| Amphibians and squamates are together the most diverse clade of terrestrial vertebrates, and their biodiversity is thought to reflect many of the most important biogeographic and ecological forces that have generated species richness through time. To understand patterns of relatedness and the drivers of diversification, phylogenetic trees are instrumental to estimate the relative contribution of evolutionary and ecological processes. My dissertation comprises four chapters related to phylogenetic patterns of biodiversity in amphibians and squamates. First, I tested across the frog Tree of Life whether species could escape the constraint imposed by body size on sound frequency and evolve new types of calls. The results show that frogs have multiple shifts in body-size allometry for calls. These shifts comprise species endemic to hyper-diverse regions such as Africa, Australia, New Guinea, Southeast Asia, and the Neotropics. Those shifts seem to reflect biogeographic invasions and instances of ecomorphological escape. Second, I asked what drives species co-occurrence and community assembly in Neotropical frogs? I find that the composition of most communities has been generated by stochastic variation of speciation, local extinction, and colonization rates. Thus, Neotropical ecoregions comprise distinct assemblages of frogs, as demonstrated by several regionalization studies, but community assemblages are a random sample of the regional pool. Third, I asked how many times has phytotelm-breeding evolved across Neotropical frogs, and do these lineages ever revert to pond- or stream-breeding? If not, is phytotelm-breeding an evolutionary dead end, preventing diversification and raising extinction rates? I find that the history of phytotelm-breeding is labile, with support for at least 68 potential origins and 107 reversals. There is some support for state-dependent extinction (higher for phytotelm-breeding lineages), but I cannot uniformly reject state-independent models. Fourth, I asked whether extinction risk in squamates is clustered evolutionarily and whether high-risk species represent a disproportionate amount of total evolutionary history. I found currently assessed threat status to be phylogenetically clustered at broad level in Squamata, suggesting it is critical to assess extinction risks for close relatives of threatened lineages. There is no association between threat and distinctiveness, suggesting that extinctions may not result in a disproportionate loss of evolutionary history. The results show that immediate efforts should focus on geckos, iguanas, and chameleons, in Amazon, Southeast Asia, and New Guinea. |
