Ancient Dna Evidence of Prolonged Population Persistence With Negligible Genetic Diversity in an Endemic Tuco-Tuco (Ctenomys Sociabilis)

We traced a population of Ctenomys sociabilis, a highly endemic South American tucotuco, through 1,000 years to assess its response to climatic change and recent human disturbance. Samples were obtained from a late-Holocene raptor roost in Parque Nacional Nahuel Huapi, Argentina, which produced a diverse and abundant rodent fauna, with 10 genera extending from the present to 950 50 years ago (CAMS-45936). The site (Estancia Nahuel Huapi locality 1) was located near the center of the present geographic range of C. sociabilis, which occurs throughout 8 of 9 stratigraphic levels in the site. To examine genetic structure through time, we extracted ancient DNA from 16 teeth at those levels and from 1 modern tooth at the surface for a total of 17 specimens. Cytochrome-b sequences from ancient and modern specimens were compared with a modern tuco-tuco sequence from the extant local population. Our results show that of those 17 specimens, all but 1 had identical sequences. Further, these sequences were identical to a representative of the modern population. Thus, that population has remained genetically identical for at least 1,000 years in the face of climatic change, human disturbance, and proximity of other tucotuco species (C. haigi, C. maulinus) with adjacent geographic distributions. Our findings indicate that a population bottleneck contributing to low genetic diversity of C. sociabilis occurred before 1,000 years ago and that late-Holocene climatic change occurred without a corresponding impact on the genetic diversity of this species.