Contrasting patterns of Holocene genetic variation in two parapatric species of Ctenomys from Northern Patagonia, Argentina

Abstract

Analyses of DNA from fossil specimens can generate critical insights into the demographic histories of natural populations. Previous analyses of fossil specimens from a single cave site in the Limay Valley in Patagonia have revealed striking historical differences in genetic variability between two species of Ctenomys, the colonial tuco-tuco (C. sociabilis) and the Patagonian tuco-tuco (C. haigi). As a first step towards identifying environmental or other factors contributing to this outcome, we assessed whether these differences in variability are generally characteristic of these species. We sequenced a 136-bp fragment of the cytochrome b locus for fossil specimens of Ctenomys excavated from two additional cave sites in the Limay Valley. Analyses of this expanded data set revealed that while C. sociabilis has undergone a pronounced loss of genetic diversity at all three cave sites over the past ~12 000 years, genetic diversity in C. haigi has remained relatively constant over the same temporal and geographic scales. The generality of these patterns suggests that although the factors affecting genetic diversity in C. sociabilis were widespread in the Limay Valley, impacts on the study species differed, probably due to known behavioural, ecological and demographic differences between these taxa.