A century of stasis: Taxonomy of Ctenomys (Rodentia: Hystricomorpha) populations in northeastern Patagonia limits, Argentina

The South American rodent genus Ctenomys is well represented throughout much of southern Patagonia by the polytypic “magellanicus” lineage. In western Argentina, members of this lineage occur from 35 °S to 54 °S latitude. In comparison, the taxonomy of Ctenomys in northeastern Patagonia remains poorly known. This ∼160,000 km2 region consists primarily of mostly flat, homogenous tracts of austral Monte desert covering a gravel substrate and is cut by two major fluvial systems associated with the Colorado and the Negro rivers. Here, we use mitochondrial sequences and morphological comparisons to describe phylogenetic relationships among recently sampled populations of Ctenomys from this region. These analyses indicate that the “magellanicus” lineage extends into northeastern Patagonia to at least the Negro river (40°S). Contained within this lineage are three latitudinally distinct clades that are separated by geographic features such as rivers and basaltic plateaus. Identification of these clades generates new insights into the phylogeographic history of the “magellanicus” lineage and marks the end to nearly a century of stasis regarding taxonomic studies of Ctenomys from northeastern Patagonia.