Disentangling the Historical and Ecological Factors That Govern Species Accumulation in Neotropical Mountains

Mountains are biodiversity hotspots, and their astonishing diversity is attributed mainly to high diversification rates and longer times for speciation. Although these historical factors help explain how species accumulate, it is unclear how ecological interactions mediate species maintenance over evolutionary time. As regional diversity increases, it may reach a point where niche space limits the number of species. By implementing a multiscale framework, we tested the relative contributions of ecological and historical processes to the build‐up of diversity in tropical mountains. Neotropics. Present. Birds. To map spatial patterns of species richness in Neotropical mountains, we choose three avian radiations (hummingbirds, nine‐primaried oscines, and Tyranni), which collectively comprise ~2210 spp. (54% of the Neotropical avifauna). We combined phylogenetic information of these clades with geographical and morphological data as proxies for historical (diversification rates and average assemblage age) and ecological (morphological disparity and species segregation) factors and their effect on species richness using structural equation models (SEMs). Even though we observed similar patterns of species richness along the elevation gradient in the three avian radiations, we found differential support for the contribution of ecological factors among clades. In the nine‐primaried oscines, for example, morphological disparity was associated with species coexistence at elevations with higher diversification. In contrast, Tyranni and hummingbirds exhibited decoupling among elevational patterns of spatial and morphological divergence and historical species accumulation, suggesting how species richness is unbounded by species interactions in these clades. We found that both historical and ecological factors interact to generate and maintain high avian diversity in Neotropical mountains, but regional diversity may or may not be constrained by ecological interactions. These findings provide a link among ecological and historical factors in explaining species‐richness patterns by revealing potential eco‐evolutionary paths driving the maintenance of exceptional diversity in tropical mountains.