Diversification and evolution of treefrogs in the Cerrado savanna of South America : from population structure to biogeographic patterns
Historical and ecological factors underlying population structure and speciation of organisms are fundamental to uncover diversification mechanisms that lead to biogeographic patterns. The main goal of this dissertation is to determine the relative roles of geography and climate promoting diversification in a diverse group of treefrogs in the Cerrado savanna of South America, a hotspot of biodiversity. This dissertation approaches diversification at two different time-scales: from a macro-temporal scale of factors that promote species diversification in the Cerrado region, and from a micro-temporal scale of population divergence and recent cryptic speciation. Three main research goals were developed in separate chapters: (1) Phylogenetic and biogeographic analyses of the species in the Hypsiboas pulchellus group were used to quantify dispersal events between the Cerrado and other dry/open or humid/forested neighboring habitats, and to evaluate how this dynamic historical interchange affected diversification. The evolutionary relationships among the species in this group showed a pattern of multiple recent origins of the endemic Cerrado lineages, indicating recent colonization events. These analyses indicate an interesting pattern of recurrent dispersal among open and forest ecoregions accounting for the accelerated diversification in this group. (2) Species delimitation methods using molecular, morphological and mating call characters were used to study the recent speciation of a small clade of Cerrado endemics. This integrative approach allowed for a better resolution to detect species boundaries and the discovery of cryptic species in spite of conserved morphology and mating calls. (3) Population structure in a widespread Cerrado species was investigated using historical species distribution modeling and next generation sequencing data to evaluate the role of recent climatic fluctuations on population differentiation. Divergence among populations seems strongly affected by Pleistocene climatic instability, a pattern we call isolation-by-instability. In conclusion, this study highlights how diversification and biogeographic patterns in the Cerrado savanna can be affected by its historical dynamic climate and landscape.