Amphibian functional diversity is related to high annual precipitation and low precipitation seasonality in the New World

Aim We examined the geographical distribution of functional diversity for American amphibians and tested the relationship between functional diversity and environment. We also explored how the functional evenness of life‐history traits varies across biogeographical regions. Location Continental Americas. Methods We performed a trait classification based on an Eltonian approach and calculated functional diversity using Hill numbers, Shannon and Gini–Simpson indices. We tested the relationship between functional diversity and different axes of environmental variation by using a series of spatial autoregressive (SAR) models. Results Based on 212 different functional attributes for 2,776 species, we found that functional diversity has a latitudinal gradient consistent with that of species richness, regardless of the diversity index used. Evenness of functional diversity of amphibian assemblages varies depending on the region, but in general they are close to the maximum possible value. Areas with more functional richness relative to species richness are associated with high annual precipitation and low precipitation seasonality regardless of temperature; in contrast, areas with fewer functions than expected are associated with high aridity. Main conclusions The highest functional diversity is located in mountainous regions. Overall, functional diversity is positively correlated with humid environments with low precipitation seasonality and low aridity regardless of temperature. This is especially relevant for amphibians facing contemporary climate change because it suggests that future variation in rainfall patterns, but not in annual mean temperature, might interact with functional diversity to pose an imminent threat to amphibian functional diversity.