In the middle course of the São Francisco River, inserted in the semiarid Caatingas of northeastern Brazil, there is an extensive field of continental paleodunes, in which a diverse fauna of psamophilic reptiles, with high proportion of endemism, was discovered. Based on the geomorphological, paleoclimatic, and distributional patterns congruent among different reptile lineages, a vicariant diversification scenario was proposed for the fauna of the region. In this model, after an endorreic phase during the last glacial maximum, the São Francisco River made way for the Atlantic Ocean through the dunes separating the ancestral population of at least four lineages of reptiles in opposite margins. Molecular studies with populations of the lizards Eurolophosaurus (Tropiduridae), Calyptommatus and Nothobachia (Gymnophthalmidae) show a partially concordant pattern with the vicariant model but, estimates basal divergences prior to the Pleistocene. The present project proposal aims to comparatively investigate patterns of diversification of lineages of reptiles from the dunes based on temporally calibrated phylogenies to evaluate the role of the São Francisco River in the process of diversification of the psamophilous fauna. Second, to use a coalescent-based molecular approach at the genomic level, focusing on lizards of the genus Calyptommatus from the dune fields, to quantitatively test alternative speciation models and infer demographic history.
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