Stefanie; Tedin, Lydia; Männer, Klaus; Mader, Anneluise; Vahjen, Wilfried

    2013-03-14

    Fenugreek seed has been shown to affect the intestinal microbiota and immunological responses in animals. A feeding trial with male castrated piglets was performed over 28 d without or with the addition of 1·5 g fenugreek seeds/kg complete diet in ten and eleven piglets, weaned at 21 d. In the intestinal tract, pH, lactate and SCFA were measured as major bacterial metabolites. Immune cell phenotypes, phagocytic activity and lymphocyte proliferation after stimulation with pokeweed mitogen, concanavalin A and phytohaemagglutinin M were measured by flow cytometry. Health status and performance of the piglets were not affected by fenugreek. The pH in the caecum and colon were reduced compared with the control (P< 0·05). Higher concentrations of l-lactic acid were recorded in the small-intestinal digesta (average concentrations from the duodenum, jejunum and ileum; P< 0·05), while the concentrations of SCFA remained unchanged except an increase in n-butyric acid in colon contents (P< 0·05). The piglets fed the fenugreek diet had higher Lactobacillus and clostridium cluster I concentrations and lower Escherichia, Hafnia and Shigella concentrations in the small intestine. The addition of fenugreek increased the relative concentration of the γδ T-cell population (TCR1+CD8α-) in the blood with a simultaneous reduction of antigen-presenting cells (MHCII+CD5-) (P< 0·05). Proliferation rate and phagocytosis activity of monocytes were not affected by the additive. In conclusion, fenugreek seeds might be interesting as a feed ingredient for young piglets due to their effects on the intestinal microbiota and immunological variables. The impact on performance and animal health has to be further evaluated.

  14. CRF receptor blockade prevents initiation and consolidation of stress effects on affect in the predator stress model of PTSD.

    PubMed

    Adamec, Robert; Fougere, Dennis; Risbrough, Victoria

    2010-07-01

    Post traumatic stress disorder (PTSD) is a chronic anxiety disorder initiated by an intensely threatening, traumatic event. There is a great need for more efficacious pharmacotherapy and preventive treatments for PTSD. In animals, corticotropin-releasing factor (CRF) and the CRF1 receptor play a critical role in behavioural and neuroendocrine responses to stress. We tested the hypothesis that CRF1 activation is required for initiation and consolidation of long-term effects of trauma on anxiety-like behaviour in the predator exposure (predator stress) model of PTSD. Male C57BL6 mice were treated with the selective CRF1 antagonist CRA0450 (2, 20 mg/kg) 30 min before or just after predator stress. Long-term effects of stress on rodent anxiety were measured 7 d later using acoustic startle, elevated plus maze (EPM), light/dark box, and hole-board tests. Predator stress increased startle amplitude and delayed startle habituation, increased time in and decreased exits from the dark chamber in the light/dark box test, and decreased risk assessment in the EPM. CRF1 antagonism had limited effects on these behaviours in non-stressed controls, with the high dose decreasing risk assessment in the EPM. However, in stressed animals CRF1 antagonism blocked initiation and consolidation of stressor effects on startle, and returned risk assessment to baseline levels in predator-stressed mice. These findings implicate CRF1 activation in initiation and post-trauma consolidation of predator stress effects on anxiety-like behaviour, specifically on increased arousal as measured by exaggerated startle behaviours. These data support further research of CRF1 antagonists as potential prophylactic treatments for PTSD.

  15. 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...

  16. Does Cold Plasma Affect Breaking Dormancy and Seed Germination? A Study on Seeds of Lamb's Quarters (Chenopodium album agg.)

    NASA Astrophysics Data System (ADS)

    Božena, Šerá; Michal, Šerý; Vitězslav, Štrañák; Petr, Špatenka; Milan, tichý

    2009-12-01

    Low-pressure discharge is applied for stimulation of germination of two seed lots of Lamb's Quarters (Chenopodium album agg.) with different starting germinations (17%, 8%) and in different stages of dormancy. Different exposition durations with cold plasma treatment were applied. The variable of the ratio cumulative germination was calculated. The Richards' equation was used for curve-fitting and simulation of the growth curves. Population parameters, namely Vi - viability, Me - time, Qu - dispersion, and Sk - skewness, counted from the curves described the germination rate well. Significant differences among Qu confirmed the erratic dormancy and gradual germination of Lamb's Quarters. No difference in the Me parameter was found between two tested seed lots, and no interspecies characteristics were changed using low-pressure discharge. The results suggested that plasma treatment changed seed germination in Lamb's Quarters seeds.

  17. Silencing of BnTT1 family genes affects seed flavonoid biosynthesis and alters seed fatty acid composition in Brassica napus.

    PubMed

    Lian, Jianping; Lu, Xiaochun; Yin, Nengwen; Ma, Lijuan; Lu, Jing; Liu, Xue; Li, Jiana; Lu, Jun; Lei, Bo; Wang, Rui; Chai, Yourong

    2017-01-01

    TRANSPARENT TESTA1 (TT1) is a zinc finger protein that contains a WIP domain. It plays important roles in controlling differentiation and pigmentation of the seed coat endothelium, and can affect the expression of early biosynthetic genes and late biosynthetic genes of flavonoid biosynthesis in Arabidopsis thaliana. In Brassica napus (AACC, 2n=38), the functions of BnTT1 genes remain unknown and few studies have focused on their roles in fatty acid (FA) biosynthesis. In this study, BnTT1 family genes were silenced by RNA interference, which resulted in yellow rapeseed, abnormal testa development (a much thinner testa), decreased seed weight, and altered seed FA composition in B. napus. High-throughput sequencing of genes differentially expressed between developing transgenic B. napus and wild-type seeds revealed altered expression of numerous genes involved in flavonoid and FA biosynthesis. As a consequence of this altered expression, we detected a marked decrease of oleic acid (C18:1) and notable increases of linoleic acid (C18:2) and α-linolenic acid (C18:3) in mature transgenic B. napus seeds by gas chromatography and near-infrared reflectance spectroscopy. Meanwhile, liquid chromatography-mass spectrometry showed reduced accumulation of flavonoids in transgenic seeds. Therefore, we propose that BnTT1s are involved in the regulation of flavonoid biosynthesis, and may also play a role in FA biosynthesis in B. napus.

  18. The Anthelmintic Ingredient Moxidectin Negatively Affects Seed Germination of Three Temperate Grassland Species

    PubMed Central

    Eichberg, Carsten; Wohde, Manuel; Müller, Kerstin; Rausch, Anja; Scherrmann, Christina; Scheuren, Theresa; Düring, Rolf-Alexander; Donath, Tobias W.

    2016-01-01

    In animal farming, anthelmintics are regularly applied to control gastrointestinal nematodes. There is plenty of evidence that also non-target organisms, such as dung beetles, are negatively affected by residues of anthelmintics in faeces of domestic ungulates. By contrast, knowledge about possible effects on wild plants is scarce. To bridge this gap of knowledge, we tested for effects of the common anthelmintic formulation Cydectin and its active ingredient moxidectin on seed germination. We conducted a feeding experiment with sheep and germination experiments in a climate chamber. Three wide-spread plant species of temperate grasslands (Centaurea jacea, Galium verum, Plantago lanceolata) were studied. We found significant influences of both, Cydectin and moxidectin, on germination of the tested species. Across species, both formulation and active ingredient solely led to a decrease in germination percentage and synchrony of germination and an increase in mean germination time with the formulation showing a more pronounced response pattern. Our study shows for the first time that anthelmintics have the potential to negatively affect plant regeneration. This has practical implications for nature conservation since our results suggest that treatments of livestock with anthelmintics should be carefully timed to not impede endozoochorous seed exchange between plant populations. PMID:27846249

  19. Predators determine how weather affects the spatial niche of lizard prey: exploring niche dynamics at a fine scale.

    PubMed

    Lopez-Darias, Marta; Schoener, Thomas W; Spiller, David A; Losos, Jonathan B

    2012-12-01

    Although abiotic and biotic factors can interact to shape the spatial niche of a species, studies that explore the interactive effects of both at a local scale are rare. We demonstrate that one of the main axes (perch height) characterizing the spatial niche of a common lizard, Anolis sagrei, varies according to the interactive effects of weather and the activity of a larger predatory lizard, Leiocephalus carinatus. Results were completely consistent: no matter how favorable the weather conditions for using the ground (mainly characterized by temperature, humidity, wind speed, rain), A. sagrei did not do so if the predator was present. Hence, great behavioral plasticity enabled A. sagrei to adjust its use of space very quickly. To the best of our knowledge, these results constitute the first field demonstration for anoles (and possibly for other animals as well) of how time-varying environmental conditions and predator presence interact to produce short-term changes in utilization along a major niche axis.

  20. Factors affecting post-control reinvasion by seed of an invasive species, Phragmites australis, in the central Platte River, Nebraska.

    USGS Publications Warehouse

    Galatowitsch, Susan M.; Larson, Diane L.; Larson, Jennifer L.

    2016-01-01

    Invasive plants, such as Phragmites australis, can profoundly affect channel environments of large rivers by stabilizing sediments and altering water flows. Invasive plant removal is considered necessary where restoration of dynamic channels is needed to provide critical habitat for species of conservation concern. However, these programs are widely reported to be inefficient. Post-control reinvasion is frequent, suggesting increased attention is needed to prevent seed regeneration. To develop more effective responses to this invader in the Central Platte River (Nebraska, USA), we investigated several aspects of Phragmites seed ecology potentially linked to post-control reinvasion, in comparison to other common species: extent of viable seed production, importance of water transport, and regeneration responses to hydrology. We observed that although Phragmites seed does not mature until very late in the ice-free season, populations produce significant amounts of viable seed (>50 % of filled seed). Most seed transported via water in the Platte River are invasive perennial species, although Phragmites abundances are much lower than species such as Lythrum salicaria, Cyperus esculentus and Phalaris arundinacea. Seed regeneration of Phragmites varies greatly depending on hydrology, especially timing of water level changes. Flood events coinciding with the beginning of seedling emergence reduced establishment by as much as 59 % compared to flood events that occurred a few weeks later. Results of these investigations suggest that prevention of seed set (i.e., by removal of flowering culms) should be a priority in vegetation stands not being treated annually. After seeds are in the seedbank, preventing reinvasion using prescribed flooding has a low chance of success given that Phragmites can regenerate in a wide variety of hydrologic microsites.

  1. Growth environment but not seed position on the parent plant affect seed germination of two Thlaspi arvense L. populations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Thlaspi arvense L. is a common weed found in most temperate regions throughout the world that also shows excellent potential for domestication as an oilseed crop. The complexity of T. arvense seed dormancy presently makes it difficult to manage as a weed or oilseed crop. Therefore, a better understa...

  2. Ecological meltdown in predator-free forest fragments.

    PubMed

    Terborgh, J; Lopez, L; Nuñez, P; Rao, M; Shahabuddin, G; Orihuela, G; Riveros, M; Ascanio, R; Adler, G H; Lambert, T D; Balbas, L

    2001-11-30

    The manner in which terrestrial ecosystems are regulated is controversial. The "top-down" school holds that predators limit herbivores and thereby prevent them from overexploiting vegetation. "Bottom-up" proponents stress the role of plant chemical defenses in limiting plant depredation by herbivores. A set of predator-free islands created by a hydroelectric impoundment in Venezuela allows a test of these competing world views. Limited area restricts the fauna of small (0.25 to 0.9 hectare) islands to predators of invertebrates (birds, lizards, anurans, and spiders), seed predators (rodents), and herbivores (howler monkeys, iguanas, and leaf-cutter ants). Predators of vertebrates are absent, and densities of rodents, howler monkeys, iguanas, and leaf-cutter ants are 10 to 100 times greater than on the nearby mainland, suggesting that predators normally limit their populations. The densities of seedlings and saplings of canopy trees are severely reduced on herbivore-affected islands, providing evidence of a trophic cascade unleashed in the absence of top-down regulation.

  3. Salinity affects production and salt tolerance of dimorphic seeds of Suaeda salsa.

    PubMed

    Wang, Fengxia; Xu, Yan-Ge; Wang, Shuai; Shi, Weiwei; Liu, Ranran; Feng, Gu; Song, Jie

    2015-10-01

    The effect of salinity on brown seeds/black seeds ratio, seed weight, endogenous hormone concentrations, and germination of brown and black seeds in the euhalophyte Suaeda salsa was investigated. The brown seeds/black seeds ratio, seed weight of brown and black seeds and the content of protein increased at a concentration of 500 mM NaCl compared to low salt conditions (1 mM NaCl). The germination percentage and germination index of brown seeds from plants cultured in 500 mM NaCl were higher than those cultured in 1 mM NaCl, but it was not true for black seeds. The concentrations of IAA (indole-3-acetic acid), ZR (free zeatin riboside) and ABA (abscisic acid) in brown seeds were much greater than those in black seeds, but there were no differences in the level of GAs (gibberellic acid including GA1 and GA3) regardless of the degree of salinity. Salinity during plant culture increased the concentration of GAs, but salinity had no effect on the concentrations of the other three endogenous hormones in brown seeds. Salinity had no effect on the concentration of IAA but increased the concentrations of the other three endogenous hormones in black seeds. Accumulation of endogenous hormones at different concentrations of NaCl during plant growth may be related to seed development and to salt tolerance of brown and black S. salsa seeds. These characteristics may help the species to ensure seedling establishment and population succession in variable saline environments.

  4. Manipulation of Auxin Response Factor 19 affects seed size in the woody perennial Jatropha curcas

    PubMed Central

    Sun, Yanwei; Wang, Chunming; Wang, Ning; Jiang, Xiyuan; Mao, Huizhu; Zhu, Changxiang; Wen, Fujiang; Wang, Xianghua; Lu, Zhijun; Yue, Genhua; Xu, Zengfu; Ye, Jian

    2017-01-01

    Seed size is a major determinant of seed yield but few is known about the genetics controlling of seed size in plants. Phytohormones cytokinin and brassinosteroid were known to be involved in the regulation of herbaceous plant seed development. Here we identified a homolog of Auxin Response Factor 19 (JcARF19) from a woody plant Jatropha curcas and genetically demonstrated its functions in controlling seed size and seed yield. Through Virus Induced Gene Silencing (VIGS), we found that JcARF19 was a positive upstream modulator in auxin signaling and may control plant organ size in J. curcas. Importantly, transgenic overexpression of JcARF19 significantly increased seed size and seed yield in plants Arabidopsis thaliana and J. curcas, indicating the importance of auxin pathway in seed yield controlling in dicot plants. Transcripts analysis indicated that ectopic expression of JcARF19 in J. curcas upregulated auxin responsive genes encoding essential regulators in cell differentiation and cytoskeletal dynamics of seed development. Our data suggested the potential of improving seed traits by precisely engineering auxin signaling in woody perennial plants. PMID:28102350

  5. Habitat-specific Tradeoffs Between Risk of Flow-induced Dislodgment and Fish Predation Affect Shell Morphologies of Potamopyrgus antipodarum in New Zealand

    NASA Astrophysics Data System (ADS)

    Holomuzki, J. R.; Biggs, B. J.

    2005-05-01

    Smooth and spiny shell-morphs exist in populations of the mudsnail Potamopyrgus antipodarum in New Zealand streams and lakes. We estimated the relative frequencies of smooth and spiny shell-morphs from 11 rivers and 9 lakes on the South Island and used stepwise regression to identify environmental variables that affected shell-morph frequencies. Habitat (stream or lake) explained 57% of the variation in morph frequency. Nearly 70% of snails in streams were smooth-shelled, whereas >80% of snails in lakes were spiny. Results from flow tank experiments showed that spines collected seston (sloughing algae and leaf matter) at current speeds <40 cm/s, making spiny-morphs more prone to flow-induced dislodgment than smooth-morphs. Moreover, individuals with longer spines collected more seston, and hence were more susceptible to dislodgment, than those with shorter ones. However, an advantage of spines was lower predation rates by common bullies (Gobiomorphus cotidianus), a widespread benthic fish in New Zealand streams and lakes. All snails egested by bullies were dead, suggesting common bullies may help regulate mudsnail populations in nature. Our results suggest tradeoffs between susceptibility to flow-induced dislodgment and fish predation affect habitat-specific frequencies of shell morphologies for this snail.

  6. Male seminal fluid substances affect sperm competition success and female reproductive behavior in a seed beetle.

    PubMed

    Yamane, Takashi; Goenaga, Julieta; Rönn, Johanna Liljestrand; Arnqvist, Göran

    2015-01-01

    Male seminal fluid proteins are known to affect female reproductive behavior and physiology by reducing mating receptivity and by increasing egg production rates. Such substances are also though to increase the competitive fertilization success of males, but the empirical foundation for this tenet is restricted. Here, we examined the effects of injections of size-fractioned protein extracts from male reproductive organs on both male competitive fertilization success (i.e., P2 in double mating experiments) and female reproduction in the seed beetle Callosobruchus maculatus. We found that extracts of male seminal vesicles and ejaculatory ducts increased competitive fertilization success when males mated with females 1 day after the females' initial mating, while extracts from accessory glands and testes increased competitive fertilization success when males mated with females 2 days after the females' initial mating. Moreover, different size fractions of seminal fluid proteins had distinct and partly antagonistic effects on male competitive fertilization success. Collectively, our experiments show that several different seminal fluid proteins, deriving from different parts in the male reproductive tract and of different molecular weight, affect male competitive fertilization success in C. maculatus. Our results highlight the diverse effects of seminal fluid proteins and show that the function of such proteins can be contingent upon female mating status. We also document effects of different size fractions on female mating receptivity and egg laying rates, which can serve as a basis for future efforts to identify the molecular identity of seminal fluid proteins and their function in this model species.

  7. Male Seminal Fluid Substances Affect Sperm Competition Success and Female Reproductive Behavior in a Seed Beetle

    PubMed Central

    Yamane, Takashi; Goenaga, Julieta; Rönn, Johanna Liljestrand; Arnqvist, Göran

    2015-01-01

    Male seminal fluid proteins are known to affect female reproductive behavior and physiology by reducing mating receptivity and by increasing egg production rates. Such substances are also though to increase the competitive fertilization success of males, but the empirical foundation for this tenet is restricted. Here, we examined the effects of injections of size-fractioned protein extracts from male reproductive organs on both male competitive fertilization success (i.e., P2 in double mating experiments) and female reproduction in the seed beetle Callosobruchus maculatus. We found that extracts of male seminal vesicles and ejaculatory ducts increased competitive fertilization success when males mated with females 1 day after the females’ initial mating, while extracts from accessory glands and testes increased competitive fertilization success when males mated with females 2 days after the females’ initial mating. Moreover, different size fractions of seminal fluid proteins had distinct and partly antagonistic effects on male competitive fertilization success. Collectively, our experiments show that several different seminal fluid proteins, deriving from different parts in the male reproductive tract and of different molecular weight, affect male competitive fertilization success in C. maculatus. Our results highlight the diverse effects of seminal fluid proteins and show that the function of such proteins can be contingent upon female mating status. We also document effects of different size fractions on female mating receptivity and egg laying rates, which can serve as a basis for future efforts to identify the molecular identity of seminal fluid proteins and their function in this model species. PMID:25893888

  8. Can salvage logging affect seed dispersal by birds into burned forests?

    NASA Astrophysics Data System (ADS)

    Rost, J.; Pons, P.; Bas, J. M.

    2009-09-01

    The recovery of vegetation in Mediterranean ecosystems after wildfire is mostly a result of direct regeneration, since the same species existing before the fire regenerate on-site by seeding or resprouting. However, the possibility of plant colonization by dispersal of seeds from unburned areas remains poorly studied. We addressed the role of the frugivorous, bird-dependent seed dispersal (seed rain) of fleshy-fruited plants in a burned and managed forest in the second winter after a fire, before on-site fruit production had begun. We also assessed the effect on seed rain of different microhabitats resulting from salvage logging (erosion barriers, standing snags, open areas), as well as the microhabitats of unlogged patches and an unburned control forest, taking account of the importance of perches as seed rain sites. We found considerable seed rain by birds in the burned area. Seeds, mostly from Olive trees Olea europaea and Evergreen pistaches Pistacia lentiscus, belonged to plants fruiting only in surrounding unburned areas. Seed rain was heterogeneous, and depended on microhabitat, with the highest seed density in the unburned control forest but closely followed by the wood piles of erosion barriers. In contrast, very low densities were found under perches of standing snags. Furthermore, frugivorous bird richness seemed to be higher in the erosion barriers than elsewhere. Our results highlight the importance of this specific post-fire management in bird-dependent seed rain and also may suggest a consequent heterogeneous distribution of fleshy-fruited plants in burned and managed areas. However, there needs to be more study of the establishment success of dispersed seeds before an accurate assessment can be made of the role of bird-mediated seed dispersal in post-fire regeneration.

  9. 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.

  10. Temperature and water stress during conditioning and incubation phase affecting Orobanche crenata seed germination and radicle growth

    PubMed Central

    Moral, Juan; Lozano-Baena, María Dolores; Rubiales, Diego

    2015-01-01

    Orobanche crenata is a holoparasitic plant that is potentially devastating to crop yield of legume species. Soil temperature and humidity are known to affect seed germination, however, the extent of their influence on germination and radicle growth of those of O. crenata is largely unknown. In this work, we studied the effects of temperature, water potential (Ψt) and the type of water stress (matric or osmotic) on O. crenata seeds during conditioning and incubation periods. We found that seeds germinated between 5 and 30°C during both periods, with a maximum around 20°C. Germination increased with increasing Ψt from −1.2 to 0 MPa during conditioning and incubation periods. Likewise, seed germination increased logarithmically with length of conditioning period until 40 days. The impact of the type of water stress on seed germination was similar, although the radicle growth of seeds under osmotic stress was lower than under matric stress, what could explain the lowest infestation of Orobanche sp. in regions characterized by saline soil. The data in this study will be useful to forecast infection of host roots by O. crenata. PMID:26089829

  11. Differences in hoarding behaviors among six sympatric rodent species on seeds of oil tea ( Camellia oleifera) in Southwest China

    NASA Astrophysics Data System (ADS)

    Chang, Gang; Zhang, Zhibin

    2011-05-01

    Seed hoarding is an important behavioral adaptation to food shortages for many rodent species. Sympatric rodents may affect the natural regeneration of large-seeded trees differently as seed dispersers or seed predators. Using seeds of oil tea ( Camellia oleifera), we investigated differences in hoarding behaviors among six sympatric rodent species in semi-natural enclosures in a subtropical forest in southwest of China. We found that all these six species ate seeds of C. oleifera, but only Edward's long-tailed rats ( Leopoldamys edwardsi) were predominantly scatter hoarders; chestnut rats ( Niviventer fulvescens) and white-bellied rats ( Niviventer confucianus) scatter hoarded and larder hoarded few seeds, but were seed predators; South China field mice ( Apodemus draco) exhibited little larder-hoarding behavior; and Chevrier's field mice ( A. chevrieri) as well as Himalayan rats ( Rattus nitidusa) did not hoard seeds at all. The rodents that engaged in scatter hoarding often formed single-seed caches and tended to cache seeds under grass or shrubs. Our findings indicate that sympatric rodents consuming seeds of the same species of plant can have different hoarding strategies, affecting seed dispersal and plant regeneration differently. We conclude by discussing the role of these species in hoarding seeds of C. oleifera and highlight the essential role of Edward's long-tailed rats as predominantly potential dispersers of this plant species.

  12. Common gas phase molecules from fungi affect seed germination and plant health in Arabidopsis thaliana

    PubMed Central

    2014-01-01

    Fungal volatile organic compounds (VOCs) play important ecophysiological roles in mediating inter-kingdom signaling with arthropods but less is known about their interactions with plants. In this study, Arabidopsis thaliana was used as a model in order to test the physiological effects of 23 common vapor-phase fungal VOCs that included alcohols, aldehydes, ketones, and other chemical classes. After exposure to a shared atmosphere with the 23 individual VOCs for 72 hrs, seeds were assayed for rate of germination and seedling formation; vegetative plants were assayed for fresh weight and chlorophyll concentration. All but five of the VOCs tested (1-decene, 2-n-heptylfuran, nonanal, geosmin and -limonene) had a significant effect in inhibiting either germination, seedling formation or both. Seedling formation was entirely inhibited by exposure to 1-octen-3-one, 2-ethylhexanal, 3-methylbutanal, and butanal. As assayed by a combination of fresh weight and chlorophyll concentration, 2-ethylhexanal had a negative impact on two-week-old vegetative plants. Three other compounds (1-octen-3-ol, 2-ethylhexanal, and 2-heptylfuran) decreased fresh weight alone. Most of the VOCs tested did not change the fresh weight or chlorophyll concentration of vegetative plants. In summary, when tested as single compounds, fungal VOCs affected A. thaliana in positive, negative or neutral ways. PMID:25045602

  13. Natural variation in ARF18 gene simultaneously affects seed weight and silique length in polyploid rapeseed

    PubMed Central

    Liu, Jing; Hua, Wei; Hu, Zhiyong; Yang, Hongli; Zhang, Liang; Li, Rongjun; Deng, Linbin; Sun, Xingchao; Wang, Xinfa; Wang, Hanzhong

    2015-01-01

    Seed weight (SW), which is one of the three major factors influencing grain yield, has been widely accepted as a complex trait that is controlled by polygenes, particularly in polyploid crops. Brassica napus L., which is the second leading crop source for vegetable oil around the world, is a tetraploid (4×) species. In the present study, we identified a major quantitative trait locus (QTL) on chromosome A9 of rapeseed in which the genes for SW and silique length (SL) were colocated. By fine mapping and association analysis, we uncovered a 165-bp deletion in the auxin-response factor 18 (ARF18) gene associated with increased SW and SL. ARF18 encodes an auxin-response factor and shows inhibitory activity on downstream auxin genes. This 55-aa deletion prevents ARF18 from forming homodimers, in turn resulting in the loss of binding activity. Furthermore, reciprocal crossing has shown that this QTL affects SW by maternal effects. Transcription analysis has shown that ARF18 regulates cell growth in the silique wall by acting via an auxin-response pathway. Together, our results suggest that ARF18 regulates silique wall development and determines SW via maternal regulation. In addition, our study reveals the first (to our knowledge) QTL in rapeseed and may provide insights into gene cloning involving polyploid crops. PMID:26324896

  14. Does solar radiation affect the growth of tomato seeds relative to their environment?

    NASA Technical Reports Server (NTRS)

    Holzer, Kristi

    1995-01-01

    The purpose of this experiment is to sequentially study and analyze the data collected from the germination and growth of irradiated Rutgers Supreme tomato seeds to adult producing plants. This experiment will not use irradiated seeds as a control as I plan to note growth in artificial verses natural environment as the basic experiment.

  15. Modification of AtGRDP1 gene expression affects silique and seed development in Arabidopsis thaliana.

    PubMed

    Rodríguez-Hernández, Aída Araceli; Muro-Medina, Carlos Vladimir; Ramírez-Alonso, Jocelin Itzel; Jiménez-Bremont, Juan Francisco

    2017-03-08

    Glycine Rich Proteins (GRPs) are induced at different developmental stages and in specific plant tissues. Recently, we described a novel Arabidopsis gene encoding a short glycine-rich domain protein (AtGRDP1). This gene is involved in abiotic stress responsiveness; the Atgrdp1-null mutant seeds were more sensitive to stress, while the opposite phenotype was achieved by AtGRDP1 overexpression. In this study, we analyzed the phenotype of the fruits produced by Arabidopsis Atgrdp1 mutants and 35S::AtGRDP1 overexpression lines. Our analyses revealed important changes in silique length, seed number, seed weight and morphology in the analyzed lines. In particular, Atgrdp1 mutant lines exhibited several defects including short siliques, a diminished number of seeds per silique, and reduction in seed size and weight as compared to Col-0. The overexpression of the AtGRDP1 gene also generated phenotypes with alterations in size of silique, number of seeds per silique, and size and weight of seed. In addition, the expression analysis of AtGRDP1 gene showed that it was expressed in floral and fruit organs, with the highest expression level in mature siliques. The alterations in the siliques and seeds traits in the Atgrdp1 mutant line, as well as the phenotypes observed in AtGRDP1 overexpression lines, suggest a role of the AtGRDP1 gene in the Arabidopsis fruit development.

  16. Does solar radiation affect the growth of tomato seeds relative to their environment?

    SciTech Connect

    Holzer, K.

    1995-09-01

    The purpose of this experiment is to sequentially study and analyze the data collected from the germination and growth of irradiated Rutgers Supreme tomato seeds to adult producing plants. This experiment will not use irradiated seeds as a control as the authors plans to note growth in artificial verses natural environment as the basic experiment.

  17. Seed and seedling traits affecting critical life stage transitions and recruitment outcomes in dryland grasses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    1. Seeding native plants is a key management practice to counter land degradation across the globe, yet the majority of seeding efforts fail, limiting the ability of this tool to accelerate ecosystem recovery. 2. Seedling recruitment requires transitions through several life stages, some of which ma...

  18. Seed dormancy and germination in Jeffersonia dubia (Berberidaceae) as affected by temperature and gibberellic acid.

    PubMed

    Rhie, Y H; Lee, S Y; Kim, K S

    2015-03-01

    The genus Jeffersonia, which contains only two species, has a trans-Atlantic disjunct distribution. The aims of this study were to determine the requirements for breaking dormancy and germination of J. dubia seeds and to compare its dormancy characteristics with those of the congener in eastern North America. Ripe seeds of J. dubia contain an underdeveloped embryo and were permeable to water. In nature, seeds were dispersed in May, while embryos began to grow in September, and were fully elongated by late November. Germination started in March of the next year, and seeds emerged as seedlings soon after germination. In laboratory experiments, incubation at high temperatures (25 °C, 25/15 °C) for at least 8 weeks was required to initiate embryo growth, while a transfer to moderate temperatures (20/10 °C, 15/6 °C) was needed for the completion of embryo growth. At least 8 weeks at 5 °C was effective in overcoming physiological dormancy and for germination in seeds after the embryos had fully elongated. Thus, both high and low temperatures were essential to break dormancy. Gibberellic acid (GA3 ) treatment could substitute for the high temperature requirement, but not for the low temperature requirement. Based on the dormancy-breaking requirements, it is confirmed that the seeds have deep simple morphophysiological dormancy. This dormancy type is similar to that of seeds of the eastern North American species J. diphylla. Although seeds require 10-11 months from seed dispersal to germination in nature, under controlled conditions they required only 3 months after treatment with 1000 mg·l(-1) GA3 , followed by incubation at 15/6 °C. This represents practical knowledge for propagation of these plants from seed.

  19. 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.

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

    PubMed Central

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

    2016-01-01

    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. PMID:27435026

  1. Predator diversity, intraguild predation, and indirect effects drive parasite transmission.

    PubMed

    Rohr, Jason R; Civitello, David J; Crumrine, Patrick W; Halstead, Neal T; Miller, Andrew D; Schotthoefer, Anna M; Stenoien, Carl; Johnson, Lucinda B; Beasley, Val R

    2015-03-10

    Humans are altering biodiversity globally and infectious diseases are on the rise; thus, there is interest in understanding how changes to biodiversity affect disease. Here, we explore how predator diversity shapes parasite transmission. In a mesocosm experiment that manipulated predator (larval dragonflies and damselflies) density and diversity, non-intraguild (non-IG) predators that only consume free-living cercariae (parasitic trematodes) reduced metacercarial infections in tadpoles, whereas intraguild (IG) predators that consume both parasites and tadpole hosts did not. This likely occurred because IG predators reduced tadpole densities and anticercarial behaviors, increasing per capita exposure rates of the surviving tadpoles (i.e., via density- and trait-mediated effects) despite the consumption of parasites. A mathematical model demonstrated that non-IG predators reduce macroparasite infections, but IG predation weakens this "dilution effect" and can even amplify parasite burdens. Consistent with the experiment and model, a wetland survey revealed that the diversity of IG predators was unrelated to metacercarial burdens in amphibians, but the diversity of non-IG predators was negatively correlated with infections. These results are strikingly similar to generalities that have emerged from the predator diversity-pest biocontrol literature, suggesting that there may be general mechanisms for pest control and that biocontrol research might inform disease management and vice versa. In summary, we identified a general trait of predators--where they fall on an IG predation continuum--that predicts their ability to reduce infections and possibly pests in general. Consequently, managing assemblages of predators represents an underused tool for the management of human and wildlife diseases and pest populations.

  2. Maternal presence and rearing condition affect responses to a live predator in kangaroo rats (Dipodomys heermanni arenae).

    PubMed

    Yoerg, S I; Shier, D M

    1997-12-01

    Experiment 1 compared the responses of wild-caught adult and captive-born adult and juvenile kangaroo rats (Dipodomys heermanni arenae) to a live snake. Wild-caught adult rats were less active and monitored the snake more than during a control condition; captive-born juvenile rats did not behave differently during snake and control tests. Snake-naive adult rats behaved more like the wild-caught adult rats, but not on all measures. In Experiment 2, pups were tested at 25 and 50 days of age in 4 conditions: no-snake control, alone with the snake, with a sibling and the snake, and with the mother and the snake. Pups did not behave differently during control and snake tests, but during tests with the mother, pups faced the snake less and followed the mother. Younger pups were more often near the mother than a sibling and followed the mother more when the snake was present. Development of defensive behavior may depend on both predator experience and maternal influence.

  3. 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

  4. Male inbreeding status affects female fitness in a seed-feeding beetle.

    PubMed

    Fox, Charles W; Xu, J; Wallin, W G; Curtis, C L

    2012-01-01

    Inbreeding generally reduces male mating activity such that inbred males are less successful in male-male competition. Inbred males can also have smaller accessory glands, transfer less sperm and produce sperm that are less motile, less viable or have a greater frequency of abnormalities, all of which can reduce the fertilization success and fitness of inbred males relative to outbred males. However, few studies have examined how male inbreeding status affects the fitness of females with whom they mate. In this study, we examine the effect of male inbreeding status (inbreeding coefficient f = 0.25 vs. f = 0) on the fecundity, adult longevity and the fate of eggs produced by outbred females in the seed-feeding beetle, Callosobruchus maculatus. Females mated to inbred males were less likely to lay eggs. Of those that laid eggs, females mated to inbred males laid 6-12% fewer eggs. Females mated to inbred males lived on average 5.4% longer than did females mated to outbred males, but this effect disappeared when lifetime fecundity was used as a covariate in the analysis. There was no effect of male inbreeding status on the proportion of a female's eggs that developed or hatched, and no evidence that inbred males produced smaller nuptial gifts. However, ejaculates of inbred males contained 17-33% fewer sperm, on average, than did ejaculates of outbred males. Our study demonstrates that mating with inbred males has significant direct consequences for the fitness of female C. maculatus, likely mediated by effects of inbreeding status on the number of sperm in male ejaculates. Direct effects of male inbreeding status on female fitness should be more widely considered in theoretical models and empirical studies of mate choice.

  5. Glycosaminoglycan Sulphation Affects the Seeded Misfolding of a Mutant Prion Protein

    PubMed Central

    Lawson, Victoria A.; Lumicisi, Brooke; Welton, Jeremy; Machalek, Dorothy; Gouramanis, Katrina; Klemm, Helen M.; Stewart, James D.; Masters, Colin L.; Hoke, David E.; Collins, Steven J.; Hill, Andrew F.

    2010-01-01

    Background The accumulation of protease resistant conformers of the prion protein (PrPres) is a key pathological feature of prion diseases. Polyanions, including RNA and glycosaminoglycans have been identified as factors that contribute to the propagation, transmission and pathogenesis of prion disease. Recent studies have suggested that the contribution of these cofactors to prion propagation may be species specific. Methodology/Principal Finding In this study a cell-free assay was used to investigate the molecular basis of polyanion stimulated PrPres formation using brain tissue or cell line derived murine PrP. Enzymatic depletion of endogenous nucleic acids or heparan sulphate (HS) from the PrPC substrate was found to specifically prevent PrPres formation seeded by mouse derived PrPSc. Modification of the negative charge afforded by the sulphation of glycosaminoglycans increased the ability of a familial PrP mutant to act as a substrate for PrPres formation, while having no effect on PrPres formed by wildtype PrP. This difference may be due to the observed differences in the binding of wild type and mutant PrP for glycosaminoglycans. Conclusions/Significance Cofactor requirements for PrPres formation are host species and prion strain specific and affected by disease associated mutations of the prion protein. This may explain both species and strain dependent propagation characteristics and provide insights into the underlying mechanisms of familial prion disease. It further highlights the challenge of designing effective therapeutics against a disease which effects a range of mammalian species, caused by range of aetiologies and prion strains. PMID:20808809

  6. 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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  7. 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.

  8. Predator diversity, intraguild predation, and indirect effects drive parasite transmission

    PubMed Central

    Rohr, Jason R.; Civitello, David J.; Crumrine, Patrick W.; Halstead, Neal T.; Miller, Andrew D.; Schotthoefer, Anna M.; Stenoien, Carl; Johnson, Lucinda B.; Beasley, Val R.

    2015-01-01

    Humans are altering biodiversity globally and infectious diseases are on the rise; thus, there is interest in understanding how changes to biodiversity affect disease. Here, we explore how predator diversity shapes parasite transmission. In a mesocosm experiment that manipulated predator (larval dragonflies and damselflies) density and diversity, non-intraguild (non-IG) predators that only consume free-living cercariae (parasitic trematodes) reduced metacercarial infections in tadpoles, whereas intraguild (IG) predators that consume both parasites and tadpole hosts did not. This likely occurred because IG predators reduced tadpole densities and anticercarial behaviors, increasing per capita exposure rates of the surviving tadpoles (i.e., via density- and trait-mediated effects) despite the consumption of parasites. A mathematical model demonstrated that non-IG predators reduce macroparasite infections, but IG predation weakens this “dilution effect” and can even amplify parasite burdens. Consistent with the experiment and model, a wetland survey revealed that the diversity of IG predators was unrelated to metacercarial burdens in amphibians, but the diversity of non-IG predators was negatively correlated with infections. These results are strikingly similar to generalities that have emerged from the predator diversity–pest biocontrol literature, suggesting that there may be general mechanisms for pest control and that biocontrol research might inform disease management and vice versa. In summary, we identified a general trait of predators—where they fall on an IG predation continuum—that predicts their ability to reduce infections and possibly pests in general. Consequently, managing assemblages of predators represents an underused tool for the management of human and wildlife diseases and pest populations. PMID:25713379

  9. A proteomic analysis of rice seed germination as affected by high temperature and ABA treatment.

    PubMed

    Liu, Shu-Jun; Xu, Heng-Heng; Wang, Wei-Qing; Li, Ni; Wang, Wei-Ping; Møller, Ian Max; Song, Song-Quan

    2015-05-01

    Seed germination is a critical phase in the plant life cycle, but the specific events associated with seed germination are still not fully understood. In this study, we used two-dimensional gel electrophoresis followed by mass spectrometry to investigate the changes in the proteome during imbibition of Oryza sativa seeds at optimal temperature with or without abscisic acid (ABA) and high temperature (germination thermoinhibition) to further identify and quantify key proteins required for seed germination. A total of 121 protein spots showed a significant change in abundance (1.5-fold increase/decrease) during germination under all conditions. Among these proteins, we found seven proteins specifically associated with seed germination including glycosyl hydrolases family 38 protein, granule-bound starch synthase 1, Os03g0842900 (putative steroleosin-B), N-carbamoylputrescine amidase, spermidine synthase 1, tubulin α-1 chain and glutelin type-A; and a total of 20 imbibition response proteins involved in energy metabolism, cell growth, cell defense and storage proteins. High temperature inhibited seed germination by decreasing the abundance of proteins involved in methionine metabolism, amino acid biosynthesis, energy metabolism, reserve degradation, protein folding and stress responses. ABA treatment inhibited germination and decreased the abundance of proteins associated with methionine metabolism, energy production and cell division. Our results show that changes in many biological processes including energy metabolism, protein synthesis and cell defense and rescue occurred as a result of all treatments, while enzymes involved in methionine metabolism and weakening of cell wall specifically accumulated when the seeds germinated at the optimal temperature.

  10. Effects of habitat and season on removal and hoarding of seeds of wild apricot (Prunus armeniaca) by small rodents

    NASA Astrophysics Data System (ADS)

    Ji-Qi, Lu; Zhi-Bin, Zhang

    2004-12-01

    The wild apricot (Prunus armeniaca) is widely distributed in the Donglingshan Mountains of Mentougou District of Beijing, China, where its seeds may be an important food resource for rodents. Predation, removal and hoarding of seeds by rodents will inevitably affect the spatio-temporal pattern of seed fate of wild apricot in this area. By marking and releasing tagged seeds of wild apricot, we investigated seeds survival, scatter-hoarding, cache size and seedling establishment, and the preference of micro-habitats used by rodents to store seeds. The results showed that: (1) rodents in this area hoarded food intensively in autumn, as well as in spring and summer. (2) There were significant effects of habitat and season on removal rate of tagged seeds at releasing plots. In both two types of habitats, Low and High shrub, tagged seeds were removed most rapidly by rodents in autumn, at intermediate rates in spring and least rapidly in summer. (3) During three seasons, mean dispersal distance of scatter-hoarded seeds in Low shrub habitat was greater than that in High shrub. Most removed seeds were buried within 21.0 m of the releasing plots. (4) In both two types of habitats, Low and High shrub, rodents tended to carry seeds to US (Under shrub) and SE (Shrub edge) microhabitats for scatter-hoarding or predation. (5) Among the caches made by rodents, most caches contained only one seed, but up to three seeds were observed; caches of 2-3 seeds were common in autumn. (6) By comparing dental marks, we determined that large field mice (Apodemus peninsulae) and David's rock squirrels (Sciurotamias davidianus) contributed to removal and predation of released tagged seeds. However, only the large field mice exerted a pivotal and positive role on the burial of dispersed seeds. (7) Establishment of three seedlings originated from seeds buried by rodents was documented in High shrub habitat.

  11. Identification of quantitative trait loci (QTL) affecting seed mineral content in the model legume Medicago truncatula

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increasing the amount of bioavailable micronutrients such as iron and zinc in plant foods for human consumption is a challenge especially in developing countries where plant foods comprise a significant portion of the diet. Legume seeds have the potential to provide the essential nutrients required...

  12. Identification of QTL affecting seed mineral concentrations and content in the model legume Medicago truncatula

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increasing the amount of bioavailable micronutrients such as iron and zinc in plant foods for human consumption is a challenge, especially in developing countries where plant foods comprise a significant portion of the diet. Legume seeds have the potential to provide the essential nutrients require...

  13. Hydrodistillation time affects dill seed essential oil yield, composition, and bioactivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dill (Anethum graveolens L.) essential oil is widely used by the food and pharmaceutical industries. We hypothesized that the chemical constituents of dill seed essential oil are eluted at different times during the hydrodistillation process, resulting in oils with different composition and bioactiv...

  14. Foliar and Seed Application of Amino Acids Affects the Antioxidant Metabolism of the Soybean Crop

    PubMed Central

    Teixeira, Walquíria F.; Fagan, Evandro B.; Soares, Luís H.; Umburanas, Renan C.; Reichardt, Klaus; Neto, Durval D.

    2017-01-01

    In recent years, the application of natural substances on crops has been intensified in order to increase the resistance and yield of the soybean crop. Among these products are included plant biostimulants that may contain algae extracts, amino acids, and plant regulators in their composition. However, there is little information on the isolated effect of each of these constituents. The objective of this research was to evaluate the effect of the application of isolated amino acids on the antioxidant metabolism of the soybean crop. Experiments were carried out in a greenhouse and in the field with the application of the amino acids glutamate, phenylalanine, cysteine, glycine in seed treatment, and foliar application at V4 growth stage. Antioxidant metabolism constituents evaluated were superoxide dismutase, catalase, peroxidase, hydrogen peroxide content, proline, and lipid peroxidation. In addition, resistance enzymes as polyphenol oxidase and phenylalanine ammonia-lyase (PAL) were evaluated. In both experiments, the use of cysteine, only in seed treatment and in both seed treatment and foliar application increased the activity of the enzyme PAL and catalase. Also in both experiments, the use of phenylalanine increased the activity of the enzyme PAL when the application was carried out as foliar application or both in seed treatment and foliar application. In the field experiment, the application of glutamate led to an increase in the activity of the catalase and PAL enzymes for seed treatment and foliar application. The use of the set of amino acids was only efficient in foliar application, which led to a greater activity of the enzymes peroxidase, PAL, and polyphenol oxidase. The other enzymes as well as lipid peroxidation and hydrogen peroxide presented different results according to the experiment. Therefore, glutamate, cysteine, phenylalanine, and glycine can act as signaling amino acids in soybean plants, since small doses are enough to increase the activity

  15. Predator Arithmetic

    ERIC Educational Resources Information Center

    Shutler, Paul M. E.; Fong, Ng Swee

    2010-01-01

    Modern Hindu-Arabic numeration is the end result of a long period of evolution, and is clearly superior to any system that has gone before, but is it optimal? We compare it to a hypothetical base 5 system, which we dub Predator arithmetic, and judge which of the two systems is superior from a mathematics education point of view. We find that…

  16. Pasta Predation.

    ERIC Educational Resources Information Center

    Waugh, Michael L.

    1986-01-01

    Presents a predator-prey simulation which involves students in collecting data, solving problems, and making predictions on the evolution of prey populations. Provides directives on how to perform the chi-square test and also includes an Applesoft BASK program that performs the calculations. (ML)

  17. Regulation of forest defoliating insects through small mammal predation: reconsidering the mechanisms.

    PubMed

    Kollberg, Ida; Bylund, Helena; Huitu, Otso; Björkman, Christer

    2014-12-01

    Population densities of forest defoliating insects may be regulated by small mammal predation on the pupae. When outbreaks do occur, they often coincide with warm, dry weather and at barren forest sites. A proposed reason for this is that weather and habitat affect small mammal population density (numerical response) and hence pupal predation. We propose an alternative explanation: weather and habitat affect small mammal feeding behaviour (functional response) and hence the outbreak risks of forest pest insects. We report results from laboratory and field-enclosure experiments estimating rates of pupal predation by bank voles (Myodes glareolus) on an outbreak insect, the European pine sawfly (Neodiprion sertifer), at different temperatures (15 and 20 °C), in different microhabitats (sheltered and non-sheltered), and with or without access to alternative food (sunflower seeds). We found that the probability of a single pupa being eaten at 20 °C was lower than at 15 °C (0.49 and 0.72, respectively). Pupal predation was higher in the sheltered microhabitat than in the open one, and the behaviour of the voles differed between microhabitats. More pupae were eaten in situ in the sheltered microhabitat whereas in the open area more pupae were removed and eaten elsewhere. Access to alternative food did not affect pupal predation. The results suggest that predation rates on pine sawfly pupae by voles are influenced by temperature- and habitat-induced variation in the physiology and behaviour of the predator, and not necessarily solely through effects on predator densities as previously proposed.

  18. Soybean seed protein oil fatty acids sugars and minerals as affected by seeding rates and row spacing in the Midsouth USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Research on the effects of seeding rates (SDR) and row spacing (RS) on soybean seed composition is almost non-existent. The objective of this research was to investigate the effect of SDR and RS on soybean seed protein, oil, fatty acids, sugars, and minerals using two soybean cultivars, P 93M90 (ear...

  19. 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

    NASA Astrophysics Data System (ADS)

    Fan, Xuetong; Sokorai, Kimberly; Weidauer, André; Gotzmann, Gaby; Rögner, Frank-Holm; Koch, Eckhard

    2017-01-01

    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 artificially inoculated on three seeds (fenugreek, clover and mung bean) that differed in size and surface morphology. Furthermore, the germination and growth of irradiated seeds were evaluated. Results showed that the D10 values (dose required to achieve 1 log reduction) for E. coli K12 on mung bean, clover, and fenugreek were 1.11, 1.21 and 1.40 kGy, respectively. To achieve a minimum 5-log reduction of E. coli, higher doses were needed on fenugreek than on mung bean or clover. Electron beam treatment at doses up to 12 kGy could not completely inactivate E. coli inoculated on all seeds even though most of the seeds were E. coli-free after 4-12 kGy irradiation. Gamma irradiation at doses up to 6 kGy did not significantly affect the germination rate of clover and fenugreek seeds but reduced the germination rate of mung bean seeds. Doses of 2 kGy gamma irradiation did not influence the growth of seeds while higher doses of gamma irradiation reduced the growth rate. Electron beam treatment at doses up to 12 kGy did not have any significant effect on germination or growth of the seeds. SEM imaging indicated there were differences in surface morphology among the three seeds, and E. coli resided in cracks and openings of seeds, making surface decontamination of seeds with low energy electron beam a challenge due to the low penetration ability. Overall, our results suggested that gamma rays and electron beam had different effects on E. coli inactivation and germination or growth of seeds. Future efforts should focus on optimization of electron bean parameters to increase penetration to inactivate E. coli without causing damage to the seeds.

  20. 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.

  1. Intraguild predation and competition impacts on a subordinate predator.

    PubMed

    Björklund, Heidi; Santangeli, Andrea; Blanchet, F Guillaume; Huitu, Otso; Lehtoranta, Hannu; Lindén, Harto; Valkama, Jari; Laaksonen, Toni

    2016-05-01

    Intraguild (IG) predation and interspecific competition may affect the settlement and success of species in their habitats. Using data on forest-dwelling hawks from Finland, we addressed the impact of an IG predator, the northern goshawk Accipiter gentilis (goshawk), on the breeding of an IG prey, the common buzzard Buteo buteo. We hypothesized that the subordinate common buzzard avoids breeding in the proximity of goshawks and that interspecific competitors, mainly Strix owls, may also disturb common buzzards by competing for nests and food. Our results show that common buzzards more frequently occupied territories with a low IG predation threat and with no interspecific competitors. We also observed that common buzzards avoided territories with high levels of grouse, the main food of goshawks, possibly due to a risk of IG predation since abundant grouse can attract goshawks. High levels of small rodents attracted interspecific competitors to common buzzard territories and created a situation where there was not only an abundance of food but also an abundance of competitors for the food. These results suggest interplay between top-down and bottom-up processes which influence the interactions between avian predator species. We conclude that the common buzzard needs to balance the risks of IG predation and interference competition with the availability of its own resources. The presence of other predators associated with high food levels may impede a subordinate predator taking full advantage of the available food. Based on our results, it appears that interspecific interactions with dominant predators have the potential to influence the distribution pattern of subordinate predators.

  2. Predation risk increases dispersal distance in prey

    NASA Astrophysics Data System (ADS)

    Otsuki, Hatsune; Yano, Shuichi

    2014-06-01

    Understanding the ecological factors that affect dispersal distances allows us to predict the consequences of dispersal. Although predator avoidance is an important cause of prey dispersal, its effects on dispersal distance have not been investigated. We used simple experimental setups to test dispersal distances of the ambulatory dispersing spider mite ( Tetranychus kanzawai) in the presence or absence of a predator ( Neoseiulus womersleyi). In the absence of predators, most spider mites settled in adjacent patches, whereas the majority of those dispersing in the presence of predators passed through adjacent patches and settled in distant ones. This is the first study to experimentally demonstrate that predators induce greater dispersal distance in prey.

  3. The emergence of defective predators who never hunt by themselves

    NASA Astrophysics Data System (ADS)

    Wang, Xueting; Pan, Qiuhui; Kang, Yibin; He, Mingfeng

    2013-06-01

    We propose a lattice Monte Carlo model of two populations, predators and prey. We divide predators into cooperative predators and defective predators. Cooperative predators participate in hunting. On the other hand, defective predators only participate to dominate, i.e. take possession of, the food when a kill has already been made by a cooperative predator. Numerous factors have been taken into account in our research, such as individual mobility, predation and hunger time. The model we have constructed displays the features of the population that evolve through time and the spatial distribution of the population. We focus on the emergence of defective predators and how the parameters affect the system. The results indicate that prey can profit from the appearance of these defective predators in some specific situations. It has even been shown that the emergence of defective predators can sometimes save endangered systems.

  4. Predator hunting mode and habitat domain alter nonconsumptive effects in predator-prey interactions.

    PubMed

    Preisser, Evan L; Orrock, John L; Schmitz, Oswald J

    2007-11-01

    Predators can affect prey populations through changes in traits that reduce predation risk. These trait changes (nonconsumptive effects, NCEs) can be energetically costly and cause reduced prey activity, growth, fecundity, and survival. The strength of nonconsumptive effects may vary with two functional characteristics of predators: hunting mode (actively hunting, sit-and-pursue, sit-and-wait) and habitat domain (the ability to pursue prey via relocation in space; can be narrow or broad). Specifically, cues from fairly stationary sit-and-wait and sit-and-pursue predators should be more indicative of imminent predation risk, and thereby evoke stronger NCEs, compared to cues from widely ranging actively hunting predators. Using a meta-analysis of 193 published papers, we found that cues from sit-and-pursue predators evoked stronger NCEs than cues from actively hunting predators. Predator habitat domain was less indicative of NCE strength, perhaps because habitat domain provides less reliable information regarding imminent risk to prey than does predator hunting mode. Given the importance of NCEs in determining the dynamics of prey communities, our findings suggest that predator characteristics may be used to predict how changing predator communities translate into changes in prey. Such knowledge may prove particularly useful given rates of local predator change due to habitat fragmentation and the introduction of novel predators.

  5. Genome-wide association mapping and biochemical markers reveal that seed ageing and longevity are intricately affected by genetic background and developmental and environmental conditions in barley.

    PubMed

    Nagel, Manuela; Kranner, Ilse; Neumann, Kerstin; Rolletschek, Hardy; Seal, Charlotte E; Colville, Louise; Fernández-Marín, Beatriz; Börner, Andreas

    2015-06-01

    Globally, over 7.4 million accessions of crop seeds are stored in gene banks, and conservation of genotypic variation is pivotal for breeding. We combined genetic and biochemical approaches to obtain a broad overview of factors that influence seed storability and ageing in barley (Hordeum vulgare). Seeds from a germplasm collection of 175 genotypes from four continents grown in field plots with different nutrient supply were subjected to two artificial ageing regimes. Genome-wide association mapping revealed 107 marker trait associations, and hence, genotypic effects on seed ageing. Abiotic and biotic stresses were found to affect seed longevity. To address aspects of abiotic, including oxidative, stress, two major antioxidant groups were analysed. No correlation was found between seed deterioration and the lipid-soluble tocochromanols, nor with oil, starch and protein contents. Conversely, the water-soluble glutathione and related thiols were converted to disulphides, indicating a strong shift towards more oxidizing intracellular conditions, in seeds subjected to long-term dry storage at two temperatures or to two artificial ageing treatments. The data suggest that intracellular pH and (bio)chemical processes leading to seed deterioration were influenced by the type of ageing or storage. Moreover, seed response to ageing or storage treatment appears to be significantly influenced by both maternal environment and genetic background.

  6. Copper affects the cotyledonary carbohydrate status during the germination of bean seed.

    PubMed

    Sfaxi-Bousbih, Amira; Chaoui, Abdelilah; El Ferjani, Ezzedine

    2010-10-01

    Seeds of bean (Phaseolus vulgaris L.) were germinated by soaking in distilled water or copper chloride solution. The relationships among copper excess treatment, germination rate, dry weight, sugar contents, and carbohydrase activities in cotyledon were investigated. Heavy metal stress provoked a diminution in germination rate and biomass mobilization, as compared with the control. A drastic disorder in soluble sugars export, especially glucose and fructose liberation, was also imposed after exposure to excess copper. This restricted the starch and sucrose breakdown in reserve tissue, as evidenced by the inhibition in the activities of alpha-amylase and invertase isoenzymes (soluble acid, soluble neutral, cell wall-bound acid).

  7. Fruitful factors: what limits seed production of flowering plants in the alpine?

    PubMed

    Straka, Jason R; Starzomski, Brian M

    2015-05-01

    Predicting demographic consequences of climate change for plant communities requires understanding which factors influence seed set, and how climate change may alter those factors. To determine the effects of pollen availability, temperature, and pollinators on seed production in the alpine, we combined pollen-manipulation experiments with measurements of variation in temperature, and abundance and diversity of potential pollinators along a 400-m elevation gradient. We did this for seven dominant species of flowering plants in the Coast Range Mountains, British Columbia, Canada. The number of viable seeds set by plants was influenced by pollen limitation (quantity of pollen received), mate limitation (quality of pollen), temperature, abundance of potential pollinators, seed predation, and combinations of these factors. Early flowering species (n = 3) had higher seed set at high elevation and late-flowering species (n = 4) had higher seed set at low elevation. Degree-days >15 °C were good predictors of seed set, particularly in bee-pollinated species, but had inconsistent effects among species. Seed production in one species, Arnica latifolia, was negatively affected by seed-predators (Tephritidae) at mid elevation, where there were fewer frost-hours during the flowering season. Anemone occidentalis, a fly-pollinated, self-compatible species had high seed set at all elevations, likely due to abundant potential pollinators. Simultaneously measuring multiple factors affecting reproductive success of flowering plants helped identify which factors were most important, providing focus for future studies. Our work suggests that responses of plant communities to climate change may be mediated by flowering time, pollination syndrome, and susceptibility to seed predators.

  8. Interstellar Predation

    NASA Astrophysics Data System (ADS)

    Cockell, C. S.; Lee, M.

    Although chemosynthesis and photosynthesis can theoretically supply enough energy for intelligence, for reasons elucidated here, heterotrophy and specifically phagotrophy (ingestion of prey) are likely to make predation a characteristic of life and extraterrestrial intelligence (ETI). Here, the Earth's biota is used to consider the nature of interstellar predation. The ability of the ETI to directly ingest a biota will be determined by the chiral preference of the ETI, the compatibility of the biochemistry used in life on Earth with the molecules required by the ETI and the potential toxicity of the macromolecules. If chirality is determined by astrophysical factors and not by the specificities of terrestrial origins of life and if molecules found in terrestrial organisms are also represented in ETIs (which could plausibly include hydrated carbohydrides and many amino acids that are similar or identical to amino acids found in meteoritic or cometary material) then the Earth might represent a universally appreciated resource. The Earth's biota could be used as an energy supply or, if other forms of technology have advanced to the point where bioreactors can be exclusively used to supply a civilization with food, as a culinary curiosity. Even in the absence of metabolic compatibility, technology can be used to extract useful products from an undigestible biota, similarly to the industrial biotransformation of cellulose. The value of the resource will also be determined by the availability of prey. Planets at stages in biological evolution where the surface is dominated by just one or several large (>5kg), abundant, easily captured organisms are particu- larly attractive to predators because harvesting techniques can be standardized. We discuss implications for exobiology and the `Fermi Paradox'.

  9. 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.

  10. Germination season and watering regime, but not seed morph, affect life history traits in a cold desert diaspore-heteromorphic annual.

    PubMed

    Lu, Juan J; Tan, Dun Y; Baskin, Jerry M; Baskin, Carol C

    2014-01-01

    Seed morph, abiotic conditions and time of germination can affect plant fitness, but few studies have tested their combined effects on plasticity of plant life history traits. Thus, we tested the hypothesis that seed morph, germination season and watering regime influence phenotypic expression of post-germination life history traits in the diaspore-heteromorphic cold desert winter annual/spring ephemeral Diptychocarpus strictus. The two seed morphs were sown in watered and non-watered plots in late summer, and plants derived from them were watered or not-watered throughout the study. Seed morph did not affect phenology, growth and morphology, survival, dry mass accumulation and allocation or silique and seed production. Seeds in watered plots germinated in autumn (AW) and spring (SW) but only in spring for non-watered plots (SNW). A high percentage of AW, SW and SNW plants survived and reproduced, but flowering date and flowering period of autumn- vs. spring-germinated plants differed. Dry mass also differed with germination season/watering regime (AW > SW > SNW). Number of siliques and seeds increased with plant size (AW > SW > SNW), whereas percent dry mass allocated to reproduction was higher in small plants: SNW > SW > AW. Thus, although seed morph did not affect the expression of life history traits, germination season and watering regime significantly affected phenology, plant size and accumulation and allocation of biomass to reproduction. Flexibility throughout the life cycle of D. strictus is an adaptation to the variation in timing and amount of rainfall in its cold desert habitat.

  11. The Arabidopsis DELAY OF GERMINATION 1 gene affects ABSCISIC ACID INSENSITIVE 5 (ABI5) expression and genetically interacts with ABI3 during Arabidopsis seed development.

    PubMed

    Dekkers, Bas J W; He, Hanzi; Hanson, Johannes; Willems, Leo A J; Jamar, Diaan C L; Cueff, Gwendal; Rajjou, Loïc; Hilhorst, Henk W M; Bentsink, Leónie

    2016-02-01

    The seed expressed gene DELAY OF GERMINATION (DOG) 1 is absolutely required for the induction of dormancy. Next to a non-dormant phenotype, the dog1-1 mutant is also characterized by a reduced seed longevity suggesting that DOG1 may affect additional seed processes as well. This aspect however, has been hardly studied and is poorly understood. To uncover additional roles of DOG1 in seeds we performed a detailed analysis of the dog1 mutant using both transcriptomics and metabolomics to investigate the molecular consequences of a dysfunctional DOG1 gene. Further, we used a genetic approach taking advantage of the weak aba insensitive (abi) 3-1 allele as a sensitized genetic background in a cross with dog1-1. DOG1 affects the expression of hundreds of genes including LATE EMBRYOGENESIS ABUNDANT and HEAT SHOCK PROTEIN genes which are affected by DOG1 partly via control of ABI5 expression. Furthermore, the content of a subset of primary metabolites, which normally accumulate during seed maturation, was found to be affected in the dog1-1 mutant. Surprisingly, the abi3-1 dog1-1 double mutant produced green seeds which are highly ABA insensitive, phenocopying severe abi3 mutants, indicating that dog1-1 acts as an enhancer of the weak abi3-1 allele and thus revealing a genetic interaction between both genes. Analysis of the dog1 and dog1 abi3 mutants revealed additional seed phenotypes and therefore we hypothesize that DOG1 function is not limited to dormancy but that it is required for multiple aspects of seed maturation, in part by interfering with ABA signalling components.

  12. Survival of weed seeds and animal parasites as affected by anaerobic digestion at meso- and thermophilic conditions.

    PubMed

    Johansen, Anders; Nielsen, Henrik B; Hansen, Christian M; Andreasen, Christian; Carlsgart, Josefine; Hauggard-Nielsen, Henrik; Roepstorff, Allan

    2013-04-01

    Anaerobic digestion of residual materials from animals and crops offers an opportunity to simultaneously produce bioenergy and plant fertilizers at single farms and in farm communities where input substrate materials and resulting digested residues are shared among member farms. A surplus benefit from this practice may be the suppressing of propagules from harmful biological pests like weeds and animal pathogens (e.g. parasites). In the present work, batch experiments were performed, where survival of seeds of seven species of weeds and non-embryonated eggs of the large roundworm of pigs, Ascaris suum, was assessed under conditions similar to biogas plants managed at meso- (37°C) and thermophilic (55°C) conditions. Cattle manure was used as digestion substrate and experimental units were sampled destructively over time. Regarding weed seeds, the effect of thermophilic conditions (55°C) was very clear as complete mortality, irrespective of weed species, was reached after less than 2 days. At mesophilic conditions, seeds of Avena fatua, Sinapsis arvensis, Solidago canadensis had completely lost germination ability, while Brassica napus, Fallopia convolvulus and Amzinckia micrantha still maintained low levels (~1%) of germination ability after 1 week. Chenopodium album was the only weed species which survived 1 week at substantial levels (7%) although after 11 d germination ability was totally lost. Similarly, at 55°C, no Ascaris eggs survived more than 3h of incubation. Incubation at 37°C did not affect egg survival during the first 48 h and it took up to 10 days before total elimination was reached. In general, anaerobic digestion in biogas plants seems an efficient way (thermophilic more efficient than mesophilic) to treat organic farm wastes in a way that suppresses animal parasites and weeds so that the digestates can be applied without risking spread of these pests.

  13. Top-Predator Survivor Region Is Affected by Bottom-Prey Mortality Rate on the Monte-Carlo Simulation in Lattice Model

    NASA Astrophysics Data System (ADS)

    Nagata, Minori; Nagata, Hiroyasu

    This article is a continuance of [9] that study brings into focus on the n species systems food chain. Computer simulation is important today, and its results may be reflected to policy. Now, we change the mortality rate of the bottom-prey, in order to inspect the survivor region of the top-predator that is crucial for the conservation of the ecosystem. We carry out Monte-Carlo simulations on finite-size lattices composed of the species . The bottom-prey mortality rate is changed from 0 to the extinction value. Thereafter, we find the steady state densities against the species n and plot the predator survivor region. To realize the conservation of the top-predator population, substantial amount of hardship is anticipated, because the bottom-prey density gradually becomes a little.

  14. Impacts of foraging facilitation among predators on predator-prey dynamics.

    PubMed

    Berec, Ludek

    2010-01-01

    Whereas impacts of predator interference on predator-prey dynamics have received considerable attention, the "inverse" process-foraging facilitation among predators-have not been explored yet. Here we show, via mathematical models, that impacts of foraging facilitation on predator-prey dynamics depend on the way this process is modeled. In particular, foraging facilitation destabilizes predator-prey dynamics when it affects the encounter rate between predators and prey. By contrast, it might have a stabilizing effect if the predator handling time of prey is affected. Foraging facilitation is an Allee effect mechanism among predators and we show that for many parameters, it gives rise to a demographic Allee effect or a critical predator density in need to be crossed for predators to persist. We explore also the effects of predator interference, to make the picture "symmetric" and complete. Predator interference is shown to stabilize predator-prey dynamics once its strength is not too high, and thus corroborates results of others. On the other hand, there is a wide range of model parameters for which predator interference gives rise to three co-occurring co-existence equilibria. Such a multi-equilibrial regime is rather robust as we observe it for all the functional response types we explore. This is a previously unreported phenomenon which we show cannot occur for the Beddington-DeAngelis functional response. An interesting topic for future research thus might be to seek for general conditions on predator functional responses that would produce multiple co-existence equilibria in a predator-prey model.

  15. Predators and Prey

    ERIC Educational Resources Information Center

    Kramm, Kenneth R.

    1975-01-01

    Reviews basic concepts of predator-prey interaction, encourages the presentation of the predator's role and describes a model of predator behavior to be used in secondary school or college classes. (LS)

  16. Predator arithmetic

    NASA Astrophysics Data System (ADS)

    Shutler, Paul M. E.; Swee Fong, Ng

    2010-01-01

    Modern Hindu-Arabic numeration is the end result of a long period of evolution, and is clearly superior to any system that has gone before, but is it optimal? We compare it to a hypothetical base 5 system, which we dub Predator arithmetic, and judge which of the two systems is superior from a mathematics education point of view. We find that complex calculations such as long multiplication can be carried out more efficiently in base 5 than in base 10, and that base 5 is in fact close to being optimal in this regard. We also show that base 5 is small enough so that the intuitiveness of simple grouping and the efficiency of fully ciphered numerals can be combined effectively in a single notation, something which Hindu-Arabic numeration tries but fails to achieve. Furthermore, as a consequence of these notational advantages, we show that the basic operations of arithmetic, addition and subtraction, also borrowing and carrying (regrouping), are easier to teach and to learn in base 5 than in base 10. Finally we show that, even though a shift from base 10 to base 5 may not be a realistic possibility, there are many ways in which the teaching of elementary arithmetic could be improved significantly, along the lines of Predator arithmetic, and which could be implemented at little cost within our current Hindu-Arabic system.

  17. Neonicotinoid-Coated Zea mays Seeds Indirectly Affect Honeybee Performance and Pathogen Susceptibility in Field Trials.

    PubMed

    Alburaki, Mohamed; Boutin, Sébastien; Mercier, Pierre-Luc; Loublier, Yves; Chagnon, Madeleine; Derome, Nicolas

    2015-01-01

    Thirty-two honeybee (Apis mellifera) colonies were studied in order to detect and measure potential in vivo effects of neonicotinoid pesticides used in cornfields (Zea mays spp) on honeybee health. Honeybee colonies were randomly split on four different agricultural cornfield areas located near Quebec City, Canada. Two locations contained cornfields treated with a seed-coated systemic neonicotinoid insecticide while the two others were organic cornfields used as control treatments. Hives were extensively monitored for their performance and health traits over a period of two years. Honeybee viruses (brood queen cell virus BQCV, deformed wing virus DWV, and Israeli acute paralysis virus IAPV) and the brain specific expression of a biomarker of host physiological stress, the Acetylcholinesterase gene AChE, were investigated using RT-qPCR. Liquid chromatography-mass spectrometry (LC-MS) was performed to detect pesticide residues in adult bees, honey, pollen, and corn flowers collected from the studied hives in each location. In addition, general hive conditions were assessed by monitoring colony weight and brood development. Neonicotinoids were only identified in corn flowers at low concentrations. However, honeybee colonies located in neonicotinoid treated cornfields expressed significantly higher pathogen infection than those located in untreated cornfields. AChE levels showed elevated levels among honeybees that collected corn pollen from treated fields. Positive correlations were recorded between pathogens and the treated locations. Our data suggests that neonicotinoids indirectly weaken honeybee health by inducing physiological stress and increasing pathogen loads.

  18. Neonicotinoid-Coated Zea mays Seeds Indirectly Affect Honeybee Performance and Pathogen Susceptibility in Field Trials

    PubMed Central

    Alburaki, Mohamed; Boutin, Sébastien; Mercier, Pierre-Luc; Loublier, Yves; Chagnon, Madeleine; Derome, Nicolas

    2015-01-01

    Thirty-two honeybee (Apis mellifera) colonies were studied in order to detect and measure potential in vivo effects of neonicotinoid pesticides used in cornfields (Zea mays spp) on honeybee health. Honeybee colonies were randomly split on four different agricultural cornfield areas located near Quebec City, Canada. Two locations contained cornfields treated with a seed-coated systemic neonicotinoid insecticide while the two others were organic cornfields used as control treatments. Hives were extensively monitored for their performance and health traits over a period of two years. Honeybee viruses (brood queen cell virus BQCV, deformed wing virus DWV, and Israeli acute paralysis virus IAPV) and the brain specific expression of a biomarker of host physiological stress, the Acetylcholinesterase gene AChE, were investigated using RT-qPCR. Liquid chromatography-mass spectrometry (LC-MS) was performed to detect pesticide residues in adult bees, honey, pollen, and corn flowers collected from the studied hives in each location. In addition, general hive conditions were assessed by monitoring colony weight and brood development. Neonicotinoids were only identified in corn flowers at low concentrations. However, honeybee colonies located in neonicotinoid treated cornfields expressed significantly higher pathogen infection than those located in untreated cornfields. AChE levels showed elevated levels among honeybees that collected corn pollen from treated fields. Positive correlations were recorded between pathogens and the treated locations. Our data suggests that neonicotinoids indirectly weaken honeybee health by inducing physiological stress and increasing pathogen loads. PMID:25993642

  19. Increasing the stearate content in seed oil of Brassica juncea by heterologous expression of MlFatB affects lipid content and germination frequency of transgenic seeds.

    PubMed

    Bhattacharya, Surajit; Sinha, Saheli; Das, Natasha; Maiti, Mrinal K

    2015-11-01

    Fatty acids from dietary lipids can impart both beneficial and harmful health effects. The compositional balance between saturated and unsaturated fatty acids plays a decisive role in maintaining the physiological harmony, proper growth and development in the human system. In case of Brassica juncea seed oil, the level of saturated fatty acid, especially desirable stearate is very much lower than the recommended value, along with a high content of nutritionally undesirable erucic acid. Therefore, in order to shift the carbon flux towards the production of stearate at the expense of erucate, the MlFatB gene encoding a FatB thioesterase from Madhuca longifolia (latifolia) was expressed heterologously in seed tissues of B. juncea. The functional MlFatB competed with the highly active endogenous BjFatA thioesterase, and the transgenic B. juncea lines showed noteworthy changes in their seed fatty acid profiles. The proportion of stearate increased up to 16-fold, constituting almost 31% of the total fatty acids along with the production of arachidic acid in significant amount (up to ∼11%). Moreover, the content of erucate was reduced up to 71% in the seed oils of transgenic lines. Although a nutritionally desirable fatty acid profile was achieved, the transgenic seeds exhibit reduction or abolition of seed germination in addition to a decrease in seed lipid content. The findings of the present study revealing the stearoyl-ACP thioesterase-mediated enhancement of the stearate content that is associated with reduced germination frequency of transgenic B. juncea seeds, may explain why no natural or induced stearate-rich Brassica has been found or developed. Furthermore, this study also suggests that the newly characterized MlFatB is a potential candidate gene for refined metabolic engineering strategy in B. juncea or other plant species for increasing stearate content in seed oil.

  20. Denaturation and Oxidative Stability of Hemp Seed (Cannabis sativa L.) Protein Isolate as Affected by Heat Treatment.

    PubMed

    Raikos, Vassilios; Duthie, Garry; Ranawana, Viren

    2015-09-01

    The present study investigated the impact of heat treatments on the denaturation and oxidative stability of hemp seed protein during simulated gastrointestinal digestion (GID). Heat-denatured hemp protein isolate (HPI) solutions were prepared by heating HPI (2 mg/ml, pH 6.8) to 40, 60, 80 and 100 °C for 10 min. Heat-induced denaturation of the protein isolates was monitored by polyacrylamide gel electrophoresis. Heating HPI at temperatures above 80 °C significantly reduced solubility and led to the formation of large protein aggregates. The isolates were then subjected to in vitro GID and the oxidative stability of the generated peptides was investigated. Heating did not significantly affect the formation of oxidation products during GID. The results suggest that heat treatments should ideally remain below 80 °C if heat stability and solubility of HPI are to be preserved.

  1. Identification and characterization of large DNA deletions affecting oil quality traits in soybean seeds through transcriptome sequencing analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the molecular and genetic mechanisms underlying variation in seed composition and contents among different genotypes is important for soybean oil quality improvement. We designed a bioinformatics approach to compare seed transcriptomes of 9 soybean genotypes varying in oil composition ...

  2. Intraguild interactions among three spider mite predators: predation preference and effects on juvenile development and oviposition.

    PubMed

    Rahmani, Hasan; Daneshmandi, Aliakbar; Walzer, Andreas

    2015-12-01

    A first step to evaluate potential negative effects of intraguild predation (IGP) when using multiple predators against a pest species is the determination of the predation behavior of the predators and the nutritional value of intraguild (IG) prey in terms of development and oviposition. Here, we investigated the predation preference of the female predatory mites Neoseiulus californicus, Typhlodromus bagdasarjani and Phytoseius plumifer, when having choice between larvae of the two other predatory mite species (IG prey) with and without extraguild prey, the spider mite Tetranychus urticae (EG prey). Additionally, we evaluated the juvenile development and oviposition of the three predator species when provided with larvae from each other species. Irrespective of EG prey, IG prey species affected neither the first attack nor attack times of the three female IG predator species. The IG predation rates of the predator females, however, were influenced by prey species in the absence of EG prey. Neoseiulus californicus females killed more P. plumifer than T. bagdasarjani larvae, whereas T. bagdasarjani and P. plumifer females killed more N. californicus than P. plumifer and T. bagdasarjani larvae, respectively. All IG predator species consumed significantly more EG than IG prey. IG prey species did not influence juvenile and adult survival probabilities of the IG predators. We conclude that IGP is a weak force among the three predators and the potential consequences of IGP should not result in the elimination of one by another tested predatory mite species at least in the presence of spider mites.

  3. The transcriptomes of dormant leafy spurge seeds under alternating temperature are differentially affected by a germination-enhancing pretreatment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seed dormancy is an important stage in the life cycle of many non-domesticated plants, often characterized by the temporary failure to germinate under conditions that normally favor the process. Pre-treating dormant imbibed seeds at a constant temperate accelerated germination of leafy spurge seeds ...

  4. Predator behaviour and predation risk in the heterogeneous Arctic environment.

    PubMed

    Lecomte, Nicolas; Careau, Vincent; Gauthier, Gilles; Giroux, Jean-François

    2008-05-01

    1. Habitat heterogeneity and predator behaviour can strongly affect predator-prey interactions but these factors are rarely considered simultaneously, especially when systems encompass multiple predators and prey. 2. In the Arctic, greater snow geese Anser caerulescens atlanticus L. nest in two structurally different habitats: wetlands that form intricate networks of water channels, and mesic tundra where such obstacles are absent. In this heterogeneous environment, goose eggs are exposed to two types of predators: the arctic fox Vulpes lagopus L. and a diversity of avian predators. We hypothesized that, contrary to birds, the hunting ability of foxes would be impaired by the structurally complex wetland habitat, resulting in a lower predation risk for goose eggs. 3. In addition, lemmings, the main prey of foxes, show strong population cycles. We thus further examined how their fluctuations influenced the interaction between habitat heterogeneity and fox predation on goose eggs. 4. An experimental approach with artificial nests suggested that foxes were faster than avian predators to find unattended goose nests in mesic tundra whereas the reverse was true in wetlands. Foxes spent 3.5 times more time between consecutive attacks on real goose nests in wetlands than in mesic tundra. Their attacks on goose nests were also half as successful in wetlands than in mesic tundra whereas no difference was found for avian predators. 5. Nesting success in wetlands (65%) was higher than in mesic tundra (56%) but the difference between habitats increased during lemming crashes (15%) compared to other phases of the cycle (5%). Nests located at the edge of wetland patches were also less successful than central ones, suggesting a gradient in accessibility of goose nests in wetlands for foxes. 6. Our study shows that the structural complexity of wetlands decreases predation risk from foxes but not avian predators in arctic-nesting birds. Our results also demonstrate that cyclic

  5. Does the passage of seeds through frugivore gut affect their storage: A case study on the endangered plant Euryodendron excelsum.

    PubMed

    Shikang, Shen; Fuqin, Wu; Yuehua, Wang

    2015-06-25

    Plant-frugivore mutualism serves an important function in multiple ecological processes. Although previous studies have highlighted the effect of frugivore gut passage on fresh seed germinability, no study has investigated the effect on seed storage after frugivore gut passage. We used the endangered plant, Euryodendron excelsum, to determine the combined effects of frugivore gut passage and storage conditions on the germination percentage and rate of seeds. In particular, three treatments that included storage periods, storage methods, and seed types were designed in the experiment. We hypothesized that seeds that passed through the gut will exhibit enhanced germination capacity and rate during storage. Results showed that the final germination percentage decreased in seeds that passed through the gut, whereas the germination rate increased during seed storage. Germination decreased in most types of seeds under both dry and wet storage after 6 months compared with storage after 1 and 3 months. The results suggest that after frugivore gut passage, E. excelsum seeds cannot form persistent soil seed bank in the field, and were not suitable for species germplasm storage. These finding underscore that seeds that passed through frugivore gut have long-term impact on their viability and germination performance.

  6. Does the passage of seeds through frugivore gut affect their storage: A case study on the endangered plant Euryodendron excelsum

    PubMed Central

    Shikang, Shen; Fuqin, Wu; Yuehua, Wang

    2015-01-01

    Plant-frugivore mutualism serves an important function in multiple ecological processes. Although previous studies have highlighted the effect of frugivore gut passage on fresh seed germinability, no study has investigated the effect on seed storage after frugivore gut passage. We used the endangered plant, Euryodendron excelsum, to determine the combined effects of frugivore gut passage and storage conditions on the germination percentage and rate of seeds. In particular, three treatments that included storage periods, storage methods, and seed types were designed in the experiment. We hypothesized that seeds that passed through the gut will exhibit enhanced germination capacity and rate during storage. Results showed that the final germination percentage decreased in seeds that passed through the gut, whereas the germination rate increased during seed storage. Germination decreased in most types of seeds under both dry and wet storage after 6 months compared with storage after 1 and 3 months. The results suggest that after frugivore gut passage, E. excelsum seeds cannot form persistent soil seed bank in the field, and were not suitable for species germplasm storage. These finding underscore that seeds that passed through frugivore gut have long-term impact on their viability and germination performance. PMID:26109456

  7. Predator population depending on lemming cycles

    NASA Astrophysics Data System (ADS)

    Anashkina, Ekaterina I.; Chichigina, Olga A.; Valenti, Davide; Kargovsky, Aleksey V.; Spagnolo, Bernardo

    2016-07-01

    In this paper, a Langevin equation for predator population with multiplicative correlated noise is analyzed. The noise source, which is a nonnegative random pulse noise with regulated periodicity, corresponds to the prey population cycling. The increase of periodicity of noise affects the average predator density at the stationary state.

  8. Growth of salmonellae on sprouting alfalfa seeds as affected by the inoculum size, native microbial load, and Pseudomonas fluorescens 2-79

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The incidence of human illness associated with the consumption of fresh sprouts has increased very sharply during the past decade. The objective of this study was to investigate the growth dynamics of salmonellae on sprouting alfalfa seeds as affected by the inoculum size, native microbial load, an...

  9. Seeding rate and date and timing of termination affect hairy vetch (Vicia villosa Roth) biomass production across the eastern United States

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hairy vetch (Vicia villosa Roth) is a winter annual legume cover crop that is often grown because it can provide a substantial amount of N to the following cash crop. Nitrogen accumulation is dependent on biomass production, which in turn is affected by climate, seeding rate and date, and timing of ...

  10. Consumption of endophyte-infected fescue seed during the dry period and lactation affects mammary gland gene expression in dairy cows

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ergot alkaloids in endophyte-infected grasses inhibit prolactin (PRL) secretion and reduce milk production when fed to lactating cows. However, we have shown this affect is temporal in that pre-partum consumption of inflected seed throughout the dry period does not inhibit subsequent milk productio...

  11. Imbalance of predator and prey armament: geographic clines in phenotypic interface and natural selection.

    PubMed

    Toju, Hirokazu; Sota, Teiji

    2006-01-01

    The escalation of defensive/offensive arms is ubiquitous in prey-predator evolutionary interactions. However, there may be a geographically varying imbalance in the armaments of participating species that affects the outcome of local interactions. In a system involving the Japanese camellia (Camellia japonica) and its obligate seed predator, the camellia weevil (Curculio camelliae), we investigated the geographic variation in physical defensive/offensive traits and that in natural selection on the plant's defense among 17 populations over a 700-km-wide area in Japan. The sizes of the plant defensive apparatus (pericarp thickness) and the weevil offensive apparatus (rostrum length) clearly correlated with each other across populations. Nevertheless, the balance in armaments between the two species was geographically structured. In the populations for which the balance was relatively advantageous for the plant's defense, natural selection on the trait was stronger because in the other populations, most plant individuals were too vulnerable to resist the attacks of the weevil, and their seeds were infested independent of pericarp thickness. We also found that the imbalance between the defensive/offensive armaments and the intensity of natural selection showed clear latitudinal clines. Overall, our results suggest that the imbalance of armament between sympatric prey and predator could determine the strength of local selection and that climatic conditions could affect the local and overall trajectory of coevolutionary arms races.

  12. Chemical properties and oxidative stability of perilla oils obtained from roasted perilla seeds as affected by extraction methods.

    PubMed

    Jung, Dong Min; Yoon, Suk Hoo; Jung, Mun Yhung

    2012-12-01

    The chemical properties and oxidative stability of perilla oils obtained from roasted perilla seeds as affected by extraction methods (supercritical carbon dioxide [SC-CO(2)], mechanical press, and solvent extraction) were studied. The SC-CO(2) extraction at 420 bar and 50 °C and hexane extraction showed significantly higher oil yield than mechanical press extraction (P < 0.05). The fatty acid compositions in the oils were virtually identical regardless of the extraction methods. The contents of tocopherol, sterol, policosanol, and phosphorus in the perilla oils greatly varied with the extraction methods. The SC-CO(2) -extracted perilla oils contained significantly higher contents of tocopherols, sterols, and policosanols than the mechanical press-extracted and hexane-extracted oils (P < 0.05). The SC-CO(2) -extracted oil showed the greatly lower oxidative stability than press-extracted and hexane-extracted oils during the storage in the oven under dark at 60 °C. However, the photooxidative stabilities of the oils were not considerably different with extraction methods.

  13. Steady shear flow behavior of sage seed gum affected by various salts and sugars: Time-independent properties.

    PubMed

    Yousefi, Ali R; Eivazlou, Razieh; Razavi, Seyed M A

    2016-10-01

    The rheological properties of food hydrocolloids are remarkably influenced by the quality of solvent/cosolutes in a food system. In this work, the steady shear flow behavior of sage seed gum (SSG, 0.5% w/w) at the presence of different levels of salts (KCl & MgCl2, 0-100mM) and sugars (sucrose, lactose & glucose, 0-6% w/w) was studied. It was found that the rheological properties of SSG were affected by the type of sugars and salts and their concentrations as well. Synergistic interaction was observed between SSG and sugars which enhanced the viscosity of gum solutions, while salts addition diminished the viscosity. SSG solutions exhibited a shear thinning behavior at all conditions tested. Various time-independent rheological models were used to fit the shear stress-shear rate data, although the Herschel-Bulkley (R(2)=0.994-0.999) and Sisko (R(2)=0.995-0.999) models showed the best results to describe the flow behavior of SSG. In the presence of salts, the yield stress (τ0), consistency coefficient (k), and flow behavior index (n) values decreased. The k and τ0 values enhanced and the n value lowered in the presence of sugars. Divalent cations of Mg(2+) and sucrose roughly showed more effect on rheological parameters than others.

  14. Does sheep selectivity along grazing paths negatively affect biological crusts and soil seed banks in arid shrublands? A case study in the Patagonian Monte, Argentina.

    PubMed

    Bertiller, M B; Ares, J O

    2011-08-01

    Domestic animals potentially affect the reproductive output of plants by direct removal of aboveground plant parts but also could alter the structure and fertility of the upper soil and the integrity of biological crusts through trampling. We asked whether sheep selectivity of plant patches along grazing paths could lead to negative changes in biological crusts and soil seed banks. We randomly selected ten floristically homogeneous vegetation stands distributed across an area (1250 ha) grazed by free ranging sheep. Vegetation stands were differently selected by sheep as estimated through sheep-collaring techniques combined with remote imagery mapping. At each stand, we extracted 15 paired cylindrical soil cores from biological crusts and from neighboring soil without crusts. We evaluated the crust cover enclosed in each core and incubated the soil samples at field capacity at alternating 10-18 °C during 24 months. We counted the emerged seedlings and identified them by species. Sheep selectivity along grazing paths was largest at mid-distances to the watering point of the paddock. Increasing sheep selectivity was associated with the reduction of the cover of biological crusts and the size and species number of the soil seed bank of preferred perennial grasses under biological crusts. The size of the soil seed bank of annual grasses was reduced with increasing sheep selectivity under both crust and no crust soil conditions. We did not detect changes in the soil seed banks of less- and non- preferred species (shrubs and forbs) related to sheep selectivity. Our findings highlight the negative effects of sheep selectivity on biological crusts and the soil seed bank of preferred plant species and the positive relationship between biological crusts and the size of the soil seed bank of perennial grasses. Accordingly, the state of conservation of biological crusts could be useful to assess the state of the soil seed banks of perennial grasses for monitoring, conservation

  15. Fluctuation in seed abundance has contrasting effects on the fate of seeds from two rapidly germinating tree species in an Asian tropical forest.

    PubMed

    Cao, Lin; Guo, Cong; Chen, Jin

    2017-01-01

    The seed predator satiation hypothesis states that high seed abundance can satiate seed predators or seed dispersers, thus promoting seed survival. However, for rapidly germinating seeds in tropical forests, high seed abundance may limit dispersal as the seeds usually remain under parent trees for long periods, which may lead to high mortality due to rodent predation or fungal infestations. By tracking 2 species of rapidly germinating seeds (Pittosporopsis kerrii, family Icacinaceae; Camellia kissi, family Theaceae), which depend on dispersal by scatter-hoarding rodents, we investigated the effects of seed abundance at the community level on predation and seed dispersal in the tropical forest of Xishuangbanna Prefecture, Southwest China. We found that high seed abundance at the community level was associated with delayed and reduced seed removal, decreased dispersal distance and increased pre-dispersal seed survival for both plant species. High seed abundance was also associated with reduced seed caching of C. kissi, but it showed little effect on seed caching of P. kerrii. However, post-dispersal seed survival for the 2 plant species followed the reverse pattern. High seed abundance in the community was associated with higher post-dispersal survival of P. kerrii seeds, but with lower post-dispersal survival of C. kissi seeds. Our results suggest that different plant species derive benefit from fluctuations in seed production in different ways.

  16. Leafy spurge (Euphorbia esula) affects vegetation more than seed banks in mixed-grass prairies of the Northern Great Plains

    USGS Publications Warehouse

    Larson, Diane L.; Haines, Dustin F.; Larson, Jennifer L.

    2013-01-01

    Exotic plants have the ability to modify soil seed banks in habitats they invade, but little is known about the legacy of invasion on seed banks once an exotic plant has successfully been controlled. Natural areas previously invaded by leafy spurge in the northern Great Plains typically have one of two fates following its removal: a return of native plants, or a secondary invasion of other exotic plants. It is unknown, however, if this difference in plant communities following leafy spurge control is due to seed bank differences. To answer this question, we monitored seed banks and standing vegetation for 2 yr in mixed-grass prairies that were previously invaded by leafy spurge but controlled within 5 yr of our study. We found that native plant seed banks were largely intact in areas previously invaded by leafy spurge, regardless of the current living plant community, and leafy spurge invasion history had a larger impact on cover and diversity of the vegetation than on the seed banks. Differences in plant communities following leafy spurge control do not appear to be related to the seed banks, and soil conditions may be more important in determining trajectories of these postinvasion communities.

  17. Predator satiation and recruitment in a mast fruiting monocarpic forest herb

    PubMed Central

    Tsvuura, Zivanai; Griffiths, Megan E.; Gunton, Richard M.; Lawes, Michael J.

    2011-01-01

    Background and Aims Cross-pollination and satiation of seed predators are often invoked to explain synchronous mast reproduction in long-lived plants. However, explanations for the synchronous death of parent plants are elusive. The roles of synchronous seeding and post-reproductive mortality were investigated in a perennial monocarpic herb (Isoglossa woodii) in coastal dune forest in South Africa. Methods Pre-dispersal seed predation and seed production were assessed by measuring fruit and seed set of inflorescences sprayed with insecticide or water and with no spray treatments. Seed predation was measured at different densities of I. woodii plants by monitoring removal rates of seed from the forest floor. The influence of adult plants on establishment of I. woodii seedlings was assessed by monitoring growth and survivorship of seedlings in caged and uncaged 1 × 1 m plots in understorey gaps and thickets. Key Results Fruit and seed set were similar between spray treatments. An I. woodii stem produced 767·8 ± 160·8 seeds (mean ± s.e.) on dune crests and 1359·0 ± 234·4 seeds on the foredune. Seed rain was greater on the foredune than in other topographic locations. Seed predation rates were 32 and 54 % on dune crests and in dune slacks, respectively, and decreased with seed abundance, number of inflorescences per stem and plant height. Seedling recruitment was greater beneath synchronously dying adult plants than in natural understorey gaps (no I. woodii). However, seedling growth rate beneath I. woodii mid-way through its life-cycle was less than in gaps, although survivorship was similar. Conclusions The selective advantage of masting in I. woodii derives from satiation of both pre- and post-dispersal seed predators. In addition, post-seeding mortality of adult plants facilitates seedling establishment. Satiation of seed predators and the benefits of seedling establishment are strong drivers of the evolution of synchronous monocarpy in I. woodii. PMID

  18. Effects of stream predator richness on the prey community and ecosystem attributes.

    PubMed

    Nilsson, Erika; Olsson, Karin; Persson, Anders; Nyström, Per; Svensson, Gustav; Nilsson, Ulf

    2008-10-01

    It is important to understand the role that different predators can have to be able to predict how changes in the predator assemblage may affect the prey community and ecosystem attributes. We tested the effects of different stream predators on macroinvertebrates and ecosystem attributes, in terms of benthic algal biomass and accumulation of detritus, in artificial stream channels. Predator richness was manipulated from zero to three predators, using two fish and one crayfish species, while density was kept equal (n = 6) in all treatments with predators. Predators differed in their foraging strategies (benthic vs. drift feeding fish and omnivorous crayfish) but had overlapping food preferences. We found effects of both predator species richness and identity, but the direction of effects differed depending on the response variable. While there was no effect on macroinvertebrate biomass, diversity of predatory macroinvertebrates decreased with increasing predator species richness, which suggests complementarity between predators for this functional feeding group. Moreover, the accumulation of detritus was affected by both predator species richness and predator identity. Increasing predator species richness decreased detritus accumulation and presence of the benthic fish resulted in the lowest amounts of detritus. Predator identity (the benthic fish), but not predator species richness had a positive effect on benthic algal biomass. Furthermore, the results indicate indirect negative effects between the two ecosystem attributes, with a negative correlation between the amount of detritus and algal biomass. Hence, interactions between different predators directly affected stream community structure, while predator identity had the strongest impact on ecosystem attributes.

  19. Risk of predation and weather events affect nest site selection by sympatric Pacific (Gavia pacifica) and Yellow-billed (Gavia adamsii) loons in Arctic habitats

    USGS Publications Warehouse

    Haynes, Trevor B.; Schmutz, Joel A.; Lindberg, Mark S.; Rosenberger, Amanda E.

    2014-01-01

    Pacific (Gavia pacifica) and Yellow-billed (G. adamsii) loons nest sympatrically in Arctic regions. These related species likely face similar constraints and requirements for nesting success; therefore, use of similar habitats and direct competition for nesting habitat is likely. Both of these loon species must select a breeding lake that provides suitable habitat for nesting and raising chicks; however, characteristics of nest site selection by either species on interior Arctic lakes remains poorly understood. Here, logistic regression was used to compare structural and habitat characteristics of all loon nest locations with random points from lakes on the interior Arctic Coastal Plain, Alaska. Results suggest that both loon species select nest sites to avoid predation and exposure to waves and shifting ice. Loon nest sites were more likely to be on islands and peninsulas (odds ratio = 16.13, 95% CI = 4.64–56.16) than mainland shoreline, which may help loons avoid terrestrial predators. Further, nest sites had a higher degree of visibility (mean degrees of visibility to 100 and 200 m) of approaching predators than random points (odds ratio = 2.57, 95% CI = 1.22–5.39). Nests were sheltered from exposure, having lower odds of being exposed to prevailing winds (odds ratio = 0.34, 95% CI = 0.13–0.92) and lower odds of having high fetch values (odds ratio = 0.46, 95% CI = 0.22–0.96). Differences between Pacific and Yellow-billed loon nesting sites were subtle, suggesting that both species have similar general nest site requirements. However, Yellow-billed Loons nested at slightly higher elevations and were more likely to nest on peninsulas than Pacific Loons. Pacific Loons constructed built up nests from mud and vegetation, potentially in response to limited access to suitable shoreline due to other territorial loons. Results suggest that land managers wishing to protect habitats for these species should focus on lakes with islands as well as shorelines

  20. Predation at the Shore.

    ERIC Educational Resources Information Center

    Cook, Helen M.; Matthews, Catherine E.; Hildreth, David P.; Couch, Emma

    2003-01-01

    Describes 10 predator/prey relationships that occur on the coast. Predators are compared to criminals and prey to their victims along with details of crime scenes. Accurately describes the habits and habitats of the criminals and presents games and activities that feature the relationships between predators and their prey. (Author/SOE)

  1. A quantitative approach to identifying predators from nest remains

    USGS Publications Warehouse

    Anthony, R. Michael; Grand, J.B.; Fondell, T.F.; Manly, B.F.

    2004-01-01

    Nesting success of Dusky Canada Geese (Branta canadensis occidentalis) has declined greatly since a major earthquake affected southern Alaska in 1964. To identify nest predators, we collected predation data at goose nests and photographs of predators at natural nests containing artificial eggs in 1997-2000. To document feeding behavior by nest predators, we compiled the evidence from destroyed nests with known predators on our study site and from previous studies. We constructed a profile for each predator group and compared the evidence from 895 nests with unknown predators to our predator profiles using mixture-model analysis. This analysis indicated that 72% of destroyed nests were depredated by Bald Eagles and 13% by brown bears, and also yielded the probability that each nest was correctly assigned to a predator group based on model fit. Model testing using simulations indicated that the proportion estimated for eagle predation was unbiased and the proportion for bear predation was slightly overestimated. This approach may have application whenever there are adequate data on nests destroyed by known predators and predators exhibit different feeding behavior at nests.

  2. Sexual dimorphism of staminate- and pistillate-phase flowers of Saponaria officinalis (bouncing bet) affects pollinator behavior and seed set.

    PubMed

    Davis, Sandra L; Dudle, Dana A; Nawrocki, Jenna R; Freestone, Leah M; Konieczny, Peter; Tobin, Michael B; Britton, Michael M

    2014-01-01

    The sequential separation of male and female function in flowers of dichogamous species allows for the evolution of differing morphologies that maximize fitness through seed siring and seed set. We examined staminate- and pistillate-phase flowers of protandrous Saponaria officinalis for dimorphism in floral traits and their effects on pollinator attraction and seed set. Pistillate-phase flowers have larger petals, greater mass, and are pinker in color, but due to a shape change, pistillate-phase flowers have smaller corolla diameters than staminate-phase flowers. There was no difference in nectar volume or sugar content one day after anthesis, and minimal evidence for UV nectar guide patterns in staminate- and pistillate-phase flowers. When presented with choice arrays, pollinators discriminated against pistillate-phase flowers based on their pink color. Finally, in an experimental garden, in 2012 there was a negative correlation between seed set of an open-pollinated, emasculated flower and pinkness (as measured by reflectance spectrometry) of a pistillate-phase flower on the same plant in plots covered with shade cloth. In 2013, clones of genotypes chosen from the 2012 plants that produced pinker flowers had lower seed set than those from genotypes with paler flowers. Lower seed set of pink genotypes was found in open-pollinated and hand-pollinated flowers, indicating the lower seed set might be due to other differences between pink and pale genotypes in addition to pollinator discrimination against pink flowers. In conclusion, staminate- and pistillate-phase flowers of S. officinalis are dimorphic in shape and color. Pollinators discriminate among flowers based on these differences, and individuals whose pistillate-phase flowers are most different in color from their staminate-phase flowers make fewer seeds. We suggest morphological studies of the two sex phases in dichogamous, hermaphroditic species can contribute to understanding the evolution of sexual

  3. Modeling of extraction process of crude polysaccharides from Basil seeds (Ocimum basilicum l.) as affected by process variables.

    PubMed

    Salehi, Fakhreddin; Kashaninejad, Mahdi; Tadayyon, Ali; Arabameri, Fatemeh

    2015-08-01

    Basil seed (Ocimum basilicum L.) has practical amounts of gum with good functional properties. In this work, extraction of gum from Basil seed was studied. Effect of pH, temperature and water/seed ratio on the kinetic and thermodynamic parameters; entropy, enthalpy and free energy of extraction were investigated. The maximum gum yield was 17.95 % at 50 °C for pH=7 and water/seed ratio 30:1. In this study, the experimental data were fitted to a mathematical model of mass transfer and equations constants were obtained. The kinetic of Basil seed gum extraction was found to be a first order mass transfer model. Statistical results indicated that the model used in this study will be able to predict the gum extraction from Basil seed adequately. It also found that ΔH and ΔS were positive and ΔG was negative indicating that the extraction process was spontaneous, irreversible and endothermic. The ΔH, ΔS and ΔG values were 0.26-7.87 kJ/mol, 8.12-33.2 J/mol K and 1.62-4.42 kJ/mol, respectively.

  4. 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

  5. Predator dispersal determines the effect of connectivity on prey diversity.

    PubMed

    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

  6. 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

  7. Effects of uniform rotational flow on predator-prey system

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Hee

    2012-12-01

    Rotational flow is often observed in lotic ecosystems, such as streams and rivers. For example, when an obstacle interrupts water flowing in a stream, energy dissipation and momentum transfer can result in the formation of rotational flow, or a vortex. In this study, I examined how rotational flow affects a predator-prey system by constructing a spatially explicit lattice model consisting of predators, prey, and plants. A predation relationship existed between the species. The species densities in the model were given as S (for predator), P (for prey), and G (for plant). A predator (prey) had a probability of giving birth to an offspring when it ate prey (plant). When a predator or prey was first introduced, or born, its health state was assigned an initial value of 20 that subsequently decreased by one with every time step. The predator (prey) was removed from the system when the health state decreased to less than zero. The degree of flow rotation was characterized by the variable, R. A higher R indicates a higher tendency that predators and prey move along circular paths. Plants were not affected by the flow because they were assumed to be attached to the streambed. Results showed that R positively affected both predator and prey survival, while its effect on plants was negligible. Flow rotation facilitated disturbances in individuals’ movements, which consequently strengthens the predator and prey relationship and prevents death from starvation. An increase in S accelerated the extinction of predators and prey.

  8. Nutritional composition, antinutritional factors, bioactive compounds and antioxidant activity of guava seeds (Psidium Myrtaceae) as affected by roasting processes.

    PubMed

    El Anany, Ayman Mohammed

    2015-04-01

    The purpose of this study was to explore the influences of roasting process on the nutritional composition and nutritive value, antinutritional factors, bioactive compounds and antioxidant activity of guava seeds. Roasting process caused significant (P ≤ 0.05) decreases in moisture content, crude protein, crude fiber, ash and mineral contents, isoleucine, arginine, glutamic and total aromatic and sulfur amino acids, antinutritional factors (tannins and phytic acid) and flavonoids, while oil content increased. Subjecting guava seeds to 150 °C for 10, 15 and 20 min increased the total essential amino acids from 35.19 g/100 g protein in the raw sample to 36.96, 37.30 and 37.47 g/100 g protein in roasted samples, respectively. Protein efficiency ratio (PER) of guava seeds roasted at 150 °C for 10, 15 and 20 min were about 1.08, 1.14 and 1.18 times as high as that in unroasted seeds. Lysine was the first limiting amino acid, while leucine was the second limiting amino acid in raw and roasted guava seeds. Total phenolic contents was significantly (P ≤ 0.05) increased by roasting at 150 °C for 10 min. However, roasting at 150 °C for 15 and 20 min caused significant decrease in the phenolic content of guava seeds. Guava seeds subjected to roasting process showed higher DPPH radical scavenging and reducing power activities.

  9. 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.

  10. The plastid outer envelope protein OEP16 affects metabolic fluxes during ABA-controlled seed development and germination

    PubMed Central

    Pudelski, Birgit; Schock, Annette; Hoth, Stefan; Radchuk, Ruslana; Weber, Hans; Hofmann, Jörg; Sonnewald, Uwe; Soll, Jürgen; Philippar, Katrin

    2012-01-01

    Previously, the OEP16.1 channel pore in the outer envelope membrane of mature pea (Pisum sativum) chloroplasts in vitro has been characterized to be selective for amino acids. Isolation of OEP16.2, a second OEP16 isoform from pea, in the current study allowed membrane localization and gene expression of OEP16 to be followed throughout seed development and germination of Arabidopsis thaliana and P. sativum. Thereby it can be shown on the transcript and protein level that the isoforms OEP16.1 and OEP16.2 in both plant species are alternating: whereas OEP16.1 is prominent in early embryo development and first leaves of the growing plantlet, OEP16.2 dominates in late seed development stages, which are associated with dormancy and desiccation, as well as early germination events. Further, OEP16.2 expression in seeds is under control of the phytohormone abscisic acid (ABA), leading to an ABA-hypersensitive phenotype of germinating oep16 knockout mutants. In consequence, the loss of OEP16 causes metabolic imbalance, in particular that of amino acids during seed development and early germination. It is thus concluded that in vivo OEP16 most probably functions in shuttling amino acids across the outer envelope of seed plastids. PMID:22155670

  11. Dynamics of additional food provided predator-prey system with mutually interfering predators.

    PubMed

    Prasad, B S R V; Banerjee, Malay; Srinivasu, P D N

    2013-11-01

    Use of additional/alternative food source to predators is one of the widely recognised practices in the field of biological control. Both theoretical and experimental works point out that quality and quantity of additional food play a vital role in the controllability of the pest. Theoretical studies carried out previously in this direction indicate that incorporating mutual interference between predators can stabilise the system. Experimental evidence also point out that mutual interference between predators can affect the outcome of the biological control programs. In this article dynamics of additional food provided predator-prey system in the presence of mutual interference between predators has been studied. The mutual interference between predators is modelled using Beddington-DeAngelis type functional response. The system analysis highlights the role of mutual interference on the success of biological control programs when predators are provided with additional food. The model results indicate the possibility of stable coexistence of predators with low prey population levels. This is in contrast to classical predator-prey models wherein this stable co-existence at low prey population levels is not possible. This study classifies the characteristics of biological control agents and additional food (of suitable quality and quantity), permitting the eco-managers to enhance the success rate of biological control programs.

  12. Inoculation Preparation Affects Survival of Salmonella enterica on Whole Black Peppercorns and Cumin Seeds Stored at Low Water Activity.

    PubMed

    Bowman, Lauren S; Waterman, Kim M; Williams, Robert C; Ponder, Monica A

    2015-07-01

    Salmonellosis has been increasingly associated with contaminated spices. Identifying inoculation and stabilization methods for Salmonella on whole spices is important for development of validated inactivation processes. The objective of this study was to examine the effects of inoculation preparation on the recoverability of Salmonella enterica from dried whole peppercorns and cumin seeds. Whole black peppercorns and cumin seeds were inoculated with S. enterica using one dry transfer method and various wet inoculation methods: immersion of spice seeds in tryptic soy broth (TSB) plus Salmonella for 24 h (likely leading to inclusion of Salmonella in native microbiota biofilms formed around the seeds), application of cells grown in TSB, and/or application of cells scraped from tryptic soy agar (TSA). Postinoculation seeds were dried to a water activity of 0.3 within 24 h and held for 28 days. Seeds were sampled after drying (time 0) and periodically during the 28 days of storage. Salmonella cells were enumerated by serial dilution and plated onto xylose lysine Tergitol (XLT4) agar and TSA. Recovery of Salmonella was high after 28 days of storage but was dependent on inoculation method, with 4.05 to 6.22 and 3.75 to 8.38 log CFU/g recovered from peppercorns and cumin seeds, respectively, on XLT4 agar. The changes in surviving Salmonella (log CFU per gram) from initial inoculation levels after 28 days were significantly smaller for the biofilm inclusion method (+0.142pepper, +0.186cumin) than for the other inoculation methods (-0.425pepper, -2.029cumin for cells grown on TSA; -0.641pepper, -0.718cumin for dry transfer; -1.998pepper for cells grown in TSB). In most cases, trends for reductions of total aerobic bacteria were similar to those of Salmonella. The inoculation method influenced the recoverability of Salmonella from whole peppercorns and cumin seeds after drying. The most stable inoculum strategies were dry transfer, 24-h incubation of Salmonella and spices in

  13. Dry matter, lipids, and proteins of canola seeds as affected by germination and seedling growth under illuminated and dark environments.

    PubMed

    Zhang, Haiyan; Vasanthan, Thava; Wettasinghe, Mahinda

    2004-12-29

    The effect of germination and growth under illuminated and dark environments on canola seed reserves was investigated. Depletion of proteins and lipids in whole seedlings and their top (leaf/cotyledons) and bottom parts (stem/roots/seed coat) was independent of light, whereas the protein solubility increased at a faster rate under an illuminated environment than in the dark. A rapid increase in free fatty acids but a net decrease of dry matter content in seedlings grown in the dark environment was observed. The dry matter content of seedlings grown in the illuminated environment increased due to photosynthetic biomass accumulation.

  14. Predation risk shapes thermal physiology of a predaceous damselfly.

    PubMed

    Culler, Lauren E; McPeek, Mark A; Ayres, Matthew P

    2014-11-01

    Predation risk has strong effects on organismal physiology that can cascade to impact ecosystem structure and function. Physiological processes in general are sensitive to temperature. Thus, the temperature at which predators and prey interact may shape physiological response to predation risk. We measured and evaluated how temperature and predation risk affected growth rates of predaceous damselfly nymphs (Enallagma vesperum, Odonata: Coenagrionidae). First, we conducted growth trials at five temperatures crossed with two levels of predation risk (fish predator present versus absent) and measured growth rates, consumption rates, assimilation efficiencies, and production efficiencies of 107 individual damselflies. Second, we used a model to evaluate if and how component physiological responses to predation risk affected growth rates across temperatures. In the absence of mortality threat, growth rates of damselflies increased with warming until about 23.5 °C and then began to decline, a typical unimodal response to changes in temperature. Under predation risk, growth rates were lower and the shape of the thermal response was less apparent. Higher metabolic and survival costs induced by predation risk were only partially offset by changes in consumption rates and assimilation efficiencies and the magnitude of non-consumptive effects varied as a function of temperature. Furthermore, we documented that thermal physiology was mediated by predation risk, a known driver of organismal physiology that occurs in the context of species interactions. A general understanding of climatic impacts on ectothermic populations requires consideration of the community context of thermal physiology, including non-consumptive effects of predators.

  15. 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.

  16. Effects of seed abundance on seed scatter-hoarding of Edward's rat (Leopoldamys edwardsi Muridae) at the individual level.

    PubMed

    Zhang, Hongmao; Cheng, Jinrui; Xiao, Zhishu; Zhang, Zhibin

    2008-11-01

    Mast seeding is a common phenomenon, and has important effects on seed dispersal and hoarding by animals. At population level, the predator satiation hypothesis proposes that the satiating effect of a large amount of seeds on a relatively small number of predators benefits seed survival in mast-seeding years. However, the effect of mast seeding on the scatter-hoarding of rodents at the individual level is largely unknown. In this study, we investigated the effects of seed abundance (by simulating mast seeding and non-mast seeding) on the removal, consumption and scatter-hoarding of seeds of Camellia oleifera (Theaceae) by Edward's rat Leopoldamys edwardsi (Muridae) in seminatural enclosures in southwest China. We wanted to test the masting-enhanced hoarding hypothesis, which suggests that rodents tend to scatter-hoard more seeds in mast-seeding years in order to occupy more food resources. Our results indicate that L. edwardsi tended to disperse and scatter-hoard more seeds of C. oleifera per night with increasing seed abundance, and to eat less seeds per night when there was a high level of seed abundance in the enclosure experiments. These results support the masting-enhanced hoarding hypothesis. This capacity of rodents may be an evolutionary adaptation to the mast-seeding phenomenon. Our results suggest that mast seeding benefits forest regeneration not only through the predator satiation effect at the population level, but also through increased hoarding by animals at the individual level.

  17. The impact of parasite manipulation and predator foraging behavior on predator-prey communities.

    PubMed

    Fenton, A; Rands, S A

    2006-11-01

    Parasites are known to directly affect their hosts at both the individual and population level. However, little is known about their more subtle, indirect effects and how these may affect population and community dynamics. In particular, trophically transmitted parasites may manipulate the behavior of intermediate hosts, fundamentally altering the pattern of contact between these individuals and their predators. Here, we develop a suite of population dynamic models to explore the impact of such behavioral modifications on the dynamics and structure of the predator-prey community. We show that, although such manipulations do not directly affect the persistence of the predator and prey populations, they can greatly alter the quantitative dynamics of the community, potentially resulting in high amplitude oscillations in abundance. We show that the precise impact of host manipulation depends greatly on the predator's functional response, which describes the predator's foraging efficiency under changing prey availabilities. Even if the parasite is rarely observed within the prey population, such manipulations extend beyond the direct impact on the intermediate host to affect the foraging success of the predator, with profound implications for the structure and stability of the predator-prey community.

  18. Ozone and density affect the response of biomass and seed yield to elevated CO2 in rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tropospheric O3 reduces growth and yield of many crop species, whereas CO2 ameliorates the negative effects of O3. Thus in a combined elevated CO2 and O3 atmosphere, seed yield is at least restored to that of charcoal-filtered (CF) air at ambient CO2. The CO2-induced yield increase in CF air is hi...

  19. Procyanidin content of grape seed and pomace, and total anthocyanin content of grape pomace as affected by extrusion processing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grape juice processing by-products, namely grape seed and pomace, are a rich source of procyanidins, compounds that may afford protection against coronary heart disease, type II diabetes, and obesity. This study was undertaken to identify optimal extrusion conditions to enhance the contents of monom...

  20. Alteration of seed fatty acid composition by an ethyl methanesulfonate-induced mutation in Arabidopsis thaliana affecting diacylglycerol acyltransferase activity.

    PubMed Central

    Katavic, V; Reed, D W; Taylor, D C; Giblin, E M; Barton, D L; Zou, J; Mackenzie, S L; Covello, P S; Kunst, L

    1995-01-01

    In characterizing the enzymes involved in the formation of very long-chain fatty acids (VLCFAs) in the Brassicaceae, we have generated a series of mutants of Arabidopsis thaliana that have reduced VLCFA content. Here we report the characterization of a seed lipid mutant, AS11, which, in comparison to wild type (WT), has reduced levels of 20:1 and 18:1 and accumulates 18:3 as the major fatty acid in triacylglycerols. Proportions of 18:2 remain similar to WT. Genetic analyses indicate that the fatty acid phenotype is caused by a semidominant mutation in a single nuclear gene, designated TAG1, located on chromosome 2. Biochemical analyses have shown that the AS11 phenotype is not due to a deficiency in the capacity to elongate 18:1 or to an increase in the relative delta 15 or delta 12 desaturase activities. Indeed, the ratio of desaturase/elongase activities measured in vitro is virtually identical in developing WT and AS11 seed homogenates. Rather, the fatty acid phenotype of AS11 is the result of reduced diacylglycerol acyltransferase activity throughout development, such that triacylglycerol biosynthesis is reduced. This leads to a reduction in 20:1 biosynthesis during seed development, leaving more 18:1 available for desaturation. Thus, we have demonstrated that changes to triacylglycerol biosynthesis can result in dramatic changes in fatty acid composition and, in particular, in the accumulation of VLCFAs in seed storage lipids. PMID:7784510

  1. Proteomic analysis of anti-nutritional factors (ANF’s) in soybean seeds as affected by environmental and genetic factors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The genotype (G), environment (E), and the relationship between G and E on soybean seed anti-nutritional factors (ANFs) were examined under three different agro-climatic conditions. The field trials were conducted at Maryland, South Carolina, and South Dakota using nine region specific genotypes. At...

  2. 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

  3. 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.

  4. Proteolytic Cleavage at Twin Arginine Residues Affects Structural and Functional Transitions of Lupin Seed 11S Storage Globulin

    PubMed Central

    Capraro, Jessica; Sessa, Fabio; Magni, Chiara; Scarafoni, Alessio; Maffioli, Elisa; Tedeschi, Gabriella; Croy, Ron R. D.; Duranti, Marcello

    2015-01-01

    The 11S storage globulin of white lupin seeds binds to a metal affinity chromatography matrix. Two unusual stretches of contiguous histidine residues, reminiscent of the multiple histidines forming metal binding motifs, at the C-terminal end of 11S globulin acidic chains were hypothesized as candidate elements responsible for the binding capacity. To prove this, the protein was incubated with a lupin seed endopeptidase previously shown to cleave at twin arginine motifs, recurrent in the sequence region of interest. Upon incubation with this enzyme, the loss of metal binding capacity paralleled that of the anti-his-tag reactive polypeptides. The recovered small proteolytic fragment was analyzed by mass spectrometry and N-terminal sequencing and found to correspond to the 24-mer region cleaved off at twin arginine residues and containing the natural his-tag-like region. Similarly, when lupin seeds were germinated for a few days, the his-tag containing 11S globulin chain was converted to a form devoid of such region, suggesting that this mechanism is a part of the natural degradatory process of the protein. The hypothesis that the ordered and controlled dismantling of storage proteins may generate peptide fragments with potential functional roles in plant ontogenesis is presented and discussed. PMID:25658355

  5. Proteolytic cleavage at twin arginine residues affects structural and functional transitions of lupin seed 11S storage globulin.

    PubMed

    Capraro, Jessica; Sessa, Fabio; Magni, Chiara; Scarafoni, Alessio; Maffioli, Elisa; Tedeschi, Gabriella; Croy, Ron R D; Duranti, Marcello

    2015-01-01

    The 11S storage globulin of white lupin seeds binds to a metal affinity chromatography matrix. Two unusual stretches of contiguous histidine residues, reminiscent of the multiple histidines forming metal binding motifs, at the C-terminal end of 11S globulin acidic chains were hypothesized as candidate elements responsible for the binding capacity. To prove this, the protein was incubated with a lupin seed endopeptidase previously shown to cleave at twin arginine motifs, recurrent in the sequence region of interest. Upon incubation with this enzyme, the loss of metal binding capacity paralleled that of the anti-his-tag reactive polypeptides. The recovered small proteolytic fragment was analyzed by mass spectrometry and N-terminal sequencing and found to correspond to the 24-mer region cleaved off at twin arginine residues and containing the natural his-tag-like region. Similarly, when lupin seeds were germinated for a few days, the his-tag containing 11S globulin chain was converted to a form devoid of such region, suggesting that this mechanism is a part of the natural degradatory process of the protein. The hypothesis that the ordered and controlled dismantling of storage proteins may generate peptide fragments with potential functional roles in plant ontogenesis is presented and discussed.

  6. 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.

  7. A predator-prey model with diseases in both prey and predator

    NASA Astrophysics Data System (ADS)

    Gao, Xubin; Pan, Qiuhui; He, Mingfeng; Kang, Yibin

    2013-12-01

    In this paper, we present and analyze a predator-prey model, in which both predator and prey can be infected. Each of the predator and prey is divided into two categories, susceptible and infected. The epidemics cannot be transmitted between prey and predator by predation. The predation ability of susceptible predators is stronger than infected ones. Likewise, it is more difficult to catch a susceptible prey than an infected one. And the diseases cannot be hereditary in both of the predator and prey populations. Based on the assumptions above, we find that there are six equilibrium points in this model. Using the base reproduction number, we discuss the stability of the equilibrium points qualitatively. Then both of the local and global stabilities of the equilibrium points are analyzed quantitatively by mathematical methods. We provide numerical results to discuss some interesting biological cases that our model exhibits. Lastly, we discuss how the infectious rates affect the stability, and how the other parameters work in the five possible cases within this model.

  8. Soil seed banks and their germination responses to cadmium and salinity stresses in coastal wetlands affected by reclamation and urbanization based on indoor and outdoor experiments.

    PubMed

    Bai, Junhong; Huang, Laibin; Gao, Zhaoqin; Lu, Qiongqiong; Wang, Junjing; Zhao, Qingqing

    2014-09-15

    Indoor and outdoor seedling emergence experiments were conducted to thoroughly investigate germination patterns as affected by reclamation and urbanization, the ecological characteristics of soil seed banks, and their relationships with environmental factors in both urbanized and reclaimed regions of the Pearl River Delta in coastal wetlands. The germination rate of the soil seed bank was higher in the indoor experiment compared with that in the outdoor experiment, whereas the number and destiny of the germinated seedlings were greater in the outdoor experiment. The species diversity and number, as well as the richness and evenness indices, were higher in the urbanized region compared with the reclaimed region. However, the dominance and Sørensen similarity indices were greater in the reclaimed region compared with those indices in the urbanized region. Higher salinity and Cadmium (Cd) levels could inhibit seed germination; however, their suitable ranges (i.e. [0-2,000 mg kg(-1)] for salinity and [0-4.0 mg kg(-1)] for available Cd) can activate seedling emergence, and more seedlings germinated under the intersectional levels at 0.34 mg kg(-1) available Cd and 778.6 mg kg(-1) salinity. Seawater intrusion caused by the sea level rise will possibly result in the salt-tolerant community in this area due to increasing salinity.

  9. Rice folate enhancement through metabolic engineering has an impact on rice seed metabolism, but does not affect the expression of the endogenous folate biosynthesis genes.

    PubMed

    Blancquaert, Dieter; Van Daele, Jeroen; Storozhenko, Sergei; Stove, Christophe; Lambert, Willy; Van Der Straeten, Dominique

    2013-11-01

    Folates are key-players in one-carbon metabolism in all organisms. However, only micro-organisms and plants are able to synthesize folates de novo and humans rely entirely on their diet as a sole folate source. As a consequence, folate deficiency is a global problem. Although different strategies are currently implemented to fight folate deficiency, up until now, all of them have their own drawbacks. As an alternative and complementary means to those classical strategies, folate biofortification of rice by metabolic engineering was successfully achieved a couple of years ago. To gain more insight into folate biosynthesis regulation and the effect of folate enhancement on general rice seed metabolism, a transcriptomic study was conducted in developing transgenic rice seeds, overexpressing 2 genes of the folate biosynthetic pathway. Upon folate enhancement, the expression of 235 genes was significantly altered. Here, we show that rice folate biofortification has an important effect on folate dependent, seed developmental and plant stress response/defense processes, but does not affect the expression of the endogenous folate biosynthesis genes.

  10. Efficiency of pollination and satiation of predators determine reproductive output in Iberian Juniperus thurifera woodlands.

    PubMed

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

    2016-01-01

    Fruit production in animal-dispersed plants has a strong influence on fitness because large crops increase the number of seeds dispersed by frugivores. Large crops are costly, and environmental control of plant resources is likely play a role in shaping temporal and spatial variations in seed production, particularly in fluctuating environments such as the Mediterranean. The number of fruits that start to develop and the proportion of viable seeds produced are also linked to the number of flowers formed and the efficiency of pollination in wind-pollinated plants. Finally, large fruit displays also attract seed predators, having a negative effect on seed output. We assessed the relative impact of environmental conditions on fruit production, and their combined effect on seed production, abortion and seed loss through three predispersal predators in Juniperus thurifera L., sampling 14 populations across the Iberian Peninsula. Wetter than average conditions during flowering and early fruit development led to larger crop sizes; this effect was amplified at tree level, with the most productive trees during more favourable years yielding fruits with more viable seeds and less empty and aborted seeds. In addition, large crops satiated the less mobile seed predator. The other two predispersal predators responded to plant traits, the presence of other seed predators and environmental conditions, but did not show a satiation response to the current-year crop. Our large-scale study on a dioecious, wind-pollinated Mediterranean juniper indicates that pollination efficiency and satiation of seed predators, mediated by environmental conditions, are important determinants of reproductive output in this juniper species.

  11. Decontamination method using heat and relative humidity for radish seeds achieves a 7-log reduction of Escherichia coli O157:H7 without affecting product quality.

    PubMed

    Kim, Y B; Kim, H W; Song, M K; Rhee, M S

    2015-05-18

    We developed a novel decontamination method to inactivate Escherichia coli O157:H7 on radish seeds without adversely affecting seed germination or product quality. The use of heat (55, 60, and 65 °C) combined with relative humidity (RH; 25, 45, 65, 85, and 100%) for 24h was evaluated for effective microbial reduction and preservation of seed germination rates. A significant two-way interaction of heat and RH was observed for both microbial reduction and germination rate (P<0.0001). Increases in heat and RH were associated with corresponding reductions in E. coli O157:H7 and in germination rate (P<0.05). The order of lethality for the different treatments was generally as follows: no treatment <55 °C/25-65% RH ≒60 °C/25-45% RH ≒65 °C/25% RH <55 °C/85% RH =60 °C/65% RH <55 °C/100% RH =60 °C/85-100% RH =65 °C/45-100% RH. The most effective condition, 65 °C/45% RH, completely inactivated E. coli O157:H7 on the seeds (7.0 log CFU/g reduction) and had no significant effect on the germination rate (85.4%; P>0.05) or product quality. The method uses only heat and relative humidity without chemicals, and is thus applicable as a general decontamination procedure in spout producing plants where the use of growth chambers is the norm.

  12. Factors affecting stress tolerance in recalcitrant embryonic axes from seeds of four Quercus (Fagaceae) species native to the USA or China

    PubMed Central

    Xia, Ke; Hill, Lisa M.; Li, De-Zhu; Walters, Christina

    2014-01-01

    Background and Aims Quercus species are often considered ‘foundation’ components of several temperate and/or subtropical forest ecosystems. However, the populations of some species are declining and there is considerable urgency to develop ex situ conservation strategies. In this study, the storage physiology of seeds within Quercus was explored in order to determine factors that affect survival during cryopreservation and to provide a quantitative assessment of seed recalcitrance to support future studies of this complex trait. Methods Water relations and survival of excised axes in response to water loss and cryo-exposure were compared for four Quercus species from subtropical China (Q. franchetii, Q. schottkyana) and temperate USA (Q. gambelii, Q. rubra). Key Results Seed tissues initially had high water contents and water potentials. Desiccation tolerance of the embryonic axis was not correlated with the post-shedding rainfall patterns where the samples originated. Instead, higher desiccation tolerance was observed in samples growing in areas with colder winters. Survival following cryo-exposure correlated with desiccation tolerance. Among species, plumule tissues were more sensitive than radicles to excision, desiccation and cryo-exposure, and this led to a higher proportion of abnormally developing embryos during recovery following stress. Conclusions Quercus species adapted to arid and semi-humid climates still produce recalcitrant seeds. The ability to avoid freezing rather than drought may be a more important selection factor to increase desiccation tolerance. Cryopreservation of recalcitrant germplasm from temperate species is currently feasible, whilst additional protective treatments are needed for ex situ conservation of Quercus from tropical and subtropical areas. PMID:25326139

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

    SciTech Connect

    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 destroyed 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  15. Unidirectional prey-predator facilitation: apparent prey enhance predators' foraging success on cryptic prey.

    PubMed

    Zhang, Yixin; Richardson, John S

    2007-06-22

    Food availability can strongly affect predator-prey dynamics. When change in habitat condition reduces the availability of one prey type, predators often search for other prey, perhaps in a different habitat. Interactions between behavioural and morphological traits of different prey may influence foraging success of visual predators through trait-mediated indirect interactions (TMIIs), such as prey activity and body coloration. We tested the hypothesis that foraging success of stream-dwelling cutthroat trout (Onchorhyncus clarki) on cryptically coloured, less-active benthic prey (larval mayfly; Paraleptophebia sp.) can be enhanced by the presence of distinctly coloured, active prey (larval stonefly shredder; Despaxia augusta). Cutthroat trout preyed on benthic insects when drifting invertebrates were unavailable. When stonefly larvae were present, the trout ate most of the stoneflies and also consumed a higher proportion of mayflies than under mayfly only treatment. The putative mechanism is that active stonefly larvae supplied visual cues to the predator that alerted trout to the mayfly larvae. Foraging success of visual predators on cryptic prey can be enhanced by distinctly coloured, active benthic taxa through unidirectional facilitation to the predators, which is a functional change of interspecific interaction caused by a third species. This study suggests that prey-predator facilitation through TMIIs can modify species interactions, affecting community dynamics.

  16. Antioxidant activities of lead (Leucaena leucocephala) seed as affected by extraction solvent, prior dechlorophyllisation and drying methods.

    PubMed

    Benjakul, Soottawat; Kittiphattanabawon, Phanat; Sumpavapol, Punnanee; Maqsood, Sajid

    2014-11-01

    Extracts of brown lead (Leucaena leucocephala) seed prepared using different extraction solvents were determined for antioxidative activities using different assays. The highest yield (3.4-4.0%) was obtained when water was used as an extraction solvent, compared with all ethanolic extracts used (1.2-2.0 %) (P < 0.05). Much lower chlorophyll content was found in the water extract. When hot water was used, the resulting extract contained lower total phenolic and mimosine contents (P < 0.05). In general, 60-80 % ethanolic extracts had higher 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities, ferric reducing antioxidant power (FRAP) and metal chelating activity than water extracts (P < 0.05). When brown lead seed was dechlorophyllised prior to extraction, the water extract had slightly increased yield with lower chlorophyll content. Nevertheless, prior chlorophyll removal resulted in the increase in antioxidative activities but lower total phenolic and mimosine contents (P < 0.05). Generally, phenolic compounds and mimosine were more released when water was used as the extraction solvent, while the lower amount of chlorophyll was extracted. Oven-drying exhibited the negative effect on antioxidative activities and mimosine content. The higher antioxidative activities with concomitant higher total phenolic and mimosine contents were found in water extract dried by freeze drying. Thus, extraction solvent, dechlorophyllisation and drying methods directly influenced the yield and antioxidative activity of lead seed extract.

  17. Predator-driven elemental cycling: the impact of predation and risk effects on ecosystem stoichiometry.

    PubMed

    Leroux, Shawn J; Schmitz, Oswald J

    2015-11-01

    Empirical evidence is beginning to show that predators can be important drivers of elemental cycling within ecosystems by propagating indirect effects that determine the distribution of elements among trophic levels as well as determine the chemical content of organic matter that becomes decomposed by microbes. These indirect effects can be propagated by predator consumptive effects on prey, nonconsumptive (risk) effects, or a combination of both. Currently, there is insufficient theory to predict how such predator effects should propagate throughout ecosystems. We present here a theoretical framework for exploring predator effects on ecosystem elemental cycling to encourage further empirical quantification. We use a classic ecosystem trophic compartment model as a basis for our analyses but infuse principles from ecological stoichiometry into the analyses of elemental cycling. Using a combined analytical-numerical approach, we compare how predators affect cycling through consumptive effects in which they control the flux of nutrients up trophic chains; through risk effects in which they change the homeostatic elemental balance of herbivore prey which accordingly changes the element ratio herbivores select from plants; and through a combination of both effects. Our analysis reveals that predators can have quantitatively important effects on elemental cycling, relative to a model formalism that excludes predator effects. Furthermore, the feedbacks due to predator nonconsumptive effects often have the quantitatively strongest impact on whole ecosystem elemental stocks, production and efficiency rates, and recycling fluxes by changing the stoichiometric balance of all trophic levels. Our modeling framework predictably shows how bottom-up control by microbes and top-down control by predators on ecosystems become interdependent when top predator effects permeate ecosystems.

  18. 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.

  19. An event of alternative splicing affects the expression of the NTRC gene, encoding NADPH-thioredoxin reductase C, in seed plants.

    PubMed

    Nájera, Victoria A; González, María Cruz; Pérez-Ruiz, Juan Manuel; Cejudo, Francisco Javier

    2017-05-01

    The NTRC gene encodes a NADPH-dependent thioredoxin reductase with a joint thioredoxin domain, exclusive of photosynthetic organisms. An updated search shows that although most species harbor a single copy of the NTRC gene, two copies were identified in different species of the genus Solanum, Glycine max and the moss Physcomitrella patens. The phylogenetic analysis of NTRCs from different sources produced a tree with the major groups of photosynthetic organisms: cyanobacteria, algae and land plants, indicating the evolutionary success of the NTRC gene among photosynthetic eukaryotes. An event of alternative splicing affecting the expression of the NTRC gene was identified, which is conserved in seed plants but not in algae, bryophytes and lycophytes. The alternative splicing event results in a transcript with premature stop codon, which would produce a truncated form of the enzyme. The standard splicing/alternative splicing (SS/AS) transcripts ratio was higher in photosynthetic tissues from Arabidopsis, Brachypodium and tomato, in line with the higher content of the NTRC polypeptide in these tissues. Moreover, environmental stresses such as cold or high salt affected the SS/AS ratio of the NTRC gene transcripts in Brachypodium seedlings. These results suggest that the alternative splicing of the NTRC gene might be an additional mechanism for modulating the content of NTRC in photosynthetic and non-photosynthetic tissues of seed plants.

  20. Optimal control of native predators

    USGS Publications Warehouse

    Martin, Julien; O'Connell, Allan F.; Kendall, William L.; Runge, Michael C.; Simons, Theodore R.; Waldstein, Arielle H.; Schulte, Shiloh A.; Converse, Sarah J.; Smith, Graham W.; Pinion, Timothy; Rikard, Michael; Zipkin, Elise F.

    2010-01-01

    We apply decision theory in a structured decision-making framework to evaluate how control of raccoons (Procyon lotor), a native predator, can promote the conservation of a declining population of American Oystercatchers (Haematopus palliatus) on the Outer Banks of North Carolina. Our management objective was to maintain Oystercatcher productivity above a level deemed necessary for population recovery while minimizing raccoon removal. We evaluated several scenarios including no raccoon removal, and applied an adaptive optimization algorithm to account for parameter uncertainty. We show how adaptive optimization can be used to account for uncertainties about how raccoon control may affect Oystercatcher productivity. Adaptive management can reduce this type of uncertainty and is particularly well suited for addressing controversial management issues such as native predator control. The case study also offers several insights that may be relevant to the optimal control of other native predators. First, we found that stage-specific removal policies (e.g., yearling versus adult raccoon removals) were most efficient if the reproductive values among stage classes were very different. Second, we found that the optimal control of raccoons would result in higher Oystercatcher productivity than the minimum levels recommended for this species. Third, we found that removing more raccoons initially minimized the total number of removals necessary to meet long term management objectives. Finally, if for logistical reasons managers cannot sustain a removal program by removing a minimum number of raccoons annually, managers may run the risk of creating an ecological trap for Oystercatchers.

  1. 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

  2. The roles of dispersal, fecundity, and predation in the population persistence of an oak (Quercus engelmannii) under global change.

    PubMed

    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.

  3. 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

  4. The Predator-Prey Relationship

    ERIC Educational Resources Information Center

    Mitchell, Charles W.

    1977-01-01

    Many children develop a mistaken attitude about the predator-prey relationship in the ecosystem. Fairy tales portray the predator as evil or worthless. This article attempts to clarify the role of the predator by giving numerous examples of the value of predators. (MA)

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  6. Molecular insights into how a deficiency of amylose affects carbon allocation – carbohydrate and oil analyses and gene expression profiling in the seeds of a rice waxy mutant

    PubMed Central

    2012-01-01

    Background Understanding carbon partitioning in cereal seeds is of critical importance to develop cereal crops with enhanced starch yields for food security and for producing specified end-products high in amylose, β-glucan, or fructan, such as functional foods or oils for biofuel applications. Waxy mutants of cereals have a high content of amylopectin and have been well characterized. However, the allocation of carbon to other components, such as β-glucan and oils, and the regulation of the altered carbon distribution to amylopectin in a waxy mutant are poorly understood. In this study, we used a rice mutant, GM077, with a low content of amylose to gain molecular insight into how a deficiency of amylose affects carbon allocation to other end products and to amylopectin. We used carbohydrate analysis, subtractive cDNA libraries, and qPCR to identify candidate genes potentially responsible for the changes in carbon allocation in GM077 seeds. Results Carbohydrate analysis indicated that the content of amylose in GM077 seeds was significantly reduced, while that of amylopectin significantly rose as compared to the wild type BP034. The content of glucose, sucrose, total starch, cell-wall polysaccharides and oil were only slightly affected in the mutant as compared to the wild type. Suppression subtractive hybridization (SSH) experiments generated 116 unigenes in the mutant on the wild-type background. Among the 116 unigenes, three, AGP, ISA1 and SUSIBA2-like, were found to be directly involved in amylopectin synthesis, indicating their possible roles in redirecting carbon flux from amylose to amylopectin. A bioinformatics analysis of the putative SUSIBA2-like binding elements in the promoter regions of the upregulated genes indicated that the SUSIBA2-like transcription factor may be instrumental in promoting the carbon reallocation from amylose to amylopectin. Conclusion Analyses of carbohydrate and oil fractions and gene expression profiling on a global scale in the

  7. Proteomic analysis of anti-nutritional factors (ANF's) in soybean seeds as affected by environmental and genetic factors.

    PubMed

    Maria John, K M; Khan, Farooq; Luthria, Davanand L; Garrett, Wesley; Natarajan, Savithiry

    2017-03-01

    The genotype (G), environment (E), and the relationship between G and E on soybean seed anti-nutritional factors (ANF's) were examined under three different agro-climatic conditions. The field trials were conducted at Maryland, South Carolina and South Dakota using nine region specific genotypes. At each location, the nine genotypes were grown with two planting/sowing dates. Differentially expressed protein spots from the two-dimensional gel electrophoresis were analyzed using mass spectrometry. Seven ANF's corresponding to soybean agglutinin and Kunitz trypsin inhibitor were identified based on the statistical significance levels at p<0.005. The G and E conditions (planting/sowing season) influences the ANF's content. This initial study suggests that early sowing reduces the total ANF's content irrespective of genotypes and their growing locations.

  8. Narrow Bottlenecks Affect Pea Seedborne Mosaic Virus Populations during Vertical Seed Transmission but not during Leaf Colonization

    PubMed Central

    Johansen, Elisabeth Ida; Simon, Vincent; Jacquemond, Mireille; Senoussi, Rachid

    2014-01-01

    The effective size of populations (Ne) determines whether selection or genetic drift is the predominant force shaping their genetic structure and evolution. Populations having high Ne adapt faster, as selection acts more intensely, than populations having low Ne, where random effects of genetic drift dominate. Estimating Ne for various steps of plant virus life cycle has been the focus of several studies in the last decade, but no estimates are available for the vertical transmission of plant viruses, although virus seed transmission is economically significant in at least 18% of plant viruses in at least one plant species. Here we study the co-dynamics of two variants of Pea seedborne mosaic virus (PSbMV) colonizing leaves of pea plants (Pisum sativum L.) during the whole flowering period, and their subsequent transmission to plant progeny through seeds. Whereas classical estimators of Ne could be used for leaf infection at the systemic level, as virus variants were equally competitive, dedicated stochastic models were needed to estimate Ne during vertical transmission. Very little genetic drift was observed during the infection of apical leaves, with Ne values ranging from 59 to 216. In contrast, a very drastic genetic drift was observed during vertical transmission, with an average number of infectious virus particles contributing to the infection of a seedling from an infected mother plant close to one. A simple model of vertical transmission, assuming a cumulative action of virus infectious particles and a virus density threshold required for vertical transmission to occur fitted the experimental data very satisfactorily. This study reveals that vertically-transmitted viruses endure bottlenecks as narrow as those imposed by horizontal transmission. These bottlenecks are likely to slow down virus adaptation and could decrease virus fitness and virulence. PMID:24415934

  9. Multiple predator effects in an intertidal food web.

    PubMed

    Van Son, Thijs Christiaan; Thiel, Martin

    2006-01-01

    1. We examined the effects of multiple predators from an intertidal boulder food web to test whether and how three different predator species affected the survival of a small amphipod species. 2. Predators were chosen because they differ in their foraging mode, two feeding at the bottom and in benthic refuges (nemertean and shrimp) and one in the water-column (juveniles of a fish). 3. Mortality of amphipods was not affected by nemerteans, but was high in the presence of shrimp or fish. Highest mortalities were observed in predator-combinations that contained both shrimp and fish. Amphipods responded to shrimp by escaping into the water column, while they avoided fish by remaining in the refuge. We conclude that predator-specific defence causes conflicts for prey when both shrimp and fish are present. 4. Comparing observed effects of multiple predators with expected effects revealed risk enhancement for the shrimp + fish combination. A comparison of different predictive models revealed that the multiplicative model was most appropriate, although additive models may work well under certain conditions. 5. Based on known consumption-ranges of the predators used, we conclude that nemerteans were saturated with prey while fish were far from their saturation point. A predator's functional response curve (prey consumption in relation to prey abundance) determines its impact on prey populations. This knowledge appears essential in order to predict whether prey organisms face risk enhancement, risk reduction or additive effects of multiple predators.

  10. Predator cannibalism can intensify negative impacts on heterospecific prey.

    PubMed

    Takatsu, Kunio; Kishida, Osamu

    2015-07-01

    Although natural populations consist of individuals with different traits, and the degree of phenotypic variation varies among populations, the impact of phenotypic variation on ecological interactions has received little attention, because traditional approaches to community ecology assume homogeneity of individuals within a population. Stage structure, which is a common way of generating size and developmental variation within predator populations, can drive cannibalistic interactions, which can affect the strength of predatory effects on the predator's heterospecific prey. Studies have shown that predator cannibalism weakens predatory effects on heterospecific prey by reducing the size of the predator population and by inducing less feeding activity of noncannibal predators. We predict, however, that predator cannibalism, by promoting rapid growth of the cannibals, can also intensify predation pressure on heterospecific prey, because large predators have large resource requirements and may utilize a wider variety of prey species. To test this hypothesis, we conducted an experiment in which we created carnivorous salamander (Hynobius retardatus) populations with different stage structures by manipulating the salamander's hatch timing (i.e., populations with large or small variation in the timing of hatching), and explored the resultant impacts on the abundance, behavior, morphology, and life history of the salamander's large heterospecific prey, Rana pirica frog tadpoles. Cannibalism was rare in salamander populations having small hatch-timing variation, but was frequent in those having large hatch-timing variation. Thus, giant salamander cannibals occurred only in the latter. We clearly showed that salamander giants exerted strong predation pressure on frog tadpoles, which induced large behavioral and morphological defenses in the tadpoles and caused them to metamorphose late at large size. Hence, predator cannibalism arising from large variation in the timing

  11. Reproductive success of individuals with different fruit production patterns. What does it mean for the predator satiation hypothesis?

    PubMed

    Zywiec, Magdalena; Holeksa, Jan; Ledwoń, Mateusz; Seget, Piotr

    2013-06-01

    The predator satiation hypothesis states that synchronous periodic production of seeds is an adaptive strategy evolved to reduce the pressure of seed predators. The seed production pattern is crucial to the predator satiation hypothesis, but there are few studies documenting the success of individuals that are in synchrony and out of synchrony with the whole population. This study is based on long-term data on seed production of Sorbus aucuparia and specialised pre-dispersal seed predation by Argyresthia conjugella, in a subalpine spruce forest in the Western Carpathians (Poland). At the population level, we tested whether functional and numerical responses of predators to the variation of fruit production operate. At the individual level, we tested whether individuals with higher interannual variability in their own seed crops and higher synchrony with the population have higher percentages of uninfested fruits. The intensity of pre-dispersal seed predation was high (average 70 %; range 19-100 %). There were both functional and numerical responses of predators to the variation of fruit production at the population level. We found that individuals that were expected to be preferred under seed predator pressure had higher reproductive success. With increasing synchrony of fruit production between individual trees and the population, the percentage of infested fruits decreased. There was also a negative relationship between the interannual variation in individual fruit production and the percentage of infested fruits. These results confirm selection for individuals with a masting strategy. However, the population does not seem well adapted to strong seed predation pressure and we suggest that this may be a result of prolonged diapause of A. conjugella.

  12. Intraguild relationships between sympatric predators exposed to lethal control: predator manipulation experiments

    PubMed Central

    2013-01-01

    populations of native prey fauna at lower trophic levels are unlikely to be negatively affected by contemporary dingo control practices through the release of mesopredators. We conclude that contemporary lethal control practices used on some top-predator populations do not produce the conditions required to generate positive responses from mesopredators. Functional relationships between sympatric terrestrial predators may not be altered by exposure to spatially and temporally sporadic application of non-selective lethal control. PMID:23842144

  13. Factors affecting establishment and recovery of Sasajiscymnus tsugae (Coleoptera: Coccinellidae), an introduced predator of hemlock woolly adelgid (Hemiptera: Adelgidae) on eastern hemlock (Pinales: Pinaceae).

    PubMed

    Hakeem, A; Grant, J F; Wiggins, G J; Lambdin, P L; Hale, F A; Buckley, D S; Rhea, J R; Parkman, J P; Taylor, G

    2013-12-01

    To reduce populations of hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), >500,000 Sasajiscymnus tsugae (Sasaji and McClure) (Coleoptera: Coccinellidae) have been released in the Great Smoky Mountains National Park since 2002. To determine factors affecting establishment and recovery of these predatory beetles, 65 single release sites were sampled using beat sheets from 2008 to 2012. Several abiotic and biotic factors were evaluated for their association with establishment and recovery of S. tsugae. Information on predatory beetle releases (location, year of release, number released, and season of release), topographic features (elevation, slope, Beers transformed aspect, and topographic relative moisture index), and temperature data (minimum and maximum temperatures 1 d after release and average minimum and maximum temperatures 7 d after release) were obtained from Great Smoky Mountains National Park personnel. These factors were evaluated using stepwise logistic regression and Pearson correlation. S. tsugae was recovered from 13 sites 2 to 10 yr after release, and the greatest number was recovered from 2002 release sites. Regression indicated establishment and recovery was negatively associated with year of release and positively associated with the average maximum temperature 7 d after release and elevation (generally, recovery increased as temperatures increased). Several significant correlations were found between presence and number of S. tsugae and year of release, season of release, and temperature variables. These results indicate that releases of S. tsugae should be made in warmer (≍10-25°C) temperatures and monitored for at least 5 yr after releases to enhance establishment and recovery efforts.

  14. The effect of hydroperiod and predation on the diversity of temporary pond zooplankton communities

    PubMed Central

    Zokan, Marcus; Drake, John M

    2015-01-01

    In temporary pond ecosystems, it is hypothesized that the two dominant structuring forces on zooplankton communities are predation and demographic constraints due to wetland drying. Both of these forces are deterministic processes that act most strongly at opposing ends of a hydroperiod gradient. Our objective was to test how these two processes affect α- and β-diversity of zooplankton communities derived from a diverse temporary pond system. We hypothesized that decreased hydroperiod length and the presence of salamander larvae as predators would decrease β-diversity and that intermediate hydroperiod communities would have the greatest species richness. Our 1-year mesocosm experiment (n = 36) consisted of two predation treatments (present/absent) and three hydroperiod treatments (short/medium/long) fully crossed, seeded from the resting egg bank of multiple temporary ponds. In total, we collected 37 species of microcrustacean zooplankton from our mesocosms. A reduction in hydroperiod length resulted in lower α-diversity, with short-hydroperiod treatments affected most strongly. Endpoint community dissimilarity (β-diversity) was greatest in the medium-hydroperiod treatment with regard to species presence/absence, but was greatest in the long-hydroperiod treatment when abundances were included. Predation by salamander larvae led to reduced β-diversity with respect to species presence/absence, but not among abundant species, and had no effect on α-diversity. Our results suggest that environmental changes that reduce hydroperiod length would result in reduced α-diversity; however, intermediate hydroperiod length appear to enhance β-diversity within a group of wetlands. PMID:26357537

  15. Nitrate affects sensu-stricto germination of after-ripened Sisymbrium officinale seeds by modifying expression of SoNCED5, SoCYP707A2 and SoGA3ox2 genes.

    PubMed

    Carrillo-Barral, Néstor; Matilla, Angel J; Rodríguez-Gacio, María del Carmen; Iglesias-Fernández, Raquel

    2014-03-01

    The influence of nitrate upon the germination of Sisymbrium officinale seeds is not entirely controlled by after-ripening (AR), a process clearly influenced by nitrate. Recently, we have reported that nitrate affects sensu-stricto germination of non-AR (AR0) seeds by modifying the expression of crucial genes involved in the metabolism of GA and ABA. In this study, we demonstrate that nitrate affects also the germination of AR seeds because: (i) the AR negatively alters the ABA sensitivity being the seed more ABA-sensible as the AR is farthest from optimal (AR0 and AR20 versus AR7); in the presence of diniconazole (DZ), a competitive inhibitor of ABA 8'-hydroxylase, testa rupture is affected while the endosperm rupture is not. (ii) AR7 seed-coat rupture is not inhibited by paclobutrazol (PBZ) suggesting that nitrate can act by a mechanism GA-independent. (iii) The germination process is accelerated by nitrate, most probably by the increase in the expression of SoNCED5, SoCYP707A2 and SoGA3ox2 genes. Taken together, these and previous results demonstrate that nitrate promotes germination of AR and non-AR seeds through transcriptional changes of different genes involved in ABA and GA metabolism.

  16. 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.

  17. Predator interference and stability of predator-prey dynamics.

    PubMed

    Přibylová, Lenka; Berec, Luděk

    2015-08-01

    Predator interference, that is, a decline in the per predator consumption rate as predator density increases, is generally thought to promote predator-prey stability. Indeed, this has been demonstrated in many theoretical studies on predator-prey dynamics. In virtually all of these studies, the stabilization role is demonstrated as a weakening of the paradox of enrichment. With predator interference, stable limit cycles that appear as a result of environmental enrichment occur for higher values of the environmental carrying capacity of prey, and even a complete absence of the limit cycles can happen. Here we study predator-prey dynamics using the Rosenzweig-MacArthur-like model in which the Holling type II functional response has been replaced by a predator-dependent family which generalizes many of the commonly used descriptions of predator interference. By means of a bifurcation analysis we show that sufficiently strong predator interference may bring about another stabilizing mechanism. In particular, hysteresis combined with (dis)appearance of stable limit cycles imply abrupt increases in both the prey and predator densities and enhanced persistence and resilience of the predator-prey system. We encourage refitting the previously collected data on predator consumption rates as well as for conducting further predation experiments to see what functional response from the explored family is the most appropriate.

  18. Nonconsumptive Predator-Prey Interactions: Sensitivity of the Detritivore Sinella curviseta (Collembola: Entomobryidae) to Cues of Predation Risk From the Spider Pardosa milvina (Araneae: Lycosidae).

    PubMed

    Sitvarin, Michael I; Romanchek, Christian; Rypstra, Ann L

    2015-04-01

    Predators can affect prey indirectly when prey respond to cues indicating a risk of predation by altering activity levels. Changes in prey behavior may cascade through the food web to influence ecosystem function. The response of the collembolan Sinella curviseta Brook (Collembola: Entomobryidae) to cues indicating predation risk (necromones and cues from the wolf spider Pardosa milvina (Hentz) (Araneae: Lycosidae)) was tested. Additionally, necromones and predator cues were paired in a conditioning experiment to determine whether the collembolan could form learned associations. Although collembolans did not alter activity levels in response to predator cues, numerous aspects of behavior differed in the presence of necromones. There was no detectable conditioned response to predator cues after pairing with necromones. These results provide insight into how collembolans perceive and respond to predation threats that vary in information content. Previously detected indirect impacts of predator cues on ecosystem function are likely due to changes in prey other than activity level.

  19. Functional responses: a question of alternative prey and predator density.

    PubMed

    Tschanz, Britta; Bersier, Louis-Felix; Bacher, Sven

    2007-05-01

    Throughout the study of ecology, there has been a growing realization that indirect effects among species cause complexity in food webs. Understanding and predicting the behavior of ecosystems consequently depends on our ability to identify indirect effects and their mechanisms. The present study experimentally investigates indirect interactions arising between two prey species that share a common predator. In a natural field experiment, we introduced different densities of mealworms (Tenebrio molitor), an alternative prey, to a previously studied predator-prey system in which paper wasps (Polistes dominulus) preyed on shield beetle larvae (Cassida rubiginosa). We tested if alternative prey affects predation on the first prey (i.e., the predator-dependent functional response of paper wasps) by modifying either interference among predators or the effective number of predators foraging on shield beetles. Presence of mealworms significantly reduced the effective number of predators, whereas predator interference was not affected. In this way, the experimentally introduced alternative prey altered the wasps' functional response and thereby indirectly influenced C. rubiginosa density. In all prey-density combinations offered, paper wasps constantly preferred T. molitor. This led to an asymmetrical, indirect interaction between both prey species: an increase in mealworm density significantly relaxed predation on C. rubiginosa, whereas an increase in C. rubiginosa density intensified predation on mealworms. Such asymmetrical outcomes of a fixed food preference can significantly affect the population dynamics of the species involved. In spite of the repeated finding of a Type III functional response in this system, our experiment did not reveal switching behavior in paper wasps. The variety of mechanisms underlying direct and indirect interactions within our study system exemplifies the importance of incorporating alternative prey when investigating the impact of a

  20. Burial of Zostera marina seeds in sediment inhabited by three polychaetes: Laboratory and field studies

    NASA Astrophysics Data System (ADS)

    Delefosse, M.; Kristensen, E.

    2012-07-01

    The large number of seeds produced by eelgrass, Zostera marina, provides this plant with a potential to disperse widely and colonise new areas. After dispersal, seeds must be buried into sediment for assuring long-term survival, successful germination and safe seedling development. Seeds may be buried passively by sedimentation or actively through sediment reworking by benthic fauna. We evaluated the effect of three polychaetes on the burial rate and depth of eelgrass seeds. Burial was first measured in controlled laboratory experiments using different densities of Nereis (Hediste) diversicolor (400-3200 ind m- 2), Arenicola marina (20-80 ind m- 2), and the invasive Marenzelleria viridis (400-1600 ind m- 2). The obtained results were subsequently compared with burial rates of seed mimics in experimental field plots (1 m2) dominated by the respective polychaetes. High recovery of seeds in the laboratory (97-100%) suggested that none of these polychaetes species feed on eelgrass seeds. N. diversicolor transported seeds rapidly (< 1 day) into its burrow, where they remained buried at a median depth of 0.5 cm. A. marina and M. viridis buried seeds by depositing their faeces on top of the sediment. At their highest abundance, A. marina and M. viridis buried seeds to a median depth of 6.7 cm and 0.5 cm, respectively, after a month. The burial efficiency and depth of these species were, in contrast to N. diversicolor, dependent on animal abundance. Only 2% of seed mimics casted in the field plots were recovered, suggesting that physical dispersion by waves and currents was considerably important for horizontal distribution. However, polychaete affected significantly the vertical distribution of seeds. Overall the effects of these three polychaetes indicate that benthic macroinvertebrates may significantly impact eelgrass seed bank at the ecosystem scale. Some species have a positive effect by burying seeds to shallow depths and thereby reducing seed predation and

  1. Cryopreservation of recalcitrant seeds: factors affecting survival of embryonic axes from four Quercus (Fagaceae) species native to the US or China

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Numerous tree species of economic and environmental importance are facing pressures from diseases or pests, climate change or habitat fragmentation. Seed banking to preserve the genetic diversity within these species would aid conservation. However, several tree species produce recalcitrant seeds, ...

  2. Molecular weight and galloylation affect grape seed extract constituents’ ability to cross-link dentin collagen in clinically relevant time

    PubMed Central

    Liu, Yi; Bai, Xinyan; Li, Shaohua; Liu, Ying; Keightley, Andrew; Wang, Yong

    2015-01-01

    Objective To investigate the relationship between the structures of polyphenolic compounds found in grape seed extract (GSE) and their activity in cross-linking dentin collagen in clinically relevant settings. Methods Representative monomeric and dimeric GSE constituents including (+)-catechin (pCT), (−)-catechin (CT), (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin gallate (EGCG), procyanidin B2 and a pCT-pCT dimer were purchased or synthesized. GSE was separated into low (PALM) and high molecular weight (PAHM) fractions. Human molars were processed into dentin films and beams. After demineralization, 11 groups of films (n=5) were treated for 1 min with the aforementioned reagents (1 wt% in 50/50 ethanol/water) and 1 group remained untreated. The films were studied by Fourier transform infrared spectroscopy (FTIR) followed by a quantitative mass spectroscopy-based digestion assay. Tensile properties of demineralized dentin beams were evaluated (n=7) after treatments (2h and 24h) with selective GSE species that were found to protect dentin collagen from collagenase. Results Efficacy of GSE constituents in cross-linking dentin collagen was dependent on molecular size and galloylation. Non-galloylated species with degree of polymerization up to two, including pCT, CT, EC, EGC, procyanidin B2 and pCT-pCT dimer were not active. Galloylated species were active starting from monomeric form, including ECG, EGCG, PALM, GSE and PAHM. PALM induced the best overall improvement in tensile properties of dentin collagen. Significance Identification under clinically relevant settings of structural features that contribute to GSE constituents’ efficacy in stabilizing demineralized dentin matrix has immediate impact on optimizing GSE’s use in dentin bonding. PMID:25958268

  3. 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.

  4. 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

  5. Contrasting patterns of short-term indirect seed-seed interactions mediated by scatter-hoarding rodents.

    PubMed

    Xiao, Zhishu; Zhang, Zhibin

    2016-09-01

    It is well known that direct effects of seed predators or dispersers can have strong effects on seedling establishment. However, we have limited knowledge about the indirect species interactions between seeds of different species that are mediated by shared seed predators and/or dispersers and their consequences for plant demography and diversity. Because scatter-hoarding rodents as seed dispersers may leave some hoarded seeds uneaten, scatter hoarding may serve to increase seed survival and dispersal. Consequently, the presence of heterospecific seeds could alter whether the indirect interactions mediated by scatter-hoarding rodents have a net positive effect, creating apparent mutualism between seed species, or a net negative effect, creating apparent competition between seed species. We present a testable framework to measure short-term indirect effects between co-occurring plant species mediated by seed scatter-hoarding rodents. We tested this framework in a subtropical forest in south-west China using a replacement design and tracked the fate of individually tagged seeds in experimental patches. We manipulated the benefits to rodents by using low-tannin dormant chestnuts as palatable food and high-tannin non-dormant acorns as unpalatable food. We found that seed palatability changed the amount of scatter hoarding that occurred when seeds co-occurred either among or within patches. Consistent with our predictions, scatter-hoarding rodents created apparent mutualism through increasing seed removal and seed caching, and enhancing survival, of both plant species in mixed patches compared with monospecific patches. However, if we ignore scatter hoarding and treat all seed harvest as seed predation (and not dispersal), then apparent competition between palatable chestnuts and unpalatable acorns was also observed. This study is the first to demonstrate that foraging decisions by scatter-hoarding animals to scatter hoard seeds for later consumption (or loss) or

  6. Anthropogenic noise increases fish mortality by predation.

    PubMed

    Simpson, Stephen D; Radford, Andrew N; Nedelec, Sophie L; Ferrari, Maud C O; Chivers, Douglas P; McCormick, Mark I; Meekan, Mark G

    2016-02-05

    Noise-generating human activities affect hearing, communication and movement in terrestrial and aquatic animals, but direct evidence for impacts on survival is rare. We examined effects of motorboat noise on post-settlement survival and physiology of a prey fish species and its performance when exposed to predators. Both playback of motorboat noise and direct disturbance by motorboats elevated metabolic rate in Ambon damselfish (Pomacentrus amboinensis), which when stressed by motorboat noise responded less often and less rapidly to simulated predatory strikes. Prey were captured more readily by their natural predator (dusky dottyback, Pseudochromis fuscus) during exposure to motorboat noise compared with ambient conditions, and more than twice as many prey were consumed by the predator in field experiments when motorboats were passing. Our study suggests that a common source of noise in the marine environment has the potential to impact fish demography, highlighting the need to include anthropogenic noise in management plans.

  7. Anthropogenic noise increases fish mortality by predation

    PubMed Central

    Simpson, Stephen D.; Radford, Andrew N.; Nedelec, Sophie L.; Ferrari, Maud C. O.; Chivers, Douglas P.; McCormick, Mark I.; Meekan, Mark G.

    2016-01-01

    Noise-generating human activities affect hearing, communication and movement in terrestrial and aquatic animals, but direct evidence for impacts on survival is rare. We examined effects of motorboat noise on post-settlement survival and physiology of a prey fish species and its performance when exposed to predators. Both playback of motorboat noise and direct disturbance by motorboats elevated metabolic rate in Ambon damselfish (Pomacentrus amboinensis), which when stressed by motorboat noise responded less often and less rapidly to simulated predatory strikes. Prey were captured more readily by their natural predator (dusky dottyback, Pseudochromis fuscus) during exposure to motorboat noise compared with ambient conditions, and more than twice as many prey were consumed by the predator in field experiments when motorboats were passing. Our study suggests that a common source of noise in the marine environment has the potential to impact fish demography, highlighting the need to include anthropogenic noise in management plans. PMID:26847493

  8. Cumulative human impacts on marine predators.

    PubMed

    Maxwell, Sara M; Hazen, Elliott L; Bograd, Steven J; Halpern, Benjamin S; Breed, Greg A; Nickel, Barry; Teutschel, Nicole M; Crowder, Larry B; Benson, Scott; Dutton, Peter H; Bailey, Helen; Kappes, Michelle A; Kuhn, Carey E; Weise, Michael J; Mate, Bruce; Shaffer, Scott A; Hassrick, Jason L; Henry, Robert W; Irvine, Ladd; McDonald, Birgitte I; Robinson, Patrick W; Block, Barbara A; Costa, Daniel P

    2013-01-01

    Stressors associated with human activities interact in complex ways to affect marine ecosystems, yet we lack spatially explicit assessments of cumulative impacts on ecologically and economically key components such as marine predators. Here we develop a metric of cumulative utilization and impact (CUI) on marine predators by combining electronic tracking data of eight protected predator species (n=685 individuals) in the California Current Ecosystem with data on 24 anthropogenic stressors. We show significant variation in CUI with some of the highest impacts within US National Marine Sanctuaries. High variation in underlying species and cumulative impact distributions means that neither alone is sufficient for effective spatial management. Instead, comprehensive management approaches accounting for both cumulative human impacts and trade-offs among multiple stressors must be applied in planning the use of marine resources.

  9. Cortisol affects tight junction morphology between pavement cells of rainbow trout gills in single-seeded insert culture.

    PubMed

    Sandbichler, Adolf Michael; Farkas, Julia; Salvenmoser, Willi; Pelster, Bernd

    2011-12-01

    A primary culture system of rainbow trout gill pavement cells grown on permeable support (single-seeded insert, SSI) was used to examine histological and physiological changes induced by the addition of the corticosteroid hormone cortisol. Pavement cell epithelia were cultured under symmetrical conditions (L15 apical/L15 basolateral) and developed a high transepithelial resistance (TER, 6.84 ± 1.99 kΩ cm(2), mean ± SEM) with a low phenol red diffusion rate (PRD, 0.15 ± 0.03 μmol l(-1)/day). Addition of cortisol to the basolateral compartment increased TER twofold and reduced PRD threefold over a 5-day period. A similar increase in TER could be seen after 24 h apical freshwater (FW) in control cultures. In cortisol-treated cultures FW exposure did not change TER, but PRD increased significantly. Histochemical staining of the cytoskeleton of cells in SSI culture revealed a morphological partitioning into a single mucosal layer of polarized, polygonal cells featuring cortical F-actin rings which were comparable to F-actin rings of epithelial cells on the lamellar and filamental surface, and several unorganized serosal layers of cells with F-actin stress fibers. Addition of cortisol increased cell density by 18% and in the mucosal layer it led to smaller, less polygonal cells with increased height and increased cell contact area. In transmission electron microscopic images two pairs of cytoplasmatic electron-dense structures confining the zonula occludens apically and basally toward the zonula adhaerens were found. Addition of cortisol increased the distance between those paired structures, hence led to deeper tight junctions. The cortisol-induced increase in barrier properties, therefore, involves a structural fortification of the tight junctions which was not generally modified by a short 24-h apical freshwater stress. These results identify cortisol as a regulator of tight junction morphology between pavement cells of euryhaline fish such as the

  10. Inducible defenses in prey intensify predator cannibalism.

    PubMed

    Kishida, Osamu; Trussell, Geoffrey C; Nishimura, Kinya; Ohgushi, Takayuki

    2009-11-01

    Trophic cascades are often a potent force in ecological communities, but abiotic and biotic heterogeneity can diffuse their influence. For example, inducible defenses in many species create variation in prey edibility, and size-structured interactions, such as cannibalism, can shift predator diets away from heterospecific prey. Although both factors diffuse cascade strength by adding heterogeneity to trophic interactions, the consequences of their interactioh remain poorly understood. We show that inducible defenses in tadpole prey greatly intensify cannibalism in predatory larval salamanders. The likelihood of cannibalism was also strongly influenced by asymmetries in salamander size that appear to be most important in the presence of defended prey. Hence, variation in prey edibility and the size structure of the predator may synergistically affect predator-prey population dynamics by reducing prey mortality and increasing predator mortality via cannibalism. We also suggest that the indirect effects of prey defenses may shape the evolution of predator traits that determine diet breadth and how trophic dynamics unfold in natural systems.

  11. Bioinsecticide-Predator Interactions: Azadirachtin Behavioral and Reproductive Impairment of the Coconut Mite Predator Neoseiulus baraki

    PubMed Central

    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. PMID:25679393

  12. 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.

  13. Seed coat color and seed weight contribute differential responses of targeted metabolites in soybean seeds.

    PubMed

    Lee, Jinwook; Hwang, Young-Sun; Kim, Sun Tae; Yoon, Won-Byong; Han, Won Young; Kang, In-Kyu; Choung, Myoung-Gun

    2017-01-01

    The distribution and variation of targeted metabolites in soybean seeds are affected by genetic and environmental factors. In this study, we used 192 soybean germplasm accessions collected from two provinces of Korea to elucidate the effects of seed coat color and seeds dry weight on the metabolic variation and responses of targeted metabolites. The effects of seed coat color and seeds dry weight were present in sucrose, total oligosaccharides, total carbohydrates and all measured fatty acids. The targeted metabolites were clustered within three groups. These metabolites were not only differently related to seeds dry weight, but also responded differentially to seed coat color. The inter-relationship between the targeted metabolites was highly present in the result of correlation analysis. Overall, results revealed that the targeted metabolites were diverged in relation to seed coat color and seeds dry weight within locally collected soybean seed germplasm accessions.

  14. Predator biomass determines the magnitude of non-consumptive effects (NCEs) in both laboratory and field environments.

    PubMed

    Hill, Jennifer M; Weissburg, Marc J

    2013-05-01

    Predator body size often indicates predation risk, but its significance in non-consumptive effects (NCEs) and predator risk assessment has been largely understudied. Although studies often recognize that predator body size can cause differing cascading effects, few directly examine prey foraging behavior in response to individual predator sizes or investigate how predator size is discerned. These mechanisms are important since perception of the risk imposed by predators dictates behavioral responses to predators and subsequent NCEs. Here, we evaluate the role of predator body size and biomass on risk assessment and the magnitude of NCEs by investigating mud crab foraging behavior and oyster survival in response to differing biomasses of blue crab predators using both laboratory and field methods. Cues from high predator biomass treatments including large blue crab predators and multiple small blue crab predators decreased mud crab foraging and increased oyster survival, whereas mud crab foraging in response to a single small blue crab did not differ from controls. Mud crabs also increased refuge use in the presence of large and multiple small, but not single small, blue crab predators. Thus, both predator biomass and aggregation patterns may affect the expression of NCEs. Understanding the impact of predator biomass may therefore be necessary to successfully predict the role of NCEs in shaping community dynamics. Further, the results of our laboratory experiments were consistent with observed NCEs in the field, suggesting that data from mesocosm environments can provide insight into field situations where flow and turbulence levels are moderate.

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

    PubMed

    Klinger, Rob; Rejmánek, Marcel

    2010-04-01

    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, Heteromys desmarestianus, 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.

  16. 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.

  17. A new hypothesis for the importance of seed dispersal in time.

    PubMed

    Guzmán, Adriana; Stevenson, Pablo R

    2011-12-01

    Most studies on seed dispersal in time have focused on seed dormancy and the physiological triggers for germination. However, seed dispersed by animals with low metabolic and moving rates, and long gut-passage times such as terrestrial turtles, could be considered another type of dispersal in time. This study tests the hypothesis that seeds dispersed in time may lower predation rates. We predicted that seeds deposited below parent trees after fruiting fall has finished is advantageous to minimize seed predators and should show higher survival rates. Four Amazonian plant species, Dicranostyles ampla, Oenocarpus bataua, Guatteria atabapensis and Ocotea floribunda, were tested for seed survival probabilities in two periods: during fruiting and 10-21 days after fruiting. Experiments were carried out in two biological stations located in the Colombian Amazon (Caparú and Zafire Biological Stations). Seed predation was high and mainly caused by non-vertebrates. Out of the four plant species tested, only Guatteria atabapensis supported the time escape hypothesis. For this species, seed predation by vertebrates after the fruiting period increased (from 4.1% to 9.2%) while seed predation by non-vertebrates decreased (from 54.0% to 40.2%). In contrast, seed predation by vertebrates and by non-vertebrates after the fruiting period in D. ampla increased (from 7.9% to 22.8% and from 40.4% to 50.6%, respectively), suggesting predator satiation. Results suggest that for some species dispersal in time could be advantageous to avoid some type of seed predators. Escape in time could be an additional dimension in which seeds may reach adequate sites for recruitment. Thus, future studies should be address to better understand the survival advantages given by an endozoochory time-dispersal process.

  18. Production of coleopteran predators

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The research literature reveals moderate advances in technology to produce coleopteran predators especially lady beetles. We have several factitious prey/foods and insect-free artificial diets for polyphagous species. It might be more time and cost effective to develop artificial diet-based producti...

  19. Production of heteropteran predators

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter treats several key aspects of rearing procedures for predatory bugs. The value of natural, factitious, and artificial foods for the major species used in biological control is reviewed. Whereas several types of factitious foods are routinely used in the production of heteropteran predat...

  20. Predator richness has no effect in a diverse marine food web.

    PubMed

    O'Connor, Mary I; Bruno, John F

    2009-07-01

    1. In many ecosystems, predator abundance, composition and diversity vary naturally among seasons and habitats. In addition, predator assemblages are changing due to overharvesting, habitat destruction and species invasions. 2. Predator species composition and richness can influence prey community structure and these effects can cascade to influence plant abundance and composition. 3. To test the effects of predator presence, composition and species richness on prey abundance, species richness and composition, we conducted three experiments in a subtidal marine food web. Experimental food webs were drawn from species pools of 5-7 predator species, 19-52 prey species, benthic micro-algae and 5 macro-algae. 4. Predators reduced prey abundance in the mesocosm experiment, but this effect was diminished or absent in field experiments. Predator species differed in their effects on prey, but we found no effect of predator richness (via complementarity or selection) on any aspect of prey community structure. 5. The absence of a predator richness effect could be due to several factors including potentially opposing effects of individual predator species, intraguild predation, or greater importance