Extreme environments filter functionally rich communities of Atlantic Forest treefrogs along altitudinal and latitudinal gradients

Abstract

Understanding how environmental filtering and biotic interactions structure communities across elevational and latitudinal gradients is still a matter of debate. To provide insight into their relative importance, we explore the mismatch between three dimensions of biodiversity (taxonomic, functional and phylogenetic), and compare their patterns to null models of random community assembly. We focus on a highly diverse tropical group: the tree frogs (hylids) of the Atlantic Forest of Brazil. For that, we combined geographic distribution data with phylogenetic and trait information for 158 species to produce maps of the three dimensions of diversity. We show that communities of tree frogs of the Hylidae family tend to have high functional richness along the Atlantic Forest, potentially driven by niche partitioning. However, environmental filtering gains importance in extreme environments, both at high elevations and higher latitudes. In these areas of the forest, clustering of both functional and phylogenetic diversity is observed. Trait overdispersion is found in areas of contact between vegetation types, or of adjacent biomes, reflecting the encounter of amphibian species adapted to distinct environmental conditions and landscape configurations. Considering all three dimensions of diversity along with multiple axes of environmental variation allows for a more comprehensive understanding of the processes shaping amphibian community assembly in this biodiversity hotspot.