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

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.