How climate affects species distributions is a longstanding question receiving renewed interest owing to the need to predict the impacts of global warming on biodiversity. Is climate change forcing species to live near their critical thermal limits? Are these limits likely to change through natural selection? These and other important questions can be addressed with models relating geographical distributions of species with climate data, but inferences made with these models are highly contingent on non-climatic factors such as biotic interactions. Improved understanding of climate change effects on species will require extensive analysis of thermal physiological traits, but such data are both scarce and scattered. To overcome current limitations, we created the GlobTherm database. The database contains experimentally derived species’ thermal tolerance data currently comprising over 2,000 species of terrestrial, freshwater, intertidal and marine multicellular algae, plants, fungi, and animals. The GlobTherm database will be maintained and curated by iDiv with the aim to keep expanding it, and enable further investigations on the effects of climate on the distribution of life on Earth.
Summary1. The current availability of large ecological data sets and the computational capacity to handle them have fostered the testing and development of theory at broad spatial and temporal scales. Macroecology has particularly benefited from this era of big data, but tools are still required to help transforming this data into information and knowledge. 2. Here, we present 'letsR', a package for the R statistical computing environment, designed to handle and analyse macroecological data such as species' geographic distributions (polygons in shapefile format and point occurrences) and environmental variables (in raster format). The package also includes functions to obtain data on species' habitat use, description year and current as well as temporal trends in conservation status as provided by the IUCN RedList online data base. 3. 'letsR' main functionalities are based on the presence-absence matrices that can be created with the package's functions and from which other functions can be applied to generate, for example species richness rasters, geographic mid-points of species and species-and site-based attributes. 4. We exemplify the package's functionality by describing and evaluating the geographic pattern of species' description year in tailless amphibians. All data preparation and most analyses were made using the 'letsR' functions. Our example illustrates the package's capability for conducting macroecological analyses under a single computer platform, potentially helping researchers to save time and effort in this endeavour.
Understanding how species’ thermal limits have evolved across the tree of life is central to predicting species’ responses to climate change. Here, using experimentally-derived estimates of thermal tolerance limits for over 2000 terrestrial and aquatic species, we show that most of the variation in thermal tolerance can be attributed to a combination of adaptation to current climatic extremes, and the existence of evolutionary ‘attractors’ that reflect either boundaries or optima in thermal tolerance limits. Our results also reveal deep-time climate legacies in ectotherms, whereby orders that originated in cold paleoclimates have presently lower cold tolerance limits than those with warm thermal ancestry. Conversely, heat tolerance appears unrelated to climate ancestry. Cold tolerance has evolved more quickly than heat tolerance in endotherms and ectotherms. If the past tempo of evolution for upper thermal limits continues, adaptive responses in thermal limits will have limited potential to rescue the large majority of species given the unprecedented rate of contemporary climate change.
Differential coexistence among species underlies geographical patterns of biodiversity. Understanding such patterns has relied either on ecological or historical approaches applied separately. Recently, macroecology and community phylogenetics have tried to integrate both ecological and historical approaches. However, macroecology is mostly non-phylogenetic, whereas community phylogenetics is largely focused on local scales. Here, we propose a conceptual framework to link macroecology and community phylogenetics by exploring the evolutionary context of large-scale species coexistence, introducing the phylogenetic field concept. This is defined as the phylogenetic structure of species co-occurrence within a focal species' geographical range. We developed concepts and methods for analysing phylogenetic fields and applied them to study coexistence patterns of the bat family Phyllostomidae. Our analyses showed that phyllostomid bats coexist mostly with closely related species, revealing a north -south gradient from overdispersed to clustered phylogenetic fields. Patterns at different phylogenetic levels (i.e. all species versus close relatives only) presented the same gradient. Results support the tropical niche conservatism hypothesis, potentially mediated by higher speciation rates in the region of origin coupled with shared environmental preferences among species. The phylogenetic field approach enables species-based community phylogenetics, instead of those that are site-based, allowing the description of historical processes at more appropriate macroecological and biogeographic scales.
Summary1. Geographic gradients in the species richness of non-human primates have traditionally been attributed to the variation in forest productivity (related to precipitation levels), although an all-inclusive, global-scale analysis has never been conducted. 2. We perform a more comprehensive test on the role of precipitation and biomass production and propose an alternative hypothesis -the variation in vertical structure of forest habitats as measured by forest canopy height -in determining primate species richness on a global scale. 3. Considering the potential causal relationships among precipitation, productivity and forest structure, we arranged these variables within a path framework to assess their direct and indirect associations with the pattern of primate species richness using structural equation modelling. The analysis also accounted for the influence of spatial autocorrelation in the relationships and assessed possible historical differences among biogeographical regions. 4. The path coefficients indicate that forest canopy height (used as a proxy for vertical forest structure) is a better predictor of primate species richness than either precipitation or productivity on both global and continental scales. The only exception was Asia, where precipitation prevailed, albeit independently from productivity or forest structure. The influence of spatially structured processes varied markedly among biogeographical regions. 5. Our results challenge the traditional rainfall-based viewpoint in favour of forest distribution and structure as primary drivers of primate species richness, which aggregate potential effects from both climatic factors and habitat complexity. These findings may support predictions of the impact of forest removal on primate species richness.
Identifying the drivers and processes that determine globally the geographic range size of species is crucial to understanding the geographic distribution of biodiversity and further predicting the response of species to current global changes. However, these drivers and processes are still poorly understood, and no ecological explanation has emerged yet as preponderant in explaining the extent of species’ geographical range. Here, we identify the main drivers of the geographic range size variation in freshwater fishes at global and biogeographic scales and determine how these drivers affect range size both directly and indirectly. We tested the main hypotheses already proposed to explain range size variation, using geographic ranges of 8,147 strictly freshwater fish species (i.e., 63% of all known species). We found that, contrary to terrestrial organisms, for which climate and topography seem preponderant in determining species’ range size, the geographic range sizes of freshwater fishes are mostly explained by the species’ position within the river network, and by the historical connection among river basins during Quaternary low-sea-level periods. Large-ranged fish species inhabit preferentially lowland areas of river basins, where hydrological connectivity is the highest, and also are found in river basins that were historically connected. The disproportionately high explanatory power of these two drivers suggests that connectivity is the key component of riverine fish geographic range sizes, independent of any other potential driver, and indicates that the accelerated rates in river fragmentation might strongly affect fish species distribution and freshwater biodiversity.
Aim To inve stigate geographical patterns of phylogenetic beta diversity (PBD) and its turnover and nestedness-resultant components for terrestrial mammals. We expect an increase in the importance of the nestedness-resultant component towards temperate regions given the historical loss of lineages caused by environmental and spatial constraints. Analogously, we expect to find a similar increase in the contribution of the nestedness-resultant component towards higher elevations. We expect these patterns to be stronger for Rodentia because they have poor dispersal ability and may have been less efficient in recolonizing areas after glaciations.Location World-wide.Methods We generated the species composition of terrestrial Mammalia for 200 km 3 200 km cells to calculate PBD and its turnover and nestednessresultant components. All measures were computed for each cell and the cells in the surrounding radius of one, two or three adjacent layers. We calculated the relative importance of the nestedness-resultant component as the proportion of the total PBD (PBD ratio ) and also PBD deviation given taxonomic beta diversity (PBD dev ). PBD dev measures the importance of phylogenetic beta diversity after factoring out taxonomic beta diversity. We used simple linear regressions and piecewise regressions to investigate relationships between PBD ratio and mean annual temperature and elevation. ResultsWe found a major contribution of the nestedness-resultant component linked to temperate climate, especially for groups with better dispersal capacity. Higher elevations were associated with a major contribution of the turnoverresultant component, particularly for Rodentia. Main conclusionsWe provide the first global representation of PBD in terrestrial mammals and demonstrate that at higher latitudes PBD is mostly a result of lineage loss, whereas in highlands it is linked to lineage turnover. By analysing global patterns of the contribution of PBD components, we demonstrate that dispersal capacity is essential in determining the response of different lineages to geographical and environmental barriers.
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