Resolving species boundaries in a recent evolutionary radiation: An integrative approach to the Ctenomys Corrientes group (Mammalia: Rodentia: Ctenomyidae)

Species delimitation in recently evolving taxa presents unique challenges. Such taxa may not have accumulated enough genetic or morphological differences to be easily distinguished using traditional methods, while processes such as incomplete lineage sorting or gene flow may obscure these distinctions. One paradigmatic recently evolved taxon is the Corrientes group of the subterranean genus Ctenomys (Rodentia, Ctenomyidae), a set of populations with different chromosomal forms occurring in the homonymous province of Argentina.

Previously, three nominal species and several independently evolving lineages had been proposed; however, a comprehensive integrative approach — including qualitative and quantitative morphological analyses, as well as additional molecular proxies for lineage delimitation — was still lacking, and these results had not been evaluated in a taxonomic context. In this study, we added new lines of evidence, including Bayesian phylogenetics and divergence time estimation, haplotype networks, and genetic distances.

We integrated this information with karyotypic and microsatellite data to discuss previously proposed lineages, as well as to analyze the evolutionary processes that shaped the history of this group. Finally, we analyzed the qualitative and quantitative morphology of individuals from the nominal species and a chromosomally derived lineage, and we propose a revised species-level and infraspecific classification for this complex group of rodents.

This resulted in the delimitation of two species, C. roigi and C. perrensi, the latter being subdivided into three subspecies: Ctenomys perrensi perrensi, C. perrensi dorbignyi, and C. perrensi iberaensis subsp. nov. In addition, other identified lineages, such as Sarandicito, Manantiales, and Santa Rosa, deserve future taxonomic investigation.