Ecography
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Sắp xếp:
Phylogenetic community structure and phylogenetic turnover across space and edaphic gradients in western Amazonian tree communities
Ecography - Tập 34 Số 4 - Trang 552-565 - 2011
Comprehensive estimation of spatial and temporal migratory connectivity across the annual cycle to direct conservation efforts Migratory connectivity is the degree to which populations are linked in space and time across the annual cycle. Low connectivity indicates mixing of populations while high connectivity indicates population separation in space or time. High migratory connectivity makes individual populations susceptible to local environmental conditions; therefore, evaluating migratory connectivity continuously across a species range is important for understanding differential population trends and revealing places and times contributing to these differences. The common nighthawk Chordeiles minor is a widespread, declining, long‐distance migratory bird. Variable population trends across the nighthawk breeding range suggest that knowledge of migratory connectivity is needed to direct conservation. We used GPS tags to track 52 individuals from 12 breeding populations. We estimated migratory connectivity as 0.29 (Mantel coefficient: 0 = no connectivity, 1 = full connectivity) between the breeding and wintering grounds. We then estimated migratory connectivity at every latitude (spatial connectivity) or day (temporal connectivity) of migration and smoothed those migratory connectivity estimates to produce continuous migratory connectivity ‘profiles'. Spatial and temporal connectivity were highest during migration through North America (around 0.3–0.6), with values generally around 0 in Central and South America due to mixing of populations along a common migratory route and similar migration timing across populations. We found local peaks in spatial and temporal connectivity during migration associated with crossing the Gulf of Mexico. We used simulations to estimate the probability that our method missed peaks (spatial: 0.12, temporal: 0.18) or detected false peaks (spatial: 0.11, temporal: 0.37) due to data gaps and showed that our approach remains useful even for sparse and/or sporadic location data. Our study presents a generalizable approach to evaluating migratory connectivity across the full annual cycle that can be used to focus migratory bird conservation towards places and times of the annual cycle where populations are more likely to be limited.
Ecography - Tập 44 Số 5 - Trang 665-679 - 2021
Where do animals come from during post‐fire population recovery? Implications for ecological and genetic patterns in post‐fire landscapes Identifying where animals come from during population recovery can help to understand the impacts of disturbance events and regimes on species distributions and genetic diversity. Alternative recovery processes for animal populations affected by fire include external recolonization, nucleated recovery from refuges, or in situ survival and population growth. We used simulations to develop hypotheses about ecological and genetic patterns corresponding to these alternative models. We tested these hypotheses in a study of the recovery of two small mammals, the Australian bush rat and the agile antechinus, after a large (> 50 000 ha), severe wildfire. The abundance of both species was severely reduced by fire and recovered to near or above pre‐fire levels within two generations, yet we rejected a hypothesis of recovery by external recolonization. While the agile antechinus showed genetic evidence for far greater dispersal capacity than the bush rat, neither species showed gradients in abundance or genetic diversity with distance from unburnt forest during population recovery. Population recovery was driven by local‐scale processes. However, the mechanisms differed between species, resulting from the spatial impacts of fire on habitat suitability. Agile antechinus populations recovered through population growth from in situ survivors. The bush rat followed a model of nucleated recovery, involving local recolonization from micro‐refuges in topographic drainage lines. Nucleated recovery by the bush rat was associated with changes in dispersal, and fine‐scale patterns of genetic admixture. We identified increased dispersal by females during recovery, contrasting with male‐biased dispersal in unburnt forest. Such flexibility in dispersal can potentially increase recovery rates compared to expectations based on dispersal behavior within undisturbed populations. Our study shows how the initial distribution of survivors, determined by fire effects on resource distribution, determines the subsequent scaling of population recovery patterns, and the sensitivity of population distribution and genetic diversity to changing disturbance regimes.
Ecography - Tập 40 Số 11 - Trang 1325-1338 - 2017
Do stream fish track climate change? Assessing distribution shifts in recent decades Understanding the ability of species to shift their distribution ranges in response to climate change is crucial for conservation biologists and resources managers. Although freshwater ecosystems include some of the most imperilled fauna worldwide, such range shifts have been poorly documented in streams and rivers and have never been compared to the current velocity of climate change. Based on national monitoring data, we examined the distributional changes of 32 stream fish species in France and quantified potential time lags in species responses, providing a unique opportunity to analyze range shifts over recent decades of warming in freshwater environments. A multi‐facetted approach, based on several range measures along spatial gradients, allowed us to quantify range shifts of numerous species across the whole hydrographic network between an initial period (1980–1992) and a contemporary one (2003–2009), and to contrast them to the rates of isotherm shift in elevation and stream distance. Our results highlight systematic species shifts towards higher elevation and upstream, with mean shifts in range centre of 13.7 m decade−1 and 0.6 km decade−1 , respectively. Fish species displayed dispersal‐driven expansions along the altitudinal gradient at their upper range limit (61.5 m decade−1 ), while substantial range contractions at the lower limit (6.3 km decade−1 ) were documented for most species along the upstream–downstream gradient. Despite being consistent with the geographic variation in climate change velocities, these patterns reveal that the majority of stream fish have not shifted at a pace sufficient to track changing climate, in particular at their range centre where range shifts lag far behind expectation. Our study provides evidence that stream fish are currently responding to recent climate warming at a greater rate than many terrestrial organisms, although not as much as needed to cope with future climate modifications.
Ecography - Tập 36 Số 11 - Trang 1236-1246 - 2013
Awesome or ordinary? Global diversity patterns of oribatid mites Diversity of most above‐ground organisms increases with decreasing latitude, but the biogeographical and macroecological diversity patterns of below‐ground animals have been poorly studied. We investigated the latitudinal diversity gradient in a primarily below‐ground living soil taxon, oribatid mites. Furthermore, oribatid mite species richness from islands and mainlainds was tested for correlation with the size of the respective area (island or mainland) to evaluate if their species–area relationships are similar to those of above‐ground taxa. The results suggest that for oribatid mites 1) diversity increases from the boreal to the warm temperate region but not further to the tropics, and 2) species–area relationships for islands and mainlands are similar to those of above‐ground taxa, but this is mainly caused by very small islands, such as Cocos islands, and very large islands, such as Madagascar. When these islands are excluded the species–area relationship strongly differs from those of typical islands. The results support the view that below‐ground animal taxa are generalists that inhabit wide niches. Most small islands have relatively rich oribatid mite faunas, supporting the observation that a large number of species can coexist in a small area (high α‐diversity).
Ecography - Tập 30 Số 2 - Trang 209-216 - 2007
The structure of oribatid mite communities (Acari, Oribatida): patterns, mechanisms and implications for future research
Ecography - Tập 23 Số 3 - Trang 374-382 - 2000
Food‐web structure varies along environmental gradients in a high‐latitude marine ecosystem Large‐scale patterns in species diversity and community composition are associated with environmental gradients, but the implications of these patterns for food‐web structure are still unclear. Here, we investigated how spatial patterns in food‐web structure are associated with environmental gradients in the Barents Sea, a highly productive shelf sea of the Arctic Ocean. We compared food webs from 25 subregions in the Barents Sea and examined spatial correlations among food‐web metrics, and between metrics and spatial variability in seawater temperature, bottom depth and number of days with ice cover. Several food‐web metrics were positively associated with seawater temperature: connectance, level of omnivory, clustering, cannibalism, and high variability in generalism, while other food‐web metrics such as modularity and vulnerability were positively associated with sea ice and negatively with temperature. Food‐web metrics positively associated with habitat heterogeneity were: number of species, link density, omnivory, path length, and trophic level. This finding suggests that habitat heterogeneity promotes food‐web complexity in terms of number of species and link density. Our analyses reveal that spatial variation in food‐web structure along the environmental gradients is partly related to species turnover. However, the higher interaction turnover compared to species turnover along these gradients indicates a consistent modification of food‐web structure, implying that interacting species may co‐vary in space. In conclusion, our study shows how environmental heterogeneity, via environmental filtering, influences not only turnover in species composition, but also the structure of food webs over large spatial scales.
Ecography - Tập 42 Số 2 - Trang 295-308 - 2019
Defaunation and fragmentation erode small mammal diversity dimensions in tropical forests Forest fragmentation and defaunation are considered the main drivers of biodiversity loss, yet the synergistic effects of landscape changes and biotic interactions on assemblage structure have been poorly investigated. Here, we use an extensive dataset of 283 assemblages and 105 species of small mammals to understand how defaunation of medium and large mammals and forest fragmentation change the community composition and diversity of rodents and marsupials in tropical forests of South America. We used structured equation models to investigate the relationship between small mammal species, functional and phylogenetic diversity with forest size, forest cover and the occurrence of medium and large mammals. The best‐fit model showed that defaunation reduced functional diversity, and that species diversity of small mammals increased with forest patch size. Forest cover did not affect functional and phylogenetic diversity. Our results indicate that occurrence of medium and large sized mammals (probably acting as predators, or competitors of small mammals) and forest patch size help to retain species and functional diversity in small mammal communities. Further, the number of species in a small mammal community was critical to the maintenance of phylogenetic diversity, and may have a pronounced influence on the ecological functions played by small mammals. Identifying how phylogenetic and functional diversity change in function of human pressures allows us to better understand the contribution of extant lineages to ecosystem functioning in tropical forests.
Ecography - Tập 42 Số 1 - Trang 23-35 - 2019
Predicting species diversity with ED: the quest for evidence
Ecography - Tập 26 Số 3 - Trang 380-383 - 2003
Environmental diversity (ED) as surrogate information for species‐level biodiversity
Ecography - Tập 26 Số 3 - Trang 374-379 - 2003
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