Evolutionary Imprints on Species Distribution Patterns Across the Neotropics

Abstract

Species diversity is unevenly distributed across the Neotropical region. Distinct biological groups have notably similar patterns of species richness, with peaks in richness usually associated with tropical regions. However, how diversification occurred across space and time for each group, leading to the current diversity patterns, are less understood. Differences among clades can be expected from their distinct ecologies and evolutionary histories. We mapped the occurrence of 1100 + species of Neotropical vertebrates belonging to seven clades with evolutionary histories primarily confined to the Neotropics. For each clade, we analyzed the spatial distribution of phylogenetic turnover of species assemblages, and contrasted the observed patterns among different clades. We also investigated which environmental or biogeographic factors were most associated with phylogenetic turnover, using permutational regression on dissimilarity matrices. We discovered that spatial patterns of phylogenetic turnover between sites are strikingly similar for distinct vertebrate groups, and cannot be predicted from within-lineage relatedness—a surprising result given the differences in ecology and history of colonization among clades. For most groups, biogeographic units predicted phylogenetic turnover better than environmental variables. This suggests that vicariant and dispersal events that took place during the settlement of each vertebrate clade may have been similar in mode and place, even if the timing was different. The fact that environmental variables alone were less predictive of phylogenetic turnover for most clades suggests that current climatic and topographical features are less determinant of phylogenetic lineage distribution than former, biogeographic processes.