Spatial and temporal divergence of the torquatus species group of the subterranean rodent Ctenomys

DIEGO A. CARABALLO; MARÍA SUSANA ROSSI

CONTRIBUTIONS TO ZOOLOGY - (Print)

Universidad de Amsterdam

Lugar: Amsterdam; Año: 2018 vol. 87 p. 11 - 24

0067-8546

Subterranean rodents of the genus Ctenomys have experienced an explosive radiation and rapidly colonized the southern cone of South America. The torquatus group, one of the main groups of the genus, comprises several species and species complexes which inhabit the easternpart of the distribution of Ctenomys including southern Brazil, northern and central Uruguay and north-eastern Argentina. This group has undergone a high chromosomal diversification with diploid numbers varying from 41 to 70. The aim of this study was to investigate the origins of the torquatus group as well as itsdiversification patterns in relation to geography and cladogenesis. Based on mitochondrialcytochrome b nucleotide sequences we conducted a Bayesian multi-calibrated relaxed clockanalysis to estimate the ages of the torquatus group and its main lineages. Using the estimated evolutionary rate we performed a continuous phylogeographic analysis, using a relaxed randomwalk model to reconstruct the geographic diffusion of the torquatus group in a temporal frame.The torquatus group originated during the early Pleistocene between 1.25 and 2.32 million years from the present in a region that includes the northwest of Uruguay and thesoutheast of the Brazilian state of Río Grande do Sul. Most lineages have dispersed early towards their present distribution areas going through subsequent range expansions in the last 800,000 ? 700,000 years. Ctenomys torquatus went through a rapid range expansion for the last200,000 years, becoming the most widespread species of the group. The colonization of theCorrientes and Entre Ríos Argentinean provinces supposes at least two crossing events acrossthe Uruguay River between 1.0 and 0.5 million years before the present, in the context of a coldand dry paleoenvironment. The resulting temporal and geographic frame enables thecomprehension of the incidence of both, the amplitude of distribution areas and divergencetimes into the patterns of chromosomal diversification found in the group.