Less than expected: species diversity of the Ctenomys mendocinus species group (Rodentia, Ctenomyidae) in north–central Argentina

The genus Ctenomys is one of the most species-rich genera among mammals. The taxonomy of its species is under constant revision as new data and analytical tools become available. Integrative approaches provide a valuable framework for incorporating morphological, genetic, and biogeographic criteria, helping to clarify ambiguous species boundaries. This study uses an integrative approach to evaluate the phylogenetic relationships among some nominal forms of the Mendocinus group of the genus Ctenomys, distributed in north–central Argentina: Ctenomys bergi, Ctenomys bonettoi, Ctenomys rionegrensis and C. “yolandae”. From a morphological perspective, craniodental measurements were compared using descriptive statistics and multivariate statistical analyses. From a genetic perspective, Bayesian and Maximum Likelihood phylogenetic trees were reconstructed using complete sequences of the mitochondrial cytochrome b gene. Our results showed that both C. bonettoi and C. “yolandae” are genetically and morphologically indistinguishable from C. bergi and should therefore be synonymized with the latter. Additionally, it was found that the genetic and morphological divergence between C. rionegrensis and C. bergi is considerably low; even below the interspecific values for the Mendocinus group. The genetic divergence between the two species could be related to the Paraná River, the second largest river in South America. The results of this study may have a significant impact on the conservation status assessment of the taxa under study, as they considerably expand the distribution range of the synonymized species.