Species limits and recent diversification of (Sigmodontinae: Oryzomyini) during the Pleistocene.

is a genus of the tribe Oryzomyini with eight species currently recognized, and a controversial taxonomy. These species are mainly distributed in the South America dry diagonal, but some species extend into Atlantic Forest, reaching the coastal sandy plains known as Restingas. This study aimed to address species limits and patterns of diversification of species. For this purpose, we performed cytogenetic and molecular analyses (phylogeny, coalescent species delimitation, barcoding, and divergence times estimation) using multiple mitochondrial and nuclear markers on a comprehensive sampling, representing all nominal taxa reported so far. Chromosomal information was a robust marker recognizing eight species. Reciprocal monophyly was recovered for all the species, except for . These results together with coalescent analyses recovered eight species as the most congruent species delimitation scenario for the genus (mean C : 0.72). Divergence time estimates revealed that ' diversification occurred about 1.32 million years ago (Mya) during the Pleistocene. Although our results conservatively support the eight species described so far, different lines of evidence suggest that and could potentially be species-complexes. We discussed this scenario in the light of multiple evolutionary processes within and between species and populations, since comprises a species group with recent diversification affected by Pleistocene climatic changes and by the complex biogeographic history of South America dry diagonal. This work supports that the diversity of is underestimated and reiterates that interdisciplinary approaches are mandatory to identify small rodent species properly, and to unhide cryptic species.