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Sample records for heterogeneous tropical habitats

  1. Habitat availability and heterogeneity and the indo-pacific warm pool as predictors of marine species richness in the tropical Indo-Pacific.

    PubMed

    Sanciangco, Jonnell C; Carpenter, Kent E; Etnoyer, Peter J; Moretzsohn, Fabio

    2013-01-01

    Range overlap patterns were observed in a dataset of 10,446 expert-derived marine species distribution maps, including 8,295 coastal fishes, 1,212 invertebrates (crustaceans and molluscs), 820 reef-building corals, 50 seagrasses, and 69 mangroves. Distributions of tropical Indo-Pacific shore fishes revealed a concentration of species richness in the northern apex and central region of the Coral Triangle epicenter of marine biodiversity. This pattern was supported by distributions of invertebrates and habitat-forming primary producers. Habitat availability, heterogeneity, and sea surface temperatures were highly correlated with species richness across spatial grains ranging from 23,000 to 5,100,000 km(2) with and without correction for autocorrelation. The consistent retention of habitat variables in our predictive models supports the area of refuge hypothesis which posits reduced extinction rates in the Coral Triangle. This does not preclude support for a center of origin hypothesis that suggests increased speciation in the region may contribute to species richness. In addition, consistent retention of sea surface temperatures in models suggests that available kinetic energy may also be an important factor in shaping patterns of marine species richness. Kinetic energy may hasten rates of both extinction and speciation. The position of the Indo-Pacific Warm Pool to the east of the Coral Triangle in central Oceania and a pattern of increasing species richness from this region into the central and northern parts of the Coral Triangle suggests peripheral speciation with enhanced survival in the cooler parts of the Coral Triangle that also have highly concentrated available habitat. These results indicate that conservation of habitat availability and heterogeneity is important to reduce extinction of marine species and that changes in sea surface temperatures may influence the evolutionary potential of the region. PMID:23457533

  2. Habitat filtering across tree life stages in tropical forest communities

    PubMed Central

    Baldeck, C. A.; Harms, K. E.; Yavitt, J. B.; John, R.; Turner, B. L.; Valencia, R.; Navarrete, H.; Bunyavejchewin, S.; Kiratiprayoon, S.; Yaacob, A.; Supardi, M. N. N.; Davies, S. J.; Hubbell, S. P.; Chuyong, G. B.; Kenfack, D.; Thomas, D. W.; Dalling, J. W.

    2013-01-01

    Tropical tree communities are shaped by local-scale habitat heterogeneity in the form of topographic and edaphic variation, but the life-history stage at which habitat associations develop remains poorly understood. This is due, in part, to the fact that previous studies have not accounted for the widely disparate sample sizes (number of stems) that result when trees are divided into size classes. We demonstrate that the observed habitat structuring of a community is directly related to the number of individuals in the community. We then compare the relative importance of habitat heterogeneity to tree community structure for saplings, juveniles and adult trees within seven large (24–50 ha) tropical forest dynamics plots while controlling for sample size. Changes in habitat structuring through tree life stages were small and inconsistent among life stages and study sites. Where found, these differences were an order of magnitude smaller than the findings of previous studies that did not control for sample size. Moreover, community structure and composition were very similar among tree sub-communities of different life stages. We conclude that the structure of these tropical tree communities is established by the time trees are large enough to be included in the census (1 cm diameter at breast height), which indicates that habitat filtering occurs during earlier life stages. PMID:23843384

  3. Habitat filtering across tree life stages in tropical forest communities.

    PubMed

    Baldeck, C A; Harms, K E; Yavitt, J B; John, R; Turner, B L; Valencia, R; Navarrete, H; Bunyavejchewin, S; Kiratiprayoon, S; Yaacob, A; Supardi, M N N; Davies, S J; Hubbell, S P; Chuyong, G B; Kenfack, D; Thomas, D W; Dalling, J W

    2013-09-01

    Tropical tree communities are shaped by local-scale habitat heterogeneity in the form of topographic and edaphic variation, but the life-history stage at which habitat associations develop remains poorly understood. This is due, in part, to the fact that previous studies have not accounted for the widely disparate sample sizes (number of stems) that result when trees are divided into size classes. We demonstrate that the observed habitat structuring of a community is directly related to the number of individuals in the community. We then compare the relative importance of habitat heterogeneity to tree community structure for saplings, juveniles and adult trees within seven large (24-50 ha) tropical forest dynamics plots while controlling for sample size. Changes in habitat structuring through tree life stages were small and inconsistent among life stages and study sites. Where found, these differences were an order of magnitude smaller than the findings of previous studies that did not control for sample size. Moreover, community structure and composition were very similar among tree sub-communities of different life stages. We conclude that the structure of these tropical tree communities is established by the time trees are large enough to be included in the census (1 cm diameter at breast height), which indicates that habitat filtering occurs during earlier life stages. PMID:23843384

  4. Testing heterogeneity-diversity relationships in tropical forest restoration.

    PubMed

    Holl, Karen D; Stout, Victoria M; Reid, J Leighton; Zahawi, Rakan A

    2013-10-01

    Restoring small-scale habitat heterogeneity in highly diverse systems, like tropical forests, is a conservation challenge and offers an excellent opportunity to test factors affecting community assembly. We investigated whether (1) the applied nucleation restoration strategy (planting tree islands) resulted in higher habitat heterogeneity than more homogeneous forest restoration approaches, (2) increased heterogeneity resulted in more diverse tree recruitment, and (3) the mean or coefficient of variation of habitat variables best explained tree recruitment. We measured soil nutrients, overstory and understory vegetation structure, and tree recruitment at six sites with three 5- to 7-year-old restoration treatments: control (no planting), planted tree islands, and conventional, mixed-species tree plantations. Canopy openness and soil base saturation were more variable in island treatments than in controls and plantations, whereas most soil nutrients had similar coefficients of variation across treatments, and bare ground was more variable in control plots. Seedling and sapling species density were equivalent in plantations and islands, and were substantially higher than in controls. Species spatial turnover, diversity, and richness were similar in island and plantation treatments. Mean canopy openness, rather than heterogeneity, explained the largest proportion of variance in species density. Our results show that, whereas canopy openness and soil base saturation are more heterogeneous with the applied nucleation restoration strategy, this pattern does not translate into greater tree diversity. The lack of a heterogeneity-diversity relationship is likely due to the fact that recruits respond more strongly to mean resource gradients than variability at this early stage in succession, and that seed dispersal limitation likely reduces the available species pool. Results show that planting tree islands facilitates tree recruitment to a similar degree as intensive

  5. Habitat heterogeneity favors asexual reproduction in natural populations of grassthrips.

    PubMed

    Lavanchy, Guillaume; Strehler, Marie; Llanos Roman, Maria Noemi; Lessard-Therrien, Malie; Humbert, Jean-Yves; Dumas, Zoé; Jalvingh, Kirsten; Ghali, Karim; Fontcuberta García-Cuenca, Amaranta; Zijlstra, Bart; Arlettaz, Raphaël; Schwander, Tanja

    2016-08-01

    Explaining the overwhelming success of sex among eukaryotes is difficult given the obvious costs of sex relative to asexuality. Different studies have shown that sex can provide benefits in spatially heterogeneous environments under specific conditions, but whether spatial heterogeneity commonly contributes to the maintenance of sex in natural populations remains unknown. We experimentally manipulated habitat heterogeneity for sexual and asexual thrips lineages in natural populations and under seminatural mesocosm conditions by varying the number of hostplants available to these herbivorous insects. Asexual lineages rapidly replaced the sexual ones, independently of the level of habitat heterogeneity in mesocosms. In natural populations, the success of sexual thrips decreased with increasing habitat heterogeneity, with sexual thrips apparently only persisting in certain types of hostplant communities. Our results illustrate how genetic diversity-based mechanisms can favor asexuality instead of sex when sexual lineages co-occur with genetically variable asexual lineages. PMID:27346066

  6. Fine-scale habitat structure complexity determines insectivorous bird diversity in a tropical forest

    NASA Astrophysics Data System (ADS)

    Castaño-Villa, Gabriel J.; Ramos-Valencia, Santiago A.; Fontúrbel, Francisco E.

    2014-11-01

    Habitat complexity in reforested stands has been acknowledged as a key factor that influences habitat use by birds, being especially critical for habitat disturbance-sensitive species such as tropical understory insectivorous birds. Most studies regarding the relationship between forest structure and species diversity were conducted at the landscape scale, but different diversity patterns may emerge at a finer scale (i.e., within a habitat patch). We examined a tropical reforested area (State of Caldas, Colombia), hypothesizing that insectivorous bird richness, abundance, and foraging guild abundance would increase as intra-habitat complexity increases. We established 40 monitoring plots within a reforested area, measured their structural features, and determined their relationships with species richness, total abundance, and foraging guild abundance, using Generalized Additive Models. We found that the increasing variation in basal area, stem diameter, and number of stems was positively correlated with species richness, total abundance, and foraging guild abundance. Relationships between richness or abundance and structural features were not lineal, but showing curvilinear responses and thresholds. Our results show that heterogeneity on basal area, stem diameter, and the number of stems was more correlated to insectivorous bird richness and abundance than the average of those structural features. Promoting structural variation on reforested areas by planting species with different growth rates may contribute to increase the richness and abundance of a tropical vulnerable group of species such as the understory insectivorous birds.

  7. Habitat Specialization in Tropical Continental Shelf Demersal Fish Assemblages

    PubMed Central

    Fitzpatrick, Ben M.; Harvey, Euan S.; Heyward, Andrew J.; Twiggs, Emily J.; Colquhoun, Jamie

    2012-01-01

    The implications of shallow water impacts such as fishing and climate change on fish assemblages are generally considered in isolation from the distribution and abundance of these fish assemblages in adjacent deeper waters. We investigate the abundance and length of demersal fish assemblages across a section of tropical continental shelf at Ningaloo Reef, Western Australia, to identify fish and fish habitat relationships across steep gradients in depth and in different benthic habitat types. The assemblage composition of demersal fish were assessed from baited remote underwater stereo-video samples (n = 304) collected from 16 depth and habitat combinations. Samples were collected across a depth range poorly represented in the literature from the fringing reef lagoon (1–10 m depth), down the fore reef slope to the reef base (10–30 m depth) then across the adjacent continental shelf (30–110 m depth). Multivariate analyses showed that there were distinctive fish assemblages and different sized fish were associated with each habitat/depth category. Species richness, MaxN and diversity declined with depth, while average length and trophic level increased. The assemblage structure, diversity, size and trophic structure of demersal fishes changes from shallow inshore habitats to deeper water habitats. More habitat specialists (unique species per habitat/depth category) were associated with the reef slope and reef base than other habitats, but offshore sponge-dominated habitats and inshore coral-dominated reef also supported unique species. This suggests that marine protected areas in shallow coral-dominated reef habitats may not adequately protect those species whose depth distribution extends beyond shallow habitats, or other significant elements of demersal fish biodiversity. The ontogenetic habitat partitioning which is characteristic of many species, suggests that to maintain entire species life histories it is necessary to protect corridors of connected

  8. Roles of Clonal Integration in both Heterogeneous and Homogeneous Habitats.

    PubMed

    Zhang, Haijie; Liu, Fenghong; Wang, Renqing; Liu, Jian

    2016-01-01

    Many studies have shown that clonal integration can promote the performance of clonal plants in heterogeneous habitats, but the roles of clonal integration in both heterogeneous and homogeneous habitats were rarely studied simultaneously. Ramet pairs of Alternanthera philoxeroides (Mart.) Griseb were placed in two habitats either heterogeneous or homogeneous in soil nutrient availability, with stolon connections left intact or severed. Total biomass, total length of stolons, and number of new ramets of distal (relatively young) ramets located in low-nutrient environments were significantly greater when the distal ramets were connected to than when they were disconnected from proximal (relatively old) ramets located in high-nutrient environments. Total length of stolons of proximal ramets growing in low-nutrient environments was significantly higher when the proximal ramets were connected to than when they were disconnected from the distal ramets growing in high-nutrient environments, but stolon connection did not affect total biomass or number of new ramets of the proximal ramets. Stolon severing also did not affect the growth of the whole ramet pairs in heterogeneous environments. In homogeneous high-nutrient environments stolon severing promoted the growth of the proximal ramets and the ramet pairs, but in homogeneous low-nutrient environments it did not affect the growth of the proximal or distal ramets. Hence, for A. philoxeroides, clonal fragmentation appears to be more advantageous than clonal integration in resource-rich homogeneous habitats, and clonal integration becomes beneficial in heterogeneous habitats. Our study contributes to revealing roles of clonal integration in both heterogeneous and homogeneous habitats and expansion patterns of invasive clonal plants such as A. philoxeroides in multifarious habitats. PMID:27200026

  9. Roles of Clonal Integration in both Heterogeneous and Homogeneous Habitats

    PubMed Central

    Zhang, Haijie; Liu, Fenghong; Wang, Renqing; Liu, Jian

    2016-01-01

    Many studies have shown that clonal integration can promote the performance of clonal plants in heterogeneous habitats, but the roles of clonal integration in both heterogeneous and homogeneous habitats were rarely studied simultaneously. Ramet pairs of Alternanthera philoxeroides (Mart.) Griseb were placed in two habitats either heterogeneous or homogeneous in soil nutrient availability, with stolon connections left intact or severed. Total biomass, total length of stolons, and number of new ramets of distal (relatively young) ramets located in low-nutrient environments were significantly greater when the distal ramets were connected to than when they were disconnected from proximal (relatively old) ramets located in high-nutrient environments. Total length of stolons of proximal ramets growing in low-nutrient environments was significantly higher when the proximal ramets were connected to than when they were disconnected from the distal ramets growing in high-nutrient environments, but stolon connection did not affect total biomass or number of new ramets of the proximal ramets. Stolon severing also did not affect the growth of the whole ramet pairs in heterogeneous environments. In homogeneous high-nutrient environments stolon severing promoted the growth of the proximal ramets and the ramet pairs, but in homogeneous low-nutrient environments it did not affect the growth of the proximal or distal ramets. Hence, for A. philoxeroides, clonal fragmentation appears to be more advantageous than clonal integration in resource-rich homogeneous habitats, and clonal integration becomes beneficial in heterogeneous habitats. Our study contributes to revealing roles of clonal integration in both heterogeneous and homogeneous habitats and expansion patterns of invasive clonal plants such as A. philoxeroides in multifarious habitats. PMID:27200026

  10. Spatial Heterogeneity of Rana boylii Habitat: Quantification and Ecological Meaningfulness

    NASA Astrophysics Data System (ADS)

    Yarnell, S. M.

    2005-05-01

    Analysis of the heterogeneity of stream habitat and how biological communities respond to that complexity are fundamental components of ecosystem analysis that are often inadequately addressed in watershed assessments and restoration practices. Many aquatic species, such as the Foothill Yellow-legged Frog (Rana boylii), known to associate with certain physical habitats at various times throughout their lifecycle may require some degree of habitat complexity at a larger reach scale for a population to persist. Recent research in the field of landscape ecology has expanded the use of spatial heterogeneity indices to other fields of ecology as an objective method to quantify variability in habitat. Provided that indices are used in an appropriate context and are shown to be ecologically meaningful, they provide a potentially useful tool for quantifying the variability in riverine habitat for aquatic species such as R. boylii. This study evaluated whether stream reaches with a high heterogeneity of geomorphic features, as measured by several key spatial heterogeneity indices, correlated with a greater relative abundance of R. boylii. R. boylii habitat associations were quantified throughout a single season to obtain further insight into the local hydraulic and geomorphic conditions preferred by each lifestage. The two best predictors of habitat associations by lifestage were velocity and substrate size, two key characteristics of geomorphic units such as riffles and pools. The heterogeneity of geomorphic units was then quantified and measured at the reach scale using a variety of spatial indices. Indices of spatial composition, such as Shannon's Diversity Index, were found to correlate well with frog abundance, while indices of spatial configuration, such as Contagion, were not significant. These findings indicate R. boylii may select stream reaches with increased geomorphic complexity that potentially provide habitats suitable to each lifestage with multiple functions

  11. The Vulnerability of Tropical Ectotherms to Warming Is Modulated by the Microclimatic Heterogeneity.

    PubMed

    Pincebourde, Sylvain; Suppo, Christelle

    2016-07-01

    Most tropical ectotherms live near their physiological limits for temperature. Substantial ecological effects of global change are predicted in the tropics despite the low amplitude of temperature change. These predictions assume that tropical ectotherms experience air temperature as measured by weather stations or predicted by global circulation models. The body temperature of ectotherms, however, can deviate from ambient air when the organism samples the mosaic of microclimates at fine scales. The thermal heterogeneity of tropical landscapes has been quantified only rarely in comparison to temperate habitats, limiting our ability to infer the vulnerability to warming of tropical ectotherms. Here, we used thermal imaging to quantify the heterogeneity in surface temperatures across spatial scales, from the micro- up to landscape scale, at the top of an Inselberg in French Guiana. We measured the thermal heterogeneity at the scale of Clusia nemorosa leaves, by categorizing leaves in full sun versus leaves in the shade to quantify the microclimatic variance available to phytophagous insects. Then, we measured the thermal heterogeneity at the scales of the single shrub and the landscape, for several sites differing in their orientation toward the sun to quantify the microclimatic heterogeneity available for larger ectotherms. All measurements were made three times per day over four consecutive days. There was a high level of thermal heterogeneity at all spatial scales. The thermal variance varied between scales, increasing from the within-leaf surface to the landscape scale. It also shifted across the day in different ways depending on the spatial scale. Then, using a set of published data, we compared the critical temperature (CTmax) of neo-tropical ectotherms and temperature distributions. The portion of space above the CTmax varied substantially depending on spatial scale and taxa. Insects were particularly at risk at the surface of leaves exposed to solar

  12. Measuring habitat heterogeneity reveals new insights into bird community composition.

    PubMed

    Stirnemann, Ingrid A; Ikin, Karen; Gibbons, Philip; Blanchard, Wade; Lindenmayer, David B

    2015-03-01

    Fine-scale vegetation cover is a common variable used to explain animal occurrence, but we know less about the effects of fine-scale vegetation heterogeneity. Theoretically, fine-scale vegetation heterogeneity is an important driver of biodiversity because it captures the range of resources available in a given area. In this study we investigated how bird species richness and birds grouped by various ecological traits responded to vegetation cover and heterogeneity. We found that both fine-scale vegetation cover (of tall trees, medium-sized trees and shrubs) and heterogeneity (of tall trees, and shrubs) were important predictors of bird richness, but the direction of the response of bird richness to shrub heterogeneity differed between sites with different proportions of tall tree cover. For example, bird richness increased with shrub heterogeneity in sites with high levels of tall tree cover, but declined in sites with low levels of tall tree cover. Our findings indicated that an increase in vegetation heterogeneity will not always result in an increase in resources and niches, and associated higher species richness. We also found birds grouped by traits responded in a predictable way to vegetation heterogeneity. For example, we found small birds benefited from increased shrub heterogeneity supporting the textual discontinuity hypothesis and non-arboreal (ground or shrub) nesting species were associated with high vegetation cover (low heterogeneity). Our results indicated that focusing solely on increasing vegetation cover (e.g. through restoration) may be detrimental to particular animal groups. Findings from this investigation can help guide habitat management for different functional groups of birds. PMID:25376157

  13. Beaver dams maintain fish biodiversity by increasing habitat heterogeneity throughout a low-gradient stream network

    USGS Publications Warehouse

    Smith, Joseph M.; Mather, Martha E.

    2013-01-01

    In summary, within a stream network, beaver dams maintained fish biodiversity by altering in-stream habitat and increasing habitat heterogeneity. Understanding the relationship between habitat heterogeneity and biodiversity can advance basic freshwater ecology and provide science-based support for applied aquatic conservation

  14. Multi- and hyperspectral remote sensing of tropical marine benthic habitats

    NASA Astrophysics Data System (ADS)

    Mishra, Deepak R.

    Tropical marine benthic habitats such as coral reef and associated environments are severely endangered because of the environmental degradation coupled with hurricanes, El Nino events, coastal pollution and runoff, tourism, and economic development. To monitor and protect this diverse environment it is important to not only develop baseline maps depicting their spatial distribution but also to document their changing conditions over time. Remote sensing offers an important means of delineating and monitoring coral reef ecosystems. Over the last twenty years the scientific community has been investigating the use and potential of remote sensing techniques to determine the conditions of the coral reefs by analyzing their spectral characteristics from space. One of the problems in monitoring coral reefs from space is the effect of the water column on the remotely sensed signal. When light penetrates water its intensity decreases exponentially with increasing depth. This process, known as water column attenuation, exerts a profound effect on remotely sensed data collected over water bodies. The approach presented in this research focuses on the development of semi-analytical models that resolves the confounding influence water column attenuation on substrate reflectance to characterize benthic habitats from high resolution remotely sensed imagery on a per-pixel basis. High spatial resolution satellite and airborne imagery were used as inputs in the models to derive water depth and water column optical properties (e.g., absorption and backscattering coefficients). These parameters were subsequently used in various bio-optical algorithms to deduce bottom albedo and then to classify the benthos, generating a detailed map of benthic habitats. IKONOS and QuickBird multispectral satellite data and AISA Eagle hyperspectral airborne data were used in this research for benthic habitat mapping along the north shore of Roatan Island, Honduras. The AISA Eagle classification was

  15. Sensitivity of Heterogeneous Marine Benthic Habitats to Subtle Stressors

    PubMed Central

    Rodil, Iván F.; Lohrer, Andrew M.; Thrush, Simon F.

    2013-01-01

    It is important to understand the consequences of low level disturbances on the functioning of ecological communities because of the pervasiveness and frequency of this type of environmental change. In this study we investigated the response of a heterogeneous, subtidal, soft-sediment habitat to small experimental additions of organic matter and calcium carbonate to examine the sensitivity of benthic ecosystem functioning to changes in sediment characteristics that relate to the environmental threats of coastal eutrophication and ocean acidification. Our results documented significant changes between key biogeochemical and sedimentary variables such as gross primary production, ammonium uptake and dissolved reactive phosphorus flux following treatment additions. Moreover, the application of treatments affected relationships between macrofauna communities, sediment characteristics (e.g., chlorophyll a content) and biogeochemical processes (oxygen and nutrient fluxes). In this experiment organic matter and calcium carbonate showed persistent opposing effects on sedimentary processes, and we demonstrated that highly heterogeneous sediment habitats can be surprisingly sensitive to subtle perturbations. Our results have important biological implications in a world with relentless anthropogenic inputs of atmospheric CO2 and nutrients in coastal waters. PMID:24312332

  16. Microhabitat Selection by Marine Mesoconsumers in a Thermally Heterogeneous Habitat: Behavioral Thermoregulation or Avoiding Predation Risk?

    PubMed Central

    Vaudo, Jeremy J.; Heithaus, Michael R.

    2013-01-01

    Habitat selection decisions by consumers has the potential to shape ecosystems. Understanding the factors that influence habitat selection is therefore critical to understanding ecosystem function. This is especially true of mesoconsumers because they provide the link between upper and lower tropic levels. We examined the factors influencing microhabitat selection of marine mesoconsumers – juvenile giant shovelnose rays (Glaucostegus typus), reticulate whiprays (Himantura uarnak), and pink whiprays (H. fai) – in a coastal ecosystem with intact predator and prey populations and marked spatial and temporal thermal heterogeneity. Using a combination of belt transects and data on water temperature, tidal height, prey abundance, predator abundance and ray behavior, we found that giant shovelnose rays and reticulate whiprays were most often found resting in nearshore microhabitats, especially at low tidal heights during the warm season. Microhabitat selection did not match predictions derived from distributions of prey. Although at a course scale, ray distributions appeared to match predictions of behavioral thermoregulation theory, fine-scale examination revealed a mismatch. The selection of the shallow nearshore microhabitat at low tidal heights during periods of high predator abundance (warm season) suggests that this microhabitat may serve as a refuge, although it may come with metabolic costs due to higher temperatures. The results of this study highlight the importance of predators in the habitat selection decisions of mesoconsumers and that within thermal gradients, factors, such as predation risk, must be considered in addition to behavioral thermoregulation to explain habitat selection decisions. Furthermore, increasing water temperatures predicted by climate change may result in complex trade-offs that might have important implications for ecosystem dynamics. PMID:23593501

  17. Microhabitat selection by marine mesoconsumers in a thermally heterogeneous habitat: behavioral thermoregulation or avoiding predation risk?

    PubMed

    Vaudo, Jeremy J; Heithaus, Michael R

    2013-01-01

    Habitat selection decisions by consumers has the potential to shape ecosystems. Understanding the factors that influence habitat selection is therefore critical to understanding ecosystem function. This is especially true of mesoconsumers because they provide the link between upper and lower tropic levels. We examined the factors influencing microhabitat selection of marine mesoconsumers - juvenile giant shovelnose rays (Glaucostegus typus), reticulate whiprays (Himantura uarnak), and pink whiprays (H. fai) - in a coastal ecosystem with intact predator and prey populations and marked spatial and temporal thermal heterogeneity. Using a combination of belt transects and data on water temperature, tidal height, prey abundance, predator abundance and ray behavior, we found that giant shovelnose rays and reticulate whiprays were most often found resting in nearshore microhabitats, especially at low tidal heights during the warm season. Microhabitat selection did not match predictions derived from distributions of prey. Although at a course scale, ray distributions appeared to match predictions of behavioral thermoregulation theory, fine-scale examination revealed a mismatch. The selection of the shallow nearshore microhabitat at low tidal heights during periods of high predator abundance (warm season) suggests that this microhabitat may serve as a refuge, although it may come with metabolic costs due to higher temperatures. The results of this study highlight the importance of predators in the habitat selection decisions of mesoconsumers and that within thermal gradients, factors, such as predation risk, must be considered in addition to behavioral thermoregulation to explain habitat selection decisions. Furthermore, increasing water temperatures predicted by climate change may result in complex trade-offs that might have important implications for ecosystem dynamics. PMID:23593501

  18. Landscape Context Mediates Avian Habitat Choice in Tropical Forest Restoration

    PubMed Central

    Reid, J. Leighton; Mendenhall, Chase D.; Rosales, J. Abel; Zahawi, Rakan A.; Holl, Karen D.

    2014-01-01

    Birds both promote and prosper from forest restoration. The ecosystem functions birds perform can increase the pace of forest regeneration and, correspondingly, increase the available habitat for birds and other forest-dependent species. The aim of this study was to learn how tropical forest restoration treatments interact with landscape tree cover to affect the structure and composition of a diverse bird assemblage. We sampled bird communities over two years in 13 restoration sites and two old-growth forests in southern Costa Rica. Restoration sites were established on degraded farmlands in a variety of landscape contexts, and each included a 0.25-ha plantation, island treatment (trees planted in patches), and unplanted control. We analyzed four attributes of bird communities including frugivore abundance, nectarivore abundance, migrant insectivore richness, and compositional similarity of bird communities in restoration plots to bird communities in old-growth forests. All four bird community variables were greater in plantations and/or islands than in control treatments. Frugivore and nectarivore abundance decreased with increasing tree cover in the landscape surrounding restoration plots, whereas compositional similarity to old-growth forests was greatest in plantations embedded in landscapes with high tree cover. Migrant insectivore richness was unaffected by landscape tree cover. Our results agree with previous studies showing that increasing levels of investment in active restoration are positively related to bird richness and abundance, but differences in the effects of landscape tree cover on foraging guilds and community composition suggest that trade-offs between biodiversity conservation and bird-mediated ecosystem functioning may be important for prioritizing restoration sites. PMID:24595233

  19. Guild-specific responses of avian species richness to LiDAR-derived habitat heterogeneity

    USGS Publications Warehouse

    Weisberg, Peter J.; Dilts, Thomas E.; Becker, Miles E.; Young, Jock S.; Wong-Kone, Diane C.; Newton, Wesley E.; Ammon, Elisabeth M.

    2014-01-01

    Ecological niche theory implies that more heterogeneous habitats have the potential to support greater biodiversity. Positive heterogeneity-diversity relationships have been found for most studies investigating animal taxa, although negative relationships also occur and the scale dependence of heterogeneity-diversity relationships is little known. We investigated multi-scale, heterogeneity-diversity relationships for bird communities in a semi-arid riparian landscape, using airborne LiDAR data to derive key measures of structural habitat complexity. Habitat heterogeneity-diversity relationships were generally positive, although the overall strength of relationships varied across avian life history guilds (R2 range: 0.03–0.41). Best predicted were the species richness indices of cavity nesters, habitat generalists, woodland specialists, and foliage foragers. Heterogeneity-diversity relationships were also strongly scale-dependent, with strongest associations at the 200-m scale (4 ha) and weakest associations at the 50-m scale (0.25 ha). Our results underscore the value of LiDAR data for fine-grained quantification of habitat structure, as well as the need for biodiversity studies to incorporate variation among life-history guilds and to simultaneously consider multiple guild functional types (e.g. nesting, foraging, habitat). Results suggest that certain life-history guilds (foliage foragers, cavity nesters, woodland specialists) are more susceptible than others (ground foragers, ground nesters, low nesters) to experiencing declines in local species richness if functional elements of habitat heterogeneity are lost. Positive heterogeneity-diversity relationships imply that riparian conservation efforts need to not only provide high-quality riparian habitat locally, but also to provide habitat heterogeneity across multiple scales.

  20. Guild-specific responses of avian species richness to LiDAR-derived habitat heterogeneity

    NASA Astrophysics Data System (ADS)

    Weisberg, Peter J.; Dilts, Thomas E.; Becker, Miles E.; Young, Jock S.; Wong-Kone, Diane C.; Newton, Wesley E.; Ammon, Elisabeth M.

    2014-08-01

    Ecological niche theory implies that more heterogeneous habitats have the potential to support greater biodiversity. Positive heterogeneity-diversity relationships have been found for most studies investigating animal taxa, although negative relationships also occur and the scale dependence of heterogeneity-diversity relationships is little known. We investigated multi-scale, heterogeneity-diversity relationships for bird communities in a semi-arid riparian landscape, using airborne LiDAR data to derive key measures of structural habitat complexity. Habitat heterogeneity-diversity relationships were generally positive, although the overall strength of relationships varied across avian life history guilds (R2 range: 0.03-0.41). Best predicted were the species richness indices of cavity nesters, habitat generalists, woodland specialists, and foliage foragers. Heterogeneity-diversity relationships were also strongly scale-dependent, with strongest associations at the 200-m scale (4 ha) and weakest associations at the 50-m scale (0.25 ha). Our results underscore the value of LiDAR data for fine-grained quantification of habitat structure, as well as the need for biodiversity studies to incorporate variation among life-history guilds and to simultaneously consider multiple guild functional types (e.g. nesting, foraging, habitat). Results suggest that certain life-history guilds (foliage foragers, cavity nesters, woodland specialists) are more susceptible than others (ground foragers, ground nesters, low nesters) to experiencing declines in local species richness if functional elements of habitat heterogeneity are lost. Positive heterogeneity-diversity relationships imply that riparian conservation efforts need to not only provide high-quality riparian habitat locally, but also to provide habitat heterogeneity across multiple scales.

  1. Morphological and physiological differentiation of seedlings between dry and wet habitats in a tropical dry forest.

    PubMed

    Pineda-García, Fernando; Paz, Horacio; Tinoco-Ojanguren, Clara

    2011-09-01

    A common observation in tropical dry forests is the habitat preference of tree species along spatial soil water gradients. This pattern of habitat partitioning might be a result of species differentiation in their strategy for using water, along with competing functions such as maximizing water exploitation and tolerating soil water stress. We tested whether species from drier soil conditions exhibited a tolerance strategy compared with that of wet-habitat species. In a comparison of 12 morphophysiological traits in seedlings of 10 closely related dry and wet-habitat species pairs, we explored what trade-offs guide differentiation between habitats and species. Contrary to our expectations, dry-habitat species showed mostly traits associated with an exploitation strategy (higher carbon assimilation capacity, specific leaf area and leaf-specific conductivity and lower water-use efficiency). Strikingly, dry-habitat species tended to retain their leaves longer during drought. Additionally, we detected multiple strategies to live within each habitat, in part due to variation of strategies among lineages, as well as functional differentiation along the water storage capacity-stem density (xylem safety) trade-off. Our results suggest that fundamental trade-offs guide functional niche differentiation among tree species expressed both within and between soil water habitats in a tropical dry forest. PMID:21696402

  2. Spatial patterns of primary productivity derived from the Dynamic Habitat Indices predict patterns of species richness and distributions in the tropics

    NASA Astrophysics Data System (ADS)

    Suttidate, Naparat

    Humans are changing the Earth's ecosystems, which has profound consequences for biodiversity. To understand how species respond to these changes, biodiversity science requires accurate assessments of biodiversity. However, biodiversity assessments are still limited in tropical regions. The Dynamic Habitat Indices (DHIs), derived from satellite data, summarize dynamic patterns of annual primary productivity: (a) cumulative annual productivity, (b) minimum annual productivity, and (c) seasonal variation in productivity. The DHIs have been successfully used in temperate regions, but not yet in the tropics. My goal was to evaluate the importance of primary productivity measured via the DHIs for assessing patterns of species richness and distributions in Thailand. First, I assessed the relationships between the DHIs and tropical bird species richness. I also evaluated the complementarity of the DHIs and topography, climate, latitudinal gradients, habitat heterogeneity, and habitat area in explaining bird species richness. I found that among three DHIs, cumulative annual productivity was the most important factor in explaining bird species richness and that the DHIs outperformed other environmental variables. Second, I developed texture measures derive from DHI cumulative annual productivity, and compared them to habitat composition and fragmentation as predictors of tropical forest bird distributions. I found that adding texture measures to habitat composition and fragmentation models improved the prediction of tropical bird distributions, especially area- and edge-sensitive tropical forest bird species. Third, I predicted the effects of trophic interactions between primary productivity, prey, and predators in relation to habitat connectivity for Indochinese tigers (Panthera tigris). I found that including trophic interactions improved habitat suitability models for tigers. However, tiger habitat is highly fragmented with few dispersal corridors. I also identified

  3. Fine-Scale Habitat Heterogeneity Influences Occupancy in Terrestrial Mammals in a Temperate Region of Australia

    PubMed Central

    Stirnemann, Ingrid; Mortelliti, Alessio; Gibbons, Philip; Lindenmayer, David B.

    2015-01-01

    Vegetation heterogeneity is an inherent feature of most ecosystems, characterises the structure of habitat, and is considered an important driver of species distribution patterns. However, quantifying fine-scale heterogeneity of vegetation cover can be time consuming, and therefore it is seldom measured. Here, we determine if heterogeneity is worthwhile measuring, in addition to the amount of cover, when examining species distribution patterns. Further, we investigated the effect of the surrounding landscape heterogeneity on species occupancy. We tested the effect of cover and heterogeneity of trees and shrubs, and the context of the surrounding landscape (number of habitats and distance to an ecotone) on site occupancy of three mammal species (the black wallaby [Wallabia bicolor], the long-nosed bandicoot [Perameles nasuta], and the bush rat [Rattus fuscipes]) within a naturally heterogeneous landscape in a temperate region of Australia. We found that fine-scale heterogeneity of vegetation attributes is an important driver of mammal occurrence of two of these species. Further, we found that, although all three species responded positively to vegetation heterogeneity, different mammals vary in their response to different types of vegetation heterogeneity measurement. For example, the black wallaby responded to the proximity of an ecotone, and the bush rat and the long-nosed bandicoot responded to fine-scale heterogeneity of small tree cover, whereas none of the mammals responded to broad scale heterogeneity (i.e., the number of habitat types). Our results highlight the influence of methodological decisions, such as how heterogeneity vegetation is measured, in quantifying species responses to habitat structures. The findings confirm the importance of choosing meaningful heterogeneity measures when modelling the factors influencing occupancy of the species of interest. PMID:26394327

  4. Fine-Scale Habitat Heterogeneity Influences Occupancy in Terrestrial Mammals in a Temperate Region of Australia.

    PubMed

    Stirnemann, Ingrid; Mortelliti, Alessio; Gibbons, Philip; Lindenmayer, David B

    2015-01-01

    Vegetation heterogeneity is an inherent feature of most ecosystems, characterises the structure of habitat, and is considered an important driver of species distribution patterns. However, quantifying fine-scale heterogeneity of vegetation cover can be time consuming, and therefore it is seldom measured. Here, we determine if heterogeneity is worthwhile measuring, in addition to the amount of cover, when examining species distribution patterns. Further, we investigated the effect of the surrounding landscape heterogeneity on species occupancy. We tested the effect of cover and heterogeneity of trees and shrubs, and the context of the surrounding landscape (number of habitats and distance to an ecotone) on site occupancy of three mammal species (the black wallaby [Wallabia bicolor], the long-nosed bandicoot [Perameles nasuta], and the bush rat [Rattus fuscipes]) within a naturally heterogeneous landscape in a temperate region of Australia. We found that fine-scale heterogeneity of vegetation attributes is an important driver of mammal occurrence of two of these species. Further, we found that, although all three species responded positively to vegetation heterogeneity, different mammals vary in their response to different types of vegetation heterogeneity measurement. For example, the black wallaby responded to the proximity of an ecotone, and the bush rat and the long-nosed bandicoot responded to fine-scale heterogeneity of small tree cover, whereas none of the mammals responded to broad scale heterogeneity (i.e., the number of habitat types). Our results highlight the influence of methodological decisions, such as how heterogeneity vegetation is measured, in quantifying species responses to habitat structures. The findings confirm the importance of choosing meaningful heterogeneity measures when modelling the factors influencing occupancy of the species of interest. PMID:26394327

  5. Seasonal change in tropical habitat quality and body condition for a declining migratory songbird.

    PubMed

    McKinnon, Emily A; Rotenberg, James A; Stutchbury, Bridget J M

    2015-10-01

    Many migratory songbirds spend their non-breeding season in tropical humid forests, where climate change is predicted to increase the severity and frequency of droughts and decrease rainfall. For conservation of these songbirds, it is critical to understand how resources during the non-breeding season are affected by seasonal patterns of drying, and thereby predict potential long-term effects of climate change. We studied habitat quality for a declining tropical forest-dwelling songbird, the wood thrush (Hylocichla mustelina), and tested the hypothesis that habitat moisture and arthropod abundance are drivers of body condition during the overwintering period. We examined habitat moisture, abundance of arthropods and fruit, and condition of individual birds (n = 418) in three habitat types--mature forest, mature forest with increased presence of human activity, and riparian scrub--from October to April. We found a strong pattern of habitat drying from October (wet season) to March (prior to spring migration) in all habitats, with concurrent declines in arthropod and fruit abundance. Body condition of birds also declined (estimated ~5 % decline over the wintering period), with no significant difference by habitat. Relatively poor condition (low body condition index, low fat and pectoral muscles scores) was equally apparent in all habitat types in March. Climate change is predicted to increase the severity of dry seasons in Central America, and our results suggest that this could negatively affect the condition of individual wood thrushes. PMID:26001604

  6. The relative influence of habitat loss and fragmentation: do tropical mammals meet the temperate paradigm?

    PubMed

    Thornton, Daniel H; Branch, Lyn C; Sunquist, Melvin E

    2011-09-01

    The relative influence of habitat loss vs. habitat fragmentation per se (the breaking apart of habitat) on species distribution and abundance is a topic of debate. Although some theoretical studies predict a strong negative effect of fragmentation, consensus from empirical studies is that habitat fragmentation has weak effects compared with habitat loss and that these effects are as likely to be positive as negative. However, few empirical investigations of this issue have been conducted on tropical or wide-ranging species that may be strongly influenced by changes in patch size and edge that occur with increasing fragmentation. We tested the relative influence of habitat loss and fragmentation by examining occupancy of forest patches by 20 mid- and large-sized Neotropical mammal species in a fragmented landscape of northern Guatemala. We related patch occupancy of mammals to measures of habitat loss and fragmentation and compared the influence of these two factors while controlling for patch-level variables. Species responded strongly to both fragmentation and loss, and response to fragmentation generally was negative. Our findings support previous assumptions that conservation of large mammals in the tropics will require conservation strategies that go beyond prevention of habitat loss to also consider forest cohesion or other aspects of landscape configuration. PMID:21939064

  7. Tropical winter habitat limits reproductive success on the temperate breeding grounds in a migratory bird.

    PubMed Central

    Norris, D. Ryan; Marra, Peter P.; Kyser, T. Kurt; Sherry, Thomas W.; Ratcliffe, Laurene M.

    2004-01-01

    Identifying the factors that control population dynamics in migratory animals has been constrained by our inability to track individuals throughout the annual cycle. Using stable carbon isotopes, we show that the reproductive success of a long-distance migratory bird is influenced by the quality of habitat located thousands of kilometres away on tropical wintering grounds. For male American redstarts (Setophaga ruticilla), winter habitat quality influenced arrival date on the breeding grounds, which in turn affected key variables associated with reproduction, including the number of young fledged. Based on a winter-habitat model, females occupying high-quality winter habitat were predicted to produce more than two additional young and to fledge offspring up to a month earlier compared with females wintering in poor-quality habitat. Differences of this magnitude are highly important considering redstarts are single brooded, lay clutches of only three to five eggs and spend only two-and-a-half months on the breeding grounds. Results from this study indicate the importance of understanding how periods of the annual cycle interact for migratory animals. Continued loss of tropical wintering habitat could have negative effects on migratory populations in the following breeding season, minimizing density-dependent effects on the breeding grounds and leading to further population declines. If conservation efforts are to be successful, strategies must incorporate measures to protect all the habitats used during the entire annual cycle of migratory animals. PMID:15002772

  8. Habitat specialization predicts genetic response to fragmentation in tropical birds.

    PubMed

    Khimoun, Aurélie; Eraud, Cyril; Ollivier, Anthony; Arnoux, Emilie; Rocheteau, Vincent; Bely, Marine; Lefol, Emilie; Delpuech, Martin; Carpentier, Marie-Laure; Leblond, Gilles; Levesque, Anthony; Charbonnel, Anaïs; Faivre, Bruno; Garnier, Stéphane

    2016-08-01

    Habitat fragmentation is one of the most severe threats to biodiversity as it may lead to changes in population genetic structure, with ultimate modifications of species evolutionary potential and local extinctions. Nonetheless, fragmentation does not equally affect all species and identifying which ecological traits are related to species sensitivity to habitat fragmentation could help prioritization of conservation efforts. Despite the theoretical link between species ecology and extinction proneness, comparative studies explicitly testing the hypothesis that particular ecological traits underlies species-specific population structure are rare. Here, we used a comparative approach on eight bird species, co-occurring across the same fragmented landscape. For each species, we quantified relative levels of forest specialization and genetic differentiation among populations. To test the link between forest specialization and susceptibility to forest fragmentation, we assessed species responses to fragmentation by comparing levels of genetic differentiation between continuous and fragmented forest landscapes. Our results revealed a significant and substantial population structure at a very small spatial scale for mobile organisms such as birds. More importantly, we found that specialist species are more affected by forest fragmentation than generalist ones. Finally, our results suggest that even a simple habitat specialization index can be a satisfying predictor of genetic and demographic consequences of habitat fragmentation, providing a reliable practical and quantitative tool for conservation biology. PMID:27314987

  9. Effects of spatial habitat heterogeneity on habitat selection and annual fecundity for a migratory forest songbird

    USGS Publications Warehouse

    Cornell, K.L.; Donovan, T.M.

    2010-01-01

    Understanding how spatial habitat patterns influence abundance and dynamics of animal populations is a primary goal in landscape ecology. We used an information-theoretic approach to investigate the association between habitat patterns at multiple spatial scales and demographic patterns for black-throated blue warblers (Dendroica caerulescens) at 20 study sites in west-central Vermont, USA from 2002 to 2005. Sites were characterized by: (1) territory-scale shrub density, (2) patch-scale shrub density occurring within 25 ha of territories, and (3) landscape-scale habitat patterns occurring within 5 km radius extents of territories. We considered multiple population parameters including abundance, age ratios, and annual fecundity. Territory-scale shrub density was most important for determining abundance and age ratios, but landscape-scale habitat structure strongly influenced reproductive output. Sites with higher territory-scale shrub density had higher abundance, and were more likely to be occupied by older, more experienced individuals compared to sites with lower shrub density. However, annual fecundity was higher on sites located in contiguously forested landscapes where shrub density was lower than the fragmented sites. Further, effects of habitat pattern at one spatial scale depended on habitat conditions at different scales. For example, abundance increased with increasing territory-scale shrub density, but this effect was much stronger in fragmented landscapes than in contiguously forested landscapes. These results suggest that habitat pattern at different spatial scales affect demographic parameters in different ways, and that effects of habitat patterns at one spatial scale depends on habitat conditions at other scales. ?? Springer Science+Business Media B.V. 2009.

  10. Habitat heterogeneity, disturbance, and productivity work in concert to regulate biodiversity in deep submarine canyons.

    PubMed

    McClain, Craig R; Barry, James P

    2010-04-01

    Habitat heterogeneity is a major structuring agent of ecological assemblages promoting beta diversity and ultimately contributing to overall higher global diversity. The exact processes by which heterogeneity increases diversity are scale dependent and encompass variation in other well-known processes, e.g., productivity, disturbance, and temperature. Thus, habitat heterogeneity likely triggers multiple and cascading diversity effects through ecological assemblages. Submarine canyons, a pervasive feature of the world's oceans, likely increase habitat heterogeneity at multiple spatial scales similar to their terrestrial analogues. However, our understanding of how processes regulating diversity, and the potential for cascading effects within these important topographic features, remains incomplete. Utilizing remote-operated vehicles (ROVs) for coring and video transects, we quantified faunal turnover in the deep-sea benthos at a rarely examined scale (1 m-1 km). Macrofaunal community structure, megafaunal density, carbon flux, and sediment characteristics were analyzed for the soft-bottom benthos at the base of cliff faces in Monterey Canyon (northeast Pacific Ocean) at three depths. We documented a remarkable degree of faunal turnover and changes in overall community structure at scales < 100 m, and often < 10 m, related to geographic features of a canyon complex. Ultimately, our findings indicated that multiple linked processes related to habitat heterogeneity, ecosystem engineering, and bottom-up dynamics are important to deep-sea biodiversity. PMID:20462112

  11. Methods for Characterizing the Co-development of Biofilm and Habitat Heterogeneity

    PubMed Central

    Li, Xiaobao; Song, Jisun L.; Culotti, Alessandro; Zhang, Wei; Chopp, David L.; Lu, Nanxi; Packman, Aaron I.

    2016-01-01

    Biofilms are surface-attached microbial communities that have complex structures and produce significant spatial heterogeneities. Biofilm development is strongly regulated by the surrounding flow and nutritional environment. Biofilm growth also increases the heterogeneity of the local microenvironment by generating complex flow fields and solute transport patterns. To investigate the development of heterogeneity in biofilms and interactions between biofilms and their local micro-habitat, we grew mono-species biofilms of Pseudomonas aeruginosa and dual-species biofilms of P. aeruginosa and Escherichia coli under nutritional gradients in a microfluidic flow cell. We provide detailed protocols for creating nutrient gradients within the flow cell and for growing and visualizing biofilm development under these conditions. We also present protocols for a series of optical methods to quantify spatial patterns in biofilm structure, flow distributions over biofilms, and mass transport around and within biofilm colonies. These methods support comprehensive investigations of the co-development of biofilm and habitat heterogeneity. PMID:25866914

  12. Methods for characterizing the co-development of biofilm and habitat heterogeneity.

    PubMed

    Li, Xiaobao; Song, Jisun L; Culotti, Alessandro; Zhang, Wei; Chopp, David L; Lu, Nanxi; Packman, Aaron I

    2015-01-01

    Biofilms are surface-attached microbial communities that have complex structures and produce significant spatial heterogeneities. Biofilm development is strongly regulated by the surrounding flow and nutritional environment. Biofilm growth also increases the heterogeneity of the local microenvironment by generating complex flow fields and solute transport patterns. To investigate the development of heterogeneity in biofilms and interactions between biofilms and their local micro-habitat, we grew mono-species biofilms of Pseudomonas aeruginosa and dual-species biofilms of P. aeruginosa and Escherichia coli under nutritional gradients in a microfluidic flow cell. We provide detailed protocols for creating nutrient gradients within the flow cell and for growing and visualizing biofilm development under these conditions. We also present protocols for a series of optical methods to quantify spatial patterns in biofilm structure, flow distributions over biofilms, and mass transport around and within biofilm colonies. These methods support comprehensive investigations of the co-development of biofilm and habitat heterogeneity. PMID:25866914

  13. Tropical deforestation and habitat fragmentation in the Amazon - Satellite data from 1978 to 1988

    NASA Technical Reports Server (NTRS)

    Skole, David; Tucker, Compton

    1993-01-01

    Landsat satellite imagery covering the entire forested portion of the Brazilian Amazon Basin was used to measure, for 1978 and 1988, deforestation, fragmented forest, defined as areas less than 100 square kilometers surrounded by deforestation, and edge effects of 1 kilometer into forest from adjacent areas of deforestation. Tropical deforestation increased from 78,000 square kilometers in 1978 to 230,000 square kilometers in 1988 while tropical forest habitat, severely affected with respect to biological diversity, increased from 208,000 to 588,000 square kilometers. Although this rate of deforestation is lower than previous estimates, the effect on biological diversity is greater.

  14. Environmental Effects on Vertebrate Species Richness: Testing the Energy, Environmental Stability and Habitat Heterogeneity Hypotheses

    PubMed Central

    Luo, Zhenhua; Tang, Songhua; Li, Chunwang; Fang, Hongxia; Hu, Huijian; Yang, Ji; Ding, Jingjing; Jiang, Zhigang

    2012-01-01

    Background Explaining species richness patterns is a central issue in biogeography and macroecology. Several hypotheses have been proposed to explain the mechanisms driving biodiversity patterns, but the causes of species richness gradients remain unclear. In this study, we aimed to explain the impacts of energy, environmental stability, and habitat heterogeneity factors on variation of vertebrate species richness (VSR), based on the VSR pattern in China, so as to test the energy hypothesis, the environmental stability hypothesis, and the habitat heterogeneity hypothesis. Methodology/Principal Findings A dataset was compiled containing the distributions of 2,665 vertebrate species and eleven ecogeographic predictive variables in China. We grouped these variables into categories of energy, environmental stability, and habitat heterogeneity and transformed the data into 100×100 km quadrat systems. To test the three hypotheses, AIC-based model selection was carried out between VSR and the variables in each group and correlation analyses were conducted. There was a decreasing VSR gradient from the southeast to the northwest of China. Our results showed that energy explained 67.6% of the VSR variation, with the annual mean temperature as the main factor, which was followed by annual precipitation and NDVI. Environmental stability factors explained 69.1% of the VSR variation and both temperature annual range and precipitation seasonality had important contributions. By contrast, habitat heterogeneity variables explained only 26.3% of the VSR variation. Significantly positive correlations were detected among VSR, annual mean temperature, annual precipitation, and NDVI, whereas the relationship of VSR and temperature annual range was strongly negative. In addition, other variables showed moderate or ambiguous relations to VSR. Conclusions/Significance The energy hypothesis and the environmental stability hypothesis were supported, whereas little support was found for the

  15. Role of circulation scales and water mass distributions on larval fish habitats in the Eastern Tropical Pacific off Mexico

    NASA Astrophysics Data System (ADS)

    León-Chávez, Cristina A.; Beier, Emilio; Sánchez-Velasco, Laura; Barton, Eric Desmond; Godínez, Victor M.

    2015-06-01

    On the basis of five oceanographic cruises carried out in the Eastern Tropical Pacific off Mexico, relationships between the larval fish habitats (areas inhabited by larval fish assemblages) and the environmental circulation scales (mesoscale, seasonal, and interannual) were examined. Analysis of in situ data over a grid of hydrographic stations and oblique zooplankton hauls with bongo net (505 µm) was combined with orthogonal robust functions decomposition applied to altimetry anomalies obtained from satellite. During both cool (March and June) and warm (August and November) periods, Bray-Curtis dissimilarity Index defined three recurrent larval fish habitats which varied in species composition and extent as a function of the environmental scales. The variability of the Tropical larval fish habitat (characterized by high species richness, and dominated by Vinciguerria lucetia, Diogenichthys laternatus, and Diaphus pacificus) was associated with the seasonal changes. The Transitional-California Current larval fish habitat (dominated by V. lucetia and D. laternatus, with lower mean abundance and lower species richness than in the Tropical habitat) and Coastal-and-Upwelling larval fish habitat (dominated by Bregmaceros bathymaster) was associated mainly with mesoscale activity induced by eddies and with coastal upwelling. During February 2010, the Tropical larval fish habitat predominated offshore and the Transitional-California Current larval fish habitat was not present, which we attribute to the effect of El Niño conditions. Thus, the mesoscale, seasonal, and interannual environmental scales affect the composition and extension of larval fish habitats.

  16. Bromeliad Catchments as Habitats for Methanogenesis in Tropical Rainforest Canopies

    PubMed Central

    Goffredi, Shana K.; Jang, Gene E.; Woodside, Walter T.; Ussler, William

    2011-01-01

    Tropical epiphytic plants within the family Bromeliaceae are unusual in that they possess foliage capable of retaining water and impounded material. This creates an acidic (pH 3.5–6.5) and anaerobic (<1 ppm O2) environment suspended in the canopy. Results from a Costa Rican rainforest show that most bromeliads (n = 75/86) greater than ~20 cm in plant height or ~4–5 cm tank depth, showed presence of methanogens within the lower anoxic horizon of the tank. Archaea were dominated by methanogens (77–90% of recovered ribotypes) and community structure, although variable, was generally comprised of a single type, closely related to either hydrogenotrophic Methanoregula or Methanocella, a specific clade of aceticlastic Methanosaeta, or Methanosarcina. Juvenile bromeliads, or those species, such as Guzmania, with shallow tanks, generally did not possess methanogens, as assayed by polymerase chain reaction specific for methanogen 16S rRNA genes, nor did artificial catchments (~100 ml volume), in place 6–12 months prior to sample collection. Methanogens were not detected in soil (n = 20), except in one case, in which the dominant ribotype was different from nearby bromeliads. Recovery of methyl coenzyme M reductase genes supported the occurrence of hydrogenotrophic and aceticlastic methanogens within bromeliad tanks, as well as the trend, via QPCR analysis of mcrA, of increased methanogenic capacity with increased plant height. Methane production rates of up to 300 nmol CH4 ml tank water−1 day−1 were measured in microcosm experiments. These results suggest that bromeliad-associated archaeal communities may play an important role in the cycling of carbon in neotropical forests. PMID:22207867

  17. Bromeliad catchments as habitats for methanogenesis in tropical rainforest canopies.

    PubMed

    Goffredi, Shana K; Jang, Gene E; Woodside, Walter T; Ussler, William

    2011-01-01

    Tropical epiphytic plants within the family Bromeliaceae are unusual in that they possess foliage capable of retaining water and impounded material. This creates an acidic (pH 3.5-6.5) and anaerobic (<1 ppm O(2)) environment suspended in the canopy. Results from a Costa Rican rainforest show that most bromeliads (n = 75/86) greater than ~20 cm in plant height or ~4-5 cm tank depth, showed presence of methanogens within the lower anoxic horizon of the tank. Archaea were dominated by methanogens (77-90% of recovered ribotypes) and community structure, although variable, was generally comprised of a single type, closely related to either hydrogenotrophic Methanoregula or Methanocella, a specific clade of aceticlastic Methanosaeta, or Methanosarcina. Juvenile bromeliads, or those species, such as Guzmania, with shallow tanks, generally did not possess methanogens, as assayed by polymerase chain reaction specific for methanogen 16S rRNA genes, nor did artificial catchments (~100 ml volume), in place 6-12 months prior to sample collection. Methanogens were not detected in soil (n = 20), except in one case, in which the dominant ribotype was different from nearby bromeliads. Recovery of methyl coenzyme M reductase genes supported the occurrence of hydrogenotrophic and aceticlastic methanogens within bromeliad tanks, as well as the trend, via QPCR analysis of mcrA, of increased methanogenic capacity with increased plant height. Methane production rates of up to 300 nmol CH(4) ml tank water(-1) day(-1) were measured in microcosm experiments. These results suggest that bromeliad-associated archaeal communities may play an important role in the cycling of carbon in neotropical forests. PMID:22207867

  18. Host and habitat preferences of polypore fungi in Micronesian tropical flooded forests.

    PubMed

    Gilbert, Gregory S; Gorospe, Jennifer; Ryvarden, Leif

    2008-06-01

    The distribution and ecological impacts of plant-associated fungi is determined in large part by their degree of specificity for particular host species or environmental conditions. Here we evaluate the host and habitat preferences among the Aphyllophorales, a guild of wood-decay basidiomycete fungi usually considered to be host generalists. We determined the patterns of host association in three well-defined, floristically distinct, tropical wetlands -- freshwater forested wetlands, saltwater mangrove forests, and peatlands with scattered trees -- on the islands of Kosrae and Pohnpei in the Federated States of Micronesia. Of 33 fungal species, 20 were locally rare. Of the 11 species sufficiently common to evaluate habitat specificity, nine showed significant habitat preferences. Of eight species common enough to evaluate within-habitat host specificity, six showed strong host preferences. All except one of the nine habitat-specialized fungi showed either statistically significant host specificity or strong numerical biases toward single host species. Our results suggest that host preferences may be important in shaping the assemblages of wood-decay fungi, and that the effect of environment on the distribution of susceptible plant species, rather on the fungi themselves, may ultimately drive the apparent habitat specificity of many fungi. PMID:18495449

  19. Expansion of oxygen minimum zones may reduce available habitat for tropical pelagic fishes

    NASA Astrophysics Data System (ADS)

    Stramma, Lothar; Prince, Eric D.; Schmidtko, Sunke; Luo, Jiangang; Hoolihan, John P.; Visbeck, Martin; Wallace, Douglas W. R.; Brandt, Peter; Körtzinger, Arne

    2012-01-01

    Climate model predictions and observations reveal regional declines in oceanic dissolved oxygen, which are probably influenced by global warming. Studies indicate ongoing dissolved oxygen depletion and vertical expansion of the oxygen minimum zone (OMZ) in the tropical northeast Atlantic Ocean. OMZ shoaling may restrict the usable habitat of billfishes and tunas to a narrow surface layer. We report a decrease in the upper ocean layer exceeding 3.5mll-1 dissolved oxygen at a rate of <=1myr-1 in the tropical northeast Atlantic (0-25°N, 12-30°W), amounting to an annual habitat loss of ~5.95×1013m3, or 15% for the period 1960-2010. Habitat compression and associated potential habitat loss was validated using electronic tagging data from 47 blue marlin. This phenomenon increases vulnerability to surface fishing gear for billfishes and tunas, and may be associated with a 10-50% worldwide decline of pelagic predator diversity. Further expansion of the Atlantic OMZ along with overfishing may threaten the sustainability of these valuable pelagic fisheries and marine ecosystems.

  20. Patterns in tropical seagrass photosynthesis in relation to light, depth and habitat

    NASA Astrophysics Data System (ADS)

    Campbell, Stuart J.; McKenzie, Len J.; Kerville, Simon P.; Bité, Juanita S.

    2007-07-01

    Seagrass meadows across north-eastern Australia, survive a range of environmental conditions in coastal bays, reefs, estuarine and deepwater habitats through adaptation of a range of structural, morphological and physiological features. The aim of this study was to investigate the influence of spatial features (habitat type, site and depth) and photon flux on the photosynthetic performance of 11 tropical seagrass species. Pulse amplitude modulated (PAM) fluorometry was used to generate rapid light curves from which measures of maximal electron transport rate (ETR max), photosynthetic efficiency ( α), saturating irradiance ( Ek) and effective quantum yield (Δ F/ Fm') were derived. The amount of light absorbed by leaves (absorption factor) was also determined for each population. In intertidal habitats many seagrass species exhibited typical sun-type responses with a close coupling of both ETR max and Ek with photon flux. Photosynthetic performance ranged from minima in Thalassodendron ciliatum to maxima in Syringodium isoetifolium. The absence of a coupling between photosynthetic performance and photon flux in subtidal populations was most likely due to highly variable light climates and possible light attenuation, and hence the photo-biology of estuarine and deepwater seagrasses exhibited photosynthetic responses indicative of light limitation. In contrast seagrass species from shallow reef and coastal habitats for the most part exhibited light saturation characteristics. Of all the variables examined ETR max, Ek and Δ F/ Fm' were most responsive to changing light climates and provide reliable physiological indicators of real-time photosynthetic performance of tropical seagrasses under different light conditions.

  1. [Coexistence mechanism of ant community in lac plantation under habitat heterogeneity].

    PubMed

    Wang, Si-ming; Chen, You-qing; Lu, Zhi-xing; Liu, Chun-ju; Guo, Zu-xue

    2010-10-01

    In order to reveal the coexistence mechanism of ant community in lac plantation, an investigation was made on the ant community composition and the ability of ant species in discovering and holding food resources in a lac plantation in Yayi Town of Mojiang County, Yunnan Province, with the relationships between ant body size and its ability of finding food under habitat heterogeneity probed. There were six dominant ant species in the plantation, i. e., Tetraponera allaborans (Walker), Crematogaster macaoensis Wheeler, Crematogasterferrarii Emery, Dolichoderus thoracicus (Smith), Polyrhachis proxima Roger, and Camponotus parius Emery. The hind leg length (y) of the six ant species increased allometrically with their head width (x), and the regression equation was y = 0.56 + 1.02x + 5.97x2 - 10.85x3. Different ant species had significant differences in their actual and relative frequency in discovering food resources in different habitats, but habitat type had no significant effects on the actual frequency in holding food resources by the ant species. The ant species with bigger head width and bigger body size index could discover more food resources in simple habitat. In contrast, the ant species with smaller head width, shorter hind leg length, and smaller body size index could discover more food resources in complex habitat. The heterogeneity of habitat caused the coexistence of ants: the smaller ant species lived in complex habitat, while the larger ones lived in simple habitat. In addition, numerically dominant ant species were unable to possess all resources, and thereby, could provide the opportunity to other ant species for resources acquisition, making the species coexistence come true. PMID:21328961

  2. Spatial heterogeneity of methane ebullition in a large tropical reservoir.

    PubMed

    DelSontro, Tonya; Kunz, Manuel J; Kempter, Tim; Wüest, Alfred; Wehrli, Bernhard; Senn, David B

    2011-12-01

    Tropical reservoirs have been identified as important methane (CH(4)) sources to the atmosphere, primarily through turbine and downstream degassing. However, the importance of ebullition (gas bubbling) remains unclear. We hypothesized that ebullition is a disproportionately large CH(4) source from reservoirs with dendritic littoral zones because of ebullition hot spots occurring where rivers supply allochthonous organic material. We explored this hypothesis in Lake Kariba (Zambia/Zimbabwe; surface area >5000 km(2)) by surveying ebullition in bays with and without river inputs using an echosounder and traditional surface chambers. The two techniques yielded similar results, and revealed substantially higher fluxes in river deltas (∼10(3) mg CH(4) m(-2) d(-1)) compared to nonriver bays (<100 mg CH(4) m(-2) d(-1)). Hydroacoustic measurements resolved at 5 m intervals showed that flux events varied over several orders of magnitude (up to 10(5) mg CH(4) m(-2) d(-1)), and also identified strong differences in ebullition frequency. Both factors contributed to emission differences between all sites. A CH(4) mass balance for the deepest basin of Lake Kariba indicated that hot spot ebullition was the largest atmospheric emission pathway, suggesting that future greenhouse gas budgets for tropical reservoirs should include a spatially well-resolved analysis of ebullition hot spots. PMID:21985534

  3. Pervasive Local-Scale Tree-Soil Habitat Association in a Tropical Forest Community.

    PubMed

    Allié, Elodie; Pélissier, Raphaël; Engel, Julien; Petronelli, Pascal; Freycon, Vincent; Deblauwe, Vincent; Soucémarianadin, Laure; Weigel, Jean; Baraloto, Christopher

    2015-01-01

    related to dispersal limitation, biotic interactions and environmental filtering from species-habitat associations. Moreover, they provide a framework to generalize across tropical forest sites. PMID:26535570

  4. Pervasive Local-Scale Tree-Soil Habitat Association in a Tropical Forest Community

    PubMed Central

    Allié, Elodie; Pélissier, Raphaël; Engel, Julien; Petronelli, Pascal; Freycon, Vincent; Deblauwe, Vincent; Soucémarianadin, Laure; Weigel, Jean; Baraloto, Christopher

    2015-01-01

    related to dispersal limitation, biotic interactions and environmental filtering from species-habitat associations. Moreover, they provide a framework to generalize across tropical forest sites. PMID:26535570

  5. Relationships between Meiofaunal Biodiversity and Prokaryotic Heterotrophic Production in Different Tropical Habitats and Oceanic Regions

    PubMed Central

    Pusceddu, Antonio; Gambi, Cristina; Corinaldesi, Cinzia; Scopa, Mariaspina; Danovaro, Roberto

    2014-01-01

    Tropical marine ecosystems are among the most diverse of the world oceans, so that assessing the linkages between biodiversity and ecosystem functions (BEF) is a crucial step to predict consequences of biodiversity loss. Most BEF studies in marine ecosystems have been carried out on macrobenthic diversity, whereas the influence of the meiofauna on ecosystem functioning has received much less attention. We compared meiofaunal and nematode biodiversity and prokaryotic heterotrophic production across seagrass, mangrove and reef sediments in the Caribbean, Celebes and Red Seas. For all variables we report the presence of differences among habitats within the same region, and among regions within the same habitat. In all regions, the richness of meiofaunal taxa in reef and seagrass sediments is higher than in mangrove sediments. The sediments of the Celebes Sea show the highest meiofaunal biodiversity. The composition of meiofaunal assemblages varies significantly among habitats in the same region. The nematode beta diversity among habitats within the same region is higher than the beta diversity among regions. Although one site per habitat was considered in each region, these results suggest that the composition of meiofaunal assemblages varies primarily among biogeographic regions, whereas the composition of nematode assemblages varies more considerably among habitats. Meiofauna and nematode biodiversity and prokaryotic heterotrophic production, even after the removal of covariate effects linked with longitude and the quantity and nutritional quality of organic matter, are positively and linearly linked both across regions and within each habitat type. Our results confirm that meiofauna and nematode biodiversity may influence benthic prokaryotic activity, which, in turn, implies that diversity loss could have negative impacts on ecosystem functioning in these systems. PMID:24603709

  6. Phenotypic plasticity of the basidiomata of Thelephora sp. (Thelephoraceae) in tropical forest habitats.

    PubMed

    Ramirez-Lópezl, Itzel; Ríos, Margarita Villegas; Cano-Santana, Zenón

    2013-03-01

    Phenotypic plasticity in macroscopic fungi has been poorly studied in comparison to plants or animals and only general aspects of these changes have been described. In this work, the phenotypic variation in the basidiomata of Thelephora sp. (Thelephoraceae) was examined, as well as some aspects of its ecology and habitat, using 24 specimens collected in the tropical forests of the Chamela Biological Station, Jalisco, Mexico. Our observations showed that this taxon has clavarioid basidiomata that can become resupinate during development and growth if they are in contact with rocks, litter or live plants, establishing in the latter only an epiphytic relationship. This tropical species may form groups of up to 139 basidiomata over an area of 32.2m2, and in both types of vegetation (tropical sub-evergreen and deciduous forest) were primarily located on steep (>20 degree) South-facing slopes. It is found under closed canopy in both tropical forests, but its presence in sub-evergreen forests is greater than expected. PMID:23894987

  7. Upper thermal tolerance plasticity in tropical amphibian species from contrasting habitats: implications for warming impact prediction.

    PubMed

    Simon, Monique Nouailhetas; Ribeiro, Pedro Leite; Navas, Carlos Arturo

    2015-02-01

    Tropical ectothermic species are currently depicted as more vulnerable to increasing temperatures because of the proximity between their upper thermal limits and environmental temperatures. Yet, the acclimatory capacity of thermal limits has rarely been measured in tropical species, even though they are generally predicted to be smaller than in temperate species. We compared critical thermal maximum (CTmax) and warming tolerance (WT: the difference between CTmax and maximum temperature, Tmax), as well as CTmax acclimatory capacity of toad species from the Atlantic forest (AF) and the Brazilian Caatinga (CAA), a semi-arid habitat with high temperatures. Acclimation temperatures represented the mean temperatures of AF and CAA habitats, making estimates of CTmax and WT more ecologically realistic. CAA species mean CTmax was higher compared to AF species in both acclimation treatments. Clutches within species, as well as between AF and CAA species, differed in CTmax plasticity and we discuss the potential biological meaning of these findings. We did not find a trade-off between absolute CTmax and CTmax plasticity, indicating that species can have both high CTmax and high CTmax plasticity. Although CTmax was highly correlated to Tmax, CTmax plasticity was not related to Tmax or Tmax coefficients of variation. CAA species mean WT was lower than for AF species, but still very high for all species, diverging from other studies with tropical species. This might be partially related to over-estimation of vulnerability due to under-appreciation of realistic acclimation treatments in CTmax estimation. Thus, some tropical species might not be as vulnerable to warming as previously predicted if CTmax is considered as a shifting population parameter. PMID:25660628

  8. Remotely sensed indicators of habitat heterogeneity and biological diversity: A preliminary report

    NASA Technical Reports Server (NTRS)

    Imhoff, Marc; Sisk, Thomas; Milne, Anthony; Morgan, Garth; Orr, Tony

    1995-01-01

    The relationship between habitat area, spatial dynamics of the landscape, and species diversity is an important theme in population and conservation biology. Of particular interest is how populations of various species are affected by increasing habitat edges due to fragmentation. Over the last decade, assumptions regarding the effects of habitat edges on biodiversity have fluctuated wildly, from the belief that they have a positive effect to the belief that they have a clearly negative effect. This change in viewpoint has been brought about by an increasing recognition of the importance of geographic scale and a reinterpretation of natural history observations. In this preliminary report from an ongoing project, we explore the use of remote sensing technology and geographic information systems to further our understanding of how species diversity and population density are affected by habitat heterogeneity and landscape composition. A primary feature of this study is the investigation of SAR for making more rigorous investigations of habitat structure by exploiting the interaction between radar backscatter and vegetation structure and biomass. A major emphasis will be on the use of SAR data to define relative structural types based on measures of structural consolidation using the vegetation surface area to volume ratio (SA/V). Past research has shown that SAR may be sensitive to this form of structural expression which may affect biodiversity.

  9. From inter-specific behavioural interactions to species distribution patterns along gradients of habitat heterogeneity.

    PubMed

    Laiolo, Paola

    2013-01-01

    The strength of the behavioural processes associated with competitor coexistence may vary when different physical environments, and their biotic communities, come into contact, although empirical evidence of how interference varies across gradients of environmental complexity is still scarce in vertebrates. Here, I analyse how behavioural interactions and habitat selection regulate the local distribution of steppeland larks (Alaudidae) in a gradient from simple to heterogeneous agricultural landscapes in Spain, using crested lark Galerida cristata and Thekla lark G. theklae as study models. Galerida larks significantly partitioned by habitat but frequently co-occurred in heterogeneous environments. Irrespective of habitat divergence, however, the local densities of the two larks were negatively correlated, and the mechanisms beyond this pattern were investigated by means of playback experiments. When simulating the intrusion of the congener by broadcasting the species territorial calls, both larks responded with an aggressive response as intense with respect to warning and approach behaviour as when responding to the intrusion of a conspecific. However, birds promptly responded to playbacks only when congener territories were nearby, a phenomenon that points to learning as the mechanisms through which individuals finely tune their aggressive responses to the local competition levels. Heterospecifics occurred in closer proximity in diverse agro-ecosystems, possibly because of more abundant or diverse resources, and here engage in antagonistic interactions. The drop of species diversity associated with agricultural homogenisation is therefore likely to also bring about the disappearance of the behavioural repertoires associated with species interactions. PMID:22806401

  10. A user-friendly quantitative approach to classifying nearshore marine habitats along a heterogeneous coast

    NASA Astrophysics Data System (ADS)

    Valesini, F. J.; Clarke, K. R.; Eliot, I.; Potter, I. C.

    2003-05-01

    A scheme, which can be readily used by fisheries and environmental managers and ecologists, has been developed for quantitatively classifying the different habitats found in nearshore marine waters along the heterogeneous lower west coast of Australia. Initially, 25 beach sites, representing a wide range of nearshore environments, were separated into six a priori habitat types on the basis of characteristics that could readily be observed and were likely to influence the extent to which a particular (fish) species occupies a particular habitat. Focus was thus placed on such features as the degree of exposure to wave activity and whether or not seagrass and/or reefs were present in the nearshore vicinity. Subsequently, quantitative data for 27 environmental variables, considered likely to characterise the six habitat types, were obtained for each of the 25 sites from readily accessible sources. When the latter data were subjected to multidimensional scaling (MDS) ordination, the points for the sites representing only three of those six habitat types formed discrete groups. The BVSTEP routine in the PRIMER v5.0 statistical package (Clarke & Gorley, Primer v5.0: User Manual/Tutorial, Primer-E Ltd, Plymouth, 2001) was thus used to select a subset of the 27 environmental variables that would provide a better resolution of the six a priori habitat types. This process involved matching the distance matrix constructed from the quantitative environmental data with a matrix constructed from scored data that reflected the criteria for the initial a priori classification scheme. A subset of seven environmental variables gave the best correlation between the two matrices ( ρ=0.823), and thus provided the optimal set of quantitative data for discriminating between the six a priori habitat types. These variables comprised both the direct and north-westerly fetches, the minimum distance from the shoreline to the 2 m depth contour, the distance from the shoreline to the first

  11. Long-term demographic consequences of habitat fragmentation to a tropical understory bird community

    USGS Publications Warehouse

    Korfanta, N.M.; Newmark, W.D.; Kauffman, M.J.

    2012-01-01

    Tropical deforestation continues to cause population declines and local extinctions in centers of avian diversity and endemism. Although local species extinctions stem from reductions in demographic rates, little is known about how habitat fragmentation influences survival of tropical bird populations or the relative importance of survival and fecundity in ultimately shaping communities. We analyzed 22 years of mark-recapture data to assess how fragmentation influenced apparent survival, recruitment, and realized population growth rate within 22 forest understory bird species in the Usambara Mountains, Tanzania. This represents the first such effort, in either tropical or temperate systems, to characterize the effect of deforestation on avian survival across such a broad suite of species. Long-term demographic analysis of this suite of species experiencing the same fragmented environment revealed considerable variability in species' responses to fragmentation, in addition to general patterns that emerged from comparison among species. Across the understory bird community as a whole, we found significantly lower apparent survival and realized population growth rate in small fragments relative to large, demonstrating fragmentation effects to demographic rates long after habitat loss. Demographic rates were depressed across five feeding guilds, suggesting that fragmentation sensitivity was not limited to insectivores. Seniority analyses, together with a positive effect of fragmentation on recruitment, indicated that depressed apparent survival was the primary driver of population declines and observed extinctions. We also found a landscape effect, with lower vital rates in one mountain range relative to another, suggesting that fragmentation effects may add to other large-scale drivers of population decline. Overall, realized population growth rate (λ) estimates were < 1 for most species, suggesting that future population persistence even within large forest

  12. Estimating species richness and modelling habitat preferences of tropical forest mammals from camera trap data.

    PubMed

    Rovero, Francesco; Martin, Emanuel; Rosa, Melissa; Ahumada, Jorge A; Spitale, Daniel

    2014-01-01

    Medium-to-large mammals within tropical forests represent a rich and functionally diversified component of this biome; however, they continue to be threatened by hunting and habitat loss. Assessing these communities implies studying species' richness and composition, and determining a state variable of species abundance in order to infer changes in species distribution and habitat associations. The Tropical Ecology, Assessment and Monitoring (TEAM) network fills a chronic gap in standardized data collection by implementing a systematic monitoring framework of biodiversity, including mammal communities, across several sites. In this study, we used TEAM camera trap data collected in the Udzungwa Mountains of Tanzania, an area of exceptional importance for mammal diversity, to propose an example of a baseline assessment of species' occupancy. We used 60 camera trap locations and cumulated 1,818 camera days in 2009. Sampling yielded 10,647 images of 26 species of mammals. We estimated that a minimum of 32 species are in fact present, matching available knowledge from other sources. Estimated species richness at camera sites did not vary with a suite of habitat covariates derived from remote sensing, however the detection probability varied with functional guilds, with herbivores being more detectable than other guilds. Species-specific occupancy modelling revealed novel ecological knowledge for the 11 most detected species, highlighting patterns such as 'montane forest dwellers', e.g. the endemic Sanje mangabey (Cercocebus sanjei), and 'lowland forest dwellers', e.g. suni antelope (Neotragus moschatus). Our results show that the analysis of camera trap data with account for imperfect detection can provide a solid ecological assessment of mammal communities that can be systematically replicated across sites. PMID:25054806

  13. Habitat heterogeneity and connectivity shape microbial communities in South American peatlands.

    PubMed

    Oloo, Felix; Valverde, Angel; Quiroga, María Victoria; Vikram, Surendra; Cowan, Don; Mataloni, Gabriela

    2016-01-01

    Bacteria play critical roles in peatland ecosystems. However, very little is known of how habitat heterogeneity affects the structure of the bacterial communities in these ecosystems. Here, we used amplicon sequencing of the 16S rRNA and nifH genes to investigate phylogenetic diversity and bacterial community composition in three different sub-Antarctic peat bog aquatic habitats: Sphagnum magellanicum interstitial water, and water from vegetated and non-vegetated pools. Total and putative nitrogen-fixing bacterial communities from Sphagnum interstitial water differed significantly from vegetated and non-vegetated pool communities (which were colonized by the same bacterial populations), probably as a result of differences in water chemistry and biotic interactions. Total bacterial communities from pools contained typically aquatic taxa, and were more dissimilar in composition and less species rich than those from Sphagnum interstitial waters (which were enriched in taxa typically from soils), probably reflecting the reduced connectivity between the former habitats. These results show that bacterial communities in peatland water habitats are highly diverse and structured by multiple concurrent factors. PMID:27162086

  14. Predicting faunal fire responses in heterogeneous landscapes: the role of habitat structure.

    PubMed

    Swan, Matthew; Christie, Fiona; Sitters, Holly; York, Alan; Di Stefano, Julian

    2015-12-01

    Predicting the effects of fire on biota is important for biodiversity conservation in fire-prone landscapes. Time since fire is often used to predict the occurrence of fauna, yet for many species, it is a surrogate variable and it is temporal change in resource availability to which animals actually respond. Therefore prediction of fire-fauna relationships will be uncertain if time since fire is not strongly related to resources. In this study, we used a space-for-time substitution across a large diverse landscape to investigate interrelationships between the occurrence of ground-dwelling mammals, time since fire, and structural resources. We predicted that much variation in habitat structure would remain unexplained by time since fire and that habitat structure would predict species' occurrence better than time since fire. In line with predictions, we found that time since fire was moderately correlated with habitat structure yet was a poor surrogate for mammal occurrence. Variables representing habitat structure were better predictors of occurrence than time since fire for all species considered. Our results suggest that time since fire is unlikely to be a useful surrogate for ground-dwelling mammals in heterogeneous landscapes. Faunal conservation in fire-prone landscapes will benefit from a combined understanding of fauna-resource relationships and the ways in which fire (including planned fires and wildfires) alters the spatial and temporal distribution of faunal resources. PMID:26910956

  15. Habitat heterogeneity and connectivity shape microbial communities in South American peatlands

    PubMed Central

    Oloo, Felix; Valverde, Angel; Quiroga, María Victoria; Vikram, Surendra; Cowan, Don; Mataloni, Gabriela

    2016-01-01

    Bacteria play critical roles in peatland ecosystems. However, very little is known of how habitat heterogeneity affects the structure of the bacterial communities in these ecosystems. Here, we used amplicon sequencing of the 16S rRNA and nifH genes to investigate phylogenetic diversity and bacterial community composition in three different sub-Antarctic peat bog aquatic habitats: Sphagnum magellanicum interstitial water, and water from vegetated and non-vegetated pools. Total and putative nitrogen-fixing bacterial communities from Sphagnum interstitial water differed significantly from vegetated and non-vegetated pool communities (which were colonized by the same bacterial populations), probably as a result of differences in water chemistry and biotic interactions. Total bacterial communities from pools contained typically aquatic taxa, and were more dissimilar in composition and less species rich than those from Sphagnum interstitial waters (which were enriched in taxa typically from soils), probably reflecting the reduced connectivity between the former habitats. These results show that bacterial communities in peatland water habitats are highly diverse and structured by multiple concurrent factors. PMID:27162086

  16. Disentangling vegetation diversity from climate–energy and habitat heterogeneity for explaining animal geographic patterns

    USGS Publications Warehouse

    Jimenez-Alfaro, Borja; Chytry, Milan; Mucina, Ladislav; Grace, James B.; Rejmanek, Marcel

    2016-01-01

    Broad-scale animal diversity patterns have been traditionally explained by hypotheses focused on climate–energy and habitat heterogeneity, without considering the direct influence of vegetation structure and composition. However, integrating these factors when considering plant–animal correlates still poses a major challenge because plant communities are controlled by abiotic factors that may, at the same time, influence animal distributions. By testing whether the number and variation of plant community types in Europe explain country-level diversity in six animal groups, we propose a conceptual framework in which vegetation diversity represents a bridge between abiotic factors and animal diversity. We show that vegetation diversity explains variation in animal richness not accounted for by altitudinal range or potential evapotranspiration, being the best predictor for butterflies, beetles, and amphibians. Moreover, the dissimilarity of plant community types explains the highest proportion of variation in animal assemblages across the studied regions, an effect that outperforms the effect of climate and their shared contribution with pure spatial variation. Our results at the country level suggest that vegetation diversity, as estimated from broad-scale classifications of plant communities, may contribute to our understanding of animal richness and may be disentangled, at least to a degree, from climate–energy and abiotic habitat heterogeneity.

  17. Disentangling vegetation diversity from climate-energy and habitat heterogeneity for explaining animal geographic patterns.

    PubMed

    Jiménez-Alfaro, Borja; Chytrý, Milan; Mucina, Ladislav; Grace, James B; Rejmánek, Marcel

    2016-03-01

    Broad-scale animal diversity patterns have been traditionally explained by hypotheses focused on climate-energy and habitat heterogeneity, without considering the direct influence of vegetation structure and composition. However, integrating these factors when considering plant-animal correlates still poses a major challenge because plant communities are controlled by abiotic factors that may, at the same time, influence animal distributions. By testing whether the number and variation of plant community types in Europe explain country-level diversity in six animal groups, we propose a conceptual framework in which vegetation diversity represents a bridge between abiotic factors and animal diversity. We show that vegetation diversity explains variation in animal richness not accounted for by altitudinal range or potential evapotranspiration, being the best predictor for butterflies, beetles, and amphibians. Moreover, the dissimilarity of plant community types explains the highest proportion of variation in animal assemblages across the studied regions, an effect that outperforms the effect of climate and their shared contribution with pure spatial variation. Our results at the country level suggest that vegetation diversity, as estimated from broad-scale classifications of plant communities, may contribute to our understanding of animal richness and may be disentangled, at least to a degree, from climate-energy and abiotic habitat heterogeneity. PMID:26900451

  18. MODELING THE DYNAMICS OF THREE FUNCTIONAL GROUPS OF MACROALGAE IN TROPICAL SEAGRASS HABITATS. (R828677C004)

    EPA Science Inventory

    A model of three functional groups of macroalgae, drift algae, rhizophytic calcareous algae, and seagrass epiphytes, was developed to complement an existing seagrass production model for tropical habitats dominated by Thalassia testudinum (Turtle-grass). The current modeling e...

  19. Ecological significance of light controlled seed germination in two contrasting tropical habitats.

    PubMed

    Vàzquez-Yanes, C; Orozco-Segovia, A

    1990-06-01

    The effects of temperature, photoperiod, phytochrome photoreversion and the response to a R/FR ratio gradient were investigated in seeds of four species from two contrasting tropical habitats; two species from a rain forest (Cecropia obtusifolia and Piper umbellatum) and two from a high altitude lava field covered by low vegetation (Buddleja cordata and Chenopodium ambrosioides). In the rain forest seed species the photoblastic response seems to be adapted to light quality changes due to canopy destruction, on the other hand, the lava field seed species seem to be adapted to instantaneous light stimulus such as would be produced by the sudden exposure of a buried seed to the soil surface light environment. PMID:22160107

  20. Importance of Habitat Heterogeneity in Richness and Diversity of Moths (Lepidoptera) in Brazilian Savanna.

    PubMed

    Braga, Laura; Diniz, Ivone Rezende

    2015-06-01

    Moths exhibit different levels of fidelity to habitat, and some taxa are considered as bioindicators for conservation because they respond to habitat quality, environmental change, and vegetation types. In this study, we verified the effect of two phytophysiognomies of the Cerrado, savanna and forest, on the diversity distribution of moths of Erebidae (Arctiinae), Saturniidae, and Sphingidae families by using a hierarchical additive partitioning analysis. This analysis was based on two metrics: species richness and Shannon diversity index. The following questions were addressed: 1) Does the beta diversity of moths between phytophysiognomies add more species to the regional diversity than the beta diversity between sampling units and between sites? 2) Does the distribution of moth diversity differ among taxa? Alpha and beta diversities were compared with null models. The additive partitioning of species richness for the set of three Lepidoptera families identified beta diversity between phytophysiognomies as the component that contributed most to regional diversity, whereas the Shannon index identified alpha diversity as the major contributor. According to both species richness and the Shannon index, beta diversity between phytophysiognomies was significantly higher than expected by chance. Therefore, phytophysiognomies are the most important component in determining the richness and composition of the community. Additive partitioning also indicated that individual families of moths respond differently to the effect of habitat heterogeneity. The integrity of the Cerrado mosaic of phytophysiognomies plays a crucial role in maintaining moth biodiversity in the region. PMID:26313955

  1. Differential performance of tropical soda apple and its biological control agent Gratiana boliviana (Coleoptera: Chrysomelidae) in open and shaded habitats.

    PubMed

    Diaz, Rodrigo; Aguirre, Carlos; Wheeler, Gregory S; Lapointe, Stephen L; Rosskopf, Erin; Overholt, William A

    2011-12-01

    The leaf feeding beetle Gratiana boliviana Spaeth has been released since 2003 in the southeastern United States for biological control of tropical soda apple, Solanum viarum Dunal. In Florida, G. boliviana can be found on tropical soda apple growing in open pastures as well as in shady wooded areas. The objectives of this study were to determine the effect of light intensity on the performance of tropical soda apple and G. boliviana under greenhouse conditions, and to determine the abundance and mortality of G. boliviana in open and shaded habitats. Leaves growing in the shade were less tough, had higher water and nitrogen content, lower soluble sugars, and less dense and smaller glandular trichomes compared with leaves growing in the open. Plants grew slightly taller and wider under shaded conditions but total biomass was significantly reduced compared with plants grown in the open. In the greenhouse, G. boliviana had higher immature survival, greater folivory, larger adult size, and higher fecundity when reared on shaded plants compared with open plants. Sampling of field populations revealed that the overall abundance of G. boliviana was lower but leaf feeding damage was higher in shaded habitats compared with the open habitats. The percentage of eggs surviving to adult was greater in shaded compared with open habitats. The abundance of predators was higher in the open pasture and was positively correlated with the abundance of G. boliviana. These results indicate that not only plant quality but also habitat structure are important to the performance of weed biological control agents. PMID:22217759

  2. Regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions.

    PubMed

    Lander, Michelle E; Loughlin, Thomas R; Logsdon, Miles G; VanBlaricom, Glenn R; Fadely, Brian S; Fritz, Lowell W

    2009-09-01

    Over the past three decades, the decline and altered spatial distribution of the western stock of Steller sea lions (Eumetopias jubatus) in Alaska have been attributed to changes in the distribution or abundance of their prey due to the cumulative effects of fisheries and environmental perturbations. During this period, dietary prey occurrence and diet diversity were related to population decline within metapopulation regions of the western stock of Steller sea lions, suggesting that environmental conditions may be variable among regions. The objective of this study, therefore, was to examine regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions within the context of recent measures of diet diversity and population trajectories. Habitat use was assessed by deploying satellite-depth recorders and satellite relay data loggers on juvenile Steller sea lions (n = 45) over a five-year period (2000-2004) within four regions of the western stock, including the western, central, and eastern Aleutian Islands, and central Gulf of Alaska. Areas used by sea lions during summer months (June, July, and August) were demarcated using satellite telemetry data and characterized by environmental variables (sea surface temperature [SST] and chlorophyll a [chl a]), which possibly serve as proxies for environmental processes or prey. Spatial patterns of SST diversity and Steller sea lion population trends among regions were fairly consistent with trends reported for diet studies, possibly indicating a link between environmental diversity, prey diversity, and distribution or abundance of Steller sea lions. Overall, maximum spatial heterogeneity coupled with minimal temporal variability of SST appeared to be beneficial for Steller sea lions. In contrast, these patterns were not consistent for chl a, and there appeared to be an ecological threshold. Understanding how Steller sea lions respond to measures of environmental

  3. Habitat heterogeneity - biological association relationships in the asphalt volcano, SW Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Escobar, E.; Gaytan, A.

    2007-05-01

    A new class of cold seep, named asphalt volcano, was discovered in the Campeche Knolls region of the southern Gulf of Mexico, supporting chemosynthetic communities alike those lying at similar depth on the Angolan margin and the Barbados Prism suggesting an interesting longitudinal connectivity in the faunal components. The discovery of this novel deep-sea habitat has raised questions about diversity and process dynamics in this novel poorly described milieu. Results from two previous cruises jointly sponsored by German, US and Mexican funding agencies have allowed us to recognize the presence of large densities of background benthic megafauna, mainly represented by sea-cucumbers and galatheid crabs, which occupy diverse habitats in asphalt volcano and feed on microbial assemblages on the asphalt covering extended area. Asphalt displays different degrees of hardness suggesting ongoing activity of asphalt extrusion in the site that is reflected in biological benthic communities in different states succession and complexity. The fresh asphalt and the immediately surrounding soft sediment are colonized by mats of complex microbial assemblages where both background benthic megafauna and chemosynthetic tube worms and mussels aggregate. Our results focus on the diversity of the habitats associated with methane seepage through the example of geological structures in the asphalt volcano considering the small scale with the analysis of the relationships between biological assemblages and habitat heterogeneity assessing the role of the geological structure on biological communities. Bubbling of gas, oil and the content of thermogenic gas and gas hydrate in the asphalt suggests that the asphalt plays an important role as a reservoir of methane in this marginal deep sea.

  4. Beta diversity along environmental gradients: implications of habitat specialization in tropical montane landscapes.

    PubMed

    Jankowski, Jill E; Ciecka, Anna L; Meyer, Nola Y; Rabenold, Kerry N

    2009-03-01

    1. Understanding how species in a diverse regional pool are spatially distributed with respect to habitat types is a longstanding problem in ecology. Tropical species are expected to be specialists along environmental gradients, and this should result in rapid compositional change (high beta diversity) across landscapes, particularly when alpha diversity is a small fraction of regional diversity. Corollary challenges are then to identify controlling environmental variables and to ask whether species cluster into discrete community types along a gradient. 2. We investigated patterns of avian species' distributions in the Tilarán mountains of Costa Rica between 1000 m and 1700 m elevation where a strong moisture gradient exists. High beta diversity was found with both auditory counts adjusted for detectability and extensive capture data, revealing nearly complete change in community composition over a few kilometres on the Pacific slope. As predicted, this beta diversity was roughly twice as high as on temperate mountainsides. 3. Partial Mantel analyses and canonical correspondence analysis indicate that change in species composition is highly correlated with change in moisture (and correlated epiphyte cover) at different distances from the continental divide on the Pacific slope. Altitude was not a good predictor of change in species composition, as species composition varies substantially among sites at the same elevation. 4. Detrended correspondence analysis and cluster analysis revealed a zone of rapid transition separating a distinct cloud forest community from rainshadow forest. On the Caribbean slope, where a shallower moisture gradient was predicted to result in lower beta diversity, we found lower rates of compositional change and more continuous species turnover. 5. Results suggest that habitat specialization of birds is likely a strong ecological force generating high beta diversity in montane landscapes. Despite overall rapid rates of species turnover

  5. Contrasting changes in taxonomic vs. functional diversity of tropical fish communities after habitat degradation.

    PubMed

    Villéger, Sébastien; Ramos Miranda, Julia; Flores Hernández, Domingo; Mouillot, David

    2010-09-01

    Human activities have strong impacts on ecosystem functioning through their effect on abiotic factors and on biodiversity. There is also growing evidence that species functional traits link changes in species composition and shifts in ecosystem processes. Hence, it appears to be of utmost importance to quantify modifications in the functional structure of species communities after human disturbance in addition to changes in taxonomic structure. Despite this fact, there is still little consensus on the actual impacts of human-mediated habitat alteration on the components of biodiversity, which include species functional traits. Therefore, we studied changes in taxonomic diversity (richness and evenness), in functional diversity, and in functional specialization of estuarine fish communities facing drastic environmental and habitat alterations. The Terminos Lagoon (Gulf of Mexico) is a tropical estuary of primary concern for its biodiversity, its habitats, and its resource supply, which have been severely impacted by human activities. Fish communities were sampled in four zones of the Terminos Lagoon 18 years apart (1980 and 1998). Two functions performed by fish (food acquisition and locomotion) were studied through the measurement of 16 functional traits. Functional diversity of fish communities was quantified using three independent components: richness, evenness, and divergence. Additionally, we measured the degree of functional specialization in fish communities. We used a null model to compare the functional and the taxonomic structure of fish communities between 1980 and 1998. Among the four largest zones studied, three did not show strong functional changes. In the northern part of the lagoon, we found an increase in fish richness but a significant decrease of functional divergence and functional specialization. We explain this result by a decline of specialized species (i.e., those with particular combinations of traits), while newly occurring species are

  6. Multispecies coexistence of trees in tropical forests: spatial signals of topographic niche differentiation increase with environmental heterogeneity

    PubMed Central

    Brown, C.; Burslem, D. F. R. P.; Illian, J. B.; Bao, L.; Brockelman, W.; Cao, M.; Chang, L. W.; Dattaraja, H. S.; Davies, S.; Gunatilleke, C. V. S.; Gunatilleke, I. A. U. N.; Huang, J.; Kassim, A. R.; LaFrankie, J. V.; Lian, J.; Lin, L.; Ma, K.; Mi, X.; Nathalang, A.; Noor, S.; Ong, P.; Sukumar, R.; Su, S. H.; Sun, I. F.; Suresh, H. S.; Tan, S.; Thompson, J.; Uriarte, M.; Valencia, R.; Yap, S. L.; Ye, W.; Law, R.

    2013-01-01

    Neutral and niche theories give contrasting explanations for the maintenance of tropical tree species diversity. Both have some empirical support, but methods to disentangle their effects have not yet been developed. We applied a statistical measure of spatial structure to data from 14 large tropical forest plots to test a prediction of niche theory that is incompatible with neutral theory: that species in heterogeneous environments should separate out in space according to their niche preferences. We chose plots across a range of topographic heterogeneity, and tested whether pairwise spatial associations among species were more variable in more heterogeneous sites. We found strong support for this prediction, based on a strong positive relationship between variance in the spatial structure of species pairs and topographic heterogeneity across sites. We interpret this pattern as evidence of pervasive niche differentiation, which increases in importance with increasing environmental heterogeneity. PMID:23782876

  7. Coyotes demonstrate how habitat specialization by individuals of a generalist species can diversify populations in a heterogeneous ecoregion.

    PubMed

    Sacks, Benjamin N; Bannasch, Danika L; Chomel, Bruno B; Ernest, Holly B

    2008-07-01

    The tendency for individuals to disperse into habitat similar to their natal habitat has been observed in a wide range of species, although its population genetic consequences have received little study. Such behavior could lead to discrete habitat-specific population subdivisions even in the absence of physical dispersal barriers or habitat gaps. Previous studies of coyotes have supported this hypothesis in a small region of California, but its evolutionary significance ultimately depends on the extent and magnitude of habitat-specific subdivision. Here, we investigated these questions using autosomal, Y chromosome, and mitochondrial markers and >2,000 coyotes from a broad region, including 2 adjacent ecoregions with contrasting levels of habitat heterogeneity--the California Floristic Province (CFP) (heterogeneous landscape) and the Desert-Prairie ecoregion (DPE) (homogeneous landscape). Consistent with predictions, we found a close correspondence between population genetic structure and habitat subdivisions throughout the CFP and virtual panmixia over the larger DPE. Conversely, although genetic diversity was similar in these 2 ecoregions overall, it was lower within sites of the CFP, as would be the expected consequence of greater genetic drift within subregions. The magnitude of habitat-specific genetic subdivisions (i.e., genetic distance) in the CFP varied considerably, indicating complexity (e.g., asymmetric gene flow or extinction/recolonization), but, in general, was higher than that due to geographic distance or recent human-related barriers. Because habitat-specific structure can enhance a species' adaptive potential and resilience to changing environments, these findings suggest the CFP may constitute an evolutionarily important portion of the range for coyotes and sympatric species exhibiting habitat-specific population structure. PMID:18391065

  8. Response of megabenthic assemblages to different scales of habitat heterogeneity on the Mauritanian slope

    NASA Astrophysics Data System (ADS)

    Jones, Daniel O. B.; Brewer, Michael E.

    2012-09-01

    The topographically complex deep seabed on the Mauritanian slope, from 990 to 1460 m water depth, was imaged with video in an extensive quantitative survey of 17,199 m2 of seafloor using a Remote Operated Vehicle (ROV). This study investigated the influence of habitat heterogeneity at two scales on the megafaunal assemblages observed by ROV. Changes in megafaunal assemblages on the Mauritanian slope were assessed at a broad scale, within depth zones, and at a finer scale, in response to changes in local geomorphology associated with submarine landslides. Geomorphology was determined by classification of habitat parameters (slope, aspect, bathymetric position, curvature, fractal dimension and ruggedness) derived from an autonomous underwater vehicle-based multibeam bathymetry survey. Habitat parameters were classified by Iterative Self Organizing Clustering into six major geomorphological groups, four of which were assessed in the ROV video survey. A total of 29 megafaunal taxa were observed along the entire survey, with an overall average faunal density of 0.344 ind m-2. Megafaunal assemblage density, species richness and evenness varied significantly across the depth range of the survey in the most common geomorphological zone (sedimentary plains of low slope and complexity). Characteristic species inhabited the shallow areas (asteroid, ophiuroid, anemone, small macrourid), intermediate areas (Benthothuria funabris, black cerianthid, squat lobster) and deeper areas (the holothurians Enypniastes eximia and Elipidia echinata). Megafaunal density, species richness and evenness were not significantly different between geomorphogical groups within one depth zone (1300-1400 m). However, the steepest zone, on the edge of a major headwall feature, had four unique taxa (Parapagurus pilosimanus, a comatulid crinoid, a gorgonian and its associated ophiuroid).

  9. Deep-sea habitat heterogeneity influence on meiofaunal communities in the Gulf of Guinea

    NASA Astrophysics Data System (ADS)

    Van Gaever, Saskia; Galéron, Joëlle; Sibuet, Myriam; Vanreusel, Ann

    2009-12-01

    To estimate the degree of spatial heterogeneity of benthic deep-sea communities, we carried out a multiple-scale (from m's to 200 km) investigation in the Congo-Angola margins (Equatorial West African margin, 3150-4800 m) in which we examined the metazoan meiofauna at a variety of habitats along the Congo Channel system and in the associated cold seep. We investigate the structure, density, vertical distribution patterns in the sediment and biomass of meiofaunal communities in the Gulf of Guinea and how they are controlled by hydrologic and biogeochemical processes. The meiofaunal communities in the Gulf of Guinea were shaped by heterogeneous conditions on the margin, and reflect the multiple-scale spatial variability that corresponds with the different identified habitats. The two control sites, located at >100 km away from the canyon, were inhabited by very dense and the most diverse meiobenthic communities. Similar meiobenthic communities inhabited the transition zone between the canyon and the cold seep. Sites located along the Congo Channel were obviously affected by the local high-velocity bottom currents and unstable sedimentary conditions in this active submarine system. Extremely low meiobenthic densities and very low proportions in the most surficial sediment layers provided evidence for recently highly disturbed sediments at these sites. The remote operated vehicle (ROV) Victor 6000 provided images of the cold seep, showing a patchy distribution of several types of patchy distributed megafaunal communities dominated by three key symbiotic taxa (Mytilidae, Vesicomyidae and Siboglinidae). These cold seep sediments were colonised by a unique meiobenthic community, characterised by a high small-scale (m's) patchiness, low species richness and the prominent dominance of two large-sized nematode species: Sabatieria mortenseni, which is a cosmopolitan nematode known from littoral habitats, and an undescribed Desmodora species. The high individual body weight of

  10. Birds and butterflies respond to soil-induced habitat heterogeneity in experimental plantings of tallgrass prairie species managed as agroenergy feedstocks in Iowa, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The positive association between habitat heterogeneity and species diversity has been well-documented for many taxa at various spatial and temporal scales, and the maintenance of habitat heterogeneity in agricultural landscapes has been promoted as a key strategy in efforts to conserve biodiversity....

  11. Influence of habitat heterogeneity on the distribution of larval Pacific lamprey (Lampetra tridentata) at two spatial scales

    USGS Publications Warehouse

    Torgersen, Christian E.; Close, David A.

    2004-01-01

    1. Spatial patterns in channel morphology and substratum composition at small (1a??10 metres) and large scales (1a??10 kilometres) were analysed to determine the influence of habitat heterogeneity on the distribution and abundance of larval lamprey. 2. We used a nested sampling design and multiple logistic regression to evaluate spatial heterogeneity in the abundance of larval Pacific lamprey, Lampetra tridentata, and habitat in 30 sites (each composed of twelve 1-m2 quadrat samples) distributed throughout a 55-km section of the Middle Fork John Day River, OR, U.SA. Statistical models predicting the relative abundance of larvae both among sites (large scale) and among samples (small scale) were ranked using Akaike's Information Criterion (AIC) to identify the 'best approximating' models from a set of a priori candidate models determined from the literature on larval lamprey habitat associations. 3. Stream habitat variables predicted patterns in larval abundance but played different roles at different spatial scales. The abundance of larvae at large scales was positively associated with water depth and open riparian canopy, whereas patchiness in larval occurrence at small scales was associated with low water velocity, channel-unit morphology (pool habitats), and the availability of habitat suitable for burrowing. 4. Habitat variables explained variation in larval abundance at large and small scales, but locational factors, such as longitudinal position (river km) and sample location within the channel unit, explained additional variation in the logistic regression model. The results emphasise the need for spatially explicit analysis, both in examining fish habitat relationships and in developing conservation plans for declining fish populations.

  12. Satellite-based remote sensing of running water habitats at large riverscape scales: Tools to analyze habitat heterogeneity for river ecosystem management

    NASA Astrophysics Data System (ADS)

    Hugue, F.; Lapointe, M.; Eaton, B. C.; Lepoutre, A.

    2016-01-01

    We illustrate an approach to quantify patterns in hydraulic habitat composition and local heterogeneity applicable at low cost over very large river extents, with selectable reach window scales. Ongoing developments in remote sensing and geographical information science massively improve efficiencies in analyzing earth surface features. With the development of new satellite sensors and drone platforms and with the lowered cost of high resolution multispectral imagery, fluvial geomorphology is experiencing a revolution in mapping streams at high resolution. Exploiting the power of aerial or satellite imagery is particularly useful in a riverscape research framework (Fausch et al., 2002), where high resolution sampling of fluvial features and very large coverage extents are needed. This study presents a satellite remote sensing method that requires very limited field calibration data to estimate over various scales ranging from 1 m to many tens or river kilometers (i) spatial composition metrics for key hydraulic mesohabitat types and (ii) reach-scale wetted habitat heterogeneity indices such as the hydromorphological index of diversity (HMID). When the purpose is hydraulic habitat characterization applied over long river networks, the proposed method (although less accurate) is much less computationally expensive and less data demanding than two dimensional computational fluid dynamics (CFD). Here, we illustrate the tools based on a Worldview 2 satellite image of the Kiamika River, near Mont Laurier, Quebec, Canada, specifically over a 17-km river reach below the Kiamika dam. In the first step, a high resolution water depth (D) map is produced from a spectral band ratio (calculated from the multispectral image), calibrated with limited field measurements. Next, based only on known river discharge and estimated cross section depths at time of image capture, empirical-based pseudo-2D hydraulic rules are used to rapidly generate a two-dimensional map of flow velocity

  13. Field hydration state varies among tropical frog species with different habitat use.

    PubMed

    Tracy, Christopher R; Tixier, Thomas; Le Nöene, Camille; Christian, Keith A

    2014-01-01

    We have previously shown that ecological habit (e.g., arboreal, terrestrial, amphibious) correlates with thermoregulatory behaviors and water balance physiology among species of hylid frogs in northern Australia. We hypothesized that these frogs would be different with respect to their field hydration states because of the challenges associated with the different ecological habits. There are very few data on the hydration levels that frogs maintain in the field, and the existing data are from disparate species and locations and do not relate hydration state to habit or changes in seasonal water availability. We measured the hydration state of 15 species of frogs from tropical northern Australia to determine the influences of ecological habit and season on the hydration state that these frogs maintain. As predicted, frogs were significantly less hydrated in the dry season than they were in the wet season and showed significantly higher variation among individuals, suggesting that maintaining hydration is more challenging in the dry season. In the wet season, terrestrial species were significantly less hydrated than arboreal or amphibious species. During the dry season, amphibious species that sought refuge in cracking mud after the pond dried were significantly less hydrated than terrestrial or arboreal species. These data suggest that hydration behaviors and voluntary tolerance of dehydration vary with habitat use, even within closely related species in the same family or genus. Terrestrial and arboreal species might be expected to be the most vulnerable to changes in water availability, because they are somewhat removed from water sources, but the physiological characteristics of arboreal frogs that result in significant cutaneous resistance to water loss allow them to reduce the effects of their dehydrating microenvironment. PMID:24642537

  14. Ecomorphology, differentiated habitat use, and nocturnal activities of Rhinolophus and Hipposideros species in East Asian tropical forests.

    PubMed

    Lee, Ya-Fu; Kuo, Yen-Min; Chu, Wen-Chen; Lin, Yu-Hsiu; Chang, Hsing-Yi; Chen, Wei-Ming

    2012-02-01

    We investigated the wing morphology and foraging distributions of sympatric Rhinolophus and Hipposideros species by acoustic sampling, measuring wing parameters, and observing bats in different settings of tropical East Asian forests, to evaluate their flexibility in habitat use and edge sensitivity. R. formosae and H. terasensis were more abundant at edges/in open habitats and shared the highest overlap, with R. formosae displaying the greatest breadth in habitat use, whereas R. monoceros had a higher abundance and feeding efficiency in forest interiors with a continuous canopy. H. terasensis was significantly larger and had higher wing loading and aspect ratio than R. formosae and R. monoceros, while R. formosae had higher wing loading but a lower aspect ratio than the smaller-sized R. monoceros. Shrubs and herbs were higher at sites where bats were captured than at those without bat captures, and R. monoceros and R. formosae were associated with greater canopy and ground coverage, respectively. R. monoceros always foraged while flying at lower heights close to the herb/shrub layers, while H. terasensis and R. formosae used perching to different extents, with R. formosae preferably using fly-catching techniques and appearing farther from the path in open forests rather than in forest interiors. Our results indicate that differences in wing parameters account for the different degrees of flexibility in habitat use, yet the deviations of call frequency from the expected values in R. formosae and H. terasensis suggest additional adaptations accounting for their flexibility in exploring habitats. PMID:22230387

  15. High Bee and Wasp Diversity in a Heterogeneous Tropical Farming System Compared to Protected Forest

    PubMed Central

    Schüepp, Christof; Rittiner, Sarah; Entling, Martin H.

    2012-01-01

    It is a globally important challenge to meet increasing demands for resources and, at the same time, protect biodiversity and ecosystem services. Farming is usually regarded as a major threat to biodiversity due to its expansion into natural areas. We compared biodiversity of bees and wasps between heterogeneous small-scale farming areas and protected forest in northern coastal Belize, Central America. Malaise traps operated for three months during the transition from wet to dry season. Farming areas consisted of a mosaic of mixed crop types, open habitat, secondary forest, and agroforestry. Mean species richness per site (alpha diversity), as well as spatial and temporal community variation (beta diversity) of bees and wasps were equal or higher in farming areas compared to protected forest. The higher species richness and community variation in farmland was due to additional species that did not occur in the forest, whereas most species trapped in forest were also found in farming areas. The overall regional species richness (gamma diversity) increased by 70% with the inclusion of farming areas. Our results suggest that small-scale farming systems adjacent to protected forest may not only conserve, but even favour, biodiversity of some taxonomic groups. We can, however, not exclude possible declines of bee and wasp diversity in more intensified farmland or in landscapes completely covered by heterogeneous farming systems. PMID:23300598

  16. Diversity in skeletal architecture influences biological heterogeneity and Symbiodinium habitat in corals.

    PubMed

    Yost, Denise M; Wang, Li-Hsueh; Fan, Tung-Yung; Chen, Chii-Shiarng; Lee, Raymond W; Sogin, Emilia; Gates, Ruth D

    2013-10-01

    Scleractinian corals vary in response to rapid shifts in the marine environment and changes in reef community structure post-disturbance reveal a clear relationship between coral performance and morphology. With exceptions, massive corals are thought to be more tolerant and branching corals more vulnerable to changing environmental conditions, notably thermal stress. The typical responses of massive and branching coral taxa, respectively, are well documented; however, the biological and functional characteristics that underpin this variation are not well understood. We address this gap by comparing multiple biological attributes that are correlated with skeletal architecture in two perforate (having porous skeletal matrices with intercalating tissues) and two imperforate coral species (Montipora aequituberculata, Porites lobata, Pocillopora damicornis, and Seriatopora hystrix) representing three morphotypes. Our results reveal inherent biological heterogeneity among corals and the potential for perforate skeletons to create complex, three-dimensional internal habitats that impact the dynamics of the symbiosis. Patterns of tissue thickness are correlated with the concentration of symbionts within narrow regions of tissue in imperforate corals versus broad distribution throughout the larger tissue area in perforate corals. Attributes of the perforate and environmentally tolerant P. lobata were notable, with tissues ∼5 times thicker than in the sensitive, imperforate species P. damicornis and S. hystrix. Additionally, P. lobata had the lowest baseline levels of superoxide and Symbiodinium that provisioned high levels of energy. Given our observations, we hypothesize that the complexity of the visually obscured internal environment has an impact on host-symbiont dynamics and ultimately on survival, warranting further scientific investigation. PMID:23992772

  17. Combining Methods to Describe Important Marine Habitats for Top Predators: Application to Identify Biological Hotspots in Tropical Waters

    PubMed Central

    Thiers, Laurie; Louzao, Maite; Ridoux, Vincent; Le Corre, Matthieu; Jaquemet, Sébastien; Weimerskirch, Henri

    2014-01-01

    In tropical waters resources are usually scarce and patchy, and predatory species generally show specific adaptations for foraging. Tropical seabirds often forage in association with sub-surface predators that create feeding opportunities by bringing prey close to the surface, and the birds often aggregate in large multispecific flocks. Here we hypothesize that frigatebirds, a tropical seabird adapted to foraging with low energetic costs, could be a good predictor of the distribution of their associated predatory species, including other seabirds (e.g. boobies, terns) and subsurface predators (e.g., dolphins, tunas). To test this hypothesis, we compared distribution patterns of marine predators in the Mozambique Channel based on a long-term dataset of both vessel- and aerial surveys, as well as tracking data of frigatebirds. By developing species distribution models (SDMs), we identified key marine areas for tropical predators in relation to contemporaneous oceanographic features to investigate multi-species spatial overlap areas and identify predator hotspots in the Mozambique Channel. SDMs reasonably matched observed patterns and both static (e.g. bathymetry) and dynamic (e.g. Chlorophyll a concentration and sea surface temperature) factors were important explaining predator distribution patterns. We found that the distribution of frigatebirds included the distributions of the associated species. The central part of the channel appeared to be the best habitat for the four groups of species considered in this study (frigatebirds, brown terns, boobies and sub-surface predators). PMID:25494047

  18. Population and habitat dynamics of the white-footed mouse (Peromyscus leucopus) in a heterogeneous forest

    SciTech Connect

    Ormiston, B.G.

    1984-07-01

    Movements and demography of white-footed mice (Peromyscus leucopus) were determined by live-trapping and radiotelemetry in contiguous upland and lowland forest habitat to assess the extent of variation in local habitat distribution due to season, age, and sex factors. Mice were marked and recaptured monthly in 1980 and 1981 from April through December on a continuous 20 ha trapping grid, thus yielding 1486 captures of 397 individuals. Locations and activity of 43 mice were determined by radiotracking. Various measures of habitat suitability, including adult density, sex ratio, reproduction, persistence, home range size, and immigration, indicated a seasonal cycle of habitat suitability. Upland habitat appeared better for overwintering, and lowland habitat was superior relative to the upland from June through October. Tendencies for breeding females to be restricted to lowland, and for lowland males to display greater mean body weights and smaller home range sizes than upland males, were attributed to greater food availability in the lowland over this period. Individual P. leucopus use local habitats opportunistically, but variations in habitat distribution between the age- and sex-classes of the population noted during the breeding season suggest that local habitats provide a spatial framework for behavioral population regulation in P. leucopus. 49 references, 5 figures, 10 tables.

  19. Do Epigeal Termite Mounds Increase the Diversity of Plant Habitats in a Tropical Rain Forest in Peninsular Malaysia?

    PubMed Central

    Beaudrot, Lydia; Du, Yanjun; Rahman Kassim, Abdul; Rejmánek, Marcel; Harrison, Rhett D.

    2011-01-01

    The extent to which environmental heterogeneity can account for tree species coexistence in diverse ecosystems, such as tropical rainforests, is hotly debated, although the importance of spatial variability in contributing to species co-existence is well recognized. Termites contribute to the micro-topographical and nutrient spatial heterogeneity of tropical forests. We therefore investigated whether epigeal termite mounds could contribute to the coexistence of plant species within a 50 ha plot at Pasoh Forest Reserve, Malaysia. Overall, stem density was significantly higher on mounds than in their immediate surroundings, but tree species diversity was significantly lower. Canonical correspondence analysis showed that location on or off mounds significantly influenced species distribution when stems were characterized by basal area. Like studies of termite mounds in other ecosystems, our results suggest that epigeal termite mounds provide a specific microhabitat for the enhanced growth and survival of certain species in these species-rich tropical forests. However, the extent to which epigeal termite mounds facilitate species coexistence warrants further investigation. PMID:21625558

  20. Understanding spatial heterogeneity in soil carbon and nitrogen cycling in regenerating tropical dry forests

    NASA Astrophysics Data System (ADS)

    Waring, B. G.; Powers, J. S.; Branco, S.; Adams, R.; Schilling, E.

    2015-12-01

    Tropical dry forests (TDFs) currently store significant amounts of carbon in their biomass and soils, but these highly seasonal ecosystems may be uniquely sensitive to altered climates. The ability to quantitatively predict C cycling in TDFs under global change is constrained by tremendous spatial heterogeneity in soil parent material, land-use history, and plant community composition. To explore this variation, we examined soil carbon and nitrogen dynamics in 18 permanent plots spanning orthogonal gradients of stand age and soil fertility. Soil C and N pools, microbial biomass, and microbial extracellular enzyme activities were most variable at small (m2) spatial scales. However, the ratio of organic vs. inorganic N cycling was consistently higher in forest stands dominated by slow-growing, evergreen trees that associate with ectomycorrhizal fungi. Similarly, although bulk litter stocks and turnover rates varied greatly among plots, litter decomposition tended to be slower in ectomycorrhizae-dominated stands. Soil N cycling tended to be more conservative in older plots, although the relationship between stand age and element cycling was weak. Our results emphasize that microscale processes, particularly interactions between mycorrhizal fungi and free-living decomposers, are important controls on ecosystem-scale element cycling.

  1. Does habitat heterogeneity in a multi-use landscape influence survival rates and density of a native mesocarnivore?

    PubMed

    Gese, Eric M; Thompson, Craig M

    2014-01-01

    The relationships between predators, prey, and habitat have long been of interest to applied and basic ecologists. As a native Great Plains mesocarnivore of North America, swift foxes (Vulpes velox) depended on the historic disturbance regime to maintain open grassland habitat. With a decline in native grasslands and subsequent impacts to prairie specialists, notably the swift fox, understanding the influence of habitat on native predators is paramount to future management efforts. From 2001 to 2004, we investigated the influence of vegetation structure on swift fox population ecology (survival and density) on and around the Piñon Canyon Maneuver Site, southeastern Colorado, USA. We monitored 109 foxes on 6 study sites exposed to 3 different disturbance regimes (military training, grazing, unused). On each site we evaluated vegetation structure based on shrub density, basal coverage, vegetation height, and litter. Across all sites, annual fox survival rates ranged from 0.50 to 0.92 for adults and 0.27 to 0.78 for juveniles. Among sites, population estimates ranged from 1 to 7 foxes per 10 km transect. Fox density or survival was not related to the relative abundance of prey. A robust model estimating fox population size and incorporating both shrub density and percent basal cover as explanatory variables far outperformed all other models. Our results supported the idea that, in our region, swift foxes were shortgrass prairie specialists and also indicated a relationship between habitat quality and landscape heterogeneity. We suggest the regulation of swift fox populations may be based on habitat quality through landscape-mediated survival, and managers may effectively use disturbance regimes to create or maintain habitat for this native mesocarnivore. PMID:24963713

  2. Balancing Energy Budget in a Central-Place Forager: Which Habitat to Select in a Heterogeneous Environment?

    PubMed Central

    Patenaude-Monette, Martin; Bélisle, Marc; Giroux, Jean-François

    2014-01-01

    Foraging animals are influenced by the distribution of food resources and predation risk that both vary in space and time. These constraints likely shape trade-offs involving time, energy, nutrition, and predator avoidance leading to a sequence of locations visited by individuals. According to the marginal-value theorem (MVT), a central-place forager must either increase load size or energy content when foraging farther from their central place. Although such a decision rule has the potential to shape movement and habitat selection patterns, few studies have addressed the mechanisms underlying habitat use at the landscape scale. Our objective was therefore to determine how Ring-billed gulls (Larus delawarensis) select their foraging habitats while nesting in a colony located in a heterogeneous landscape. Based on locations obtained by fine-scale GPS tracking, we used resource selection functions (RSFs) and residence time analyses to identify habitats selected by gulls for foraging during the incubation and brood rearing periods. We then combined this information to gull survey data, feeding rates, stomach contents, and calorimetric analyses to assess potential trade-offs. Throughout the breeding season, gulls selected landfills and transhipment sites that provided higher mean energy intake than agricultural lands or riparian habitats. They used landfills located farther from the colony where no deterrence program had been implemented but avoided those located closer where deterrence measures took place. On the other hand, gulls selected intensively cultured lands located relatively close to the colony during incubation. The number of gulls was then greater in fields covered by bare soil and peaked during soil preparation and seed sowing, which greatly increase food availability. Breeding Ring-billed gulls thus select habitats according to both their foraging profitability and distance from their nest while accounting for predation risk. This supports the

  3. Predictions and retrodictions of the hierarchical representation of habitat in heterogeneous environments

    USGS Publications Warehouse

    Kolasa, Jurek; Allen, Craig R.; Sendzimir, Jan; Stow, Craig A.

    2012-01-01

    Interaction between habitat and species is central in ecology. Habitat structure may be conceived as being hierarchical, where larger, more diverse, portions or categories contain smaller, more homogeneous portions. When this conceptualization is combined with the observation that species have different abilities to relate to portions of the habitat that differ in their characteristics, a number of known patterns can be derived and new patterns hypothesized. We propose a quantitative form of this habitat–species relationship by considering species abundance to be a function of habitat specialization, habitat fragmentation, amount of habitat, and adult body mass. The model reproduces and explains patterns such as variation in rank–abundance curves, greater variation and extinction probabilities of habitat specialists, discontinuities in traits (abundance, ecological range, pattern of variation, body size) among species sharing a community or area, and triangular distribution of body sizes, among others. The model has affinities to Holling's textural discontinuity hypothesis and metacommunity theory but differs from both by offering a more general perspective. In support of the model, we illustrate its general potential to capture and explain several empirical observations that historically have been treated independently.

  4. Do ridge habitats contribute to pteridophyte diversity in tropical montane forests? A case study from southeastern Ecuador.

    PubMed

    Kessler, Michael; Lehnert, Marcus

    2009-07-01

    We address the question to which degree ridge habitats in tropical montane forests contribute to overall plant diversity by analysing patterns of pteridophyte (i.e. lycophytes and ferns) assemblages on ridges and slopes in three montane forest sites near Podocarpus National Park, Ecuador. The analyses, which involved 158 pteridophyte species (110 terrestrial, 96 epiphytic, 48 both) from 28 plots of 20 m x 20 m (or an equivalent of 400 m(2)), showed that more species were typical of one of the three study sites than of one of the two habitats (ridge/slope). As found in previous studies, alpha diversity on ridges was lower than on slopes, accounted for by the absence of numerous species that are found on slopes. Pteridophyte assemblages on ridges were more similar across study sites than those on slopes. Thus, unlike the structurally comparable (i.e. stunted, open) Amazonian forests, the studied montane ridge forests harbour fairly homogenous pteridophytes assemblages with very few specialised species. Our study implies that slope forests are of higher conservation priority for pteridophytes in the study region than ridge habitats. However, comparative studies are needed because other geographical regions and other groups of organisms may not share this pattern. PMID:19373521

  5. Habitat Fragmentation and Ecological Traits Influence the Prevalence of Avian Blood Parasites in a Tropical Rainforest Landscape

    PubMed Central

    Laurance, Susan G. W.; Jones, Dean; Westcott, David; Mckeown, Adam; Harrington, Graham; Hilbert, David W.

    2013-01-01

    In the tropical rainforests of northern Australia, we investigated the effects of habitat fragmentation and ecological parameters on the prevalence of blood-borne parasites (Plasmodium and Haemoproteus) in bird communities. Using mist-nets on forest edges and interiors, we sampled bird communities across six study sites: 3 large fragments (20–85 ha) and 3 continuous-forest sites. From 335 mist-net captures, we recorded 28 bird species and screened 299 bird samples with PCR to amplify and detect target DNA. Of the 28 bird species sampled, 19 were infected with Plasmodium and/or Haemoproteus and 9 species were without infection. Over one third of screened birds (99 individuals) were positive for Haemoproteus and/or Plasmodium. In forest fragments, bird capture rates were significantly higher than in continuous forests, but bird species richness did not differ. Unexpectedly, we found that the prevalence of the dominant haemosporidian infection, Haemoproteus, was significantly higher in continuous forest than in habitat fragments. Further, we found that ecological traits such as diet, foraging height, habitat specialisation and distributional ranges were significantly associated with blood-borne infections. PMID:24124541

  6. Consistent trophic patterns among fishes in lagoon and channel habitats of a tropical floodplain river: Evidence from stable isotopes

    NASA Astrophysics Data System (ADS)

    Roach, Katherine A.; Winemiller, Kirk O.; Layman, Craig A.; Zeug, Steven C.

    2009-07-01

    The relationship between food web dynamics and hydrological connectivity in rivers should be strongly influenced by annual flood pulses that affect primary production dynamics and movement of organic matter and consumer taxa. We sampled basal production sources and fishes from connected lagoons and the main channel of a low-gradient, floodplain river within the Orinoco River Basin in Venezuela. Stable isotope analysis was used to model the contribution of four basal production sources to fishes, and to examine patterns of mean trophic position during the falling-water period of the annual flood cycle. IsoSource, a multi-source mixing model, indicated that proportional contributions from production sources to fish assemblages were similar in lagoons and the main channel. Although distributions differed, the means for trophic positions of fish assemblages as well as individual species were similar between the two habitats. These findings contradict recent food web studies conducted in temperate floodplain rivers that described significant differences in trophic positions of fishes from slackwater and floodplain versus main channel habitats. Low between-habitat trophic variation in this tropical river probably results from an extended annual flood pulse (ca. 5 mo.) that allows mixing of sestonic and allochthonous basal production sources and extensive lateral movements of fishes throughout the riverscape.

  7. Stage-dependent responses to emergent habitat heterogeneity: consequences for a predatory insect population in a coffee agroecosystem

    PubMed Central

    Liere, Heidi; Perfecto, Ivette; Vandermeer, John

    2014-01-01

    Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community, and this heterogeneity might be crucial for their persistence. For example, stage-dependent vulnerability of a predatory lady beetle to aggression of the ant, Azteca instabilis, creates two habitat types that are utilized differently by the immature and adult life stages of the beetle. Due to a mutualistic association between A. instabilis and the hemipteran Coccus viridis – which is A. orbigera main prey in the area – only plants around ant nests have high C. viridis populations. Here, we report on a series of surveys at three different scales aimed at detecting how the presence and clustered distribution of ant nests affect the distribution of the different life stages of this predatory lady beetle in a coffee farm in Chiapas, Mexico. Both beetle adults and larvae were more abundant in areas with ant nests, but adults were restricted to the peripheries of highest ant activity and outside the reach of coffee bushes containing the highest densities of lady beetle larvae. The abundance of adult beetles located around trees with ants increased with the size of the ant nest clusters but the relationship is not significant for larvae. Thus, we suggest that A. orbigera undergoes an ontogenetic niche shift, not through shifting prey species, but through stage-specific vulnerability differences against a competitor that renders areas of abundant prey populations inaccessible for adults but not for larvae. Together with evidence presented elsewhere, this study shows how an important predator is not only dependent on the existence of two qualitatively distinct habitat types, but also on the spatial distribution of these habitats. We suggest that this dependency arises due to the different responses that the predator's life stages have to this emergent spatial pattern. PMID:25473473

  8. Indo-Pacific bottlenose dolphin (Tursiops aduncus) habitat preference in a heterogeneous, urban, coastal environment

    PubMed Central

    2013-01-01

    Background Limited information is available regarding the habitat preference of the Indo-Pacific bottlenose dolphin (Tursiops aduncus) in South Australian estuarine environments. The need to overcome this paucity of information is crucial for management and conservation initiatives. This preliminary study investigates the space-time patterns of habitat preference by the Indo-Pacific bottlenose dolphin in the Port Adelaide River-Barker Inlet estuary, a South Australian, urbanised, coastal environment. More specifically, the study aim was to identify a potential preference between bare sand substrate and seagrass beds, the two habitat types present in this environment, through the resighting frequency of recognisable individual dolphins. Results Photo-identification surveys covering the 118 km2 sanctuary area were conducted over 2 survey periods May to August 2006 and from March 2009 to February 2010. Sighting frequency of recognisable individual Indo-Pacific bottlenose dolphins established a significant preference for the bare sand habitat. More specifically, 72 and 18% of the individuals sighted at least on two occasions were observed in the bare sand and seagrass habitats respectively. This trend was consistently observed at both seasonal and annual scales, suggesting a consistency in the distinct use of these two habitats. Conclusions It is anticipated that these results will benefit the further development of management and conservation strategies. PMID:23369354

  9. Effects of habitat heterogeneity at multiple spatial scales on fish community assembly.

    PubMed

    Yeager, Lauren A; Layman, Craig A; Allgeier, Jacob E

    2011-09-01

    Habitat variability at multiple spatial scales may affect community structure within a given habitat patch, even within seemingly homogenous landscapes. In this context, we tested the importance of habitat variables at two spatial scales (patch and landscape) in driving fish community assembly using experimental artificial reefs constructed across a gradient of seagrass cover in a coastal bay of The Bahamas. We found that species richness and benthic fish abundance increased over time, but eventually reached an asymptote. The correlation between habitat variables and community structure strengthened over time, suggesting deterministic processes were detectable in community assembly. Abundance of benthic fishes, as well as overall community structure, were predicted by both patch- and landscape-scale variables, with the cover of seagrass at the landscape-scale emerging as the most important explanatory variable. Results of this study indicate that landscape features can drive differences in community assembly even within a general habitat type (i.e., within seagrass beds). A primary implication of this finding is that human activities driving changes in seagrass cover may cause significant shifts in faunal community structure well before complete losses of seagrass habitat. PMID:21409448

  10. Settlement of a Tropical Marine Epibenthic Assemblage on Artificial Panels: Influence of Substratum Heterogeneity and Complexity Scales

    NASA Astrophysics Data System (ADS)

    Pech, D.; Ardisson, P.-L.; Bourget, E.

    2002-11-01

    The influence of substratum topographic heterogeneity and complexity on the settlement of a tropical epibenthic subtidal assemblage was examined using artificial substrata offering a combination of different heterogeneity scales. A 4 week experiment was carried out in March 1999 using eight types of dark grey polyvinylchloride (PVC) panels immersed at middle depth (2 m) in the water column and arranged in the field according to a Latin square design (n=64). Four heterogeneity scales (0, 1, 10, 100 mm) and complexity (the hierarchical combination of those scales: 0+1+10, 0+1+100, 0+10+100, 0+1+10+100 mm) were used. Results show that total abundance of settlers was significantly influenced by the heterogeneity (P<0·01) and complexity (P<0·01) of substratum. Abundance was higher on panels with intermediate orders of complexity (2nd and 3rd), combining 0 and 1 mm, and 0, 1 and 10 mm scales of heterogeneity. Larvae settled more on protected (grooves) than on exposed surfaces. The choice made by larvae for particular scales of heterogeneity and orders of complexity are discussed in the light of available evidence from similar field and laboratory experiments conducted in subarctic and temperate environments.

  11. The use of invertebrates to detect small-scale habitat heterogeneity and its application to restoration practices.

    PubMed

    Pik, Anthony J; Dangerfield, J M; Bramble, Roger A; Angus, Craig; Nipperess, David A

    2002-04-01

    Recent conceptual and technological solutions to biodiversity assessment allow large numbers of invertebrate specimens to be processed rapidly and provide researchers and practitioners with a unique tool for characterizing habitats. One application of these advances is the ability to detect and monitor small-scale habitat heterogeneity and so provide a measure of ecosystem restoration. This case study presents a test of the efficacy of using invertebrates to assess and monitor ecological restoration following bush regeneration. Eight contiguous habitat patches within a suburb of northern Sydney, Australia, were selected to represent areas that had undergone different bush regeneration techniques. A nearby and relatively undisturbed area of bushland was also sampled. A total of 57,806 ground-active invertebrate specimens from 35 different orders were collected in pitfall traps. 1,246 ant (Formicidae) specimens were further sorted into 46 ant morphospecies from 20 genera. Analyses of the three taxonomic data sets, including two different data transformations, demonstrated that: (i) invertebrate communities successfully characterized different sites, providing a high degree of differentiation among sites; (ii) ordinations of the sites allowed visual assessment of the impact of each management technique on the habitat relative to undisturbed habitats; and (iii) characterization of sites could be achieved using abundance classes or binary counts of ant morphospecies, representing potential cost and time savings. The project duration was a total of three person weeks and cost less than US$3,000 (1999 prices) to complete. Measurement of invertebrate assemblages will provide a tool for both rapid assessment of management decisions and a means by which to implement adaptive management and restoration. PMID:12002286

  12. Floral resources and habitat affect the composition of hummingbirds at the local scale in tropical mountaintops.

    PubMed

    Rodrigues, L C; Rodrigues, M

    2015-01-01

    Hummingbird communities tend to respond to variation in resources, having a positive relationship between abundance and diversity of food resources and the abundance and/or diversity of hummingbirds. Here we examined the influence of floral resource availability, as well as seasonality and type of habitat on the composition of hummingbird species. The study was carried out in two habitats of eastern Brazilian mountaintops. A gradient representative of the structure of hummingbird community, based on species composition, was obtained by the ordination of samples using the method of non-metric multidimensional scaling. The composition of hummingbird species was influenced by the type of habitat and floral resource availability, but not by seasonality. Hummingbird communities differ between habitats mainly due to the relative abundance of hummingbird species. The variation in composition of hummingbird species with the variation in floral resource availability may be related to differences in feeding habits of hummingbirds. Hummingbird species with the longest bills visited higher proportions of ornithophilous species, while hummingbirds with shorter bills visited higher proportions of non-ornithophilous species. The results demonstrate that at local-scale the composition of hummingbird species is affected by the type of habitat and floral resources availability, but not by seasonality. PMID:25945619

  13. Three-dimensional distribution of larval fish habitats in the shallow oxygen minimum zone in the eastern tropical Pacific Ocean off Mexico

    NASA Astrophysics Data System (ADS)

    Davies, S. M.; Sánchez-Velasco, L.; Beier, E.; Godínez, Victor M.; Barton, Eric D.; Tamayo, A.

    2015-07-01

    Three-dimensional distribution of larval fish habitats was analyzed, from the upper limit of the shallow oxygen minimum zone (~0.2 mL/L) to the sea surface, in the eastern tropical Pacific Ocean off Mexico in February 2010. The upper limit rises from ~250 m depth in the entrance of the Gulf of California to ~80 m depth off Cabo Corrientes. Three larval fish habitats were defined statistically: (i) a Gulf of California habitat dominated by Anchoa spp. larvae (epipelagic species), constrained to the oxygenated surface layer (>3.5 mL/L) in and above the thermocline (~60 m depth), and separated by a salinity front from the Tropical Pacific habitat; (ii) a Tropical Pacific habitat, dominated by Vinciguerria lucetia larvae (mesopelagic species), located throughout the sampled water column, but with the highest abundance in the oxygenated upper layer above the thermocline; (iii) an Oxygen Minimum habitat defined mostly below the thermocline in hypoxic (<1 mL/L; ~70 m depth) and anoxic (<0.2 mL/L; ~80 m depth) water off Cabo Corrientes. This subsurface hypoxic habitat had the highest species richness and larval abundance, with dominance of Bregmaceros bathymaster, an endemic neritic pelagic species; which was an unexpected result. This may be associated with the shoaling of the upper limit of the shallow oxygen minimum zone near the coast, a result of the strong costal upwelling detected by the Bakun Index. In this region of strong and semi-continuous coastal upwelling in the eastern tropical Pacific off Mexico, the shallow hypoxic water does not have dramatic effects on the total larval fish abundance but appears to affect species composition.

  14. Thermal niche predicts tolerance to habitat conversion in tropical amphibians and reptiles.

    PubMed

    Frishkoff, Luke O; Hadly, Elizabeth A; Daily, Gretchen C

    2015-11-01

    Habitat conversion is a major driver of the biodiversity crisis, yet why some species undergo local extinction while others thrive under novel conditions remains unclear. We suggest that focusing on species' niches, rather than traits, may provide the predictive power needed to forecast biodiversity change. We first examine two Neotropical frog congeners with drastically different affinities to deforestation and document how thermal niche explains deforestation tolerance. The more deforestation-tolerant species is associated with warmer macroclimates across Costa Rica, and warmer microclimates within landscapes. Further, in laboratory experiments, the more deforestation-tolerant species has critical thermal limits, and a jumping performance optimum, shifted ~2 °C warmer than those of the more forest-affiliated species, corresponding to the ~3 °C difference in daytime maximum temperature that these species experience between habitats. Crucially, neither species strictly specializes on either habitat - instead habitat use is governed by regional environmental temperature. Both species track temperature along an elevational gradient, and shift their habitat use from cooler forest at lower elevations to warmer deforested pastures upslope. To generalize these conclusions, we expand our analysis to the entire mid-elevational herpetological community of southern Costa Rica. We assess the climatological affinities of 33 amphibian and reptile species, showing that across both taxonomic classes, thermal niche predicts presence in deforested habitat as well as or better than many commonly used traits. These data suggest that warm-adapted species carry a significant survival advantage amidst the synergistic impacts of land-use conversion and climate change. PMID:26148337

  15. Predicting Impacts of tropical cyclones and sea-Level rise on beach mouse habitat

    USGS Publications Warehouse

    Chen, Qin; Wang, Hongqing; Wang, Lixia; Tawes, Robert; Rollman, Drew

    2014-01-01

    Alabama beach mouse (ABM) (Peromyscus polionotus ammobates) is an important component of the coastal dune ecosystem along the Gulf of Mexico. Due to habitat loss and degradation, ABM is federally listed as an endangered species. In this study, we examined the impacts of storm surge and wind waves, which are induced by hurricanes and sea-level rise (SLR), on the ABM habitat on Fort Morgan Peninsula, Alabama, using advanced storm surge and wind wave models and spatial analysis tools in geographic information systems (GIS). Statistical analyses of the long-term historical data enabled us to predict the extreme values of winds, wind waves, and water levels in the study area at different return periods. We developed a series of nested domains for both wave and surge modeling and validated the models using field observations of surge hydrographs and high watermarks of Hurricane Ivan (2004). We then developed wave atlases and flood maps corresponding to the extreme wind, surge and waves without SLR and with a 0.5 m of SLR by coupling the wave and surge prediction models. The flood maps were then merged with a map of ABM habitat to determine the extent and location of habitat impacted by the 100-year storm with and without SLR. Simulation results indicate that more than 82% of ABM habitat would be inundated in such an extreme storm event, especially under SLR, making ABM populations more vulnerable to future storm damage. These results have aided biologists, community planners, and other stakeholders in the identification, restoration and protection of key beach mouse habitat in Alabama. Methods outlined in this paper could also be used to assist in the conservation and recovery of imperiled coastal species elsewhere.

  16. Comparison of neotropical migrant landbird populations wintering in tropical forest, isolated forest fragments, and agricultural habitats

    USGS Publications Warehouse

    Robbins, C.S.; Dowell, B.A.; Dawson, D.K.; Colon, J.A.; Estrada, R.; Sutton, A.; Sutton, R.; Weyer, D.

    1992-01-01

    Neotropical migrant bird populations were sampled at 76 sites in seven countries by using mist nets and point counts during a six-winter study. Populations in major agricultural habitats were compared with those in extensive forest and isolated forest fragments. Certain Neotropical migrants, such as the Northern Parula, American Redstart, and the Black-throated Blue, Magnolia, Black-and-white, and Hooded warblers, were present in arboreal agricultural habitats such as pine, cacao, citrus, and shade coffee plantations in relatively large numbers. Many north temperate zone shrub-nesting species, such as the Gray Catbird, White-eyed Vireo, Tennessee Warbler, Common Yellowthroat, and Indigo Bunting, also used agricultural habitats in winter, as did resident hummingbirds and migrant orioles. Ground-foraging migrants, such as thrushes and Kentucky Warblers, were rarely found in the agricultural habitats sampled. Although many Neotropical migrants use some croplands, this use might be severely limited by overgrazing by cattle, by intensive management (such as removal of ground cover in an orchard), or by heavy use of insecticides, herbicides, or fungicides.

  17. Habitat heterogeneity and intraguild interactions modify distribution and injury rates in two coexisting genera of damselflies

    EPA Science Inventory

    1. Sublethal effects of predation can affect both population and community structure. Despite this, little is known about how the frequency of injury varies in relation to habitat, aquatic community characteristics or between trophically similar, coexisting taxa. 2. In a tidal ...

  18. Habitat heterogeneity and intraguild interactions modify distribution and injury rates in two coexisting genera of damselflies

    USGS Publications Warehouse

    Witt, Jonathan W.; Forkner, Rebecca E.; Kraus, Richard T.

    2013-01-01

    4. The relative importance of factors hypothesised to structure odonate communities varied between coexisting Enallagma and Ischnura. Distinctive distributions and patterns of injury for each genus provided new insights on the potential for intraguild interactions to modify habitat associations in tidal freshwater ecosystems.

  19. Abyssal hills - hidden source of increased habitat heterogeneity, benthic megafaunal biomass and diversity in the deep sea

    NASA Astrophysics Data System (ADS)

    Durden, Jennifer M.; Bett, Brian J.; Jones, Daniel O. B.; Huvenne, Veerle A. I.; Ruhl, Henry A.

    2015-09-01

    Abyssal hills are the most abundant landform on Earth, yet the ecological impact of the resulting habitat heterogeneity on the wider abyss is largely unexplored. Topographic features are known to influence food availability and the sedimentary environment in other deep-sea habitats, in turn affecting the species assemblage and biomass. To assess this spatial variation, benthic assemblages and environmental conditions were compared at four hill and four plain sites at the Porcupine Abyssal Plain. Here we show that differences in megabenthic communities on abyssal hills and the adjacent plain are related to environmental conditions, which may be caused by local topography and hydrodynamics. Although these hills may receive similar particulate organic carbon flux (food supply from the surface ocean) to the adjacent plain, they differ significantly in depth, slope, and sediment particle size distribution. We found that megafaunal biomass was significantly greater on the hills (mean 13.45 g m-2, 95% confidence interval 9.25-19.36 g m-2) than the plain (4.34 g m-2, 95% CI 2.08-8.27 g m-2; ANOVA F(1, 6) = 23.8, p < 0.01). Assemblage and trophic compositions by both density and biomass measures were significantly different between the hill and plain, and correlated with sediment particle size distributions. Hydrodynamic conditions responsible for the local sedimentary environment may be the mechanism driving these assemblage differences. Since the ecological heterogeneity provided by hills in the abyss has been underappreciated, regional assessments of abyssal biological heterogeneity and diversity may be considerably higher than previously thought.

  20. [Environmental factors associated with habitat preferences by caddisfly larvae in tropical dry forest watersheds (Tolima, Colombia)].

    PubMed

    Vásquez-Ramos, Jesús M; Guevara-Cardona, Giovany; Reinoso-Flórez, Gladys

    2014-04-01

    River ecosystems, mainly those draining tropical dry forests, are among the most endangered tropical ecosystems and a major conservation priority in South America, as elsewhere. In this study, we assessed the influence of environmental factors (e.g., precipitation) and riparian vegetation on Trichoptera larval assemblages colonizing four substrates (rock, gravel, sand, and litter) in the Venadillo and Opia watersheds (Tolima, Colombia). In each river, five 20m reaches nested into two 100m segments (one at -550 and another at -250masl), were surveyed for benthic invertebrates in the above mentioned substrates. In addition, water samples were collected for physicochemical analyses and the QBR index ("qualitat del bosc de ribera" or riparian forest quality) was applied in both rivers. A total of 6,282 larvae were collected, belonging to 11 families and 22 genera, representing 73.30% and 43.13% of the Trichoptera fauna reported to Colombia, respectively. The most abundant families were Hydropsychidae (49.86%) and Philopotamidae (25.44%) and the least abundant Odontoceridae (0.16%) and Hydrobiosidae (0.06%). The genera Smicridea, Chimarra, Protoptila, Neotrichia, and Leptonema, were common during dry and rainy seasons. The main factors related to changes in composition, richness, and abundance of larval Trichoptera were seasonality and riparian vegetation, which can influence organic matter supply, availability and stability of substrates, and colonization and population dynamics. Trichoptera assemblages showed no significant differences among substrates. However sampling points located at high elevation and in non-urbanized areas offered the largest variety of substrates and richness. Our results indicate that Trichoptera larvae are an important biotic element in freshwater ecosystems and that they are sensitive to environmental changes. Hence, our study suggests that caddisflies may be used as potential organisms for the biomonitoring of tropical dry forest rivers

  1. Habitat Heterogeneity Affects Plant and Arthropod Species Diversity and Turnover in Traditional Cornfields

    PubMed Central

    Martínez, Eliana; Rös, Matthias; Bonilla, María Argenis; Dirzo, Rodolfo

    2015-01-01

    The expansion of the agricultural frontier by the clearing of remnant forests has led to human-dominated landscape mosaics. Previous studies have evaluated the effect of these landscape mosaics on arthropod diversity at local spatial scales in temperate and tropical regions, but little is known about fragmentation effects in crop systems, such as the complex tropical traditional crop systems that maintain a high diversity of weeds and arthropods in low-Andean regions. To understand the factors that influence patterns of diversity in human-dominated landscapes, we investigate the effect of land use types on plant and arthropod diversity in traditionally managed cornfields, via surveys of plants and arthropods in twelve traditional cornfields in the Colombian Andes. We estimated alpha and beta diversity to analyze changes in diversity related to land uses within a radius of 100 m to 1 km around each cornfield. We observed that forests influenced alpha diversity of plants, but not of arthropods. Agricultural lands had a positive relationship with plants and herbivores, but a negative relationship with predators. Pastures positively influenced the diversity of plants and arthropods. In addition, forest cover seemed to influence changes in plant species composition and species turnover of herbivore communities among cornfields. The dominant plant species varied among fields, resulting in high differentiation of plant communities. Predator communities also exhibited high turnover among cornfields, but differences in composition arose mainly among rare species. The crop system evaluated in this study represents a widespread situation in the tropics, therefore, our results can be of broad significance. Our findings suggest that traditional agriculture may not homogenize biological communities, but instead could maintain the regional pool of species through high beta diversity. PMID:26197473

  2. Habitat Heterogeneity Affects Plant and Arthropod Species Diversity and Turnover in Traditional Cornfields.

    PubMed

    Martínez, Eliana; Rös, Matthias; Bonilla, María Argenis; Dirzo, Rodolfo

    2015-01-01

    The expansion of the agricultural frontier by the clearing of remnant forests has led to human-dominated landscape mosaics. Previous studies have evaluated the effect of these landscape mosaics on arthropod diversity at local spatial scales in temperate and tropical regions, but little is known about fragmentation effects in crop systems, such as the complex tropical traditional crop systems that maintain a high diversity of weeds and arthropods in low-Andean regions. To understand the factors that influence patterns of diversity in human-dominated landscapes, we investigate the effect of land use types on plant and arthropod diversity in traditionally managed cornfields, via surveys of plants and arthropods in twelve traditional cornfields in the Colombian Andes. We estimated alpha and beta diversity to analyze changes in diversity related to land uses within a radius of 100 m to 1 km around each cornfield. We observed that forests influenced alpha diversity of plants, but not of arthropods. Agricultural lands had a positive relationship with plants and herbivores, but a negative relationship with predators. Pastures positively influenced the diversity of plants and arthropods. In addition, forest cover seemed to influence changes in plant species composition and species turnover of herbivore communities among cornfields. The dominant plant species varied among fields, resulting in high differentiation of plant communities. Predator communities also exhibited high turnover among cornfields, but differences in composition arose mainly among rare species. The crop system evaluated in this study represents a widespread situation in the tropics, therefore, our results can be of broad significance. Our findings suggest that traditional agriculture may not homogenize biological communities, but instead could maintain the regional pool of species through high beta diversity. PMID:26197473

  3. Suitable Environmental Ranges for Potential Coral Reef Habitats in the Tropical Ocean

    PubMed Central

    Guan, Yi; Hohn, Sönke; Merico, Agostino

    2015-01-01

    Coral reefs are found within a limited range of environmental conditions or tolerance limits. Estimating these limits is a critical prerequisite for understanding the impacts of climate change on the biogeography of coral reefs. Here we used the diagnostic model ReefHab to determine the current environmental tolerance limits for coral reefs and the global distribution of potential coral reef habitats as a function of six factors: temperature, salinity, nitrate, phosphate, aragonite saturation state, and light. To determine these tolerance limits, we extracted maximum and minimum values of all environmental variables in corresponding locations where coral reefs are present. We found that the global, annually averaged tolerance limits for coral reefs are 21.7—29.6 °C for temperature, 28.7—40.4 psu for salinity, 4.51 μmol L-1 for nitrate, 0.63 μmol L-1 for phosphate, and 2.82 for aragonite saturation state. The averaged minimum light intensity in coral reefs is 450 μmol photons m-2 s-1. The global area of potential reef habitats calculated by the model is 330.5 × 103 km2. Compared with previous studies, the tolerance limits for temperature, salinity, and nutrients have not changed much, whereas the minimum value of aragonite saturation in coral reef waters has decreased from 3.28 to 2.82. The potential reef habitat area calculated with ReefHab is about 121×103 km2 larger than the area estimated from the charted reefs, suggesting that the growth potential of coral reefs is higher than currently observed. PMID:26030287

  4. Habitat heterogeneity drives the host-diversity-begets-parasite-diversity relationship: evidence from experimental and field studies.

    PubMed

    Johnson, Pieter T J; Wood, Chelsea L; Joseph, Maxwell B; Preston, Daniel L; Haas, Sarah E; Springer, Yuri P

    2016-07-01

    Despite a century of research into the factors that generate and maintain biodiversity, we know remarkably little about the drivers of parasite diversity. To identify the mechanisms governing parasite diversity, we combined surveys of 8100 amphibian hosts with an outdoor experiment that tested theory developed for free-living species. Our analyses revealed that parasite diversity increased consistently with host diversity due to habitat (i.e. host) heterogeneity, with secondary contributions from parasite colonisation and host abundance. Results of the experiment, in which host diversity was manipulated while parasite colonisation and host abundance were fixed, further reinforced this conclusion. Finally, the coefficient of host diversity on parasite diversity increased with spatial grain, which was driven by differences in their species-area curves: while host richness quickly saturated, parasite richness continued to increase with neighbourhood size. These results offer mechanistic insights into drivers of parasite diversity and provide a hierarchical framework for multi-scale disease research. PMID:27147106

  5. Habitat quality and heterogeneity influence distribution and behavior in African buffalo (Syncerus caffer).

    PubMed

    Winnie, John A; Cross, Paul; Getz, Wayne

    2008-05-01

    Top-down effects of predators on prey behavior and population dynamics have been extensively studied. However, some populations of very large herbivores appear to be regulated primarily from the bottom up. Given the importance of food resources to these large herbivores, it is reasonable to expect that forage heterogeneity (variation in quality and quantity) affects individual and group behaviors as well as distribution on the landscape. Forage heterogeneity is often strongly driven by underlying soils, so substrate characteristics may indirectly drive herbivore behavior and distribution. Forage heterogeneity may further interact with predation risk to influence prey behavior and distribution. Here we examine differences in spatial distribution, home range size, and grouping behaviors of African buffalo as they relate to geologic substrate (granite and basalt) and variation in food quality and quantity. In this study, we use satellite imagery, forage quantity data, and three years of radio-tracking data to assess how forage quality, quantity, and heterogeneity affect the distribution and individual and herd behavior of African buffalo. We found that buffalo in an overall poorer foraging environment keyed-in on exceptionally high-quality areas, whereas those foraging in a more uniform, higher-quality area used areas of below-average quality. Buffalo foraging in the poorer-quality environment had smaller home range sizes, were in smaller groups, and tended to be farther from water sources than those foraging in the higher-quality environment. These differences may be due to buffalo creating or maintaining nutrient hotspots (small, high-quality foraging areas) in otherwise low-quality foraging areas, and the location of these hotspots may in part be determined by patterns of predation risk. PMID:18543637

  6. Ecophysiology of seed germination of wild Dahlia coccinea (Asteraceae) in a spatially heterogeneous fire-prone habitat

    NASA Astrophysics Data System (ADS)

    Vivar-Evans, Susana; Barradas, Víctor L.; Sánchez-Coronado, María E.; Gamboa de Buen, Alicia; Orozco-Segovia, Alma

    2006-03-01

    Dahlia coccinea grows on fire-prone xerophilous shrubland, on a lava field located in Mexico City. Two kinds of experiments were performed to test the role of fire and environmental heterogeneity on germination. The first experiment tested the effect of environmental conditions (constant and alternating temperatures, cold stratification and light). The second one tested the effects of fire and high temperatures (dry and moist heat) on germination. Seeds of Dahlia were indifferent to light. The seeds showed physiological dormancy, which was lost by after-ripening or by gibberellins. During simulated fires, dry seeds tolerated high temperatures of short duration and also withstood prolonged exposure to 60 °C. Dry heat treatment reduced the mechanical restriction for embryo growth in dormant seeds. Ash and prolonged exposure to moist heat inhibited germination. Exogenous gibberellins reversed the deleterious effects of prolonged exposure to moist heat. The effect of cold stratification was related to the seeds' physiological stage and to light conditions; stratification in the dark reduced germination. Seeds of D. coccinea could tolerate, evade, or be slightly favored by the effects of low intensity fires occurring in their habitat. Seed responses to treatments suggest that the spatially heterogeneous lava field could provide a wide variety of micro-sites where physiological dormancy could be broken and during fires seeds could maintain their viability and subsequently germinate and/or develop a seed bank.

  7. High genetic diversity in a potentially vulnerable tropical tree species despite extreme habitat loss.

    PubMed

    Noreen, Annika M E; Webb, Edward L

    2013-01-01

    Over the last 150 years, Singapore's primary forest has been reduced to less than 0.2% of its previous area, resulting in extinctions of native flora and fauna. Remaining species may be threatened by genetic erosion and inbreeding. We surveyed >95% of the remaining primary forest in Singapore and used eight highly polymorphic microsatellite loci to assess genetic diversity indices of 179 adults (>30 cm stem diameter), 193 saplings (>1 yr), and 1,822 seedlings (<1 yr) of the canopy tree Koompassia malaccensis (Fabaceae). We tested hypotheses relevant to the genetic consequences of habitat loss: (1) that the K. malaccensis population in Singapore experienced a genetic bottleneck and a reduction in effective population size, and (2) K. malaccensis recruits would exhibit genetic erosion and inbreeding compared to adults. Contrary to expectations, we detected neither a population bottleneck nor a reduction in effective population size, and high genetic diversity in all age classes. Genetic diversity indices among age classes were not significantly different: we detected overall high expected heterozygosity (He = 0.843-0.854), high allelic richness (R = 16.7-19.5), low inbreeding co-efficients (FIS = 0.013-0.076), and a large proportion (30.1%) of rare alleles (i.e. frequency <1%). However, spatial genetic structure (SGS) analyses showed significant differences between the adults and the recruits. We detected significantly greater SGS intensity, as well as higher relatedness in the 0-10 m distance class, for seedlings and saplings compared to the adults. Demographic factors for this population (i.e. <200 adult trees) are a cause for concern, as rare alleles could be lost due to stochastic factors. The high outcrossing rate (tm = 0.961), calculated from seedlings, may be instrumental in maintaining genetic diversity and suggests that pollination by highly mobile bee species in the genus Apis may provide resilience to acute habitat loss. PMID:24367531

  8. Tropical anvil characteristics and water vapor of the tropical tropopause layer: Impact of heterogeneous and homogeneous freezing parameterizations

    SciTech Connect

    Fan, Jiwen; Comstock, Jennifer M.; Ovchinnikov, Mikhail; McFarlane, Sally A.; McFarquhar, Greg; Allen, Grant

    2010-06-16

    Abstract Two isolated deep convective clouds (DCCs) that developed in clean-humid and polluted-dry air masses, observed during the TWP-ICE and ACTIVE campaigns, are simulated using a 3-dimensional cloud-resolving model with size-resolved aerosol and cloud microphysics. We examine the impacts of different homogeneous and immersion freezing parameterizations on the anvil characteristics and the water vapor content (WVC) in the Tropical Tropopause Layer (TTL) for the two DCCs that developed in contrasting environments. The modeled cloud properties such as liquid/ice water path and precipitation generally agree with the available radar and satellite retrievals and in situ aircraft measurements. We find that anvil size and anvil microphysical properties such as ice number concentration and ice effective radius (rei) are much more sensitive to the homogeneous freezing parameterization (HomFP) under the polluted-dry condition, while the strength of anvil convection is more sensitive to HomFP under the clean-humid condition. Specifically, the cloud anvil with the Koop et al. (2000) (KOOP) relative humidity dependent scheme has up to 2 and 4 times lower ice number than those with other schemes (temperature dependent) for the clean humid and polluted-dry cases, respectively. Consequently, the rei is increased in both cases, with a larger increase in the polluted-dry case. As a result, extinction coefficient of cloud anvils is reduced by over 25% for the polluted-dry case. Anvil size and evolution are also much affected by HomFPs in the polluted-dry case. Higher immersion-freezing rates leads to a stronger convective cloud, with higher precipitation and ice water path under both humid and dry conditions. As a result, homogeneous freezing rates are enhanced by over 20%. Also, the higher immersion-freezing rate results in stronger convection in cloud anvils, much larger anvil size (up to 3 times) and longer lifetime. The moistening effect of deep convection on the WVC in the

  9. Utilization of sugarcane habitat by feral pig (Sus scrofa) in northern tropical Queensland: evidence from the stable isotope composition of hair.

    PubMed

    Wurster, Christopher M; Robertson, Jack; Westcott, David A; Dryden, Bart; Zazzo, Antoine; Bird, Michael I

    2012-01-01

    Feral pigs (Sus scrofa) are an invasive species that disrupt ecosystem functioning throughout their introduced range. In tropical environments, feral pigs are associated with predation and displacement of endangered species, modification of habitat, and act as a vector for the spread of exotic vegetation and disease. Across many parts of their introduced range, the diet of feral pigs is poorly known. Although the remote location and difficult terrain of far north Queensland makes observing feral pig behavior difficult, feral pigs are perceived to seek refuge in World Heritage tropical rainforests and seasonally 'crop raid' into lowland sugarcane crops. Thus, identifying how feral pigs are using different components of the landscape is important to the design of management strategies. We used the stable isotope composition of captured feral pigs to determine the extent of rainforest and sugarcane habitat usage. Recently grown hair (basal hair) from feral pigs captured in remote rainforest indicated pigs met their dietary needs solely within this habitat. Stable carbon and nitrogen isotope values of basal hair from feral pigs captured near sugarcane plantations were more variable, with some individuals estimated to consume over 85% of their diet within a sugarcane habitat, while a few consumed as much as 90% of their diet from adjacent forested environments. We estimated whether feral pigs switch habitats by sequentially sampling δ(13)C and δ(15)N values of long tail hair from a subset of seven captured animals, and demonstrate that four of these individuals moved between habitats. Our results indicate that feral pigs utilize both sugarcane and forest habitats, and can switch between these resources. PMID:22957029

  10. Causes and consequences of change rates in the habitat of the threatened tropical porcupine, Sphiggurus mexicanus (Rodentia: Erethizontidae) in Oaxaca, Mexico: implications for its conservation.

    PubMed

    Lorenzo, Consuelo; Sántiz, Eugenia C; Navarrete, Darío A; Bolaños, Jorge

    2014-12-01

    Land use changes by human activities have been the main causes of habitats and wildlife population degradation. In the Tehuantepec Isthmus in Oaxaca, the tropical habitat of the porcupine Sphiggurus mexicanus has been subject to vegetation and land use changes, causing its reduction and fragmentation. In this study, we estimated vegetation cover and land use (δn) change rates and assessed habitat availability and potential cor- ridors for possible porcupine movements to avoid its isolation. In the study area, the type of vegetation with the most change rate value was the savanna (δn = -2.9), transformed into induced grasslands. Additionally, we have observed the porcupine (since 2011) in semi-deciduous (δn = -0.87) and tropical dry (δn = -0.89) forests that have been transformed in temporal agriculture and mesquite and induced grasslands. The vegetation inhabited by the porcupine resulted in recording a total of 64 plant species (44 trees, nine vines, seven herbs, four shrubs), of which the vine Bunchosia lanceolata showed the highest importance value (41.85) followed by the trees Guazuma ulmifolia (22.71), Dalbergia glabra (18.05), and Enterolobium cyclocarpum (17.02). The habitat evaluation and potential corridor analysis showed that only 1 501.93ha could be considered as suitable habitats with optimum structural conditions (coverage, surface, and distances to transformed areas) to maintain viable populations of S. mexicanus, and 293.6 ha as corridors. An increasing destruction of the porcupines' habitat has been observed in the study area due to excessive logging, and actions for this species and its habitat conserva- tion and management have to be taken urgently. PMID:25720182

  11. High Genetic Diversity in a Potentially Vulnerable Tropical Tree Species Despite Extreme Habitat Loss

    PubMed Central

    Noreen, Annika M. E.; Webb, Edward L.

    2013-01-01

    Over the last 150 years, Singapore’s primary forest has been reduced to less than 0.2% of its previous area, resulting in extinctions of native flora and fauna. Remaining species may be threatened by genetic erosion and inbreeding. We surveyed >95% of the remaining primary forest in Singapore and used eight highly polymorphic microsatellite loci to assess genetic diversity indices of 179 adults (>30 cm stem diameter), 193 saplings (>1 yr), and 1,822 seedlings (<1 yr) of the canopy tree Koompassia malaccensis (Fabaceae). We tested hypotheses relevant to the genetic consequences of habitat loss: (1) that the K. malaccensis population in Singapore experienced a genetic bottleneck and a reduction in effective population size, and (2) K. malaccensis recruits would exhibit genetic erosion and inbreeding compared to adults. Contrary to expectations, we detected neither a population bottleneck nor a reduction in effective population size, and high genetic diversity in all age classes. Genetic diversity indices among age classes were not significantly different: we detected overall high expected heterozygosity (He = 0.843–0.854), high allelic richness (R = 16.7–19.5), low inbreeding co-efficients (FIS = 0.013–0.076), and a large proportion (30.1%) of rare alleles (i.e. frequency <1%). However, spatial genetic structure (SGS) analyses showed significant differences between the adults and the recruits. We detected significantly greater SGS intensity, as well as higher relatedness in the 0–10 m distance class, for seedlings and saplings compared to the adults. Demographic factors for this population (i.e. <200 adult trees) are a cause for concern, as rare alleles could be lost due to stochastic factors. The high outcrossing rate (tm = 0.961), calculated from seedlings, may be instrumental in maintaining genetic diversity and suggests that pollination by highly mobile bee species in the genus Apis may provide resilience to acute habitat loss. PMID

  12. Four New Vining Species of Solanum (Dulcamaroid Clade) from Montane Habitats in Tropical America

    PubMed Central

    Knapp, Sandra

    2010-01-01

    Background Solanum (Solanaceae), with approximately 1500 species, is one of the largest genera of flowering plants, and has a centre of diversity in the New World tropics. The genus is divided into 13 major clades, of which two, the Dulcamaroid clade and the “African Non-Spiny” clade, exhibit vine morphology with twining petioles. I am currently preparing a worldwide monograph of these two groups, comprising some 70 species. Methods I formally describe here four new species of Solanum from montane Mexico and South America all belonging to the Dulcamaroid clade (including the traditionally recognised section Jasminosolanum Bitter). Descriptions, discussions of closely related species and preliminary conservation assessments are provided for all species; all species are illustrated. This paper is also a test case for the electronic publication of new names in flowering plants. Conclusions These new species are all relatively rare, but not currently of conservation concern. Solanum aspersum sp. nov. is distributed in Colombia and Ecuador, S. luculentum sp. nov. in Colombia and Venezuela, S. sanchez-vegae sp. nov. is endemic to northern Peru and S. sousae sp. nov. to southern Mexico. Solanum luculentum has the morphology of a dioecious species; this is the first report of this breeding system in the Dulcamaroid clade. PMID:20463921

  13. Resource seeking strategies of zoosporic true fungi in heterogeneous soil habitats at the microscale level

    PubMed Central

    Gleason, Frank H.; Crawford, John W.; Neuhauser, Sigrid; Henderson, Linda E.; Lilje, Osu

    2012-01-01

    Zoosporic true fungi have frequently been identified in samples from soil and freshwater ecosystems using baiting and molecular techniques. In fact some species can be components of the dominant groups of microorganisms in particular soil habitats. Yet these microorganisms have not yet been directly observed growing in soil ecosystems. Significant physical characteristics and features of the three-dimensional structures of soils which impact microorganisms at the microscale level are discussed. A thorough knowledge of soil structures is important for studying the distribution of assemblages of these fungi and understanding their ecological roles along spatial and temporal gradients. A number of specific adaptations and resource seeking strategies possibly give these fungi advantages over other groups of microorganisms in soil ecosystems. These include chemotactic zoospores, mechanisms for adhesion to substrates, rhizoids which can penetrate substrates in small spaces, structures which are resistant to environmental extremes, rapid growth rates and simple nutritional requirements. These adaptations are discussed in the context of the characteristics of soils ecosystems. Recent advances in instrumentation have led to the development of new and more precise methods for studying microorganisms in three-dimensional space. New molecular techniques have made identification of microbes possible in environmental samples. PMID:22308003

  14. Effects of local biotic neighbors and habitat heterogeneity on tree and shrub seedling survival in an old-growth temperate forest.

    PubMed

    Bai, Xuejiao; Queenborough, Simon A; Wang, Xugao; Zhang, Jian; Li, Buhang; Yuan, Zuoqiang; Xing, Dingliang; Lin, Fei; Ye, Ji; Hao, Zhanqing

    2012-11-01

    Seedling dynamics play a crucial role in determining species distributions and coexistence. Exploring causes of variation in seedling dynamics can therefore provide key insights into the factors affecting these phenomena. We examined the relative importance of biotic neighborhood processes and habitat heterogeneity using survival data for 5,827 seedlings in 39 tree and shrub species over 2 years from an old-growth temperate forest in northeastern China. We found significant negative density-dependence effects on survival of tree seedlings, and limited effects of habitat heterogeneity (edaphic and topographic variables) on survival of shrub seedlings. The importance of negative density dependence on young tree seedling survival was replaced by habitat in tree seedlings ≥ 4 years old. As expected, negative density dependence was more apparent in gravity-dispersed species compared to wind-dispersed and animal-dispersed species. Moreover, we found that a community compensatory trend existed for trees. Therefore, although negative density dependence was not as pervasive as in other forest communities, it is an important mechanism for the maintenance of community diversity in this temperate forest. We conclude that both negative density dependence and habitat heterogeneity drive seedling survival, but their relative importance varies with seedling age classes and species traits. PMID:22644047

  15. Enhanced land use/cover classification of heterogeneous tropical landscapes using support vector machines and textural homogeneity

    NASA Astrophysics Data System (ADS)

    Paneque-Gálvez, Jaime; Mas, Jean-François; Moré, Gerard; Cristóbal, Jordi; Orta-Martínez, Martí; Luz, Ana Catarina; Guèze, Maximilien; Macía, Manuel J.; Reyes-García, Victoria

    2013-08-01

    Land use/cover classification is a key research field in remote sensing and land change science as thematic maps derived from remotely sensed data have become the basis for analyzing many socio-ecological issues. However, land use/cover classification remains a difficult task and it is especially challenging in heterogeneous tropical landscapes where nonetheless such maps are of great importance. The present study aims at establishing an efficient classification approach to accurately map all broad land use/cover classes in a large, heterogeneous tropical area, as a basis for further studies (e.g., land use/cover change, deforestation and forest degradation). Specifically, we first compare the performance of parametric (maximum likelihood), non-parametric (k-nearest neighbor and four different support vector machines - SVM), and hybrid (unsupervised-supervised) classifiers, using hard and soft (fuzzy) accuracy assessments. We then assess, using the maximum likelihood algorithm, what textural indices from the gray-level co-occurrence matrix lead to greater classification improvements at the spatial resolution of Landsat imagery (30 m), and rank them accordingly. Finally, we use the textural index that provides the most accurate classification results to evaluate whether its usefulness varies significantly with the classifier used. We classified imagery corresponding to dry and wet seasons and found that SVM classifiers outperformed all the rest. We also found that the use of some textural indices, but particularly homogeneity and entropy, can significantly improve classifications. We focused on the use of the homogeneity index, which has so far been neglected in land use/cover classification efforts, and found that this index along with reflectance bands significantly increased the overall accuracy of all the classifiers, but particularly of SVM. We observed that improvements in producer's and user's accuracies through the inclusion of homogeneity were different

  16. Spatial scale-dependent habitat heterogeneity influences submarine canyon macrofaunal abundance and diversity off the Main and Northwest Hawaiian Islands

    NASA Astrophysics Data System (ADS)

    De Leo, Fabio C.; Vetter, Eric W.; Smith, Craig R.; Rowden, Ashley A.; McGranaghan, Matthew

    2014-06-01

    The mapping of biodiversity on continental margins on landscape scales is highly relevant to marine spatial planning and conservation. Submarine canyons are widespread topographic features on continental and island margins that enhance benthic biomass across a range of oceanic provinces and productivity regimes. However, it remains unclear whether canyons enhance faunal biodiversity on landscape scales relevant to marine protected area (MPA) design. Furthermore, it is not known which physical attributes and heterogeneity metrics can provide good surrogates for large-scale mapping of canyon benthic biodiversity. To test mechanistic hypotheses evaluating the role of different canyon-landscape attributes in enhancing benthic biodiversity at different spatial scales we conducted 34 submersible dives in six submarine canyons and nearby slopes in the Hawaiian archipelago, sampling infaunal macrobenthos in a depth-stratified sampling design. We employed multivariate multiple regression models to evaluate sediment and topographic heterogeneity, canyon transverse profiles, and overall water mass variability as potential drivers of macrobenthic community structure and species richness. We find that variables related to habitat heterogeneity at medium (0.13 km2) and large (15-33 km2) spatial scales such as slope, backscatter reflectivity and canyon transverse profiles are often good predictors of macrobenthic biodiversity, explaining 16-30% of the variance. Particulate organic carbon (POC) flux and distance from shore are also important variables, implicating food supply as a major predictor of canyon biodiversity. Canyons off the high Main Hawaiian Islands (Oahu and Moloka'i) are significantly affected by organic enrichment, showing enhanced infaunal macrobenthos abundance, whereas this effect is imperceptible around the low Northwest Hawaiian Islands (Nihoa and Maro Reef). Variable canyon alpha-diversity and high rates of species turnover (beta-diversity), particularly for

  17. Assessing diversity and phytoremediation potential of seagrass in tropical region

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seagrass ecosystem is one of the most important resources in the coastal areas. Seagrasses support and provide habitats for many coastal organisms in tropical region. Seagrasses are specialized marine flowering plants that have adapted to the nearshore environment with heterogeneous landscape struct...

  18. Habitat fragmentation and haemoparasites in the common fruit bat, Artibeus jamaicensis (Phyllostomidae) in a tropical lowland forest in Panamá.

    PubMed

    Cottontail, V M; Wellinghausen, N; Kalko, E K V

    2009-09-01

    Anthropogenic influence on ecosystems, such as habitat fragmentation, impacts species diversity and interactions. There is growing evidence that degradation of habitats favours disease and hence affects ecosystem health. The prevalence of haemoparasites in the Common Fruit Bat (Artibeus jamaicensis) in a tropical lowland forest in Panamá was studied. We assessed the relation of haemoparasite to the general condition of the animals and tested for possible association of haemoparasite prevalence to habitat fragmentation, with special focus on trypanosomes. Overall, a total of 250 A. jamaicensis sampled from fragmented sites, here man-made, forested islands in Lake Gatùn, and sites in the adjacent, continuous forest in and around the Barro Colorado Nature Monument were examined. Using microscopy and DNA-sequencing 2 dominant types of haemoparasite infections, trypanosomes and Litomosoides (Nematoda) were identified. Trypanosome prevalence was significantly higher in bats from forest fragments, than in bats captured in continuous forest. We attribute this to the loss of species richness in forest fragments and specific characteristics of the fragments favouring trypanosome transmission, in particular changes in vegetation cover. Interestingly, the effect of habitat fragmentation on the prevalence of trypanosomes as multi-host parasites could not be observed in Litomosoides which probably has a higher host specificity and might be affected less by overall diversity loss. PMID:19627629

  19. Differential performance of tropical soda apple and its biological control agent Gratiana boliviana (Coleoptera: Chrysomelidae) in open and shaded habitats

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The leaf feeding beetle Gratiana boliviana Spaeth has been released since 2003 in the southeastern United States for biological control of tropical soda apple, Solanum viarum Dunal. In Florida, G. boliviana can be found on tropical soda apple growing in open pastures as well as in shady wooded areas...

  20. Seasonal and spatial ontogenetic movements of Gerreidae in a Brazilian tropical estuarine ecocline and its application for nursery habitat conservation.

    PubMed

    Ramos, J A A; Barletta, M; Dantas, D V; Costa, M F

    2016-07-01

    The density and biomass of different ontogenetic phases (juvenile, sub-adult and adult) of the two most important sympatric Gerreidae species in the Goiana Estuary, north-east Brazil, are described in order to determine the patterns of estuarine habitat use and to identify nursery grounds. Eugerres brasilianus and Eucinostomus melanopterus were the most abundant gerreids in the main channel and adjacent estuarine beach habitats. Eugerres brasilianus is abundant in the main channel, whereas E. melanopterus is most common in the beach habitats. Significant interaction in density and biomass of juvenile and sub-adult size classes of E. brasilianus was found between season and area. In addition, E. brasilianus adults and E. melanopterus sub-adults differed significantly in density and biomass between areas of the estuary. Both the upper estuary, during the late dry season, and the middle estuary, during the early rainy season, functioned as nursery habitats for E. brasilianus. During the early rainy season and dry season, the beaches were a nursery for the E. melanopterus. The concentration of these ontogenetic phases was mainly related to the dissolved oxygen and salinity gradients of the estuary, which drive not only gerreid movement between estuarine habitats but also moves the habitats. This study reinforces the importance of conserving the habitats of the Goiana Estuary so that species such as gerreids can complete their life cycle in the face of pressure from anthropogenic activities, such as mangrove forest deforestation, overfishing, fish contamination by plastic ingestion and domestic effluent disposal. PMID:26887637

  1. A preliminary study of habitat and resource partitioning among co-occurring tropical dolphins around Mayotte, southwest Indian Ocean

    NASA Astrophysics Data System (ADS)

    Gross, Alexandra; Kiszka, Jeremy; Van Canneyt, Olivier; Richard, Pierre; Ridoux, Vincent

    2009-09-01

    Mayotte in the southwest Indian Ocean is characterized by high dolphin diversity. They may coexist within a fairly small area around the island because they exploit neither the same preferential habitats nor the same resources. This preliminary study aimed to investigate ecological niche segregation among these delphinid communities: the Indo-Pacific bottlenose dolphin, Tursiops aduncus, the pantropical spotted dolphin, Stenella attenuata, the spinner dolphin, Stenella longirostris, and the melon-headed whale, Peponocephala electra. Two approaches were used. Habitat preferences were investigated by analysing dolphin sighting data and associated physiographical characteristics. Resource partitioning was explored by analysing C and N stable isotopes in skin and blubber biopsies. Only T. aduncus, which showed clear association with coastal habitats in the lagoon, differed from the others in terms of habitat preferences, characterised by shallow depth and slope, and proximity to the coast. All other species shared similar oceanic habitats immediately outside the lagoon, these being of higher depth and slope, greater distance from the coast and were not discernable by discriminant analysis. The two Stenella species and the melon-headed whale displayed very high overlap in habitat physiographic variables. The analysis of stable isotopes confirmed the ecological isolation of T. aduncus and revealed a clear segregation of P. electra compared to the two Stenella that was not apparent in the habitat analysis. This may reflect ecological differences that were not observable from diurnal surface observations.

  2. Predicting cetacean habitats from their energetic needs and the distribution of their prey in two contrasted tropical regions.

    PubMed

    Lambert, Charlotte; Mannocci, Laura; Lehodey, Patrick; Ridoux, Vincent

    2014-01-01

    To date, most habitat models of cetaceans have relied on static and oceanographic covariates, and very few have related cetaceans directly to the distribution of their prey, as a result of the limited availability of prey data. By simulating the distribution of six functional micronekton groups between the surface and ≃1,000 m deep, the SEAPODYM model provides valuable insights into prey distributions. We used SEAPODYM outputs to investigate the habitat of three cetacean guilds with increasing energy requirements: sperm and beaked whales, Globicephalinae and Delphininae. We expected High Energy Requirements cetaceans to preferentially forage in habitats of high prey biomass and/or production, where they might easily meet their high energetic needs, and Low Energy Requirements cetaceans to forage in habitats of either high or low prey biomass and/or production. Cetacean sightings were collected from dedicated aerial surveys in the South West Indian Ocean (SWIO) and French Polynesia (FP). We examined cetacean densities in relation to simulated distributions of their potential prey using Generalised Additive Models and predicted their habitats in both regions. Results supported their known diving abilities, with Delphininae mostly related to prey present in the upper layers of the water column, and Globicephalinae and sperm and beaked whales also related to prey present in deeper layers. Explained deviances ranged from 9% for sperm and beaked whales in the SWIO to 47% for Globicephalinae in FP. Delphininae and Globicephalinae appeared to select areas where high prey biomass and/or production were available at shallow depths. In contrast, sperm and beaked whales showed less clear habitat selection. Using simulated prey distributions as predictors in cetacean habitat models is crucial to understand their strategies of habitat selection in the three dimensions of the ocean. PMID:25162643

  3. Predicting Cetacean Habitats from Their Energetic Needs and the Distribution of Their Prey in Two Contrasted Tropical Regions

    PubMed Central

    Lambert, Charlotte; Mannocci, Laura; Lehodey, Patrick; Ridoux, Vincent

    2014-01-01

    To date, most habitat models of cetaceans have relied on static and oceanographic covariates, and very few have related cetaceans directly to the distribution of their prey, as a result of the limited availability of prey data. By simulating the distribution of six functional micronekton groups between the surface and ≃1,000 m deep, the SEAPODYM model provides valuable insights into prey distributions. We used SEAPODYM outputs to investigate the habitat of three cetacean guilds with increasing energy requirements: sperm and beaked whales, Globicephalinae and Delphininae. We expected High Energy Requirements cetaceans to preferentially forage in habitats of high prey biomass and/or production, where they might easily meet their high energetic needs, and Low Energy Requirements cetaceans to forage in habitats of either high or low prey biomass and/or production. Cetacean sightings were collected from dedicated aerial surveys in the South West Indian Ocean (SWIO) and French Polynesia (FP). We examined cetacean densities in relation to simulated distributions of their potential prey using Generalised Additive Models and predicted their habitats in both regions. Results supported their known diving abilities, with Delphininae mostly related to prey present in the upper layers of the water column, and Globicephalinae and sperm and beaked whales also related to prey present in deeper layers. Explained deviances ranged from 9% for sperm and beaked whales in the SWIO to 47% for Globicephalinae in FP. Delphininae and Globicephalinae appeared to select areas where high prey biomass and/or production were available at shallow depths. In contrast, sperm and beaked whales showed less clear habitat selection. Using simulated prey distributions as predictors in cetacean habitat models is crucial to understand their strategies of habitat selection in the three dimensions of the ocean. PMID:25162643

  4. Linking movement and reproductive history of brook trout to assess habitat connectivity in a heterogeneous stream network

    USGS Publications Warehouse

    Kanno, Yoichiro; Letcher, Benjamin H.; Coombs, Jason A.; Nislow, Keith H.; Whiteley, Andrew R.

    2013-01-01

    This study highlighted the importance of characterising animal movement over the life cycle for inferring habitat connectivity accurately. Such movements of individuals can contribute to substantial gene movements in a fecund species characterised by high variation in reproductive success.

  5. Discrimination Efficacy of Fecal Pollution Detection in Different Aquatic Habitats of a High-Altitude Tropical Country, Using Presumptive Coliforms, Escherichia coli, and Clostridium perfringens Spores

    PubMed Central

    Byamukama, Denis; Mach, Robert L.; Kansiime, Frank; Manafi, Mohamad; Farnleitner, Andreas H.

    2005-01-01

    The performance of rapid and practicable techniques that presumptively identify total coliforms (TC), fecal coliforms (FC), Escherichia coli, and Clostridium perfringens spores (CP) by testing them on a pollution gradient in differing aquatic habitats in a high-altitude tropical country was evaluated during a 12-month period. Site selection was based on high and low anthropogenic influence criteria of paired sites including six spring, six stream, and four lakeshore sites spread over central and eastern parts of Uganda. Unlike the chemophysical water quality, which was water source type dependent (i.e., spring, lake, or stream), fecal indicators were associated with the anthropogenic influence status of the respective sites. A total of 79% of the total variability, including all the determined four bacteriological and five chemophysical parameters, could be assigned to either a pollution, a habitat, or a metabolic activity component by principal-component analysis. Bacteriological indicators revealed significant correlations to the pollution component, reflecting that anthropogenic contamination gradients were followed. Discrimination sensitivity analysis revealed high ability of E. coli to differentiate between high and low levels of anthropogenic influence. CP also showed a reasonable level of discrimination, although FC and TC were found to have worse discrimination efficacy. Nonpoint influence by soil erosion could not be detected during the study period by correlation analysis, although a theoretical contamination potential existed, as investigated soils in the immediate surroundings often contained relevant concentrations of fecal indicators. The outcome of this study indicates that rapid techniques for presumptive E. coli and CP determination may be reliable for fecal pollution monitoring in high-altitude tropical developing countries such as those of Eastern Africa. PMID:15640171

  6. Hantavirus seropositivity in rodents in relation to habitat heterogeneity in human-shaped landscapes of Southeast Asia.

    PubMed

    Blasdell, Kim; Morand, Serge; Henttonen, Heikki; Tran, Annelise; Buchy, Philippe

    2016-05-01

    To establish how the conversion of natural habitats for agricultural purposes may impact the distribution of hantaviruses in Southeast Asia, we tested how habitat structure affects hantavirus infection prevalence of common murine rodents that inhabit human-dominated landscapes in this region. For this, we used geo-referenced data of rodents analysed for hantavirus infection and land cover maps produced for the seven study sites in Thailand, Cambodia and Lao PDR where they were collected. Rodents were tested by serological methods that detect several hantaviruses, including pathogenic ones. Rodents with a seropositive status were more likely to be found near to agriculture on steep land, and also in environments with a high proportion of agriculture on steep land. These results suggest that in Southeast Asia, hantaviruses, which are often associated with generalist rodent species with a preference for agricultural land, may benefit from land conversion to agriculture. PMID:27246270

  7. Influence of habitat heterogeneity on distribution, occupancy patterns, and productivity of breeding peregrine falcons in central west Greenland

    USGS Publications Warehouse

    Wightman, C.; Fuller, Mark R.

    2006-01-01

    We used occupancy and productivity data collected at 67 cliffs used for nesting from 1972 to 1999 to assess patterns of distribution and nest-site selection in an increasing population of Peregrine Falcons (Falco peregrinus) in central West Greenland. Peregrine Falcons breeding at traditionally occupied cliffs used for nesting had significantly lower variation in productivity and thus these cliffs were better quality sites. This indicates that Peregrine Falcons occupied cliffs according to a pattern of despotic distribution. Falcons breeding at cliffs that were consistently occupied during the breeding season had higher average productivity and lower variation in productivity than falcons at inconsistently occupied cliffs, and thus consistent occupancy also was indicative of cliff quality. Features of high quality habitat included tall cliffs, greater change in elevation from the lowest point within 3 km of the cliff to the cliff top (elevation gain), and protection from weather on the eyrie ledge. Spacing of suitable and occupied cliffs also was an important feature, and the best cliffs generally were more isolated. Increased spacing was likely a mechanism for reducing intraspecific competition. Our results suggest that Peregrine Falcons use a resource defense strategy to compete for better quality habitats and may use spacing and physical features of a nest site to identify good quality breeding habitat.

  8. Influence of habitat heterogeneity on distribution, occupancy patterns, and productivity of breeding peregrine falcons in central West Greenland

    USGS Publications Warehouse

    Wightman, C.S.; Fuller, M.R.

    2006-01-01

    We used occupancy and productivity data collected at 67 cliffs used for nesting from 1972 to 1999 to assess patterns of distribution and nest-site selection in an increasing population of Peregrine Falcons (Falco peregrinus) in central West Greenland. Peregrine Falcons breeding at traditionally occupied cliffs used for nesting had significantly lower variation in productivity and thus these cliffs were better quality sites. This indicates that Peregrine Falcons occupied cliffs according to a pattern of despotic distribution. Falcons breeding at cliffs that were consistently occupied during the breeding season had higher average productivity and lower variation in productivity than falcons at inconsistently occupied cliffs, and thus consistent occupancy also was indicative of cliff quality. Features of high quality habitat included tall cliffs, greater change in elevation from the lowest point within 3 km of the cliff to the cliff top (elevation gain), and protection from weather on the eyrie ledge. Spacing of suitable and occupied cliffs also was an important feature, and the best cliffs generally were more isolated. Increased spacing was likely a mechanism for reducing intraspecific competition. Our results suggest that Peregrine Falcons use a resource defense strategy to compete for better quality habitats and may use spacing and physical features of a nest site to identify good quality breeding habitat. ?? The Cooper Ornithological Society 2006.

  9. Habitat selection by green turtles in a spatially heterogeneous benthic landscape in Dry Tortugas National Park, Florida

    USGS Publications Warehouse

    Fujisaki, Ikuko; Hart, Kristen M.; Sartain-Iverson, Autumn R.

    2016-01-01

    We examined habitat selection by green turtles Chelonia mydas at Dry Tortugas National Park, Florida, USA. We tracked 15 turtles (6 females and 9 males) using platform transmitter terminals (PTTs); 13 of these turtles were equipped with additional acoustic transmitters. Location data by PTTs comprised periods of 40 to 226 d in varying months from 2009 to 2012. Core areas were concentrated in shallow water (mean bathymetry depth of 7.7 m) with a comparably dense coverage of seagrass; however, the utilization distribution overlap index indicated a low degree of habitat sharing. The probability of detecting a turtle on an acoustic receiver was inversely associated with the distance from the receiver to turtle capture sites and was lower in shallower water. The estimated daily detection probability of a single turtle at a given acoustic station throughout the acoustic array was small (<0.1 in any year), and that of multiple turtle detections was even smaller. However, the conditional probability of multiple turtle detections, given at least one turtle detection at a receiver, was much higher despite the small number of tagged turtles in each year (n = 1 to 5). Also, multiple detections of different turtles at a receiver frequently occurred within a few minutes (40%, or 164 of 415, occurred within 1 min). Our numerical estimates of core area overlap, co-occupancy probabilities, and habitat characterization for green turtles could be used to guide conservation of the area to sustain the population of this species.

  10. Hemosporidian blood parasites in seabirds—a comparative genetic study of species from Antarctic to tropical habitats

    NASA Astrophysics Data System (ADS)

    Quillfeldt, Petra; Martínez, Javier; Hennicke, Janos; Ludynia, Katrin; Gladbach, Anja; Masello, Juan F.; Riou, Samuel; Merino, Santiago

    2010-09-01

    Whereas some bird species are heavily affected by blood parasites in the wild, others reportedly are not. Seabirds, in particular, are often free from blood parasites, even in the presence of potential vectors. By means of polymerase chain reaction, we amplified a DNA fragment from the cytochrome b gene to detect parasites of the genera Plasmodium, Leucocytozoon, and Haemoproteus in 14 seabird species, ranging from Antarctica to the tropical Indian Ocean. We did not detect parasites in 11 of these species, including one Antarctic, four subantarctic, two temperate, and four tropical species. On the other hand, two subantarctic species, thin-billed prions Pachyptila belcheri and dolphin gulls Larus scoresbii, were found infected. One of 28 thin-billed prions had a Plasmodium infection whose DNA sequence was identical to lineage P22 of Plasmodium relictum, and one of 20 dolphin gulls was infected with a Haemoproteus lineage which appears phylogenetically clustered with parasites species isolated from passeriform birds such as Haemoproteus lanii, Haemoproteus magnus, Haemoproteus fringillae, Haemoproteus sylvae, Haemoproteus payevskyi, and Haemoproteus belopolskyi. In addition, we found a high parasite prevalence in a single tropical species, the Christmas Island frigatebird Fregata andrewsi, where 56% of sampled adults were infected with Haemoproteus. The latter formed a monophyletic group that includes a Haemoproteus line from Eastern Asian black-tailed gulls Larus crassirostris. Our results are in agreement with those showing that (a) seabirds are poor in hemosporidians and (b) latitude could be a determining factor to predict the presence of hemosporidians in birds. However, further studies should explore the relative importance of extrinsic and intrinsic factors on parasite prevalence, in particular using phylogenetically controlled comparative analyses, systematic sampling and screening of vectors, and within-species comparisons.

  11. Hemosporidian blood parasites in seabirds—a comparative genetic study of species from Antarctic to tropical habitats

    PubMed Central

    Martínez, Javier; Hennicke, Janos; Ludynia, Katrin; Gladbach, Anja; Masello, Juan F.; Riou, Samuel; Merino, Santiago

    2010-01-01

    Whereas some bird species are heavily affected by blood parasites in the wild, others reportedly are not. Seabirds, in particular, are often free from blood parasites, even in the presence of potential vectors. By means of polymerase chain reaction, we amplified a DNA fragment from the cytochrome b gene to detect parasites of the genera Plasmodium, Leucocytozoon, and Haemoproteus in 14 seabird species, ranging from Antarctica to the tropical Indian Ocean. We did not detect parasites in 11 of these species, including one Antarctic, four subantarctic, two temperate, and four tropical species. On the other hand, two subantarctic species, thin-billed prions Pachyptila belcheri and dolphin gulls Larus scoresbii, were found infected. One of 28 thin-billed prions had a Plasmodium infection whose DNA sequence was identical to lineage P22 of Plasmodium relictum, and one of 20 dolphin gulls was infected with a Haemoproteus lineage which appears phylogenetically clustered with parasites species isolated from passeriform birds such as Haemoproteus lanii, Haemoproteus magnus, Haemoproteus fringillae, Haemoproteus sylvae, Haemoproteus payevskyi, and Haemoproteus belopolskyi. In addition, we found a high parasite prevalence in a single tropical species, the Christmas Island frigatebird Fregata andrewsi, where 56% of sampled adults were infected with Haemoproteus. The latter formed a monophyletic group that includes a Haemoproteus line from Eastern Asian black-tailed gulls Larus crassirostris. Our results are in agreement with those showing that (a) seabirds are poor in hemosporidians and (b) latitude could be a determining factor to predict the presence of hemosporidians in birds. However, further studies should explore the relative importance of extrinsic and intrinsic factors on parasite prevalence, in particular using phylogenetically controlled comparative analyses, systematic sampling and screening of vectors, and within-species comparisons. PMID:20652673

  12. Effects of Habitat Structure and Fragmentation on Diversity and Abundance of Primates in Tropical Deciduous Forests in Bolivia

    PubMed Central

    Büntge, Anna B. S.; Herzog, Sebastian K.; Kessler, Michael

    2010-01-01

    Habitat structure and anthropogenic disturbance are known to affect primate diversity and abundance. However, researchers have focused on lowland rain forests, whereas endangered deciduous forests have been neglected. We aimed to investigate the relationships between primate diversity and abundance and habitat parameters in 10 deciduous forest fragments southeast of Santa Cruz, Bolivia. We obtained primate data via line-transect surveys and visual and acoustic observations. In addition, we assessed the vegetation structure (canopy height, understory density), size, isolation time, and surrounding forest area of the fragments. We interpreted our results in the context of the historical distribution data for primates in the area before fragmentation and interviews with local people. We detected 5 of the 8 historically observed primate species: Alouatta caraya, Aotus azarae boliviensis, Callithrix melanura, Callicebus donacophilus, and Cebus libidinosus juruanus. Total species number and detection rates decreased with understory density. Detection rates also negatively correlated with forest areas in the surroundings of a fragment, which may be due to variables not assessed, i.e., fragment shape, distance to nearest town. Observations for Alouatta and Aotus were too few to conduct further statistics. Cebus and Callicebus were present in 90% and 70% of the sites, respectively, and their density did not correlate with any of the habitat variables assessed, signaling high ecological plasticity and adaptability to anthropogenic impact in these species. Detections of Callithrix were higher in areas with low forest strata. Our study provides baseline data for future fragmentation studies in Neotropical dry deciduous forests and sets a base for specific conservation measures. PMID:20949116

  13. Context-dependent effects of feather corticosterone on growth rate and fledging success of wild passerine nestlings in heterogeneous habitat.

    PubMed

    Lodjak, Jaanis; Mägi, Marko; Rooni, Uku; Tilgar, Vallo

    2015-12-01

    Life history theory seeks answers to questions about how suites of traits, like growth rate, body mass and survival, have coevolved to maximize the fitness of individuals. In stochastic environments, individual fitness may be closely linked to environmental conditions experienced early in life. When conditions deteriorate, animals have to adapt physiologically to avoid detrimental effects to growth and survival. Hormones such as glucocorticoids are potentially important mediators of developmental plasticity, although their function is quite poorly understood in free-living animals to date. In this study, we used brood-size manipulation in wild great tits (Parus major) to see whether resource (e.g. food) availability can change feather corticosterone levels, somatic growth and fledging success in nestlings raised in habitats of different quality. Recent studies suggest that feather corticosterone offers a long-term hormonal measure for the main avian glucocorticoid by integrating the plasma levels of corticosterone over the whole nestling period. We showed that feather corticosterone, growth rate and fledging success were significantly affected by the treatment only in coniferous forests where growth conditions had a tendency to be poorer than in deciduous forests. We also found that feather corticosterone was negatively related to fledging success, and this effect was more pronounced in coniferous habitat. Our results suggest that feather corticosterone could offer an important physiological measure for nestling performance, mediated by a context-dependent developmental trade-off between immediate and future survival. PMID:26025576

  14. Living in Heterogeneous Woodlands – Are Habitat Continuity or Quality Drivers of Genetic Variability in a Flightless Ground Beetle?

    PubMed Central

    Marcus, Tamar; Boch, Steffen; Durka, Walter; Fischer, Markus; Gossner, Martin M.; Müller, Jörg; Schöning, Ingo; Weisser, Wolfgang W.

    2015-01-01

    Although genetic diversity is one of the key components of biodiversity, its drivers are still not fully understood. While it is known that genetic diversity is affected both by environmental parameters as well as habitat history, these factors are not often tested together. Therefore, we analyzed 14 microsatellite loci in Abax parallelepipedus, a flightless, forest dwelling ground beetle, from 88 plots in two study regions in Germany. We modeled the effects of historical and environmental variables on allelic richness, and found for one of the regions, the Schorfheide-Chorin, a significant effect of the depth of the litter layer, which is a main component of habitat quality, and of the sampling effort, which serves as an inverse proxy for local population size. For the other region, the Schwäbische Alb, none of the potential drivers showed a significant effect on allelic richness. We conclude that the genetic diversity in our study species is being driven by current local population sizes via environmental variables and not by historical processes in the studied regions. This is also supported by lack of genetic differentiation between local populations sampled from ancient and from recent woodlands. We suggest that the potential effects of former fragmentation and recolonization processes have been mitigated by the large and stable local populations of Abax parallelepipedus in combination with the proximity of the ancient and recent woodlands in the studied landscapes. PMID:26641644

  15. Heterogeneities of the malaria vectorial system in tropical Africa and their significance in malaria epidemiology and control

    PubMed Central

    Coluzzi, Mario

    1984-01-01

    The most important units of the malaria vectorial system in tropical Africa are included in the Linnaean taxon Anopheles gambiae, which has been split into six sibling species recognized by the application of genetic techniques. More recent studies have shown further complexities involving chromosomal inversion polymorphism in some vector populations as well as incipient speciation processes. The significance for field research in malaria of the splitting of a morphological taxon into genetically defined units and subunits is discussed. PMID:6335681

  16. Heterogeneous sources of oxygenated hydrocarbons in the tropical free troposphere: Field evidence for a biogeochemical cycle of marine organic carbon?

    NASA Astrophysics Data System (ADS)

    Volkamer, R.; Apel, E. C.; Baidar, S.; Coburn, S.; Dix, B. K.; Hornbrook, R. S.; Pierce, R.; Ortega, I.; Romashkin, P.; Wang, S.

    2013-12-01

    Oceans cover 70% of the Earth surface, and the amount of dissolved organic carbon (DOC) contained in the world's oceans is comparable to that of atmospheric CO2. Yet oceans are currently believed to be a net-receptor for organic carbon that is emitted over land. Recent our observations of very short-lived and very water soluble oxygenated hydrocarbons, like glyoxal, in the remote marine boundary layer (MBL) above the Pacific Ocean (Sinreich et al., 2010, ACP) remain as of yet unexplained by atmospheric models. Organic carbon is relevant in the atmosphere because it influences the reactive chemical removal pathways of climate active gases (i.e., ozone, methane, dimethyl-sulfide), and can modify aerosols (e.g., secondary organic aerosol, SOA). This presentation provides a comprehensive field evidence that small oxygenated molecules (glyoxal, methyl ethyl ketone, butanal) from marine sources are widespread also in the tropical free troposphere. The data were collected as part of the Tropical Ocean tRoposphere Exchange experiment TORERO during Jan/Feb 2012 by means of an innovative payload of optical spectroscopic-, mass spectrometric-, and remote sensing instruments aboard the NSF/NCAR GV aircraft (HIAPER), and aboard a NOAA ship. We have measured oxygenated hydrocarbons, and volatile organic compounds (some 50+ species), aerosol size distributions, photolysis frequencies and other parameters over the full tropospheric air column (0-15km altitude) between 40N to 40S latitude over the eastern tropical Pacific Ocean. We investigate the source mechanism, present source estimates of the organic carbon flux, and compare it with other sources of organic carbon from marine sources. We also present results from numerical models that suggest a strong impact of these molecules on the oxidative capacity of the tropical free troposphere, where most of tropospheric ozone mass resides, 60-80% of the global methane destruction occurs, and mercury oxidation rates are accelerated at

  17. Continent-wide tracking to determine migratory connectivity and tropical habitat associations of a declining aerial insectivore

    PubMed Central

    Fraser, Kevin C.; Stutchbury, Bridget J. M.; Silverio, Cassandra; Kramer, Patrick M.; Barrow, John; Newstead, David; Mickle, Nanette; Cousens, Bruce F.; Lee, J. Charlene; Morrison, Danielle M.; Shaheen, Tim; Mammenga, Paul; Applegate, Kelly; Tautin, John

    2012-01-01

    North American birds that feed on flying insects are experiencing steep population declines, particularly long-distance migratory populations in the northern breeding range. We determine, for the first time, the level of migratory connectivity across the range of a songbird using direct tracking of individuals, and test whether declining northern populations have higher exposure to agricultural landscapes at their non-breeding grounds in South America. We used light-level geolocators to track purple martins, Progne subis, originating from North American breeding populations, coast-to-coast (n = 95 individuals). We show that breeding populations of the eastern subspecies, P. s. subis, that are separated by ca. 2000 km, nevertheless have almost completely overlapping non-breeding ranges in Brazil. Most (76%) P. s. subis overwintered in northern Brazil near the Amazon River, not in the agricultural landscape of southern Brazil. Individual non-breeding sites had an average of 91 per cent forest and only 4 per cent agricultural ground cover within a 50 km radius, and birds originating from declining northern breeding populations were not more exposed to agricultural landscapes than stable southern breeding populations. Our results show that differences in wintering location and habitat do not explain recent trends in breeding population declines in this species, and instead northern populations may be constrained in their ability to respond to climate change. PMID:23097508

  18. Detectability in Audio-Visual Surveys of Tropical Rainforest Birds: The Influence of Species, Weather and Habitat Characteristics

    PubMed Central

    Anderson, Alexander S.; Marques, Tiago A.; Shoo, Luke P.; Williams, Stephen E.

    2015-01-01

    Indices of relative abundance do not control for variation in detectability, which can bias density estimates such that ecological processes are difficult to infer. Distance sampling methods can be used to correct for detectability, but in rainforest, where dense vegetation and diverse assemblages complicate sampling, information is lacking about factors affecting their application. Rare species present an additional challenge, as data may be too sparse to fit detection functions. We present analyses of distance sampling data collected for a diverse tropical rainforest bird assemblage across broad elevational and latitudinal gradients in North Queensland, Australia. Using audio and visual detections, we assessed the influence of various factors on Effective Strip Width (ESW), an intuitively useful parameter, since it can be used to calculate an estimate of density from count data. Body size and species exerted the most important influence on ESW, with larger species detectable over greater distances than smaller species. Secondarily, wet weather and high shrub density decreased ESW for most species. ESW for several species also differed between summer and winter, possibly due to seasonal differences in calling behavior. Distance sampling proved logistically intensive in these environments, but large differences in ESW between species confirmed the need to correct for detection probability to obtain accurate density estimates. Our results suggest an evidence-based approach to controlling for factors influencing detectability, and avenues for further work including modeling detectability as a function of species characteristics such as body size and call characteristics. Such models may be useful in developing a calibration for non-distance sampling data and for estimating detectability of rare species. PMID:26110433

  19. Multi-proxy approach detects heterogeneous habitats for primates during the Miocene climatic optimum in Central Europe.

    PubMed

    Merceron, Gildas; Costeur, Loïc; Maridet, Olivier; Ramdarshan, Anusha; Göhlich, Ursula B

    2012-07-01

    The present study attempts to characterize the environmental conditions that prevailed along the western shores of the Central Paratethys and its hinterland during the early middle Miocene at the same time t primates reached their peak in species diversity in Central Europe. Based on faunal structure (using cenograms), paleotemperature reconstruction (using cricetid diversity), and dietary reconstruction of ruminants (using molar micro-wear analyses), four faunal assemblages are used to characterize the regional environmental context. The cenograms for Göriach and Devínska Novà Ves Zapfe's fissure site support the presence of mosaic environments with open areas under rather humid conditions. This is also supported by the dental micro-wear analyses of ruminants. The species of Palaeomerycidae were most probably the only predominant browsers. Surprisingly, the three cervids, Dicrocerus, Heteroprox, and Euprox, were highly involved in grazing. Pseudoeotragus seegrabensis was likely a generalist and the two specimens assigned to the second bovid, Eotragus clavatus, were browsers. The two species of tragulids plot between fruit browsers and generalists. Moreover, paleotemperatures based on cricetid diversity estimate mean annual temperature at about 18 °C with potential high seasonal variations. These data support the predominance of mosaic landscapes along the western shores of the Central Paratethys and its hinterland during the Miocene Climatic Optimum as primates reach a peak in species diversity. This result lends credence to the hypothesis that environmental heterogeneity favours radiation among mammals, and that the specific environmental context of the Central Paratethys western border might explain the high diversity of the middle Miocene primates. PMID:22658333

  20. An agent-based model driven by tropical rainfall to understand the spatio-temporal heterogeneity of a chikungunya outbreak.

    PubMed

    Dommar, Carlos J; Lowe, Rachel; Robinson, Marguerite; Rodó, Xavier

    2014-01-01

    Vector-borne diseases, such as dengue, malaria and chikungunya, are increasing across their traditional ranges and continuing to infiltrate new, previously unaffected, regions. The spatio-temporal evolution of these diseases is determined by the interaction of the host and vector, which is strongly dependent on social structures and mobility patterns. We develop an agent-based model (ABM), in which each individual is explicitly represented and vector populations are linked to precipitation estimates in a tropical setting. The model is implemented on both scale-free and regular networks. The spatio-temporal transmission of chikungunya is analysed and the presence of asymptomatic silent spreaders within the population is investigated in the context of implementing travel restrictions during an outbreak. Preventing the movement of symptomatic individuals is found to be an insufficient mechanism to halt the spread of the disease, which can be readily carried to neighbouring nodes via sub-clinical individuals. Furthermore, the impact of topology structure vs. precipitation levels is assessed and precipitation is found to be the dominant factor driving spatio-temporal transmission. PMID:23958228

  1. Understanding Heterogeneity in the Impact of National Neglected Tropical Disease Control Programmes: Evidence from School-Based Deworming in Kenya

    PubMed Central

    Nikolay, Birgit; Mwandawiro, Charles S.; Kihara, Jimmy H.; Okoyo, Collins; Cano, Jorge; Mwanje, Mariam T.; Sultani, Hadley; Alusala, Dorcas; Turner, Hugo C.; Teti, Caroline; Garn, Josh; Freeman, Matthew C.; Allen, Elizabeth; Anderson, Roy M.; Pullan, Rachel L.; Njenga, Sammy M.; Brooker, Simon J.

    2015-01-01

    Background The implementation of soil-transmitted helminth (STH) treatment programmes occurs in varied environmental, social and economic contexts. Programme impact will be influenced by factors that affect the reduction in the prevalence and intensity of infections following treatment, as well as the subsequent rate of reinfection. To better understand the heterogeneity of programme impact and its underlying reasons, we investigated the influence of contextual factors on reduction in STH infection as part of the national school based deworming (SBD) programme in Kenya. Materials and Methods Data on the prevalence and intensity of infection were collected within the monitoring and evaluation component of the SBD programme at baseline and after delivery of two annual treatment rounds in 153 schools in western Kenya. Using a framework that considers STH epidemiology and transmission dynamics, capacity to deliver treatment, operational feasibility and financial capacity, data were assembled at both school and district (county) levels. Geographic heterogeneity of programme impact was assessed by descriptive and spatial analyses. Factors associated with absolute reductions of Ascaris lumbricoides and hookworm infection prevalence and intensity were identified using mixed effects linear regression modelling adjusting for baseline infection levels. Principal Findings The reduction in prevalence and intensity of A. lumbricoides and hookworms varied significantly by county and within counties by school. Multivariable analysis of factors associated with programme impact showed that absolute A. lumbricoides reductions varied by environmental conditions and access to improved sanitation at schools or within the community. Larger reduction in prevalence and intensity of hookworms were found in schools located within areas with higher community level access to improved sanitation and within counties with higher economic and health service delivery indicator scores. Conclusions

  2. Structural and functional study of the nematode community from the Indian western continental margin with reference to habitat heterogeneity and oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Singh, R.; Ingole, B. S.

    2015-07-01

    We studied patterns of nematode distribution along the western Indian continental margin to determine the influence of habitat heterogeneity and oxygen minimum on the community's taxonomic and functional structure. A single transect, perpendicular to the coast at 14° N latitude was sampled from 34 to 2546 m depth for biological and environmental variables during August 2007. Nematodes were identified to species and classified according to biological/functional traits. A total of 110 nematode species belonging to 24 families were found along the transect. Mean nematode density was higher on the shelf (176 ind 10 cm-2, 34 m depth) than on the slope (124 ind 10 cm-2) or in the basin 62.9 ind 10 cm-2). Across the entire study area, the dominant species were Terschellingia longicaudata, (15.2 %), Desmodora sp 1, Sphaerolaimus gracilis, and Theristus ensifer; their maximum density was at shelf stations. Multidimensional scaling ordination (nMDS) of the nematode species abundance data indicated the effect of different zones (ANOSIM; Global R = 0.607; P = 0.028), but it was not the same in case of functional traits. Only seven species were found exclusively in the oxygen minimum zone: Pselionema sp 1, Choanolaimus sp 2, Halichoanolaimus sp 1, Cobbia dentata, Daptonema sp 1, Trissonchulus sp 1, and Minolaimus sp 1. Moreover, in our study, species diversity was higher on the shelf than on the slope or in the basin. The distinctive features of all three zones as based on nematofaunal abundance were also reflected in the functional traits (feeding types, body shape, tail shape, and life history strategy). Correlation with a number of environmental variables indicated that food quality (measured as the organic carbon content and chlorophyll content) and oxygen level were the major factors that influenced the nematode community (structural and functional).

  3. Global habitat preferences of commercially valuable tuna

    NASA Astrophysics Data System (ADS)

    Arrizabalaga, Haritz; Dufour, Florence; Kell, Laurence; Merino, Gorka; Ibaibarriaga, Leire; Chust, Guillem; Irigoien, Xabier; Santiago, Josu; Murua, Hilario; Fraile, Igaratza; Chifflet, Marina; Goikoetxea, Nerea; Sagarminaga, Yolanda; Aumont, Olivier; Bopp, Laurent; Herrera, Miguel; Marc Fromentin, Jean; Bonhomeau, Sylvain

    2015-03-01

    In spite of its pivotal role in future implementations of the Ecosystem Approach to Fisheries Management, current knowledge about tuna habitat preferences remains fragmented and heterogeneous, because it relies mainly on regional or local studies that have used a variety of approaches making them difficult to combine. Therefore in this study we analyse data from six tuna species in the Pacific, Atlantic and Indian Oceans in order to provide a global, comparative perspective of habitat preferences. These data are longline catch per unit effort from 1958 to 2007 for albacore, Atlantic bluefin, southern bluefin, bigeye, yellowfin and skipjack tunas. Both quotient analysis and Generalised Additive Models were used to determine habitat preference with respect to eight biotic and abiotic variables. Results confirmed that, compared to temperate tunas, tropical tunas prefer warm, anoxic, stratified waters. Atlantic and southern bluefin tuna prefer higher concentrations of chlorophyll than the rest. The two species also tolerate most extreme sea surface height anomalies and highest mixed layer depths. In general, Atlantic bluefin tuna tolerates the widest range of environmental conditions. An assessment of the most important variables determining fish habitat is also provided.

  4. Vertical and Horizontal Vegetation Structure across Natural and Modified Habitat Types at Mount Kilimanjaro

    PubMed Central

    Rutten, Gemma; Ensslin, Andreas; Hemp, Andreas; Fischer, Markus

    2015-01-01

    In most habitats, vegetation provides the main structure of the environment. This complexity can facilitate biodiversity and ecosystem services. Therefore, measures of vegetation structure can serve as indicators in ecosystem management. However, many structural measures are laborious and require expert knowledge. Here, we used consistent and convenient measures to assess vegetation structure over an exceptionally broad elevation gradient of 866–4550m above sea level at Mount Kilimanjaro, Tanzania. Additionally, we compared (human)-modified habitats, including maize fields, traditionally managed home gardens, grasslands, commercial coffee farms and logged and burned forests with natural habitats along this elevation gradient. We distinguished vertical and horizontal vegetation structure to account for habitat complexity and heterogeneity. Vertical vegetation structure (assessed as number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) displayed a unimodal elevation pattern, peaking at intermediate elevations in montane forests, whereas horizontal structure (assessed as coefficient of variation of number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) was lowest at intermediate altitudes. Overall, vertical structure was consistently lower in modified than in natural habitat types, whereas horizontal structure was inconsistently different in modified than in natural habitat types, depending on the specific structural measure and habitat type. Our study shows how vertical and horizontal vegetation structure can be assessed efficiently in various habitat types in tropical mountain regions, and we suggest to apply this as a tool for informing future biodiversity and ecosystem service studies. PMID:26406985

  5. Vertical and Horizontal Vegetation Structure across Natural and Modified Habitat Types at Mount Kilimanjaro.

    PubMed

    Rutten, Gemma; Ensslin, Andreas; Hemp, Andreas; Fischer, Markus

    2015-01-01

    In most habitats, vegetation provides the main structure of the environment. This complexity can facilitate biodiversity and ecosystem services. Therefore, measures of vegetation structure can serve as indicators in ecosystem management. However, many structural measures are laborious and require expert knowledge. Here, we used consistent and convenient measures to assess vegetation structure over an exceptionally broad elevation gradient of 866-4550 m above sea level at Mount Kilimanjaro, Tanzania. Additionally, we compared (human)-modified habitats, including maize fields, traditionally managed home gardens, grasslands, commercial coffee farms and logged and burned forests with natural habitats along this elevation gradient. We distinguished vertical and horizontal vegetation structure to account for habitat complexity and heterogeneity. Vertical vegetation structure (assessed as number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) displayed a unimodal elevation pattern, peaking at intermediate elevations in montane forests, whereas horizontal structure (assessed as coefficient of variation of number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) was lowest at intermediate altitudes. Overall, vertical structure was consistently lower in modified than in natural habitat types, whereas horizontal structure was inconsistently different in modified than in natural habitat types, depending on the specific structural measure and habitat type. Our study shows how vertical and horizontal vegetation structure can be assessed efficiently in various habitat types in tropical mountain regions, and we suggest to apply this as a tool for informing future biodiversity and ecosystem service studies. PMID:26406985

  6. Trees as templates for tropical litter arthropod diversity.

    PubMed

    Donoso, David A; Johnston, Mary K; Kaspari, Michael

    2010-09-01

    Increased tree species diversity in the tropics is associated with even greater herbivore diversity, but few tests of tree effects on litter arthropod diversity exist. We studied whether tree species influence patchiness in diversity and abundance of three common soil arthropod taxa (ants, gamasid mites, and oribatid mites) in a Panama forest. The tree specialization hypothesis proposes that tree-driven habitat heterogeneity maintains litter arthropod diversity. We tested whether tree species differed in resource quality and quantity of their leaf litter and whether more heterogeneous litter supports more arthropod species. Alternatively, the abundance-extinction hypothesis states that arthropod diversity increases with arthropod abundance, which in turn tracks resource quantity (e.g., litter depth). We found little support for the hypothesis that tropical trees are templates for litter arthropod diversity. Ten tree species differed in litter depth, chemistry, and structural variability. However, the extent of specialization of invertebrates on particular tree taxa was low and the more heterogeneous litter between trees failed to support higher arthropod diversity. Furthermore, arthropod diversity did not track abundance or litter depth. The lack of association between tree species and litter arthropods suggests that factors other than tree species diversity may better explain the high arthropod diversity in tropical forests. PMID:20349247

  7. Spatial extent of potential habitats of the Mesophotic Coral Ecosystem (MCE, 20-80 m) in the tropical North Atlantic (TNA)

    NASA Astrophysics Data System (ADS)

    Ginsburg, R. N.

    2012-12-01

    The Mesophotic Coral Ecosystem is the deeper-water extension of the much-studied, shallow reef community. It occurs on steep slopes and shelf areas, in the TNA off Belize, the Bahamas, the US Virgin Islands, and the Flower Garden Banks. Framework-building corals at these depths are primarily platy montastraeids and agariciids, with lesser amounts of massive encrusting species. The closely-spaced, platy colonies, expanding up to nearly two meters in diameter have up to 50% live coral cover. The colonies are elevated above the substrate. Their growth creates a thicket-like structure with large, open spaces for mobile species (fish and crustaceans) and extensive habitat for attached and grazing invertebrates. The MCE includes genera or species of zooxanthellate corals, invertebrates and fish, some of which are the same as those in shallow water. Given, the widespread, recent declines of TNA coral communities at depth less than 20 m, it is essential to know the total regional extent of the MCE. To determine the likely depth locations of these deeper coral communities we used methods pioneered by REEFS AT RISK,1998 that incorporates data from the Danish Hydrological Institute (DHI), "MIKE C-MAP" depth points and data on coastline location *NASA, "Sea WiFS" and NIMA, "VMAP," 1997. The results for the larger areas of reef development and for shelf areas are below:Potential MCE shelf habitats.t; Potential MCE platform margin habitats.t;

  8. An experimental study of habitat selection by birds in a coffee plantation.

    PubMed

    Cruz-Angón, Andrea; Sillett, T Scott; Greenberg, Russell

    2008-04-01

    Unique components of tropical habitats, such as abundant vascular epiphytes, influence the distribution of species and can contribute to the high diversity of many animal groups in the tropics. However, the role of such features in habitat selection and demography of individual species has not been established. Understanding the mechanisms of habitat selection requires both experimental manipulation of habitat structure and detailed estimation of the behavioral and demographic response of animals, e.g., changes in movement patterns and survival probabilities. Such studies have not been conducted in natural tropical forest, perhaps because of high habitat heterogeneity, high species diversity, and low abundances of potential target species. Agroforestry systems support a less diverse flora, with greater spatial homogeneity which, in turn, harbors lower overall species diversity with greater numerical dominance of common species, than natural forests. Furthermore, agroforestry systems are already extensively managed and lend themselves easily to larger scale habitat manipulations than protected natural forest. Thus, agroforestry systems provide a good model environment for beginning to understand processes underlying habitat selection in tropical forest animals. Here, we use multistate, capture-recapture models to investigate how the experimental removal of epiphytes affected monthly movement and survival probabilities of two resident bird species (Common Bush-Tanager [Chlorospingus ophthalmicus] and Golden-crowned Warbler [Basileuterus culicivorus]) in a Mexican shade coffee plantation. We established two paired plots of epiphyte removal and control. We found that Bush-Tanagers were at least five times more likely to emigrate from plots where epiphytes were removed compared to control plots. Habitat-specific movement patterns were not detected in the warbler. However, unlike the Golden-crowned Warbler, Common Bush-Tanagers depend upon epiphytes for nest sites and

  9. Outcompeted by an invader? Interference and exploitative competition between tropical house gecko (Hemidactylus mabouia) and Barbados leaf-toed gecko (Phyllodactylus pulcher) for diurnal refuges in anthropogenic coastal habitats.

    PubMed

    Williams, Robert; Pernetta, Angelo P; Horrocks, Julia A

    2016-05-01

    House geckos in the genus Hemidactylus are highly successful colonizers of regions beyond their native range, with colonization often resulting in displacement of native gecko species through competitive interactions for daytime refuge (crevices) and prey resources. We report on data collected from nighttime surveys undertaken in April-May 2014 on Barbados, West Indies, that focused on the distribution and abundance of the endemic Barbados leaf-toed gecko (Phyllodactylus pulcher) and the introduced tropical house gecko (Hemidactylus mabouia) along unlit coastal walls and among boulders in the grounds of a hotel resort. In contrast to patterns of displacement of native species by H. mabouia seen elsewhere, P. pulcher was more abundant than H. mabouia on coastal walls, whereas the latter was found in greater numbers using boulders at this site. Walls and boulders differed with regard to availability of diurnal refugia suitable for geckos, with the walls having high frequency of small crevices with openings <20 mm, and boulders offering very little cover other than the underside of the boulder itself. To investigate whether this niche separation was a result of differences in diurnal refuge use between the species, we conducted experimental trials in which geckos were allowed to select between refugia with different characteristics. Both species selected for narrower and warmer refugia, and refugia that had been previously occupied by the other species. These shared preferences for refugia type suggest that other factors underlie the niche separation observed in the field. In supporting high densities of P. pulcher, coastal walls could offer important secondary habitat by augmenting the natural cliff side habitat of this endemic gecko, a finding that could be exploited for the conservation of this candidate species for Critically Endangered classification. PMID:26923791

  10. Ecosystem services capacity across heterogeneous forest types: understanding the interactions and suggesting pathways for sustaining multiple ecosystem services.

    PubMed

    Alamgir, Mohammed; Turton, Stephen M; Macgregor, Colin J; Pert, Petina L

    2016-10-01

    As ecosystem services supply from tropical forests is declining due to deforestation and forest degradation, much effort is essential to sustain ecosystem services supply from tropical forested landscapes, because tropical forests provide the largest flow of multiple ecosystem services among the terrestrial ecosystems. In order to sustain multiple ecosystem services, understanding ecosystem services capacity across heterogeneous forest types and identifying certain ecosystem services that could be managed to leverage positive effects across the wider bundle of ecosystem services are required. We sampled three forest types, tropical rainforests, sclerophyll forests, and rehabilitated plantation forests, over an area of 32,000m(2) from Wet Tropics bioregion, Australia, aiming to compare supply and evaluate interactions and patterns of eight ecosystem services (global climate regulation, air quality regulation, erosion regulation, nutrient regulation, cyclone protection, habitat provision, energy provision, and timber provision). On average, multiple ecosystem services were highest in the rainforests, lowest in sclerophyll forests, and intermediate in rehabilitated plantation forests. However, a wide variation was apparent among the plots across the three forest types. Global climate regulation service had a synergistic impact on the supply of multiple ecosystem services, while nutrient regulation service was found to have a trade-off impact. Considering multiple ecosystem services, most of the rehabilitated plantation forest plots shared the same ordination space with rainforest plots in the ordination analysis, indicating that rehabilitated plantation forests may supply certain ecosystem services nearly equivalent to rainforests. Two synergy groups and one trade-off group were identified. Apart from conserving rainforests and sclerophyll forests, our findings suggest two additional integrated pathways to sustain the supply of multiple ecosystem services from a

  11. Production of two novel laccase isoforms by a thermotolerant strain of Pycnoporus sanguineus isolated from an oil-polluted tropical habitat.

    PubMed

    Dantán-González, Edgar; Vite-Vallejo, Odón; Martínez-Anaya, Claudia; Méndez-Sánchez, Mónica; González, María C; Palomares, Laura A; Folch-Mallol, Jorge

    2008-09-01

    A thermotolerant and halotolerant strain of Pycnoporus sanguineus was isolated from an oil-polluted site in a tropical area located in Veracruz, Mexico. This strain was able to grow at 47 degrees C and in culture medium containing 500 mM NaCl. The strain was also tolerant to the presence of 30,000 ppm of crude Maya oil. A 68-kDa protein purified from submerged cultures exhibited laccase activity towards 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), guaiacol, syringaldazine, and o-dianisidine, for which it presented the highest affinity (Km = 43 microM). Two-dimensional gel electrophoresis analysis showed that, unusual for laccases, the enzyme has two active isoforms, with isoelectric points of 7.00 and 7.08. The purified enzyme showed high thermostability, retaining 40% of its original activity after 3 h at 60 degrees C. This property seems to correlate with a long "shelf-life," given that at 40 degrees C enzyme activity was only gradually lost over a 5-day period incubation. Both the fungus and its laccase are likely to have high potential for biotechnological applications. PMID:18843594

  12. Adaptations of a tropical swamp worm, alma emini, for subsistence in a H2S-rich habitat: evolution of endosymbiotic bacteria, sulfide metabolizing bodies, and novel processes of elimination of neutralized sulfide complexes

    PubMed

    Maina; Maloiy

    1998-01-01

    The epithelial cell lining of the respiratory groove of Alma emini, an oligochaete glossoscolecid worm that lives in a hydrogen sulfide (H2S)-rich tropical swamp, was investigated by transmission electron microscopy to determine the underlying structural adaptations which enable the worm to subsist in a highly inimical habitat. The epithelium of the respiratory groove is made up of squamous cells with a highly amplified free epithelial surface. The cells are tightly packed with electron dense sulfur metabolizing bodies (SMBs) and contain endosymbiotic bacteria. Presence of sulfur in the electron dense SMBs was confirmed by X-ray microanalysis. Certain eukaryotic cells with prominent filopodia-like cytoplasmic extensions were observed under the epithelial cells and in the muscle tissue. The cells contained numerous heteromorphic endosymbiotic bacteria and scattered SMBs. Both the SMBs and the bacteria are reckoned to be involved in scavenging and detoxifying H2S. The removal of sulfide complexes was observed to occur through excision of blebs formed by epithelial cell membrane elaborations and by exocytosis of crystalline-like particles. These adaptive stratagems generally correspond with those that have been adopted by many marine and hydrothermal vent organisms that occupy sulfide-rich biomes. The congruent adaptive stratagems and ultrastructural morphologies in such a diverse community of organisms have been imposed by a common need to neutralize the insidious effects of H2S in their environments. Copyright 1998 Academic Press. PMID:9774530

  13. Disentangling How Landscape Spatial and Temporal Heterogeneity Affects Savanna Birds

    PubMed Central

    Price, Bronwyn; McAlpine, Clive A.; Kutt, Alex S.; Ward, Doug; Phinn, Stuart R.; Ludwig, John A.

    2013-01-01

    In highly seasonal tropical environments, temporal changes in habitat and resources are a significant determinant of the spatial distribution of species. This study disentangles the effects of spatial and mid to long-term temporal heterogeneity in habitat on the diversity and abundance of savanna birds by testing four competing conceptual models of varying complexity. Focussing on sites in northeast Australia over a 20 year time period, we used ground cover and foliage projected cover surfaces derived from a time series of Landsat Thematic Mapper imagery, rainfall data and site-level vegetation surveys to derive measures of habitat structure at local (1–100 ha) and landscape (100–1000s ha) scales. We used generalised linear models and an information theoretic approach to test the independent effects of spatial and temporal influences on savanna bird diversity and the abundance of eight species with different life-history behaviours. Of four competing models defining influences on assemblages of savanna birds, the most parsimonious included temporal and spatial variability in vegetation cover and site-scale vegetation structure, suggesting savanna bird species respond to spatial and temporal habitat heterogeneity at both the broader landscape scale and at the fine-scale. The relative weight, strength and direction of the explanatory variables changed with each of the eight species, reflecting their different ecology and behavioural traits. This study demonstrates that variations in the spatial pattern of savanna vegetation over periods of 10 to 20 years at the local and landscape scale strongly affect bird diversity and abundance. Thus, it is essential to monitor and manage both spatial and temporal variability in avian habitat to achieve long-term biodiversity outcomes. PMID:24066138

  14. Vegetation Cover and Habitat Heterogeneity derived from QuickBird data as proxies of Local Plant Species Richness in recently burned areas

    NASA Astrophysics Data System (ADS)

    Viedma, Olga; Torres, Ivan; Moreno, Jose Manuel

    2010-05-01

    smaller scales, herbaceous layer explained the greatest variability of species richness; whereas at higher scales, shrubs and trees increased their contribution in fitting plant species richness. Model's predictions and Moran's Index on residuals indicated that the best sampling scale to predict species richness from QuickBird data was at 100 m2. The high variance explained in most cases indicates that species richness in space can be well predicted by QuickBird derived data. Keywords: plant species richness, local nested scales, vegetation cover, spatial heterogeneity, texture, reflectivity, QuickBird.

  15. Thermal Adaptation and Diversity in Tropical Ecosystems: Evidence from Cicadas (Hemiptera, Cicadidae)

    PubMed Central

    Sanborn, Allen F.; Heath, James E.; Phillips, Polly K.; Heath, Maxine S.; Noriega, Fernando G.

    2011-01-01

    The latitudinal gradient in species diversity is a central problem in ecology. Expeditions covering approximately 16°54′ of longitude and 21°4′ of latitude and eight Argentine phytogeographic regions provided thermal adaptation data for 64 species of cicadas. We test whether species diversity relates to the diversity of thermal environments within a habitat. There are general patterns of the thermal response values decreasing in cooler floristic provinces and decreasing maximum potential temperature within a habitat except in tropical forest ecosystems. Vertical stratification of the plant communities leads to stratification in species using specific layers of the habitat. There is a decrease in thermal tolerances in species from the understory communities in comparison to middle level or canopy fauna. The understory Herrera umbraphila Sanborn & Heath is the first diurnally active cicada identified as a thermoconforming species. The body temperature for activity in H. umbraphila is less than and significantly different from active body temperatures of all other studied species regardless of habitat affiliation. These data suggest that variability in thermal niches within the heterogeneous plant community of the tropical forest environments permits species diversification as species adapt their physiology to function more efficiently at temperatures different from their potential competitors. PMID:22242117

  16. Diversity patterns of selected Andean plant groups correspond to topography and habitat dynamics, not orogeny.

    PubMed

    Mutke, Jens; Jacobs, Rana; Meyers, Katharina; Henning, Tilo; Weigend, Maximilian

    2014-01-01

    The tropical Andes are a hotspot of biodiversity, but detailed altitudinal and latitudinal distribution patterns of species are poorly understood. We compare the distribution and diversity patterns of four Andean plant groups on the basis of georeferenced specimen data: the genus Nasa (Loasaceae), the two South American sections of Ribes (sect. Parilla and sect. Andina, Grossulariaceae), and the American clade of Urtica (Urticaceae). In the tropical Andes, these often grow together, especially in (naturally or anthropogenically) disturbed or secondary vegetation at middle to upper elevations. The climatic niches of the tropical groups studied here are relatively similar in temperature and temperature seasonality, but do differ in moisture seasonality. The Amotape-Huancabamba Zone (AHZ) between 3 and 8° S shows a clear diversity peak of overall species richness as well as for narrowly endemic species across the groups studied. For Nasa, we also show a particular diversity of growth forms in the AHZ. This can be interpreted as proxy for a high diversity of ecological niches based on high spatial habitat heterogeneity in this zone. Latitudinal ranges are generally larger toward the margins of overall range of the group. Species number and number of endemic species of our taxa peak at elevations of 2,500-3,500 m in the tropical Andes. Altitudinal diversity patterns correspond well with the altitudinal distribution of slope inclination. We hypothesize that the likelihood and frequency of landslides at steeper slopes translate into temporal habitat heterogeneity. The frequency of landslides may be causally connected to diversification especially for the numerous early colonizing taxa, such as Urtica and annual species of Nasa. In contrast to earlier hypotheses, uplift history is not reflected in the pattern here retrieved, since the AHZ is the area of the most recent Andean uplift. Similarly, a barrier effect of the low-lying Huancabamba depression is not retrieved in

  17. Diversity patterns of selected Andean plant groups correspond to topography and habitat dynamics, not orogeny

    PubMed Central

    Mutke, Jens; Jacobs, Rana; Meyers, Katharina; Henning, Tilo; Weigend, Maximilian

    2014-01-01

    The tropical Andes are a hotspot of biodiversity, but detailed altitudinal and latitudinal distribution patterns of species are poorly understood. We compare the distribution and diversity patterns of four Andean plant groups on the basis of georeferenced specimen data: the genus Nasa (Loasaceae), the two South American sections of Ribes (sect. Parilla and sect. Andina, Grossulariaceae), and the American clade of Urtica (Urticaceae). In the tropical Andes, these often grow together, especially in (naturally or anthropogenically) disturbed or secondary vegetation at middle to upper elevations. The climatic niches of the tropical groups studied here are relatively similar in temperature and temperature seasonality, but do differ in moisture seasonality. The Amotape–Huancabamba Zone (AHZ) between 3 and 8° S shows a clear diversity peak of overall species richness as well as for narrowly endemic species across the groups studied. For Nasa, we also show a particular diversity of growth forms in the AHZ. This can be interpreted as proxy for a high diversity of ecological niches based on high spatial habitat heterogeneity in this zone. Latitudinal ranges are generally larger toward the margins of overall range of the group. Species number and number of endemic species of our taxa peak at elevations of 2,500–3,500 m in the tropical Andes. Altitudinal diversity patterns correspond well with the altitudinal distribution of slope inclination. We hypothesize that the likelihood and frequency of landslides at steeper slopes translate into temporal habitat heterogeneity. The frequency of landslides may be causally connected to diversification especially for the numerous early colonizing taxa, such as Urtica and annual species of Nasa. In contrast to earlier hypotheses, uplift history is not reflected in the pattern here retrieved, since the AHZ is the area of the most recent Andean uplift. Similarly, a barrier effect of the low-lying Huancabamba depression is not retrieved

  18. Habitat automation

    NASA Technical Reports Server (NTRS)

    Swab, Rodney E.

    1992-01-01

    A habitat, on either the surface of the Moon or Mars, will be designed and built with the proven technologies of that day. These technologies will be mature and readily available to the habitat designer. We believe an acceleration of the normal pace of automation would allow a habitat to be safer and more easily maintained than would be the case otherwise. This document examines the operation of a habitat and describes elements of that operation which may benefit from an increased use of automation. Research topics within the automation realm are then defined and discussed with respect to the role they can have in the design of the habitat. Problems associated with the integration of advanced technologies into real-world projects at NASA are also addressed.

  19. Restoring degraded tropical forests for carbon and biodiversity

    NASA Astrophysics Data System (ADS)

    Budiharta, Sugeng; Meijaard, Erik; Erskine, Peter D.; Rondinini, Carlo; Pacifici, Michela; Wilson, Kerrie A.

    2014-11-01

    The extensive deforestation and degradation of tropical forests is a significant contributor to the loss of biodiversity and to global warming. Restoration could potentially mitigate the impacts of deforestation, yet knowledge on how to efficiently allocate funding for restoration is still in its infancy. We systematically prioritize investments in restoration in the tropical landscape of East Kalimantan, Indonesia, and through this application demonstrate the capacity to account for a diverse suite of restoration techniques and forests of varying condition. To achieve this we develop a map of forest degradation for the region, characterized on the basis of aboveground biomass and differentiated by broad forest types. We estimate the costs of restoration as well as the benefits in terms of carbon sequestration and improving the suitability of habitat for threatened mammals through time. When the objective is solely to enhance carbon stocks, then restoration of highly degraded lowland forest is the most cost-effective activity. However, if the objective is to improve the habitat of threatened species, multiple forest types should be restored and this reduces the accumulated carbon by up to 24%. Our analysis framework provides a transparent method for prioritizing where and how restoration should occur in heterogeneous landscapes in order to maximize the benefits for carbon and biodiversity.

  20. Tropical ecotoxicology: The state of the environment in the tropics

    SciTech Connect

    Lacher, T.E. Jr. |; Goldstein, M.I.

    1995-12-31

    Ecotoxicology has focused almost exclusively on temperate zone countries and ecosystems. Tropical ecosystems, including rain forest, tropical dry forest, savanna, wetlands and freshwater ecosystems, have been neglected. These ecosystems combined might contain as much as 75% of global biodiversity. Tropical ecosystems are under increasing threat of development and alteration. The major causes of habitat degradation in the tropics include population growth and urbanization, agricultural expansion, deforestation, and mining. Some of these activities (in particular agriculture, mining, and the manufacturing and chemical industries) also lead to the release of toxic substances into the environment. Little research in ecotoxicology has been done in tropical environments and techniques and procedures developed for temperate environments are often applied, even though physical and chemical environmental parameters in the tropics can be very different. The regulatory environment also varies from country to country. The authors present an extensive literature review of tropical ecotoxicology, with a focus on Latin America and the Caribbean. Most research has focused on water quality and aquatic toxicology. Virtually no research has been done on the effects of toxic substance on tropical wildlife. They present a protocol for tropical ecotoxicology that addresses the special problems associated with doing ecotoxicological research in the tropics. The authors discuss the issue of adapting temperate zone principles and methods to tropical environments. Finally, they discuss priority areas for immediate research. These include large scale agricultural activities, especially bananas, pineapples, and soybeans and gold mining with the associated heavy use of mercury. The authors also present a prioritization of tropical wildlife that appear to be at highest risk of exposure to toxic substances.

  1. Assessing habitat quality for a migratory songbird wintering in natural and agricultural habitats.

    PubMed

    Johnson, Matthew D; Sherry, Thomas W; Holmes, Richard T; Marra, Peter P

    2006-10-01

    As tropical forests are cleared, a greater proportion of migratory songbirds are forced to winter in agricultural and disturbed habitats, which, if poorer in quality than natural forests, could contribute to population declines. We compared demographic indicators of habitat quality for a focal species, the American Redstart (Setophaga ruticilla), wintering in Jamaican citrus orchards and shade coffee plantations with those in four natural habitats: mangrove, coastal scrub, coastal palm, and dry limestone forests. Demographic measures of habitat quality included density, age and sex ratio, apparent survival, and changes in body mass. Measures of habitat quality for redstarts in citrus and coffee habitats were generally intermediate between the highest (mangrove) and lowest (dry limestone) measurements from natural habitats. The decline in mean body mass over the winter period was a strong predictor of annual survival rate among habitats, and we suggest that measures of body condition coupled with survival data provide the best measures of habitat quality for nonbreeding songbirds. Density, which is far easier to estimate, was correlated with these more labor-intensive measures, particularly in the late winter when food is likely most limiting. Thus, local density may be useful as an approximation of habitat quality for wintering migrant warblers. Our findings bolster those of previous studies based on bird abundance that suggest arboreal agricultural habitats in the tropics can be useful for the conservation of generalist, insectivorous birds, including many migratory passerines such as redstarts. PMID:17002761

  2. Tropical Rainforests.

    ERIC Educational Resources Information Center

    Nigh, Ronald B.; Nations, James D.

    1980-01-01

    Presented is a summary of scientific knowledge about the rainforest environment, a tropical ecosystem in danger of extermination. Topics include the current state of tropical rainforests, the causes of rainforest destruction, and alternatives of rainforest destruction. (BT)

  3. Temporal heterogeneity in aerosol characteristics and the resulting radiative impact at a tropical coastal station - Part 1: Microphysical and optical properties

    NASA Astrophysics Data System (ADS)

    Krishna Moorthy, K.; Babu, S. Suresh; Satheesh, S. K.

    2007-11-01

    In Part 1 of this two-part paper, we present the results of extensive and collocated measurements of the columnar and near-surface (in the well mixed region) properties of atmospheric aerosol particles at a tropical coastal location, Trivandrum (8.55° N; 76.97° E), located close to the southwest tip of Indian peninsula. These are used to evolve average, climatological pictures of the optical and microphysical properties and to delineate the distinct changes associated with the contrasting monsoon seasons as well as the transition from one season to the other. Our observations show a dramatic change in the columnar aerosol optical depth (AOD) spectra, being steep during winter monsoon season (WMS, months of December through March) and becoming quite flat during summer monsoon season (SMS, June through September). The derived Ångström exponent (α) decreases from a mean value of 1.1±0.03 in WMS to 0.32±0.02 in SMS, signifying a change in columnar aerosol size spectrum from an accumulation mode dominance in WMS to a coarse mode dominance in SMS. The composite aerosols near the surface follow suit with the share of the accumulation mode to the total mass concentration decreasing from ~70% to 34% from WMS to SMS. The overall mass burden also decreases in tandem. The changes in α are well correlated to those in the accumulation fraction of the mass concentration. Long-term measurements of the concentration of aerosol black carbon (BC), show prominent annual variations, with its mean value decreasing from as high as 6 μg m-3 in WMS to 2 μg m-3 in SMS. Correspondingly, its mass mixing ratio to the composite aerosols comes down from 11% to 4%. The changes in AOD and α are significantly positively correlated to those of BC concentration. The columnar properties are, in general well associated with the features near the surface. The implications of these changes to the optical properties and single scattering albedo and the resulting impact on direct radiative

  4. WILDLIFE HABITAT

    EPA Science Inventory

    Habitat change statistics were used to estimate the effects of alternative future scenarios for agriculture on non-fish vertebrate diversity in Iowa farmlands. Study areas were two watersheds in central Iowa of about 50 and 90 square kilometers, respectively. Future scenarios w...

  5. Saving Wild Species through Habitat Protection.

    ERIC Educational Resources Information Center

    Bohlen, Janet

    1980-01-01

    Describes the conservation approach adopted by World Wildlife Fund which focuses on habitat protection to save wild plant and animal species. Priority attention to tropical forests is explained. Examples are given of techniques (e.g., radiotelemetry and aerial survey) for studying ecological behavior patterns of specific animals. (CS)

  6. Mars habitat

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The College of Engineering & Architecture at Prairie View A&M University has been participating in the NASA/USRA Advanced Design Program since 1986. The interdisciplinary nature of the program allowed the involvement of students and faculty throughout the College of Engineering & Architecture for the last five years. The research goal for the 1990-1991 year is to design a human habitat on Mars that can be used as a permanent base for 20 crew members. The research is being conducted by undergraduate students from the Department of Architecture.

  7. Ecological drivers of shark distributions along a tropical coastline.

    PubMed

    Yates, Peter M; Heupel, Michelle R; Tobin, Andrew J; Simpfendorfer, Colin A

    2015-01-01

    As coastal species experience increasing anthropogenic pressures there is a growing need to characterise the ecological drivers of their abundance and habitat use, and understand how they may respond to changes in their environment. Accordingly, fishery-independent surveys were undertaken to investigate shark abundance along approximately 400 km of the tropical east coast of Australia. Generalised linear models were used to identify ecological drivers of the abundance of immature blacktip Carcharhinus tilstoni/Carcharhinus limbatus, pigeye Carcharhinus amboinensis, and scalloped hammerhead Sphyrna lewini sharks. Results indicated general and species-specific patterns in abundance that were characterised by a range of abiotic and biotic variables. Relationships with turbidity and salinity were similar across multiple species, highlighting the importance of these variables in the functioning of communal shark nurseries. In particular, turbid environments were especially important for all species at typical oceanic salinities. Mangrove proximity, depth, and water temperature were also important; however, their influence varied between species. Ecological drivers may promote spatial diversity in habitat use along environmentally heterogeneous coastlines and may therefore have important implications for population resilience. PMID:25853657

  8. Ecological Drivers of Shark Distributions along a Tropical Coastline

    PubMed Central

    Yates, Peter M.; Heupel, Michelle R.; Tobin, Andrew J.; Simpfendorfer, Colin A.

    2015-01-01

    As coastal species experience increasing anthropogenic pressures there is a growing need to characterise the ecological drivers of their abundance and habitat use, and understand how they may respond to changes in their environment. Accordingly, fishery-independent surveys were undertaken to investigate shark abundance along approximately 400 km of the tropical east coast of Australia. Generalised linear models were used to identify ecological drivers of the abundance of immature blacktip Carcharhinus tilstoni/Carcharhinus limbatus, pigeye Carcharhinus amboinensis, and scalloped hammerhead Sphyrna lewini sharks. Results indicated general and species-specific patterns in abundance that were characterised by a range of abiotic and biotic variables. Relationships with turbidity and salinity were similar across multiple species, highlighting the importance of these variables in the functioning of communal shark nurseries. In particular, turbid environments were especially important for all species at typical oceanic salinities. Mangrove proximity, depth, and water temperature were also important; however, their influence varied between species. Ecological drivers may promote spatial diversity in habitat use along environmentally heterogeneous coastlines and may therefore have important implications for population resilience. PMID:25853657

  9. Plate tectonics drive tropical reef biodiversity dynamics

    NASA Astrophysics Data System (ADS)

    Leprieur, Fabien; Descombes, Patrice; Gaboriau, Théo; Cowman, Peter F.; Parravicini, Valeriano; Kulbicki, Michel; Melián, Carlos J.; de Santana, Charles N.; Heine, Christian; Mouillot, David; Bellwood, David R.; Pellissier, Loïc

    2016-05-01

    The Cretaceous breakup of Gondwana strongly modified the global distribution of shallow tropical seas reshaping the geographic configuration of marine basins. However, the links between tropical reef availability, plate tectonic processes and marine biodiversity distribution patterns are still unknown. Here, we show that a spatial diversification model constrained by absolute plate motions for the past 140 million years predicts the emergence and movement of diversity hotspots on tropical reefs. The spatial dynamics of tropical reefs explains marine fauna diversification in the Tethyan Ocean during the Cretaceous and early Cenozoic, and identifies an eastward movement of ancestral marine lineages towards the Indo-Australian Archipelago in the Miocene. A mechanistic model based only on habitat-driven diversification and dispersal yields realistic predictions of current biodiversity patterns for both corals and fishes. As in terrestrial systems, we demonstrate that plate tectonics played a major role in driving tropical marine shallow reef biodiversity dynamics.

  10. Plate tectonics drive tropical reef biodiversity dynamics

    PubMed Central

    Leprieur, Fabien; Descombes, Patrice; Gaboriau, Théo; Cowman, Peter F.; Parravicini, Valeriano; Kulbicki, Michel; Melián, Carlos J.; de Santana, Charles N.; Heine, Christian; Mouillot, David; Bellwood, David R.; Pellissier, Loïc

    2016-01-01

    The Cretaceous breakup of Gondwana strongly modified the global distribution of shallow tropical seas reshaping the geographic configuration of marine basins. However, the links between tropical reef availability, plate tectonic processes and marine biodiversity distribution patterns are still unknown. Here, we show that a spatial diversification model constrained by absolute plate motions for the past 140 million years predicts the emergence and movement of diversity hotspots on tropical reefs. The spatial dynamics of tropical reefs explains marine fauna diversification in the Tethyan Ocean during the Cretaceous and early Cenozoic, and identifies an eastward movement of ancestral marine lineages towards the Indo-Australian Archipelago in the Miocene. A mechanistic model based only on habitat-driven diversification and dispersal yields realistic predictions of current biodiversity patterns for both corals and fishes. As in terrestrial systems, we demonstrate that plate tectonics played a major role in driving tropical marine shallow reef biodiversity dynamics. PMID:27151103

  11. Plate tectonics drive tropical reef biodiversity dynamics.

    PubMed

    Leprieur, Fabien; Descombes, Patrice; Gaboriau, Théo; Cowman, Peter F; Parravicini, Valeriano; Kulbicki, Michel; Melián, Carlos J; de Santana, Charles N; Heine, Christian; Mouillot, David; Bellwood, David R; Pellissier, Loïc

    2016-01-01

    The Cretaceous breakup of Gondwana strongly modified the global distribution of shallow tropical seas reshaping the geographic configuration of marine basins. However, the links between tropical reef availability, plate tectonic processes and marine biodiversity distribution patterns are still unknown. Here, we show that a spatial diversification model constrained by absolute plate motions for the past 140 million years predicts the emergence and movement of diversity hotspots on tropical reefs. The spatial dynamics of tropical reefs explains marine fauna diversification in the Tethyan Ocean during the Cretaceous and early Cenozoic, and identifies an eastward movement of ancestral marine lineages towards the Indo-Australian Archipelago in the Miocene. A mechanistic model based only on habitat-driven diversification and dispersal yields realistic predictions of current biodiversity patterns for both corals and fishes. As in terrestrial systems, we demonstrate that plate tectonics played a major role in driving tropical marine shallow reef biodiversity dynamics. PMID:27151103

  12. Efficacy of UV-Pit-light traps for discerning micro-habitat-specific beetle and ant species related with different oil palm age stands and tropical annual seasons for accurate ecology and diversity interpretations

    NASA Astrophysics Data System (ADS)

    Ahmad Bukhary, A. K.; Ruslan, M. Y.; Mohd. Fauzi, M. M.; Nicholas, S.; Muhamad Fahmi, M. H.; Izfa Riza, H.; Idris, A. B.

    2015-09-01

    A newly innovated and efficient UV-Pit-light Trap is described and the results of the experiments on its efficacy that were carried out within different oil palm age stands of the year 2013 were evaluated and compared with previous study year of 2010, with out the implementation of the UV-Pit-light Trap. In 2013 the UV-Pit-light Traps, the Malaise Traps, and the Pit-fall Traps were employed, while in 2010, the conventional canopy-height UV-Light Traps, Malaise Traps, and the Pit-fall Traps were employed. The UV-Pit-light traps caught more beetle and ant families, morpho-species, and individuals per species compared with the passive Pit-fall traps. The UV-Pit-light Trap targets different subsets of the oil palm beetles and ants' communities, specifying on epigaeic-related micro-habitats, with different oil palm age stands have different compositions of micro-habitats. The UV-Pit-light Traps have the dual quality for satisfying both the biological and statistical data requirements and evaluations. There were no significant difference between the UV-Pit-light Traps and the passive Pit-fall Traps, while the trapping difference with the Malaise traps for different seasons of the year 2013. The UV-Pit-light Traps and the Malaise Traps were complementary to each other, detecting the activities of beetles and ants around the epigaeic-related micro-habitats or having active flight activities respectively according to annual seasons. The UV-Pit-light Trap is an oil-palm specific type of passive trapping system, focusing on the insect species dwelling the upper-ground/epigaeic micro-habitats.

  13. The Habitat Connection.

    ERIC Educational Resources Information Center

    Naturescope, 1987

    1987-01-01

    Consists of activities which address the causes of habitat destruction and the effects of habitat loss on animals and plants. Identifies habitat loss as the major reason for the endangerment and extinction of plant and animal species. (ML)

  14. Habitat Demonstration Unit - Deep Space Habitat Configuration

    NASA Video Gallery

    This animated video shows the process of transporting, assembling and testing the Habitat Demonstration Unit - Deep Space Habitat (HDU DSH) configuration, which will be deployed during the 2011 Des...

  15. Tropical Deforestation.

    ERIC Educational Resources Information Center

    Raven, Peter H.

    1988-01-01

    Outlines the deforestation problem and some efforts for solving the problem. Considers the impact of population growth, poverty, and ignorance. Includes a discussion of the current rapid decline in tropical forests, the consequences of destruction, and an outlook for the future. (YP)

  16. Heterogeneous Catalysis.

    ERIC Educational Resources Information Center

    Miranda, R.

    1989-01-01

    Described is a heterogeneous catalysis course which has elements of materials processing embedded in the classical format of catalytic mechanisms and surface chemistry. A course outline and list of examples of recent review papers written by students are provided. (MVL)

  17. Western habitats - Session summary

    USGS Publications Warehouse

    Titus, K.; Fuller, M.R.

    1989-01-01

    Determining the status of all habitats in the nine western states considered in this symposium is a difficult task. The authors of habitat status papers commented that the diversity of habitat classification systems limited their ability to relate habitat status to raptors. Differences of scale, objectives and survey design have hindered integration of habitat classification methods used by land managers with the habitat relationships understood by wildlife biologists, but examples now exist for successful integration of these methods. We suggest that land managers and wildlife biologists use common survey and classification schemes so that data can be combined and that results will be applicable over broader areas.

  18. Predictive Seagrass Habitat Model

    EPA Science Inventory

    Restoration of ecosystem services provided by seagrass habitats in estuaries requires a firm understanding of the modes of action of multiple interacting stressors including nutrients, climate change, coastal land-use change, and habitat modification. We explored the application...

  19. MODELING PHYSICAL HABITAT PARAMETERS

    EPA Science Inventory

    Salmonid populations can be affected by alterations in stream physical habitat. Fish productivity is determined by the stream's physical habitat structure ( channel form, substrate distribution, riparian vegetation), water quality, flow regime and inputs from the watershed (sedim...

  20. Application of SAR Remote Sensing in Land Surface Processes Over Tropical region

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan S.

    1996-01-01

    This paper outlines the potential applications of polarimetric SAR systems over tropical regions such as mapping land use and deforestation, forest regeneration, wetland and inundation studies, and mapping land cover types for biodiversity and habitat conservation studies.

  1. Importance of environmental factors on the richness and distribution of benthic macroinvertebrates in tropical headwater streams

    EPA Science Inventory

    It is essential to understand the interactions between local environmental factors (e.g., physical habitat and water quality) and aquatic assemblages to conserve biodiversity in tropical and subtropical headwater streams. Therefore, we evaluated the relative importance of multipl...

  2. Biodiversity: Habitat Suitability

    EPA Science Inventory

    Habitat suitability quantifies the relationship between species and habitat, and is evaluated according to the species’ fitness (i.e. proportion of birth rate to death rate). Even though it might maximize evolutionary success, species are not always in habitat that optimizes fit...

  3. Urban Areas. Habitat Pac.

    ERIC Educational Resources Information Center

    Fish and Wildlife Service (Dept. of Interior), Washington, DC.

    The materials in this educational packet are designed for use with students in grades 4 through 7. They consist of an overview, teaching guides and student data sheets for three activities, and a poster. The overview discusses the city as an ecosystem, changing urban habitats, urban wildlife habitats, values of wildlife, habitat management, and…

  4. Habitat mapping of the Brazilian Pantanal using synthetic aperture radar imagery and object based image analysis

    NASA Astrophysics Data System (ADS)

    Evans, Teresa Lynne

    The Brazilian Pantanal, a continuous tropical wetland located in the center of South America, has been recognized as one of the largest and most important wetland ecosystems globally. The Pantanal exhibits a high biodiversity of flora and fauna species, and many threatened habitats. The spatial distribution of these habitats influence the distribution, abundance and interactions of animal species, and the change or destruction of habitat may cause alteration of key biological processes. The Pantanal may be divided into several distinct subregions based on geology and hydrology: flooding in these subregions is distinctly seasonal, but the timing, amplitude and duration of inundation vary considerably as a result of both the delayed release of floodwaters and regional rainfall patterns. Given the ecological importance of the Pantanal wetland ecosystem, the primary goal of this research was to utilize a dual season set of L-band (ALOS/PALSAR) and C-band (RADARSAT-2 and ENVISAT/ASAR) imagery, a comprehensive set of ground reference data, and a hierarchical object-oriented approach. This primary goal was achieved through two main research tasks. The first task was to define the diverse habitats of the Lower Nhecolândia subregion of the Pantanal at both a fine spatial resolution (12.5 m), and a relatively medium spatial resolution (50 m), thus evaluating the accuracy of the differing spatial resolutions for land cover classification of the highly spatially heterogeneous subregion. The second task was to define on a regional scale, using the 50 m spatial resolution imagery, the wetland habitats of each of the hydrological subregions of the Pantanal, thereby producing a final product covering the entire Pantanal ecosystem. The final classification maps of the Lower Nhecolândia subregion resulted in overall accuracies of 83% and 72% for the 12.5 m and 50 m spatial resolutions, respectively, and defined seven land cover classes. In general, the highest degree of confusion

  5. Beta-Diversity in Tropical Forest Trees

    NASA Astrophysics Data System (ADS)

    Condit, Richard; Pitman, Nigel; Leigh, Egbert G.; Chave, Jérôme; Terborgh, John; Foster, Robin B.; Núñez V., Percy; Aguilar, Salomón; Valencia, Renato; Villa, Gorky; Muller-Landau, Helene C.; Losos, Elizabeth; Hubbell, Stephen P.

    2002-01-01

    The high alpha-diversity of tropical forests has been amply documented, but beta-diversity-how species composition changes with distance-has seldom been studied. We present quantitative estimates of beta-diversity for tropical trees by comparing species composition of plots in lowland terra firme forest in Panama, Ecuador, and Peru. We compare observations with predictions derived from a neutral model in which habitat is uniform and only dispersal and speciation influence species turnover. We find that beta-diversity is higher in Panama than in western Amazonia and that patterns in both areas are inconsistent with the neutral model. In Panama, habitat variation appears to increase species turnover relative to Amazonia, where unexpectedly low turnover over great distances suggests that population densities of some species are bounded by as yet unidentified processes. At intermediate scales in both regions, observations can be matched by theory, suggesting that dispersal limitation, with speciation, influences species turnover.

  6. Tropical fishes dominate temperate reef fish communities within western Japan.

    PubMed

    Nakamura, Yohei; Feary, David A; Kanda, Masaru; Yamaoka, Kosaku

    2013-01-01

    Climate change is resulting in rapid poleward shifts in the geographical distribution of tropical and subtropical fish species. We can expect that such range shifts are likely to be limited by species-specific resource requirements, with temperate rocky reefs potentially lacking a range of settlement substrates or specific dietary components important in structuring the settlement and success of tropical and subtropical fish species. We examined the importance of resource use in structuring the distribution patterns of range shifting tropical and subtropical fishes, comparing this with resident temperate fish species within western Japan (Tosa Bay); the abundance, diversity, size class, functional structure and latitudinal range of reef fishes utilizing both coral reef and adjacent rocky reef habitat were quantified over a 2 year period (2008-2010). This region has undergone rapid poleward expansion of reef-building corals in response to increasing coastal water temperatures, and forms one of the global hotspots for rapid coastal changes. Despite the temperate latitude surveyed (33°N, 133°E) the fish assemblage was both numerically, and in terms of richness, dominated by tropical fishes. Such tropical faunal dominance was apparent within both coral, and rocky reef habitats. The size structure of the assemblage suggested that a relatively large number of tropical species are overwintering within both coral and rocky habitats, with a subset of these species being potentially reproductively active. The relatively high abundance and richness of tropical species with obligate associations with live coral resources (i.e., obligate corallivores) shows that this region holds the most well developed temperate-located tropical fish fauna globally. We argue that future tropicalisation of the fish fauna in western Japan, associated with increasing coral habitat development and reported increasing shifts in coastal water temperatures, may have considerable positive economic

  7. Tropical Convection's Roles in Tropical Tropopause Cirrus

    NASA Technical Reports Server (NTRS)

    Boehm, Matthew T.; Starr, David OC.; Verlinde, Johannes; Lee, Sukyoung

    2002-01-01

    The results presented here show that tropical convection plays a role in each of the three primary processes involved in the in situ formation of tropopause cirrus. First, tropical convection transports moisture from the surface into the upper troposphere. Second, tropical convection excites Rossby waves that transport zonal momentum toward the ITCZ, thereby generating rising motion near the equator. This rising motion helps transport moisture from where it is detrained from convection to the cold-point tropopause. Finally, tropical convection excites vertically propagating tropical waves (e.g. Kelvin waves) that provide one source of large-scale cooling near the cold-point tropopause, leading to tropopause cirrus formation.

  8. High Density of Tree-Cavities and Snags in Tropical Dry Forest of Western Mexico Raises Questions for a Latitudinal Gradient

    PubMed Central

    Vázquez, Leopoldo; Renton, Katherine

    2015-01-01

    It has been suggested that a latitudinal gradient exists of a low density of snags and high density of naturally-formed tree-cavities in tropical vs. temperate forests, though few cavities may have characteristics suitable for nesting by birds. We determined snag and cavity density, characteristics, and suitability for birds in a tropical dry forest biome of western Mexico, and evaluated whether our data fits the trend of snag and cavity density typically found in tropical moist and wet forests. We established five 0.25-ha transects to survey and measure tree-cavities and snags in each of three vegetation types of deciduous, semi-deciduous, and mono-dominant Piranhea mexicana forest, comprising a total of 3.75 ha. We found a high density of 77 cavities/ha, with 37 cavities suitable for birds/ha, where density, and characteristics of cavities varied significantly among vegetation types. Lowest abundance of cavities occurred in deciduous forest, and these were in smaller trees, at a lower height, and with a narrower entrance diameter. Only 8.6% of cavities were excavated by woodpeckers, and only 11% of cavities were occupied, mainly by arthropods, though 52% of all cavities were unsuitable for birds. We also found a high density of 56 snags/ha, with greatest density in deciduous forest (70 snags/ha), though these were of significantly smaller diameter, and snags of larger diameter were more likely to contain cavities. The Chamela-Cuixmala tropical dry forest had the highest density of snags recorded for any tropical or temperate forest, and while snag density was significantly correlated with mean snag dbh, neither latitude nor mean dbh predicted snag density in ten forest sites. The high spatial aggregation of snag and cavity resources in tropical dry forest may limit their availability, particularly for large-bodied cavity adopters, and highlights the importance of habitat heterogeneity in providing resources for primary and secondary cavity-nesters. PMID:25615612

  9. High density of tree-cavities and snags in tropical dry forest of western Mexico raises questions for a latitudinal gradient.

    PubMed

    Vázquez, Leopoldo; Renton, Katherine

    2015-01-01

    It has been suggested that a latitudinal gradient exists of a low density of snags and high density of naturally-formed tree-cavities in tropical vs. temperate forests, though few cavities may have characteristics suitable for nesting by birds. We determined snag and cavity density, characteristics, and suitability for birds in a tropical dry forest biome of western Mexico, and evaluated whether our data fits the trend of snag and cavity density typically found in tropical moist and wet forests. We established five 0.25-ha transects to survey and measure tree-cavities and snags in each of three vegetation types of deciduous, semi-deciduous, and mono-dominant Piranhea mexicana forest, comprising a total of 3.75 ha. We found a high density of 77 cavities/ha, with 37 cavities suitable for birds/ha, where density, and characteristics of cavities varied significantly among vegetation types. Lowest abundance of cavities occurred in deciduous forest, and these were in smaller trees, at a lower height, and with a narrower entrance diameter. Only 8.6% of cavities were excavated by woodpeckers, and only 11% of cavities were occupied, mainly by arthropods, though 52% of all cavities were unsuitable for birds. We also found a high density of 56 snags/ha, with greatest density in deciduous forest (70 snags/ha), though these were of significantly smaller diameter, and snags of larger diameter were more likely to contain cavities. The Chamela-Cuixmala tropical dry forest had the highest density of snags recorded for any tropical or temperate forest, and while snag density was significantly correlated with mean snag dbh, neither latitude nor mean dbh predicted snag density in ten forest sites. The high spatial aggregation of snag and cavity resources in tropical dry forest may limit their availability, particularly for large-bodied cavity adopters, and highlights the importance of habitat heterogeneity in providing resources for primary and secondary cavity-nesters. PMID:25615612

  10. Evidence for ecological divergence across a mosaic of soil types in an Amazonian tropical tree: Protium subserratum (Burseraceae).

    PubMed

    Misiewicz, Tracy M; Fine, Paul V A

    2014-05-01

    Soil heterogeneity is an important driver of divergent natural selection in plants. Neotropical forests have the highest tree diversity on earth, and frequently, soil specialist congeners are distributed parapatrically. While the role of edaphic heterogeneity in the origin and maintenance of tropical tree diversity is unknown, it has been posited that natural selection across the patchwork of soils in the Amazon rainforest is important in driving and maintaining tree diversity. We examined genetic and morphological differentiation among populations of the tropical tree Protium subserratum growing parapatrically on the mosaic of white-sand, brown-sand and clay soils found throughout western Amazonia. Nuclear microsatellites and leaf morphology were used to (i) quantify the extent of phenotypic and genetic divergence across habitat types, (ii) assess the importance of natural selection vs. drift in population divergence, (iii) determine the extent of hybridization and introgression across habitat types, (iv) estimate migration rates among populations. We found significant morphological variation correlated with soil type. Higher levels of genetic differentiation and lower migration rates were observed between adjacent populations found on different soil types than between geographically distant populations on the same soil type. PST -FST comparisons indicate a role for natural selection in population divergence among soil types. A small number of hybrids were detected suggesting that gene flow among soil specialist populations may occur at low frequencies. Our results suggest that edaphic specialization has occurred multiple times in P. subserratum and that divergent natural selection across edaphic boundaries may be a general mechanism promoting and maintaining Amazonian tree diversity. PMID:24703227

  11. Ecological speciation in tropical reef fishes

    PubMed Central

    Rocha, Luiz A; Robertson, D. Ross; Roman, Joe; Bowen, Brian W

    2005-01-01

    The high biodiversity in tropical seas provides a long-standing challenge to allopatric speciation models. Physical barriers are few in the ocean and larval dispersal is often extensive, a combination that should reduce opportunities for speciation. Yet coral reefs are among the most species-rich habitats in the world, indicating evolutionary processes beyond conventional allopatry. In a survey of mtDNA sequences of five congeneric west Atlantic reef fishes (wrasses, genus Halichoeres) with similar dispersal potential, we observed phylogeographical patterns that contradict expectations of geographical isolation, and instead indicate a role for ecological speciation. In Halichoeres bivittatus and the species pair Halichoeres radiatus/brasiliensis, we observed strong partitions (3.4% and 2.3% divergence, respectively) between adjacent and ecologically distinct habitats, but high genetic connectivity between similar habitats separated by thousands of kilometres. This habitat partitioning is maintained even at a local scale where H. bivittatus lineages are segregated between cold- and warm-water habitats in both Bermuda and Florida. The concordance of evolutionary partitions with habitat types, rather than conventional biogeographical barriers, indicates parapatric ecological speciation, in which adaptation to alternative environmental conditions in adjacent locations overwhelms the homogenizing effect of dispersal. This mechanism can explain the long-standing enigma of high biodiversity in coral reef faunas. PMID:15817431

  12. Linking occurrence and fitness to persistence: Habitat-based approach for endangered Greater Sage-Grouse

    USGS Publications Warehouse

    Aldridge, C.L.; Boyce, M.S.

    2007-01-01

    Detailed empirical models predicting both species occurrence and fitness across a landscape are necessary to understand processes related to population persistence. Failure to consider both occurrence and fitness may result in incorrect assessments of habitat importance leading to inappropriate management strategies. We took a two-stage approach to identifying critical nesting and brood-rearing habitat for the endangered Greater Sage-Grouse (Centrocercus urophasianus) in Alberta at a landscape scale. First, we used logistic regression to develop spatial models predicting the relative probability of use (occurrence) for Sage-Grouse nests and broods. Secondly, we used Cox proportional hazards survival models to identify the most risky habitats across the landscape. We combined these two approaches to identify Sage-Grouse habitats that pose minimal risk of failure (source habitats) and attractive sink habitats that pose increased risk (ecological traps). Our models showed that Sage-Grouse select for heterogeneous patches of moderate sagebrush cover (quadratic relationship) and avoid anthropogenic edge habitat for nesting. Nests were more successful in heterogeneous habitats, but nest success was independent of anthropogenic features. Similarly, broods selected heterogeneous high-productivity habitats with sagebrush while avoiding human developments, cultivated cropland, and high densities of oil wells. Chick mortalities tended to occur in proximity to oil and gas developments and along riparian habitats. For nests and broods, respectively, approximately 10% and 5% of the study area was considered source habitat, whereas 19% and 15% of habitat was attractive sink habitat. Limited source habitats appear to be the main reason for poor nest success (39%) and low chick survival (12%). Our habitat models identify areas of protection priority and areas that require immediate management attention to enhance recruitment to secure the viability of this population. This novel

  13. Deforestation homogenizes tropical parasitoid-host networks.

    PubMed

    Laliberté, Etienne; Tylianakis, Jason M

    2010-06-01

    Human activities drive biotic homogenization (loss of regional diversity) of many taxa. However, whether species interaction networks (e.g., food webs) can also become homogenized remains largely unexplored. Using 48 quantitative parasitoid-host networks replicated through space and time across five tropical habitats, we show that deforestation greatly homogenized network structure at a regional level, such that interaction composition became more similar across rice and pasture sites compared with forested habitats. This was not simply caused by altered consumer and resource community composition, but was associated with altered consumer foraging success, such that parasitoids were more likely to locate their hosts in deforested habitats. Furthermore, deforestation indirectly homogenized networks in time through altered mean consumer and prey body size, which decreased in deforested habitats. Similar patterns were obtained with binary networks, suggesting that interaction (link) presence-absence data may be sufficient to detect network homogenization effects. Our results show that tropical agroforestry systems can support regionally diverse parasitoid-host networks, but that removal of canopy cover greatly homogenizes the structure of these networks in space, and to a lesser degree in time. Spatiotemporal homogenization of interaction networks may alter coevolutionary outcomes and reduce ecological resilience at regional scales, but may not necessarily be predictable from community changes observed within individual trophic levels. PMID:20583715

  14. Do Spatially-Implicit Estimates of Neutral Migration Comply with Seed Dispersal Data in Tropical Forests?

    PubMed Central

    Pélissier, Raphaël; Couteron, Pierre

    2013-01-01

    Neutral community models have shown that limited migration can have a pervasive influence on the taxonomic composition of local communities even when all individuals are assumed of equivalent ecological fitness. Notably, the spatially implicit neutral theory yields a single parameter I for the immigration-drift equilibrium in a local community. In the case of plants, seed dispersal is considered as a defining moment of the immigration process and has attracted empirical and theoretical work. In this paper, we consider a version of the immigration parameter I depending on dispersal limitation from the neighbourhood of a community. Seed dispersal distance is alternatively modelled using a distribution that decreases quickly in the tails (thin-tailed Gaussian kernel) and another that enhances the chance of dispersal events over very long distances (heavily fat-tailed Cauchy kernel). Our analysis highlights two contrasting situations, where I is either mainly sensitive to community size (related to ecological drift) under the heavily fat-tailed kernel or mainly sensitive to dispersal distance under the thin-tailed kernel. We review dispersal distances of rainforest trees from field studies and assess the consistency between published estimates of I based on spatially-implicit models and the predictions of the kernel-based model in tropical forest plots. Most estimates of I were derived from large plots (10–50 ha) and were too large to be accounted for by a Cauchy kernel. Conversely, a fraction of the estimates based on multiple smaller plots (1 ha) appeared too small to be consistent with reported ranges of dispersal distances in tropical forests. Very large estimates may reflect within-plot habitat heterogeneity or estimation problems, while the smallest estimates likely imply other factors inhibiting migration beyond dispersal limitation. Our study underscores the need for interpreting I as an integrative index of migration limitation which, besides the limited

  15. Linking habitat mosaics and connectivity in a coral reef seascape.

    PubMed

    McMahon, Kelton W; Berumen, Michael L; Thorrold, Simon R

    2012-09-18

    Tropical marine ecosystems are under mounting anthropogenic pressure from overfishing and habitat destruction, leading to declines in their structure and function on a global scale. Although maintaining connectivity among habitats within a seascape is necessary for preserving population resistance and resilience, quantifying movements of individuals within seascapes remains challenging. Traditional methods of identifying and valuing potential coral reef fish nursery habitats are indirect, often relying on visual surveys of abundance and correlations of size and biomass among habitats. We used compound-specific stable isotope analyses to determine movement patterns of commercially important fish populations within a coral reef seascape. This approach allowed us to quantify the relative contributions of individuals from inshore nurseries to reef populations and identify migration corridors among important habitats. Our results provided direct measurements of remarkable migrations by juvenile snapper of over 30 km, between nurseries and reefs. We also found significant plasticity in juvenile nursery residency. Although a majority of individuals on coastal reefs had used seagrass nurseries as juveniles, many adults on oceanic reefs had settled directly into reef habitats. Moreover, seascape configuration played a critical but heretofore unrecognized role in determining connectivity among habitats. Finally, our approach provides key quantitative data necessary to estimate the value of distinctive habitats to ecosystem services provided by seascapes. PMID:22949665

  16. Linking habitat mosaics and connectivity in a coral reef seascape

    PubMed Central

    McMahon, Kelton W.; Berumen, Michael L.; Thorrold, Simon R.

    2012-01-01

    Tropical marine ecosystems are under mounting anthropogenic pressure from overfishing and habitat destruction, leading to declines in their structure and function on a global scale. Although maintaining connectivity among habitats within a seascape is necessary for preserving population resistance and resilience, quantifying movements of individuals within seascapes remains challenging. Traditional methods of identifying and valuing potential coral reef fish nursery habitats are indirect, often relying on visual surveys of abundance and correlations of size and biomass among habitats. We used compound-specific stable isotope analyses to determine movement patterns of commercially important fish populations within a coral reef seascape. This approach allowed us to quantify the relative contributions of individuals from inshore nurseries to reef populations and identify migration corridors among important habitats. Our results provided direct measurements of remarkable migrations by juvenile snapper of over 30 km, between nurseries and reefs. We also found significant plasticity in juvenile nursery residency. Although a majority of individuals on coastal reefs had used seagrass nurseries as juveniles, many adults on oceanic reefs had settled directly into reef habitats. Moreover, seascape configuration played a critical but heretofore unrecognized role in determining connectivity among habitats. Finally, our approach provides key quantitative data necessary to estimate the value of distinctive habitats to ecosystem services provided by seascapes. PMID:22949665

  17. Surface Habitat Systems

    NASA Technical Reports Server (NTRS)

    Kennedy, Kriss J.

    2009-01-01

    The Surface Habitat Systems (SHS) Focused Investment Group (FIG) is part of the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) effort to provide a focused direction and funding to the various projects that are working on human surface habitat designs and technologies for the planetary exploration missions. The overall SHS-FIG effort focuses on directing and guiding those projects that: 1) develop and demonstrate new surface habitat system concepts, innovations, and technologies to support human exploration missions, 2) improve environmental systems that interact with human habitats, 3) handle and emplace human surface habitats, and 4) focus on supporting humans living and working in habitats on planetary surfaces. The activity areas of the SHS FIG described herein are focused on the surface habitat project near-term objectives as described in this document. The SHS-FIG effort focuses on mitigating surface habitat risks (as identified by the Lunar Surface Systems Project Office (LSSPO) Surface Habitat Element Team; and concentrates on developing surface habitat technologies as identified in the FY08 gap analysis. The surface habitat gap assessment will be updated annually as the surface architecture and surface habitat definition continues to mature. These technologies are mapped to the SHS-FIG Strategic Development Roadmap. The Roadmap will bring to light the areas where additional innovative efforts are needed to support the development of habitat concepts and designs and the development of new technologies to support of the LSSPO Habitation Element development plan. Three specific areas of development that address Lunar Architecture Team (LAT)-2 and Constellation Architecture Team (CxAT) Lunar habitat design issues or risks will be focused on by the SHS-FIG. The SHS-FIG will establish four areas of development that will help the projects prepare in their planning for surface habitat systems development. Those development areas are

  18. Geographic determinants of gene flow in two sister species of tropical Andean frogs.

    PubMed

    Guarnizo, Carlos E; Cannatella, David C

    2014-01-01

    Complex interactions between topographic heterogeneity, climatic and environmental gradients, and thermal niche conservatism are commonly assumed to indicate the degree of biotic diversification in montane regions. Our aim was to investigate factors that disrupt gene flow between populations and to determine if there is evidence of downslope asymmetric migration in highland frogs with wide elevational ranges and thermal niches. We determined the role of putative impediments to gene flow (as measured by least-cost path (LCP) distances, topographic complexity, and elevational range) in promoting genetic divergence between populations of 2 tropical Andean frog sister species (Dendropsophus luddeckei, N = 114; Dendropsophus labialis, N = 74) using causal modeling and multiple matrix regression. Although the effect of geographic features was species specific, elevational range and LCP distances had the strongest effect on gene flow, with mean effect sizes (Mantel r and regression coefficients β), between 5 and 10 times greater than topographic complexity. Even though causal modeling and multiple matrix regression produced congruent results, the latter provided more information on the contribution of each geographic variable. We found moderate support for downslope migration. We conclude that the climatic heterogeneity of the landscape, the elevational distance between populations, and the inability to colonize suboptimal habitats due to thermal niche conservatism influence the magnitude of gene flow. Asymmetric migration, however, seems to be influenced by life history traits. PMID:24336965

  19. Schoolyard Habitat Project Guide.

    ERIC Educational Resources Information Center

    Mason, Rich

    This project aims to provide basic steps for students to restore and create wildlife habitats on school grounds. Four chapters are included in this guide, and each chapter is divided into teacher and student sections. Chapter 1 provides necessary information for starting a habitat project. Chapters 2, 3, and 4 discuss the details for the Forest…

  20. The Habitat Project

    ERIC Educational Resources Information Center

    Hein, Annamae J.

    2011-01-01

    The Habitat Project is a multiday, differentiated, interdisciplinary environmental science lesson that incorporates skill-building and motivational strategies to internalize ecosystem vocabulary. Middle school students research an animal, display its physical characteristics on a poster, build a three-dimensional habitat and present their work…

  1. Advanced Plant Habitat (APH)

    NASA Technical Reports Server (NTRS)

    Richards, Stephanie E. (Compiler); Levine, Howard G.; Reed, David W.

    2016-01-01

    The Advanced Plant Habitat (APH) hardware will be a large growth volume plant habitat, capable of hosting multigenerational studies, in which environmental variables (e.g., temperature, relative humidity, carbon dioxide level light intensity and spectral quality) can be tracked and controlled in support of whole plant physiological testing and Bio-regenerative Life Support System investigations.

  2. Adaptive radiation of Espeletia in the cold andean tropics.

    PubMed

    Monasterio, M; Sarmiento, L

    1991-12-01

    The genus Espeletia (Asteraceae) underwent an accelerated adaptive radiation in the new habitats of the high tropical Andes after the retreat of the glaciers. From the ancestral rainforest species, with tree-like forms, the genus diversified at high altitude, developing morphological and physiological adaptations to the peculiar combination of low-temperature, energy and nutrient stresses of the tropical periglacial environments. Espeletia offers an exceptional example of a taxon undergoing a rapid evolutionary process through the colonization of a totally original environment: the cold tropics. Here we review recent research on the ecological, biogeographical, taxonomic, morphological and physiological traits that have led to the adaptive radiation of Espeletia in this extreme habitat. PMID:21232517

  3. Habitat-based polymorphism is common in stream fishes.

    PubMed

    Senay, Caroline; Boisclair, Daniel; Peres-Neto, Pedro R

    2015-01-01

    Morphological differences (size and shape) across habitats are common in lake fish where differences relate to two dominant contrasting habitats: the pelagic and littoral habitat. Repeated occurrence of littoral and pelagic morphs across multiple populations of several lake fish species has been considered as important evidence that polymorphism is adaptive in these systems. It has been suggested that these habitat-based polymorphic differences are due to the temporal stability of the differences between littoral and pelagic habitats. Although streams are spatially heterogeneous, they are also more temporally dynamic than lakes and it is still an open question whether streams provide the environmental conditions that promote habitat-based polymorphism. We tested whether fish from riffle, run and pool habitats, respectively, differed consistently in their morphology. Our test compared patterns of morphological variation (size and shape) in 10 fish species from the three stream habitat types in 36 separate streams distributed across three watersheds. For most species, body size and shape (after controlling for body size) differed across riffle, run and pool habitats. Unlike many lake species, the nature of these differences was not consistent across species, possibly because these species use these habitat types in different ways. Our results suggest that habitat-based polymorphism is an important feature also in stream fishes despite the fact that streams are temporally variable in contrast to lake systems. Future research is required to assess whether the patterns of habitat-based polymorphism encountered in streams have a genetic basis or they are simply the result of within generation phenotypic plasticity. PMID:25041645

  4. Experimental evidence for extreme dispersal limitation in tropical forest birds.

    PubMed

    Moore, R P; Robinson, W D; Lovette, I J; Robinson, T R

    2008-09-01

    Movements of organisms between habitat remnants can affect metapopulation structure, community assembly dynamics, gene flow and conservation strategy. In the tropical landscapes that support the majority of global biodiversity and where forest fragmentation is accelerating, there is particular urgency to understand how dispersal across habitats mediates the demography, distribution and differentiation of organisms. By employing unique dispersal challenge experiments coupled with exhaustive inventories of birds in a Panamanian lacustrine archipelago, we show that the ability to fly even short distances (< 100 m) between habitat fragments varies dramatically and consistently among species of forest birds, and that this variation correlates strongly with species' extinction histories and current distributions across the archipelago. This extreme variation in flight capability indicates that species' persistence in isolated forest remnants will be differentially mediated by their respective dispersal abilities, and that corridors connecting such fragments will be essential for the maintenance of avian diversity in fragmented tropical landscapes. PMID:18513315

  5. The role of heterogeneity in structuring spatial hierarchies

    SciTech Connect

    O'Neill, R.V.

    1987-07-01

    Following a paradigm based on Statistics and Newtonian physics, ecology often emphasizes the central tendency of observations and considers heterogeneity as extraneous noise. This approach ignores heterogeneity as an important measure of ecological systems. The present paper discusses two ways that heterogeneity characterizes the spatial hierarchies we observe on a landscape. As an exogenous factor, heterogeneity transforms a uniform landscape into a diverse array of habitats. Topography, moisture gradients, etc., create a spectrum of opportunities for species establishment. Heterogeneity compresses space, allowing a larger number of species to survive in a given area. As an endogenous factor, heterogeneity results from competition and natural selection acting to fill the available niches. In either case, heterogeneity is critical to understanding spatial hierarchies and community structure.

  6. Habitat Demonstration Unit (HDU) Vertical Cylinder Habitat

    NASA Technical Reports Server (NTRS)

    Howe, Alan; Kennedy, Kriss J.; Gill, Tracy R.; Tri, Terry O.; Toups, Larry; Howard, Robert I.; Spexarth, Gary R.; Cavanaugh, Stephen; Langford, William M.; Dorsey, John T.

    2014-01-01

    NASA's Constellation Architecture Team defined an outpost scenario optimized for intensive mobility that uses small, highly mobile pressurized rovers supported by portable habitat modules that can be carried between locations of interest on the lunar surface. A compact vertical cylinder characterizes the habitat concept, where the large diameter maximizes usable flat floor area optimized for a gravity environment and allows for efficient internal layout. The module was sized to fit into payload fairings for the Constellation Ares V launch vehicle, and optimized for surface transport carried by the All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE) mobility system. Launch and other loads are carried through the barrel to a top and bottom truss that interfaces with a structural support unit (SSU). The SSU contains self-leveling feet and docking interfaces for Tri-ATHLETE grasping and heavy lift. A pressurized module needed to be created that was appropriate for the lunar environment, could be easily relocated to new locations, and could be docked together in multiples for expanding pressurized volume in a lunar outpost. It was determined that horizontally oriented pressure vessels did not optimize floor area, which takes advantage of the gravity vector for full use. Hybrid hard-inflatable habitats added an unproven degree of complexity that may eventually be worked out. Other versions of vertically oriented pressure vessels were either too big, bulky, or did not optimize floor area. The purpose of the HDU vertical habitat module is to provide pressurized units that can be docked together in a modular way for lunar outpost pressurized volume expansion, and allow for other vehicles, rovers, and modules to be attached to the outpost to allow for IVA (intra-vehicular activity) transfer between them. The module is a vertically oriented cylinder with a large radius to allow for maximal floor area and use of volume. The modular, 5- m-diameter HDU vertical habitat

  7. How does habitat filtering affect the detection of conspecific and phylogenetic density dependence?

    PubMed

    Wu, Junjie; Swenson, Nathan G; Brown, Calum; Zhang, Caicai; Yang, Jie; Ci, Xiuqin; Li, Jie; Sha, Liqing; Cao, Min; Lin, Luxiang

    2016-05-01

    Conspecific negative density dependence (CNDD) has been recognized as a key mechanism underlying species coexistence, especially in tropical forests. Recently, some studies have reported that seedling survival is also negatively correlated with the phylogenetic relatedness between neighbors and focal individuals, termed phylogenetic negative density dependence (PNDD). In contrast to CNDD or PNDD, shared habitat requirements between closely related individuals are thought to be a cause of observed positive effects of closely related neighbors, which may affect the strength and detectability of CNDD or PNDD. In order to investigate the relative importance of these mechanisms for tropical tree seedling survival, we used generalized linear mixed models to analyze how the survival of more than 10 000 seedlings of woody plant species related to neighborhood and habitat variables in a tropical rainforest in southwest China. By comparing models with and without habitat variables, we tested how habitat filtering affected the detection of CNDD and PNDD. The best-fitting model suggested that CNDD and habitat filtering played key roles in seedling survival; but that, contrary to our expectations, phylogenetic positive density dependence (PPDD) had a distinct and important effect. While habitat filtering affected the detection of CNDD by decreasing its apparent strength, it did not explain the positive effects of closely related neighbors. Our results demonstrate that a failure to control for habitat variables and phylogenetic relationships may obscure the importance of conspecific and heterospecific neighbor densities for seedling survival. PMID:27349095

  8. Spillover of functionally important organisms between managed and natural habitats

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Land use intensification has led to a mosaic landscape which juxtaposes human-managed and natural areas. In such human-dominated and heterogeneous landscapes spillover across habitat types, especially in systems which differ in resource availability, may be an important ecological process structuri...

  9. Enhancements of the "eHabitat

    NASA Astrophysics Data System (ADS)

    Santoro, M.; Dubois, G.; Schulz, M.; Skøien, J. O.; Nativi, S.; Peedell, S.; Boldrini, E.

    2012-04-01

    The number of interoperable research infrastructures has increased significantly with the growing awareness of the efforts made by the Global Earth Observation System of Systems (GEOSS). One of the Social Benefit Areas (SBA) that is benefiting most from GEOSS is biodiversity, given the costs of monitoring the environment and managing complex information, from space observations to species records including their genetic characteristics. But GEOSS goes beyond the simple sharing of the data as it encourages the connectivity of models (the GEOSS Model Web), an approach easing the handling of often complex multi-disciplinary questions such as understanding the impact of environmental and climatological factors on ecosystems and habitats. In the context of GEOSS Architecture Implementation Pilot - Phase 3 (AIP-3), the EC-funded EuroGEOSS and GENESIS projects have developed and successfully demonstrated the "eHabitat" use scenario dealing with Climate Change and Biodiversity domains. Based on the EuroGEOSS multidisciplinary brokering infrastructure and on the DOPA (Digital Observatory for Protected Areas, see http://dopa.jrc.ec.europa.eu/), this scenario demonstrated how a GEOSS-based interoperability infrastructure can aid decision makers to assess and possibly forecast the irreplaceability of a given protected area, an essential indicator for assessing the criticality of threats this protected area is exposed to. The "eHabitat" use scenario was advanced in the GEOSS Sprint to Plenary activity; the advanced scenario will include the "EuroGEOSS Data Access Broker" and a new version of the eHabitat model in order to support the use of uncertain data. The multidisciplinary interoperability infrastructure which is used to demonstrate the "eHabitat" use scenario is composed of the following main components: a) A Discovery Broker: this component is able to discover resources from a plethora of different and heterogeneous geospatial services, presenting them on a single and

  10. Integrating terrestrial laser scanning and repeat field measurements to quantify habitat changes during baseflow recession

    NASA Astrophysics Data System (ADS)

    Woelfle-Erskine, C. A.; Thompson, S. E.

    2013-12-01

    Understanding stream habitat heterogeneity is essential for evaluating stream habitat quality for salmonids, but the variability in pool sizes, groundwater sources, and the associated water quality makes characterization of habitat challenging. Habitat volume and stream connectivity are key drivers of ecosystem processes in spatially-intermittent streams, and strongly influence survival of juvenile salmonids in coastal California. Stream disconnection creates heterogeneous habitats, as disconnected pools are fed by distinct groundwater and hyporheic sources of water containing different concentrations of carbon, oxygen and nutrients. These distinct biogeochemical regimes drive production of benthic macroinvertebrates (salmonids' primary food source) and dissolved oxygen levels, which in turn govern salmonid metabolism. In this study, we use terrestrial laser scans of the streambed, topographic surveys of wetted pools, and repeat field measurements of pool depth to develop a timeseries of finely resolved pool volumes and dry riffle lengths. We overlay repeat water quality measurements onto this surface to visualize how cessation of flow creates heterogeneous habitats influenced by groundwater flux and geomorphic setting. By coupling terrestrial laser scans with traditional surveys, we create high-resolution facies surfaces that can be integrated with timeseries measurements of other biogeochemical data to characterize changes in habitat conditions during baseflow recession. Compared with traditional survey methods, this method yields improved qualitative descriptions of habitat fragmentation via visualizations and spatially and temporally explicit quantification of aquatic and riparian habitat characteristics that drive salmonid over-summer survival.

  11. Pneumatically erected rigid habitat

    NASA Technical Reports Server (NTRS)

    Salles, Bradley

    1992-01-01

    The pneumatically erected rigid habitat concept consists of a structure based on an overexpanded metal bellows. The basic concept incorporates the advantages of both inflatable and rigid structures. The design and erection detail are presented with viewgraphs.

  12. Habitat-Specific Population Growth of a Farmland Bird

    PubMed Central

    Arlt, Debora; Forslund, Pär; Jeppsson, Tobias; Pärt, Tomas

    2008-01-01

    Background To assess population persistence of species living in heterogeneous landscapes, the effects of habitat on reproduction and survival have to be investigated. Methodology/Principal Findings We used a matrix population model to estimate habitat-specific population growth rates for a population of northern wheatears Oenanthe oenanthe breeding in farmland consisting of a mosaic of distinct habitat (land use) types. Based on extensive long-term data on reproduction and survival, habitats characterised by tall field layers (spring- and autumn-sown crop fields, ungrazed grasslands) displayed negative stochastic population growth rates (log λs: −0.332, −0.429, −0.168, respectively), that were markedly lower than growth rates of habitats characterised by permanently short field layers (pastures grazed by cattle or horses, and farmyards, log λs: −0.056, +0.081, −0.059). Although habitats differed with respect to reproductive performance, differences in habitat-specific population growth were largely due to differences in adult and first-year survival rates, as shown by a life table response experiment (LTRE). Conclusions/Significance Our results show that estimation of survival rates is important for realistic assessments of habitat quality. Results also indicate that grazed grasslands and farmyards may act as source habitats, whereas crop fields and ungrazed grasslands with tall field layers may act as sink habitats. We suggest that the strong decline of northern wheatears in Swedish farmland may be linked to the corresponding observed loss of high quality breeding habitat, i.e. grazed semi-natural grasslands. PMID:18714351

  13. Tropical Convection's Roles in Tropical Tropopause Cirrus

    NASA Technical Reports Server (NTRS)

    Boehm, Matthew T.; Starr, David OC.; Verlinde, Johannes; Lee, Sukyoung

    2002-01-01

    Remote sensing observations reveal the frequent occurrence of tropopause cirrus, thin cirrus layers located near the tropical cold-point tropopause. Here, we present a theory in which tropical convection plays several important roles in tropopause cirrus formation. First, tropical convection is the primary means by which the moisture required for tropopause cirrus formation is transported into the upper troposphere. However, previous studies suggest that this convection rarely penetrates to the altitudes at which tropopause cirrus layers are observed, suggesting that additional vertical moisture transport is required to explain tropopause cirrus formation. We propose a mechanism for explaining this transport in which tropical convection plays the key role. According to this hypothesis, the transport is accomplished by meridional circulations that develop within the tropopause transition layer (TTL) in response to momentum transport by Rossby waves generated by tropical convection. Results of a series of global scale model runs designed to test this hypothesis will be presented. In addition, reanalyses vertical velocity data will be examined for evidence of the expected correlation between large-scale rising motion within the TTL and tropical convection. Once moisture is present near the cold-point tropopause, large-scale cooling is required to initiate tropopause cirrus formation. One source of this cooling is stratospheric tropical waves induced by tropical convection, as we will show using a time series of radiosonde temperature data superimposed with data on cloud occurrence from the DOE ARM Nauru99 field experiment. Observations of the global characteristics of these waves from a longer time series of reanalysis data will also be presented.

  14. Environmental synergisms and extinctions of tropical species.

    PubMed

    Laurance, William F; Useche, Diana C

    2009-12-01

    Environmental synergisms may pose the greatest threat to tropical biodiversity. Using recently updated data sets from the International Union for Conservation of Nature (IUCN) Red List, we evaluated the incidence of perceived threats to all known mammal, bird, and amphibian species in tropical forests. Vulnerable, endangered, and extinct species were collectively far more likely to be imperiled by combinations of threats than expected by chance. Among 45 possible pairwise combinations of 10 different threats, 69%, 93%, and 71% were significantly more frequent than expected for threatened mammals, birds, and amphibians, respectively, even with a stringent Bonferroni-corrected probability value (p= 0.003). Based on this analysis, we identified five key environmental synergisms in the tropics and speculate on the existence of others. The most important involve interactions between habitat loss or alteration (from agriculture, urban sprawl, infrastructure, or logging) and other anthropogenic disturbances such as hunting, fire, exotic-species invasions, or pollution. Climatic change and emerging pathogens also can interact with other threats. We assert that environmental synergisms are more likely the norm than the exception for threatened species and ecosystems, can vary markedly in nature among geographic regions and taxa, and may be exceedingly difficult to predict in terms of their ultimate impacts. The perils posed by environmental synergisms highlight the need for a precautionary approach to tropical biodiversity conservation. PMID:20078643

  15. Defaunation affects carbon storage in tropical forests

    PubMed Central

    Bello, Carolina; Galetti, Mauro; Pizo, Marco A.; Magnago, Luiz Fernando S.; Rocha, Mariana F.; Lima, Renato A. F.; Peres, Carlos A.; Ovaskainen, Otso; Jordano, Pedro

    2015-01-01

    Carbon storage is widely acknowledged as one of the most valuable forest ecosystem services. Deforestation, logging, fragmentation, fire, and climate change have significant effects on tropical carbon stocks; however, an elusive and yet undetected decrease in carbon storage may be due to defaunation of large seed dispersers. Many large tropical trees with sizeable contributions to carbon stock rely on large vertebrates for seed dispersal and regeneration, however many of these frugivores are threatened by hunting, illegal trade, and habitat loss. We used a large data set on tree species composition and abundance, seed, fruit, and carbon-related traits, and plant-animal interactions to estimate the loss of carbon storage capacity of tropical forests in defaunated scenarios. By simulating the local extinction of trees that depend on large frugivores in 31 Atlantic Forest communities, we found that defaunation has the potential to significantly erode carbon storage even when only a small proportion of large-seeded trees are extirpated. Although intergovernmental policies to reduce carbon emissions and reforestation programs have been mostly focused on deforestation, our results demonstrate that defaunation, and the loss of key ecological interactions, also poses a serious risk for the maintenance of tropical forest carbon storage. PMID:26824067

  16. Defaunation affects carbon storage in tropical forests.

    PubMed

    Bello, Carolina; Galetti, Mauro; Pizo, Marco A; Magnago, Luiz Fernando S; Rocha, Mariana F; Lima, Renato A F; Peres, Carlos A; Ovaskainen, Otso; Jordano, Pedro

    2015-12-01

    Carbon storage is widely acknowledged as one of the most valuable forest ecosystem services. Deforestation, logging, fragmentation, fire, and climate change have significant effects on tropical carbon stocks; however, an elusive and yet undetected decrease in carbon storage may be due to defaunation of large seed dispersers. Many large tropical trees with sizeable contributions to carbon stock rely on large vertebrates for seed dispersal and regeneration, however many of these frugivores are threatened by hunting, illegal trade, and habitat loss. We used a large data set on tree species composition and abundance, seed, fruit, and carbon-related traits, and plant-animal interactions to estimate the loss of carbon storage capacity of tropical forests in defaunated scenarios. By simulating the local extinction of trees that depend on large frugivores in 31 Atlantic Forest communities, we found that defaunation has the potential to significantly erode carbon storage even when only a small proportion of large-seeded trees are extirpated. Although intergovernmental policies to reduce carbon emissions and reforestation programs have been mostly focused on deforestation, our results demonstrate that defaunation, and the loss of key ecological interactions, also poses a serious risk for the maintenance of tropical forest carbon storage. PMID:26824067

  17. Estimation of tiger densities in the tropical dry forests of Panna, Central India, using photographic capture-recapture sampling

    USGS Publications Warehouse

    Karanth, K.U.; Chundawat, R.S.; Nichols, J.D.; Kumar, N.S.

    2004-01-01

    Tropical dry-deciduous forests comprise more than 45% of the tiger (Panthera tigris) habitat in India. However, in the absence of rigorously derived estimates of ecological densities of tigers in dry forests, critical baseline data for managing tiger populations are lacking. In this study tiger densities were estimated using photographic capture?recapture sampling in the dry forests of Panna Tiger Reserve in Central India. Over a 45-day survey period, 60 camera trap sites were sampled in a well-protected part of the 542-km2 reserve during 2002. A total sampling effort of 914 camera-trap-days yielded photo-captures of 11 individual tigers over 15 sampling occasions that effectively covered a 418-km2 area. The closed capture?recapture model Mh, which incorporates individual heterogeneity in capture probabilities, fitted these photographic capture history data well. The estimated capture probability/sample, 0.04, resulted in an estimated tiger population size and standard error of 29 (9.65), and a density of 6.94 (3.23) tigers/100 km2. The estimated tiger density matched predictions based on prey abundance. Our results suggest that, if managed appropriately, the available dry forest habitat in India has the potential to support a population size of about 9000 wild tigers.

  18. Phenotypic plasticity to light of two congeneric trees from contrasting habitats: Brazilian Atlantic Forest versus cerrado (savanna).

    PubMed

    Barros, F de V; Goulart, M F; Telles, S B Sá; Lovato, M B; Valladares, F; de Lemos-Filho, J P

    2012-01-01

    The Brazilian Atlantic Forest is a typically multi-layer tropical forest, while cerrado (savanna) is a patchy habitat with different physiognomy. Despite these differences, both habitats have high light heterogeneity. Functional traits of Dalbergia nigra and D. miscolobium from the Atlantic Forest and cerrado, respectively, were evaluated under shade (25% of full sunlight) and full sunlight in a nursery experiment. We hypothesised that both species should benefit from high phenotypic plasticity in relation to light. Plasticity was estimated using the relative distance phenotypic index (RDPI). D. miscolobium had lower shoot growth under both light conditions, suggesting it has low competitive capacity in the forest environment, which could explain its limited ability to expand over areas of Atlantic Forest. The studied species exhibited photoprotection strategies under high light and improved light capture under low light. Stomatal conductance, ETR(max) (maximum electron transport rate), PPFD(sat) (saturating photosynthetically active photon flux density), chlorophyll and carotenoid content had higher RDPI than stem morphological traits. Although both species showed considerable phenotypic plasticity, D. miscolobium had higher RDPI for eight of 11 evaluated traits. This high plasticity could be one of the factors that explain the occurrence of this species in a wide range of environmental conditions, from open grassland to dense woodlands, and it could also reflect its adaptation to high light. D. nigra also had considerable plasticity and good growth performance in both shade and full sunlight, but its absence in areas of cerrado suggests that factors other than light limit its occurrence in these habitats. PMID:21972934

  19. Habitat Suitability Index Models: Muskellunge

    USGS Publications Warehouse

    Cook, Mark F.; Solomon, R. Charles

    1987-01-01

    A review and synthesis of existing information were used to develop a Habitat Suitability Index (HSI) model for the muskellunge (Esox masquinongy Mitchell). The model consolidates habitat use information into a framework appropriate for field application, and is scaled to produce an index between 0.0 (unsuitable habitat) to 1.0 (optimum habitat). HSI models are designed to be used with Habitat Evaluation Procedures previously developed by the U.S. Fish and Wildlife Service.

  20. Habitat Suitability Index Models: Bobcat

    USGS Publications Warehouse

    Boyle, Katherine A.; Fendley, Timothy T.

    1987-01-01

    A review and synthesis of existing information were used to develop a Habitat Suitability Index (HSI) model for the bobcat (Felis rufus). The model consolidates habitat use information into a framework appropriate for field application, and is scaled to produce an index between 0.0 (unsuitable habitat) to 1.0 (optimum habitat). HSI models are designed to be used with Habitat Evaluation Procedures previously developed by the U.S. Fish and Wildlife Service.

  1. Habitat Suitability Index Models: Pronghorn

    USGS Publications Warehouse

    Allen, Arthur W.; Cook, John G.; Armbruster, Michael J.

    1984-01-01

    This is one of a series of publications that provide information on the habitat requirements of selected fish and wildlife species. Literature describing the relationship between habitat variables related to life requisites and habitat suitability for the pronghorn (Antilocapra americana) are synthesized. These data are subsequently used to develop Habitat Suitability Index (HSI) models. The HSI models are designed to provide information that can be used in impact assessment and habitat management.

  2. Methane Emission from Tropical Rivers

    NASA Astrophysics Data System (ADS)

    Sawakuchi, H. O.; Rasera, M. F. F. L.; Krusche, A. V.; Ballester, M. V. R.

    2012-04-01

    Inland water is already known as an important source of methane to atmosphere. Methane is produced in anaerobic environments usually find in lakes and floodplain bottom sediment. It is the main reason that almost all information regarding methane flux come from this environments. However, while floodplain dries during low water season reducing methanogenesis, rivers keep the capacity to emit methane throughout the year. Here we present preliminary results of CH4 flux measurements done in 6 large tropical rivers within the Amazon basin. We measured 17 areas using floating chamber during dry (low water) season, between September and November of 2011, in Amazon river mainstem, Araguaia, Xingu, Tapajós, Madeira, and Negro Rivers. Measured fluxes of all rivers ranged from 59.3 to 2974.4 mmol m-2 yr-1. Geomorphologic structure of channels is one important factor that contributes to this high heterogeneity due to development of low flow velocity depositional settings allowing formation of anoxic zones in rivers. Hydraulic and sediment barriers in the confluence of river channels promote the generation of natural dams which function as a trap for the suspension load favoring the deposition of organic rich muds. This kind of environment is very different from common river channels and has a stronger potential of methane emission. Average values of our flux measurements for this two river environments show that depositional areas can have much higher fluxes than the main channel, 1089.6 and 163.1 mmol m-2 yr-1, respectively. Hence, CH4 flux from these depositional zones is similar to some tropical floodplain lakes and reservoirs. Although the low flux from channel, the area covered by water is very large resulting in a significant contribution to the regional methane emission to the atmosphere. Moreover, mapping the area of these depositional river zones will give us a better idea of the magnitude of methane flux from tropical rivers.

  3. The future of tropical species on a warmer planet.

    PubMed

    Wright, S Joseph; Muller-Landau, Helene C; Schipper, Jan

    2009-12-01

    Modern global temperature and land cover and projected future temperatures suggest that tropical forest species will be particularly sensitive to global warming. Given a moderate greenhouse gas emissions scenario, fully 75% of the tropical forests present in 2000 will experience mean annual temperatures in 2100 that are greater than the highest mean annual temperature that supports closed-canopy forest today. Temperature-sensitive species might extend their ranges to cool refuges, defined here as areas where temperatures projected for 2100 match 1960s temperatures in the modern range. Distances to such cool refuges are greatest for equatorial species and are particularly large for key tropical forest areas including the Amazon and Congo River Basins, West Africa, and the upper elevations of many tropical mountains. In sum, tropical species are likely to be particularly sensitive to global warming because they are adapted to limited geographic and seasonal variation in temperature, already lived at or near the highest temperatures on Earth before global warming began, and are often isolated from cool refuges. To illustrate these three points, we examined the distributions and habitat associations of all extant mammal species. The distance to the nearest cool refuge exceeded 1000 km for more than 20% of the tropical and less than 4% of the extratropical species with small ranges. The biological impact of global warming is likely to be as severe in the tropics as at temperate and boreal latitudes. PMID:20078642

  4. Primary forests are irreplaceable for sustaining tropical biodiversity.

    PubMed

    Gibson, Luke; Lee, Tien Ming; Koh, Lian Pin; Brook, Barry W; Gardner, Toby A; Barlow, Jos; Peres, Carlos A; Bradshaw, Corey J A; Laurance, William F; Lovejoy, Thomas E; Sodhi, Navjot S

    2011-10-20

    Human-driven land-use changes increasingly threaten biodiversity, particularly in tropical forests where both species diversity and human pressures on natural environments are high. The rapid conversion of tropical forests for agriculture, timber production and other uses has generated vast, human-dominated landscapes with potentially dire consequences for tropical biodiversity. Today, few truly undisturbed tropical forests exist, whereas those degraded by repeated logging and fires, as well as secondary and plantation forests, are rapidly expanding. Here we provide a global assessment of the impact of disturbance and land conversion on biodiversity in tropical forests using a meta-analysis of 138 studies. We analysed 2,220 pairwise comparisons of biodiversity values in primary forests (with little or no human disturbance) and disturbed forests. We found that biodiversity values were substantially lower in degraded forests, but that this varied considerably by geographic region, taxonomic group, ecological metric and disturbance type. Even after partly accounting for confounding colonization and succession effects due to the composition of surrounding habitats, isolation and time since disturbance, we find that most forms of forest degradation have an overwhelmingly detrimental effect on tropical biodiversity. Our results clearly indicate that when it comes to maintaining tropical biodiversity, there is no substitute for primary forests. PMID:21918513

  5. A global model of the response of tropical and sub-tropical forest biodiversity to anthropogenic pressures

    PubMed Central

    Newbold, Tim; Hudson, Lawrence N.; Phillips, Helen R. P.; Hill, Samantha L. L.; Contu, Sara; Lysenko, Igor; Blandon, Abigayil; Butchart, Stuart H. M.; Booth, Hollie L.; Day, Julie; De Palma, Adriana; Harrison, Michelle L. K.; Kirkpatrick, Lucinda; Pynegar, Edwin; Robinson, Alexandra; Simpson, Jake; Mace, Georgina M.; Scharlemann, Jörn P. W.; Purvis, Andy

    2014-01-01

    Habitat loss and degradation, driven largely by agricultural expansion and intensification, present the greatest immediate threat to biodiversity. Tropical forests harbour among the highest levels of terrestrial species diversity and are likely to experience rapid land-use change in the coming decades. Synthetic analyses of observed responses of species are useful for quantifying how land use affects biodiversity and for predicting outcomes under land-use scenarios. Previous applications of this approach have typically focused on individual taxonomic groups, analysing the average response of the whole community to changes in land use. Here, we incorporate quantitative remotely sensed data about habitats in, to our knowledge, the first worldwide synthetic analysis of how individual species in four major taxonomic groups—invertebrates, ‘herptiles’ (reptiles and amphibians), mammals and birds—respond to multiple human pressures in tropical and sub-tropical forests. We show significant independent impacts of land use, human vegetation offtake, forest cover and human population density on both occurrence and abundance of species, highlighting the value of analysing multiple explanatory variables simultaneously. Responses differ among the four groups considered, and—within birds and mammals—between habitat specialists and habitat generalists and between narrow-ranged and wide-ranged species. PMID:25143038

  6. Deep-water kelp refugia as potential hotspots of tropical marine diversity and productivity.

    PubMed

    Graham, Michael H; Kinlan, Brian P; Druehl, Louis D; Garske, Lauren E; Banks, Stuart

    2007-10-16

    Classic marine ecological paradigms view kelp forests as inherently temperate-boreal phenomena replaced by coral reefs in tropical waters. These paradigms hinge on the notion that tropical surface waters are too warm and nutrient-depleted to support kelp productivity and survival. We present a synthetic oceanographic and ecophysiological model that accurately identifies all known kelp populations and, by using the same criteria, predicts the existence of >23,500 km(2) unexplored submerged (30- to 200-m depth) tropical kelp habitats. Predicted tropical kelp habitats were most probable in regions where bathymetry and upwelling resulted in mixed-layer shoaling above the depth of minimum annual irradiance dose for kelp survival. Using model predictions, we discovered extensive new deep-water Eisenia galapagensis populations in the Galápagos that increased in abundance with increasing depth to >60 m, complete with cold-water flora and fauna of temperate affinities. The predictability of deep-water kelp habitat and the discovery of expansive deep-water Galápagos kelp forests validate the extent of deep-water tropical kelp refugia, with potential implications for regional productivity and biodiversity, tropical food web ecology, and understanding of the resilience of tropical marine systems to climate change. PMID:17913882

  7. Ocean acidification limits temperature-induced poleward expansion of coral habitats around Japan

    NASA Astrophysics Data System (ADS)

    Yara, Y.; Vogt, M.; Fujii, M.; Yamano, H.; Hauri, C.; Steinacher, M.; Gruber, N.; Yamanaka, Y.

    2012-06-01

    Using results from four coupled global carbon cycle-climate models combined with in situ observations, we estimate the combined effects of future global warming and ocean acidification on potential habitats for tropical/subtropical and temperate coral communities in the seas around Japan. The suitability of the coral habitats are identified primarily on the basis of the currently observed ranges for temperature and saturation states Ω with regard to aragonite (Ωarag). We find that under the "business as usual" SRES A2 scenario, coral habitats will expand northward by several hundred kilometers by the end of this century. At the same time, coral habitats are projected to become sandwiched between the tropical regions, where the frequency of coral bleaching will increase, and the temperate-to-subpolar latitudes, where Ωarag will become too low to support sufficiently high calcification rates. As a result, the area of coral habitats around Japan that is suitable to tropical-subtropical communities will be reduced by half by the 2020s to 2030s, and is projected to disappear by the 2030s to 2040s. The suitable habitats for the temperate coral communities are also becoming smaller, although at a less pronounced rate due to their higher tolerance for low Ωarag.

  8. Does the habitat structure control the distribution and diversity of the Odonatofauna?

    PubMed

    Souza, A M; Fogaça, F N O; Cunico, A M; Higuti, J

    2015-08-01

    The statement that the habitat complexity and structure govern the abundance and diversity of biological communities has been widely investigated. In this context, we assumed the hypothesis of habitat heterogeneity, that is, the higher habitat complexity leads to greater diversity of Odonata. In addition, we analyzed the influence of habitat structure on the distribution of this community, and evaluated the effects of abiotic variables. Odonata larvae were collected with sieves and by electrofishing in ten neotropical streams belonging to the Pirapó River basin. Forty species of Odonata were registered, which were distributed in eight families, Libellulidae stood out with the highest richness. The high gamma diversity and distribution of Odonata were associated with habitat heterogeneity in these streams. However, the abiotic variables also seem to affect the distribution of Odonata species, in view of the impact of the land use in the vicinity of streams. PMID:26421772

  9. Habitat goes green

    SciTech Connect

    Kriescher, P.; Smith, M.

    1999-12-01

    A Denver family enjoys the financial and personal benefits of owning an affordable, energy-efficient home. On Earth Day, April 22, 1997, Habitat for Humanity of Metro Denver witnessed the realization of a dream. As Luis and Estella Valadez and their four children cut the ribbon on their 1,100 square foot (102 m{sup 2}) northwest Denver home, it signified the completion of the Denver Habitat affiliate's first ``Green'' home. Building this dream involved developing a plan to build affordable Habitat homes that also embodied a sense of stewardship of the Earth's environment. The affiliate also wanted to use this effort to achieve the additional goal of reducing the homeowner's utility and maintenance bills.

  10. Forest loss and the biodiversity threshold: an evaluation considering species habitat requirements and the use of matrix habitats.

    PubMed

    Estavillo, Candelaria; Pardini, Renata; da Rocha, Pedro Luís Bernardo

    2013-01-01

    Habitat loss is the main driver of the current biodiversity crisis, a landscape-scale process that affects the survival of spatially-structured populations. Although it is well-established that species responses to habitat loss can be abrupt, the existence of a biodiversity threshold is still the cause of much controversy in the literature and would require that most species respond similarly to the loss of native vegetation. Here we test the existence of a biodiversity threshold, i.e. an abrupt decline in species richness, with habitat loss. We draw on a spatially-replicated dataset on Atlantic forest small mammals, consisting of 16 sampling sites divided between forests and matrix habitats in each of five 3600-ha landscapes (varying from 5% to 45% forest cover), and on an a priori classification of species into habitat requirement categories (forest specialists, habitat generalists and open-area specialists). Forest specialists declined abruptly below 30% of forest cover, and spillover to the matrix occurred only in more forested landscapes. Generalists responded positively to landscape heterogeneity, peaking at intermediary levels of forest cover. Open area specialists dominated the matrix and did not spillover to forests. As a result of these distinct responses, we observed a biodiversity threshold for the small mammal community below 30% forest cover, and a peak in species richness just above this threshold. Our results highlight that cross habitat spillover may be asymmetrical and contingent on landscape context, occurring mainly from forests to the matrix and only in more forested landscapes. Moreover, they indicate the potential for biodiversity thresholds in human-modified landscapes, and the importance of landscape heterogeneity to biodiversity. Since forest loss affected not only the conservation value of forest patches, but also the potential for biodiversity-mediated services in anthropogenic habitats, our work indicates the importance of proactive

  11. Temporal overlaps of feral cats with prey and competitors in primary and human-altered habitats on Bohol Island, Philippines.

    PubMed

    Bogdan, Vlastimil; Jůnek, Tomáš; Jůnková Vymyslická, Pavla

    2016-01-01

    The vertebrate fauna of the Philippines, known for its diversity and high proportion of endemic species, comprises mainly small- to medium-sized forms with a few large exceptions. As with other tropical ecosystems, the major threats to wildlife are habitat loss, hunting and invasive species, of which the feral cat (Felis catus) is considered the most damaging. Our camera-trapping study focused on a terrestrial vertebrate species inventory on Bohol Island and tempo-spatial co-occurrences of feral cats with their prey and competitors. The survey took place in the Rajah Sikatuna Protected Landscape, and we examined the primary rainforest, its border with agricultural land, and rural areas in the vicinity of villages. Altogether, over 2,885 trap days we captured 30 species of vertebrates-10 mammals (including Sus philippensis), 19 birds and one reptile, Varanus cumingi. We trapped 81.8% of expected vertebrates. Based on the number of events, the most frequent native species was the barred rail (Gallirallus torquatus). The highest overlap in diel activity between cats and potential prey was recorded with rodents in rural areas (Δ = 0.62); the lowest was in the same habitat with ground-dwelling birds (Δ = 0.40). Cat activity was not recorded inside the rainforest; in other habitats their diel activity pattern differed. The cats' activity declined in daylight in the proximity of humans, while it peaked at the transition zone between rainforest and fields. Both rodents and ground-dwelling birds exhibited a shift in activity levels between sites where cats were present or absent. Rodents tend to become active by day in cat-free habitats. No cats' temporal response to co-occurrences of civets (Paradoxurus hermaphroditus and Viverra tangalunga) was found but cats in diel activity avoided domestic dogs (Canis lupus familiaris). Our first insight into the ecology of this invasive predator in the Philippines revealed an avoidance of homogeneous primary rainforest and a

  12. Temporal overlaps of feral cats with prey and competitors in primary and human-altered habitats on Bohol Island, Philippines

    PubMed Central

    Bogdan, Vlastimil; Jůnková Vymyslická, Pavla

    2016-01-01

    The vertebrate fauna of the Philippines, known for its diversity and high proportion of endemic species, comprises mainly small- to medium-sized forms with a few large exceptions. As with other tropical ecosystems, the major threats to wildlife are habitat loss, hunting and invasive species, of which the feral cat (Felis catus) is considered the most damaging. Our camera-trapping study focused on a terrestrial vertebrate species inventory on Bohol Island and tempo-spatial co-occurrences of feral cats with their prey and competitors. The survey took place in the Rajah Sikatuna Protected Landscape, and we examined the primary rainforest, its border with agricultural land, and rural areas in the vicinity of villages. Altogether, over 2,885 trap days we captured 30 species of vertebrates–10 mammals (including Sus philippensis), 19 birds and one reptile, Varanus cumingi. We trapped 81.8% of expected vertebrates. Based on the number of events, the most frequent native species was the barred rail (Gallirallus torquatus). The highest overlap in diel activity between cats and potential prey was recorded with rodents in rural areas (Δ = 0.62); the lowest was in the same habitat with ground-dwelling birds (Δ = 0.40). Cat activity was not recorded inside the rainforest; in other habitats their diel activity pattern differed. The cats’ activity declined in daylight in the proximity of humans, while it peaked at the transition zone between rainforest and fields. Both rodents and ground-dwelling birds exhibited a shift in activity levels between sites where cats were present or absent. Rodents tend to become active by day in cat-free habitats. No cats’ temporal response to co-occurrences of civets (Paradoxurus hermaphroditus and Viverra tangalunga) was found but cats in diel activity avoided domestic dogs (Canis lupus familiaris). Our first insight into the ecology of this invasive predator in the Philippines revealed an avoidance of homogeneous primary rainforest and a

  13. TROPICAL SPIDERWORT - AN INTRODUCTION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tropical spiderwort (also known as Benghal dayflower) has gone from relative obscurity as a roadside curiosity to troublesome weed with widespread economic impact in Georgia in less than 10 years. South Georgia and Florida are currently plagued by tropical spiderwort, but isolated populations have ...

  14. Modeling habitat suitability for Greater Rheas based on satellite image texture.

    PubMed

    Bellis, Laura M; Pidgeon, Anna M; Radeloff, Volker C; St-Louis, Véronique; Navarro, Joaquín L; Martella, Mónica B

    2008-12-01

    Many wild species are affected by human activities occurring at broad spatial scales. For instance, in South America, habitat loss threatens Greater Rhea (Rhea americana) populations, making it important to model and map their habitat to better target conservation efforts. Spatially explicit habitat modeling is a powerful approach to understand and predict species occurrence and abundance. One problem with this approach is that commonly used land cover classifications do not capture the variability within a given land cover class that might constitute important habitat attribute information. Texture measures derived from remote sensing images quantify the variability in habitat features among and within habitat types; hence they are potentially a powerful tool to assess species-habitat relationships. Our goal was to explore the utility of texture measures for habitat modeling and to develop a habitat suitability map for Greater Rheas at the home range level in grasslands of Argentina. Greater Rhea group size obtained from aerial surveys was regressed against distance to roads, houses, and water, and land cover class abundance (dicotyledons, crops, grassland, forest, and bare soil), normalized difference vegetation index (NDVI), and selected first- and second-order texture measures derived from Landsat Thematic Mapper (TM) imagery. Among univariate models, Rhea group size was most strongly positively correlated with texture variables derived from near infrared reflectance measurement (TM band 4). The best multiple regression models explained 78% of the variability in Greater Rhea group size. Our results suggest that texture variables captured habitat heterogeneity that the conventional land cover classification did not detect. We used Greater Rhea group size as an indicator of habitat suitability; we categorized model output into different habitat quality classes. Only 16% of the study area represented high-quality habitat for Greater Rheas (group size > or =15

  15. Habitat Suitability Index Models: Marten

    USGS Publications Warehouse

    Allen, Arthur W.

    1982-01-01

    Habitat preferences and species characteristics of the pine marten (Martes americana) are described in this publication. It is one of a series of Habitat Suitability Index (HSI) models and was developed through an analysis of available scientific data on the species-habitat requirements of the pine marten. Habitat use information is presented in a review of the literature, followed by the development of a HSI model. The model is presented in three formats: graphic, word and mathematical. Suitability index graphs quantify the species-habitat relationship. These data are then synthesized into a model which is designed to provide information for use in impact assessment and habitat management activities.

  16. Habitat Suitability Information: Blacknose Dace

    USGS Publications Warehouse

    Trial, Joan G.; Stanley, Jon G.; Batcheller, Mary; Gebhart, Gary; Maughan, O. Eugene; Nelson, Patrick C.

    1983-01-01

    A review and synthesis of existing information were used to develop riverine and lacustrine habitat models for Blacknose dace, a freshwater species. The models are scaled to produce an index of habitat suitability between 0 (unsuitable habitat) to 1 (optimally suitable habitat) for freshwater, marine, and estuarine areas of the continental United States. Habitat suitability indexes (HSI's) are designed for use with the habitat evaluation procedures developed by the U.S. Fish and Wildlife Service. Also included are discussions of Suitability Index (SI) curves as used in the Instream Flow Incremental Methodology (IFIM) and SI curves available for an IFIM analysis of Blacknose dace.

  17. Temporally dynamic habitat suitability predicts genetic relatedness among caribou

    PubMed Central

    Yannic, Glenn; Pellissier, Loïc; Le Corre, Maël; Dussault, Christian; Bernatchez, Louis; Côté, Steeve D.

    2014-01-01

    Landscape heterogeneity plays a central role in shaping ecological and evolutionary processes. While species utilization of the landscape is usually viewed as constant within a year, the spatial distribution of individuals is likely to vary in time in relation to particular seasonal needs. Understanding temporal variation in landscape use and genetic connectivity has direct conservation implications. Here, we modelled the daily use of the landscape by caribou in Quebec and Labrador, Canada and tested its ability to explain the genetic relatedness among individuals. We assessed habitat selection using locations of collared individuals in migratory herds and static occurrences from sedentary groups. Connectivity models based on habitat use outperformed a baseline isolation-by-distance model in explaining genetic relatedness, suggesting that variations in landscape features such as snow, vegetation productivity and land use modulate connectivity among populations. Connectivity surfaces derived from habitat use were the best predictors of genetic relatedness. The relationship between connectivity surface and genetic relatedness varied in time and peaked during the rutting period. Landscape permeability in the period of mate searching is especially important to allow gene flow among populations. Our study highlights the importance of considering temporal variations in habitat selection for optimizing connectivity across heterogeneous landscape and counter habitat fragmentation. PMID:25122223

  18. Temporally dynamic habitat suitability predicts genetic relatedness among caribou.

    PubMed

    Yannic, Glenn; Pellissier, Loïc; Le Corre, Maël; Dussault, Christian; Bernatchez, Louis; Côté, Steeve D

    2014-10-01

    Landscape heterogeneity plays a central role in shaping ecological and evolutionary processes. While species utilization of the landscape is usually viewed as constant within a year, the spatial distribution of individuals is likely to vary in time in relation to particular seasonal needs. Understanding temporal variation in landscape use and genetic connectivity has direct conservation implications. Here, we modelled the daily use of the landscape by caribou in Quebec and Labrador, Canada and tested its ability to explain the genetic relatedness among individuals. We assessed habitat selection using locations of collared individuals in migratory herds and static occurrences from sedentary groups. Connectivity models based on habitat use outperformed a baseline isolation-by-distance model in explaining genetic relatedness, suggesting that variations in landscape features such as snow, vegetation productivity and land use modulate connectivity among populations. Connectivity surfaces derived from habitat use were the best predictors of genetic relatedness. The relationship between connectivity surface and genetic relatedness varied in time and peaked during the rutting period. Landscape permeability in the period of mate searching is especially important to allow gene flow among populations. Our study highlights the importance of considering temporal variations in habitat selection for optimizing connectivity across heterogeneous landscape and counter habitat fragmentation. PMID:25122223

  19. Bird communities of natural and modified habitats in Panama

    USGS Publications Warehouse

    Petit, L.J.; Petit, D.R.; Christian, D.G.; Powell, H.D.W.

    1999-01-01

    Only a small proportion of land can realistically be protected as nature reserves and thus conservation efforts also must focus on the ecological value of agroecosystems and developed areas surrounding nature reserves. In this study, avian communities were surveyed in 11 habitat types in central Panama, across a gradient from extensive forest to intensive agricultural land uses, to examine patterns of species richness and abundance and community composition. Wooded habitats, including extensive and fragmented forests, shade coffee plantations, and residential areas supported the most species and individuals. Nearctic-Neotropical migratory species were most numerous in lowland forest fragments, shade coffee, and residential areas. Introduced Pinus caribbea and sugar cane plantations supported the fewest species compared to all other habitats. Cattle pastures left fallow for less than two years supported more than twice as many total species as actively grazed pastures, such that species richness in fallow pastures was similar to that found in wooded habitats. Community similarities were relatively low among all habitat types (none exceeding the observed 65% similarity between extensive and fragmented lowland forests), but communities in shade coffee and residential areas were 43% and 54% similar to lowland forest fragments, respectively. Fallow pastures and residential areas shared 60% of their species. Bird communities in shade coffee and residential areas were characterized by higher proportions of frugivorous and nectarivorous species than in native forests. These same guilds also were better represented in fallow than in grazed pastures. Raptors and piscivorous species were most prevalent in cattle pastures and rice fields. These results, though based upon only species richness and abundance, demonstrate that many human-altered habitats have potential ecological value for birds, and conservation efforts in tropical areas should focus greater attention on

  20. Modeling sensitive elasmobranch habitats

    NASA Astrophysics Data System (ADS)

    Pennino, M. Grazia; Muñoz, Facundo; Conesa, David; López-Quílez, Antonio; Bellido, José Marí; a

    2013-10-01

    Basic information on the distribution and habitat preferences of ecologically important species is essential for their management and protection. In the Mediterranean Sea there is increasing concern over elasmobranch species because their biological (ecological) characteristics make them highly vulnerable to fishing pressure. Their removal could affect the structure and function of marine ecosystems, inducing changes in trophic interactions at the community level due to the selective elimination of predators or prey species, competitors and species replacement. In this study Bayesian hierarchical spatial models are used to map the sensitive habitats of the three most caught elasmobranch species (Galeus melastomus, Scyliorhinus canicula, Etmopterus spinax) in the western Mediterranean Sea, based on fishery-dependent bottom trawl data. Results show that habitats associated with hard substrata and sandy beds, mainly in deep waters and with a high seabed gradient, have a greater probability registering the presence of the studied species than those associated with muddy shallow waters. Temperature and chlorophyll-α concentration show a negative relationship with S. canicula occurrence. Our results identify some of the sensitive habitats for elasmobranchs in the western Mediterranean Sea (GSA06 South), providing essential and easy-to-use interpretation tools, such as predictive distribution maps, with the final aim of improving management and conservation of these vulnerable species.

  1. MAINE MARINE WORM HABITAT

    EPA Science Inventory

    WORM provides a generalized representation at 1:24,000 scale of commercially harvested marine worm habitat in Maine, based on Maine Department of Marine Resources data from 1970's. Original maps were created by MDMR and published by USF&WS as part of the ""&quo...

  2. Earth is a Marine Habitat. Habitat Conservation Program.

    ERIC Educational Resources Information Center

    National Oceanic and Atmospheric Administration (DOC), Rockville, MD.

    This brochure is intended to educate the public about the need to conserve and preserve the earth's environment (man's habitat). It contains an introduction to the ocean world and threats to coastal habitat. Photos and narrative revolve around the theme "Earth is a Marine Habitat." Sections include: "The Web of Life,""Oceans and the United…

  3. Forest-climate interactions in fragmented tropical landscapes.

    PubMed Central

    Laurance, William F

    2004-01-01

    In the tropics, habitat fragmentation alters forest-climate interactions in diverse ways. On a local scale (less than 1 km), elevated desiccation and wind disturbance near fragment margins lead to sharply increased tree mortality, thus altering canopy-gap dynamics, plant community composition, biomass dynamics and carbon storage. Fragmented forests are also highly vulnerable to edge-related fires, especially in regions with periodic droughts or strong dry seasons. At landscape to regional scales (10-1000 km), habitat fragmentation may have complex effects on forest-climate interactions, with important consequences for atmospheric circulation, water cycling and precipitation. Positive feedbacks among deforestation, regional climate change and fire could pose a serious threat for some tropical forests, but the details of such interactions are poorly understood. PMID:15212089

  4. Forest-climate interactions in fragmented tropical landscapes.

    PubMed

    Laurance, William F

    2004-03-29

    In the tropics, habitat fragmentation alters forest-climate interactions in diverse ways. On a local scale (less than 1 km), elevated desiccation and wind disturbance near fragment margins lead to sharply increased tree mortality, thus altering canopy-gap dynamics, plant community composition, biomass dynamics and carbon storage. Fragmented forests are also highly vulnerable to edge-related fires, especially in regions with periodic droughts or strong dry seasons. At landscape to regional scales (10-1000 km), habitat fragmentation may have complex effects on forest-climate interactions, with important consequences for atmospheric circulation, water cycling and precipitation. Positive feedbacks among deforestation, regional climate change and fire could pose a serious threat for some tropical forests, but the details of such interactions are poorly understood. PMID:15212089

  5. Ability of crassulacean acid metabolism plants to overcome interacting stresses in tropical environments

    PubMed Central

    Lüttge, Ulrich

    2010-01-01

    Background and aims Single stressors such as scarcity of water and extreme temperatures dominate the struggle for life in severely dry desert ecosystems or cold polar regions and at high elevations. In contrast, stress in the tropics typically arises from a dynamic network of interacting stressors, such as availability of water, CO2, light and nutrients, temperature and salinity. This requires more plastic spatio-temporal responsiveness and versatility in the acquisition and defence of ecological niches. Crassulacean acid metabolism The mode of photosynthesis of crassulacean acid metabolism (CAM) is described and its flexible expression endows plants with powerful strategies for both acclimation and adaptation. Thus, CAM plants are able to inhabit many diverse habitats in the tropics and are not, as commonly thought, successful predominantly in dry, high-insolation habitats. Tropical CAM habitats Typical tropical CAM habitats or ecosystems include exposed lava fields, rock outcrops of inselbergs, salinas, savannas, restingas, high-altitude páramos, dry forests and moist forests. Morphotypical and physiotypical plasticity of CAM Morphotypical and physiotypical plasticity of CAM phenotypes allow a wide ecophysiological amplitude of niche occupation in the tropics. Physiological and biochemical plasticity appear more responsive by having more readily reversible variations in performance than do morphological adaptations. This makes CAM plants particularly fit for the multi-factor stressor networks of tropical forests. Thus, while the physiognomy of semi-deserts outside the tropics is often determined by tall succulent CAM plants, tropical forests house many more CAM plants in terms of quantity (biomass) and quality (species diversity). PMID:22476063

  6. Occurrence and biogeography of hydroids (Cnidaria: Hydrozoa) from deep-water coral habitats off the southeastern United States

    NASA Astrophysics Data System (ADS)

    Henry, Lea-Anne; Nizinski, Martha S.; Ross, Steve W.

    2008-06-01

    Deep-water coral habitats off the southeastern USA (SEUS) support diverse fish and invertebrate assemblages, but are poorly explored. This study is the first to report on the hydroids collected from these habitats in this area. Thirty-five species, including two species that are likely new to science, were identified from samples collected primarily by manned submersible during 2001-2005 from deep-water coral habitats off North Carolina to east-central Florida. Eleven of the species had not been reported since the 19th to mid-20th century. Ten species, and one family, the Rosalindidae, are documented for the first time in the SEUS. Latitudinal ranges of 15 species are extended, and the deepest records in the western North Atlantic for 10 species are reported. A species accumulation curve illustrated that we continue to add to our knowledge of hydroid diversity in these habitats. Sexually mature individuals were collected for 19 species during the summer to early autumn months. Most of the observed species (89%) liberate planula larvae as part of their life cycles, suggesting that these species exhibit a reproductive strategy that reduces the risk of dispersal to sub-optimal habitats. Hydroids occurred across various substrata including coral rubble, live corals, rock and other animal hosts including hydroids themselves. All observed species were regionally widespread with typically deep-neritic to bathyal sub-tropical/tropical distributions. Hydroid assemblages from deep-water SEUS coral habitats were most similar to those from adjacent deep-water habitats off the SEUS (17 shared species), and those in the Straits of Florida/Bahamas and Caribbean/West Indian regions (14 and 8 shared species, respectively). The similarity to sub-tropical and tropical assemblages and the richness of plumularioids in the SEUS deep-water coral habitats support the idea of a Pleistocene intrusion of tropical species northwards following an intensification of the Gulf Stream from the

  7. Dysgammaglobulinaemia in Tropical Sprue

    PubMed Central

    Jarnum, S.; Jeejeebhoy, K. N.; Singh, B.

    1968-01-01

    Study of immunoglobulin levels in 16 Indian control subjects showed that, compared with a Danish control series, they had a significantly higher mean level of IgG, but not of IgA or IgM. By contrast, the IgG levels in eight patients with tropical sprue were decreased or low normal in six cases and raised in only one case. Two patients with tropical sprue had agamma-A-globulinaemia. Turnover studies with 125I-labelled IgG showed a high rate of synthesis in three Indian controls and an appreciably reduced or low rate in seven of the eight cases of tropical sprue. PMID:4176829

  8. Individualistic Population Responses of Five Frog Species in Two Changing Tropical Environments over Time

    PubMed Central

    Ryan, Mason J.; Fuller, Michael M.; Scott, Norman J.; Cook, Joseph A.; Poe, Steven; Willink, Beatriz; Chaves, Gerardo; Bolaños, Federico

    2014-01-01

    Roughly 40% of amphibian species are in decline with habitat loss, disease, and climate change being the most cited threats. Heterogeneity of extrinsic (e.g. climate) and intrinsic (e.g. local adaptations) factors across a species’ range should influence population response to climate change and other threats. Here we examine relative detectability changes for five direct-developing leaf litter frogs between 42-year sampling periods at one Lowland Tropical Forest site (51 m.a.s.l.) and one Premontane Wet Forest site (1100 m.a.s.l.) in southwest Costa Rica. We identify individualistic changes in relative detectability among populations between sampling periods at different elevations. Both common and rare species showed site-specific declines, and no species exhibited significant declines at both sites. Detection changes are correlated with changes in temperature, dry season rainfall, and leaf litter depth since1969. Our study species share Least Concern conservation status, life history traits, and close phylogenetic relationship, yet their populations changed individualistically both within and among species. These results counter current views of the uniformity or predictability of amphibian decline response and suggest additional complexity for conservation decisions. PMID:24878504

  9. Organic matter dynamics control plant species coexistence in a tropical peat swamp forest

    PubMed Central

    Shimamura, Tetsuya; Momose, Kuniyasu

    2005-01-01

    We studied the relationship between the coexistence of tree species and the dynamics of organic matter in forests. A tropical peat swamp forest was selected as a model ecosystem, where abiotic factors, such as geological topography or parent rock types, are homogeneous and only biological processes create habitat heterogeneity. The temporal or spatial variation of the ground elevation of peat soils is mainly caused by changes in the balance between organic matter inputs to soils and decomposition, which is affected by the growth and death of influential trees. To clarify the processes of elevation dynamics, we measured the microtopography around some tree groups, estimated organic matter (in the form of litter and roots) in soils under three kinds of microtopographic conditions, measured decomposition rates and detected dominant species' shifting distribution patterns in different stages of growth in relation to the locations of tree groups creating specific microtopographic conditions. We found that growth or death of buttressed trees has the greatest effects on the rising or sinking of ground surfaces through changes in litter supply and root production. We discuss here the possibility of extending our model to other forest types. PMID:16011926

  10. Habitat constraints on the distribution of passerine residents and neotropical migrants in Latin America

    USGS Publications Warehouse

    Robbins, C.S.; Dowell, B.A.; Dawson, D.K.

    1994-01-01

    With continuing tropical deforestation, there is increased concern for birds that depend on forest habitats in Latin America. During the past 10 northern winters, we have conducted quantitative studies of habitat use by wintering migrant songbirds and by residents in the Greater Antilles, Mexico, Central America, and northern South America. Many migrants, but few residents, winter in forest fragments and in certain arboreal agricultural habitats (citrus, cacao, shade coffee). Many other agricultural habitats (sun coffee, mango, commercial banana plantations, and heavily grazed pasture) are avoided by most birds. Some species, such as thrushes and ground-feeding warblers, depend on closed-canopy forest. Some, such as Northern Waterthrush (Seiurus noveboracensis) and Prothonotary Warbler (Protonotaria citrea), winter primarily in mangroves or other swamp forests. The majority of neotropical migrant passerines winter in forest fragments and certain agricultural habitats, as well as mature forest; but many resident species, especially suboscines (Furnariidae, Dendrocolaptidae, Formicariidae, Papridae), are heavily impacted by loss and fragmentation of the forest.