Some Tuco-Tucos Hide More Than Others: An Integrative Approach Reveals Cryptic Diversity in Ctenomys (Rodentia:...

The diversity of the subterranean rodent genus Ctenomys remains incompletely understood, particularly in regions characterized by complex biogeographic histories. Central Argentina (Sierras de Córdoba and adjacent lowlands) represents a major zone of biotic convergence, yet its role in shaping diversification patterns within Ctenomys has received limited attention. Here, we adopt an integrative framework (molecular phylogenetics and geometric morphometrics) to reassess patterns of diversity and differentiation across this region. We analyzed cytochrome b sequences and quantified cranial shape variation. Our analyses indicate the presence of three species groups (mendocinus, talarum, and tucumanus) and two independent lineages (C. heniacamiare and C. osvaldoreigi) in the study area. Beyond confirming the presence of previously recognized species, our results reveal undocumented diversity. Based mainly on mitochondrial data, we identify two divergent lineages that may correspond to candidate species: one related to C. heniacamiare inhabiting the eastern slopes of the Sierras de Córdoba, and another belonging to the tucumanus group in the western lowlands. Newly documented localities further extend the known ranges of several species. Notably, the co-occurrence of haplotypes assigned to different species/lineages belonging to the mendocinus group points to complex evolutionary dynamics, potentially involving incomplete lineage sorting, ongoing hybridization, or historical introgression. Taken together, our findings highlight the Sierras de Córdoba and surrounding lowlands as a focal region for understanding diversification in Ctenomys. This study illustrates how integrative analyses of molecular and morphological data can uncover hidden diversity in rapidly evolving mammalian lineages and cautions against taxonomic inferences based on single data sources.