Aim: To assess the effects of historical events on the tempo and mode of diversification of the lizard Polychrus acutirostris along the South American diagonal of open formations (DOF). Location: Caatinga and Cerrado biomes in Brazil. Methods: We sequenced fragments of one mtDNA and three nuDNA genes of 68 individuals from 33 localities. We used population assignment methods to access genetic structure and estimate lineage boundaries. Next, we estimated lineage relationships, intraspecific diversity, environmental niche similarity and demographic history. Finally, we tested 12 diversification scenarios using an approximate Bayesian computation (ABC) approach. Results: We recovered three non-overlapping, geographically structured lineages corresponding to Caatinga, north-east Cerrado and south-west Cerrado, with the major divergence event dating to the Late Neogene. We also recovered a complex scenario of divergence associated with gene flow and niche divergence. Main conclusions: We show a complex history of diversification along the South American DOF. Our findings support the role of environmental features as the likely drivers of P. acutirostris intraspecific diversification during the Late Neogene. © 2018 John Wiley & Sons Ltd
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