Evolutionary affinities of the 'Lost World' mouse suggest a late Pliocene connection between the Guiana and Brazilian shields

AimTo investigate the biogeographical history of the Pantepui region based on the phylogenetic relationships and divergence dates of a tepui-endemic small mammal: the Roraima mouse, Podoxymys roraimae. This mouse is one of the rarest and most restricted mammals in terms of geographical distribution, and its evolutionary position has never been evaluated within a rigorous phylogenetic framework. LocationThe Pantepui biogeographical region of northern South America, which harbours a remarkable flora and fauna in one of the most dramatic landscapes on Earth. MethodsWe used maximum-likelihood and Bayesian analyses of mitochondrial (cytb) and nuclear (irbp) DNA sequences from a specimen of P. roraimae to infer phylogenetic affinities and estimate divergence times of Podoxymys from its closest relatives based on a relaxed molecular clock model. ResultsPodoxymys lies within the Akodontini tribe of the rodent subfamily Sigmodontinae, closely related to Thalpomys and Necromys, two taxa found on the Brazilian Plateau. The divergence of Podoxymys from its closely related genera was estimated at 2.47-3.68Ma, at the end of the Neogene (Pliocene) and before the start of the Pleistocene climatic oscillations. Main conclusionsPodoxymys roraimae is a relict species restricted to tepui summits, and its closest relatives are taxa found in open-vegetation biomes, especially the Cerrado vegetation on the Brazilian Plateau. Our results do not conform to the predictions of currently proposed models of Pantepui faunal evolution, but instead indicate a possible relationship between the Guiana and Brazilian shields during the Pliocene.