Evolution and phylogenetic relationships in subterranean rodents of the Ctenomys mendocinus species complex: Effects of Late Quaternary landscape changes of Central Argentina

Abstract

We conducted a thorough survey of populations of Ctenomys within the distributional ranges of all species that currently represent the Ctenomys mendocinus species complex in Central Argentina. From the Atlantic Southeastern coast to the heights of the Los Andes mountain range we sampled individuals for all the previously recognized species within this species complex (C. australis, C. azarae, C. porteousi, C. “chasiquensis” and C. mendocinus). Sequences of different fragments of mitochondrial DNA were used to assess the phylogenetic relationships between individuals and to understand the processes responsible for the observed geographic distribution of genetic variation. The genetic differentiation among most of the sequences was moderated, although highly divergent haplotypes were recorded in some localities in the West of our study area, suggestive of the occurrence of a new so far undescribed species. The phylogenetic reconstructions suggested the presence of three major clades into C. mendocinus complex species that do not agree with the currently proposed taxonomy. Phylogeographic and demographic estimates indicated that the C. mendocinus species complex experienced a strong and recent process of population expansion. We propose that the pattern of distribution of haplotype diversity in the C. mendocinus species complex corresponds to a scenario of mild local differentiation with subsequent expansion to the current distribution ranges. Demographic changes through time suggest that glacial-interglacial cycles of Late Quaternary, and the consequent variation in the aridity of Central plains in Argentina, had strong effects on the evolution and cladogenesis of the C. mendocinus species complex.