Explore the vast range of titles available.

Human footprint models allow visualization of human spatial pressure across the globe. Up until now, Antarctica has been omitted from global footprint models, due possibly to the lack of a permanent human population and poor accessibility to necessary datasets. Yet Antarctic ecosystems face increasing cumulative impacts from the expanding tourism industry and national Antarctic operator activities, the management of which could be improved with footprint assessment tools. Moreover, Antarctic ecosystem dynamics could be modelled to incorporate human drivers. Here we present the first model of estimated human footprint across predominantly ice-free areas of Antarctica. To facilitate integration into global models, the Antarctic model was created using methodologies applied elsewhere with land use, density and accessibility features incorporated. Results showed that human pressure is clustered predominantly in the Antarctic Peninsula, southern Victoria Land and several areas of East Antarctica. To demonstrate the practical application of the footprint model, it was used to investigate the potential threat to Antarctica's avifauna by local human activities. Relative footprint values were recorded for all 204 of Antarctica's Important Bird Areas (IBAs) identified by BirdLife International and the Scientific Committee on Antarctic Research (SCAR). Results indicated that formal protection of avifauna under the Antarctic Treaty System has been unsystematic and is lacking for penguin and flying bird species in some of the IBAs most vulnerable to human activity and impact. More generally, it is hoped that use of this human footprint model may help Antarctic Treaty Consultative Meeting policy makers in their decision making concerning avifauna protection and other issues including cumulative impacts, environmental monitoring, non-native species and terrestrial area protection.

1. Different hypotheses (geographical, ecological, evolutionary or a combination of them) have been suggested to account for the spatial variation in species richness. However, the relative importance of environment and human impacts in explaining these patterns, either globally or at the biogeographical region level, remains largely unexplored. 2. Here, we jointly evaluate how current environmental conditions and human impacts shape global and regional gradients of species richness in terrestrial mammals. 3. We processed IUCN global distributional data for 3939 mammal species and a set of seven environmental and two human impact variables at a spatial resolution of 96·5 × 96·5 km. We used simple, multiple and partial regression techniques to evaluate environmental and human effects on species richness. 4. Actual evapotranspiration (AET) is the main driver of mammal species richness globally. Together with our results at the biogeographical realm level, this lends strong support for the water-energy hypothesis (i.e. global diversity gradients are best explained by the interaction of water and energy, with a latitudinal shift in the relative importance of ambient energy vs. water availability as we move from the poles to the equator). 5. While human effects on species richness are not easily detected at a global scale due to the large proportion of shared variance with the environment, these effects significantly emerge at the regional level. In the Nearctic, Palearctic and Oriental regions, the independent contribution of human impacts is almost as important as current environmental conditions in explaining richness patterns. The intersection of human impacts with climate drives the geographical variation in mammal species richness in the Palearctic, Nearctic and Oriental regions. Using a human accessibility variable, we show, for the first time, that the zones most accessible to humans are often those where we find lower mammal species richness.

Aim: Phylogenetic niche conservatism (PNC), a pattern of closely related species retaining ancestral niche-related traits over evolutionary time, is well documented for abiotic (Grinellian) dimensions of the ecological niche. However, it remains unclear whether biotic niche (Eltonian) axes are also phylogenetically conserved, even though knowledge of biotic niches is essential to an understanding of the spatiotemporal dynamics of ecological communities. We conduct the first analysis of biotic PNC by evaluating dietary specialization in a vertebrate class. Location: Global. Methods: We analysed two global compilations of diets of living mammals and a more detailed database for large carnivores together with a species-level phylogeny to evaluate trophic PNC. We searched for evidence of PNC by estimating the phylogenetic signal in distinct descriptors of dietary niche. Results: Trophic niches were generally similar among related species but not strongly conserved under a niche-drift macroevolutionary model (Brownian motion). The degree of similarity in trophic niche varied among different taxonomic groups and was, importantly, even within the same group, contingent on the metric of dietary preferences used and the quality of information on the database. Main conclusions: Overall, our results showed limited support for PNC in the trophic niche of mammals. However, different data sources and metrics of dietary preferences sometimes offered different conclusions, highlighting the importance of gathering high-quality quantitative data and considering multiple metrics to describe dietary niche breadth and to assess PNC. The fully quantitative database for large carnivores provided some interesting evidence of PNC that could not be detected with semi-quantitative or presence/absence descriptors. Subsequent assessments of phylogenetic imprints on dietary specialization would benefit from considering different metrics and using wellresolved phylogenies jointly with detailed quantitative diet information. While Eltonian trophic niches did not show the same high levels of evolutionary conservatism often displayed by Grinnellian niches, both niche components should be considered to understand range limits of species and clades at biogeographic scales.

Among the statistical methods available to control for phylogenetic autocorrelation in ecological data, those based on eigenfunction analysis of the phylogenetic distance matrix among the species are becoming increasingly important tools. Here, we evaluate a range of criteria to select eigenvectors extracted from a phylogenetic distance matrix (using phylogenetic eigenvector regression, PVR) that can be used to measure the level of phylogenetic signal in ecological data and to study correlated evolution. We used a principal coordinate analysis to represent the phylogenetic relationships among 209 species of Carnivora by a series of eigenvectors, which were then used to model log-transformed body size. We first conducted a series of PVRs in which we increased the number of eigenvectors from 1 to 70, following the sequence of their associated eigenvalues. Second, we also investigated three non-sequential approaches based on the selection of 1) eigenvectors significantly correlated with body size, 2) eigenvectors selected by a standard stepwise algorithm, and 3) the combination of eigenvectors that minimizes the residual phylogenetic autocorrelation. We mapped the mean specific component of body size to evaluate how these selection criteria affect the interpretation of non-phylogenetic signal in Bergmann's rule. For comparison, the same patterns were analyzed using autoregressive model (ARM) and phylogenetic generalized leastsquares (PGLS). Despite the robustness of PVR to the specific approaches used to select eigenvectors, using a relatively small number of eigenvectors may be insufficient to control phylogenetic autocorrelation, leading to flawed conclusions about patterns and processes. The method that minimizes residual autocorrelation seems to be the best choice according to different criteria. Thus, our analyses show that, when the best criterion is used to control phylogenetic structure, PVR can be a valuable tool for testing hypotheses related to heritability at the species level, phylogenetic niche conservatism and correlated evolution between ecological traits.

Aim: Bergmann's rule remains unexplored in marine mammals. We first examine at a global extent whether these organisms show the same interspecific pattern reported for terrestrial mammals and then evaluate the influence of current environmental conditions and human impacts on the observed patterns. Location: Global. Methods: We used range maps to document interspecific body size gradients and examined six environmental and human-based hypotheses. We analysed the data using a comparative cross-species method and a spatially explicit assemblage approach at three different grain sizes (200 km × 200 km, 400 km × 400 km and 800 km × 800 km). The associations between hypothesis-linked predictors and body size were analysed through simple and multiple regressions that controlled for both spatial and phylogenetic autocorrelation. Results: We detected clear global latitudinal body size gradients, following a Bergmannian pattern (i.e. increasing size polewards). Consistently across methodological approaches (cross-species and assemblage analyses) and grain sizes, sea surface temperature is the best predictor. Spatially, the temperaturesize relationship is stronger in the Southern than in the Northern Hemisphere. Pinniped body sizes are critically constrained by temperature world-wide whereas cetacean size clines show a weaker, albeit dominant, association with temperature. Main conclusions: As in terrestrial mammals, our findings show that ambient temperature better explains interspecific body size patterns in cetaceans, and especially pinnipeds, world-wide. Large-bodied species are favoured in colder environments, in accordance with Bergmann's rule and the heat conservation hypothesis. However, our analyses also reveal a relevant role for salinity and primary productivity in migratory cetacean species. The large body sizes of baleen whales are essential for migration, for survival during fasting periods and minimizing the effects of temperature variation. This finding highlights the importance of spatially and phylogenetically explicit deconstructive approaches, considering alternative hypotheses to the traditional physiological mechanism, to gain a better understanding of Bergmann's rule.

Bergmann's rule is one of the best known empirical generalizations in biogeography and remains a topic of much interest and debate. Watt et al. claimed in 2010 that the only definition for the rule should be the one devised by Bergmann in the 19th-century. Based on direct translations from the original German manuscript, they concluded that tests of the rule should be restricted to interspecific studies of body size variation in endotherms. Furthermore, they suggested that Bergmann's heat conservation mechanism is an integral part of the rule and, hence, a simple falsificationist test of this mechanism might be enough to validate the rule. Here I advocate on a pluralistic approach to study ecogeographical rules, in general, and Bergmann's rule in particular. Our perceptions on the status and validity of laws and rules depend on the narrowness of the epistemological scope we adopt. Laws can have exceptions, do not necessarily have to be explanatory and may not be predictive. Also, we should differentiate between correlative and causal laws. Bergmann's rule is a correlative law, not a causal law, as Watt et al. implicitly assumed. It is a broad generalization with no inherent mechanism, and subject to the scrutiny of empirical investigation. Because of the ecological and evolutionary contingencies there will hardly be any law in ecology that is universally true. We have to consider each of these contingencies and study Bergmann's rule in a diversity of systems, organisms and levels of biological organization to gain further insight into the processes underlying the geographic variation in body size. On the basis of the empirical evidence to date, we cannot entirely dismiss a thermoregulatory mechanism to explain body size clines in both ectotherms and endotherms and support a food availability mechanism instead, as Watt et al. suggested. Even so, a unifying explanation for Bergmann's rule still remains elusive.

Aim: To analyse the geographical co-occurrence among mammal species based on their complete geographical distributions, considering their phylogenetic relationships and body size data. We describe species-level patterns and test the relative effects of ecological and evolutionary processes in determining species co-occurrence under the phylogenetic field framework. Location: Global. Methods: We gathered distributional, phylogenetic and body size information for 3697 mammal species. We defined phylogenetic fields of species by estimating the phylogenetic structure of species co-occurrence within a focal species' range. Likewise, body size structure within focal species' ranges was defined as body size fields. We applied a spatial-phylogenetic statistical framework to evaluate geographical variation on species fields. Also, we tested the significance of phylogenetic and body size fields based on biogeographically informed null models. Analyses were done for all mammal species as a whole and within particular taxonomic orders. Results: Phylogenetic and body size fields of mammal species showed significant geographical patterning beyond their spatial and phylogenetic dependence. Phylogenetic fields were strikingly different between the New and Old World, with mammals co-occurring with more closely related species in the New World and more distantly related species in the Old World. Clustered phylogenetic and body size fields showed geographically congruent patterns. Similar findings were obtained within particular mammalian orders. Main conclusions: Geographical co-occurrence among mammal species reveals the imprint of historical origins and dispersal of mammalian lineages. Phylogenetic and body size structure within mammalian ranges is driven by the distinct histories among biogeographical regions and mainly between the New and Old World. We demonstrate the usefulness of a new protocol integrating species' distributional, phylogenetic and body size information for linking evolutionary and ecological approaches to understand geographical patterns of biodiversity.

Aim: Species geographic ranges are the 'fundamental units' of macroecology. Range size is a major correlate of extinction risk in many groups, and is also critical in studies of biotic responses to climate change. Despite this, there is a lack of studies exploring the role of environmental, historical and anthropogenic processes in determining large-scale patterns in range size. We perform the first global analysis of putative drivers of range size variation in any group, choosing amphibians as our study taxon. Our aims are to disentangle the many hypothesized causes of range size variation and evaluate support for 'Rapoport's rule', the observation that range size correlates with latitude. Location: Global. Methods: We develop a global map of gridded median range size using the International Union for Conservation of Nature (IUCN) distribution maps. From this we perform spatial and non-spatial regressions to explore relationships between range size and nine hypothesized variables in six biogeographic realms. We use information-theoretic model selection to compare multiple competing variables, simultaneously evaluating the relative support for each one. Results: Current climate – environmental water and energy, and temperature seasonality – is consistently highly ranked in spatial and non-spatial analyses. Human impacts and other environmental measures (topographic and landscape complexity, effective area, climate extremes) show mixed support, and glacial history is consistently unimportant. Our findings add further evidence to the view that Rapoport's rule is a regional, not global, phenomenon. Main conclusions: The primary importance of temperature seasonality may explain why Rapoport's rule is largely restricted to northern latitudes, as this is where se asonality is most pronounced. More generally, the dominance of contemporary climate in our analyses (even when accounting for space) has stark implications for the future status of amphibians. Changes in climate will almost certainly interact with the anthropogenic processes already threatening a third of amphibians globally, with the effects being most keenly felt by species with a restricted range.

Background Body size and echolocation call frequencies are related in bats. However, it is unclear if this allometry applies to the entire clade. Differences have been suggested between nasal and oral emitting bats, as well as between some taxonomic families. Additionally, the scaling of other echolocation parameters, such as bandwidth and call duration, needs further testing. Moreover, it would be also interesting to test whether changes in body size have been coupled with changes in these echolocation parameters throughout bat evolution. Here, we test the scaling of peak frequency, bandwidth, and call duration with body mass using phylogenetically informed analyses for 314 bat species. We specifically tested whether all these scaling patterns differ between nasal and oral emitting bats. Then, we applied recently developed Bayesian statistical techniques based on large-scale simulations to test for the existence of correlated evolution between body mass and echolocation. Results Our results showed that echolocation peak frequencies, bandwidth, and duration follow significant allometric patterns in both nasal and oral emitting bats. Changes in these traits seem to have been coupled across the laryngeal echolocation bats diversification. Scaling and correlated evolution analyses revealed that body mass is more related to peak frequency and call duration than to bandwidth. We exposed two non-exclusive kinds of mechanisms to explain the link between size and each of the echolocation parameters. Conclusions The incorporation of Bayesian statistics based on large-scale simulations could be helpful for answering macroevolutionary patterns related to the coevolution of traits in bats and other taxonomic groups.

Aim Many hypotheses exist to explain the astonishing variation in geographical range size across species, but these have rarely been tested under a unifying framework that simultaneously considers direct and indirect effects of ecological niche processes and evolutionary dynamics. Here, we jointly evaluate ecological and evolutionary hypotheses that might account for global interspecific patterns of range size in the most species‐rich avian order: Passeriformes (perching birds). Location Global. Time period Current. Major taxa studied Order Passeriformes. Methods We used phylogenetic path analysis to test for the relationship between eight variables and range size. Our list of predictors included a set of niche‐related variables (both Grinellian and Eltonian), species‐specific morphological and life‐history traits (body size, dispersal ability and fertility), extrinsic (human footprint) and evolutionary factors (time since divergence from the closest extant relative). Results We found that Grinellian (climatic) and Eltonian (trophic) niche breadth are crucial to account for the observed patterns, followed by reproductive effort (as measured by clutch size). We also found a negative relationship between native range size and human footprint. The significant and positive relationship between niche breadth, either Grinnellian or Eltonian, and range size was consistent across all species, irrespective of their migratory/resident status or taxonomic grouping (Passeri versus Tyranni). Main conclusions Globally, the range sizes of passerine species are associated with the Grinellian niche, meaning that species with broader environmental tolerances exhibit larger geographical ranges. These findings give further empirical support to the positive niche breadth–range size relationship as a general pattern in ecology.