Lineages of Tuco-Tucos (Ctenomyidae: Rodentia) from Midwest and Northern Brazil: Late Irradiations of Subterranean Rodents Towards the Amazon Forest

The genus Ctenomys comprises approximately 70 recognized living species of subterranean rodents endemic to South America. Phylogeneticstudies to date, based on mitochondrial DNA data, place 44 recognized species in eight species groupsand provide evidence for a burst of speciation early in the history of the genus. Species from Argentina, Uruguay, Bolivia, and southern Brazil are well studied at the phylogeneticlevel. However, the taxonomic status of the species inhabiting midwest and northern Brazil remains poorly understood. In this study, we construct phylogenies based on maximum likelihood and Bayesian inference methods with cytochrome bgene haplotypes of Ctenomys from midwest and northern Brazil and with haplotypes representative of the genus Ctenomys to place the sampled haplotypes into a phylogeneticframework; we also evaluate skull geometric morphometrics data among sampling sites to assess whether skull morphology corroborates the phylogeneticpatterns observed. The results show that the sampling sites used in this study are represented by two species, namely, Ctenomys bicolor, which is present in the state of Rondonia, and Ctenomys nattereri, which is present in Mato Grosso and Bolivia. The results also reveal two lineages of Ctenomys distinct from C. bicolor and C. nattereri, henceforth called Ctenomys sp. “xingu” and Ctenomys sp. “central.” Both the species and lineages share a most recent common ancestorwith C. boliviensis and are part of the boliviensis species group.