Incidence of the most important climatic perturbations of the late Pleistocene and early Holocene on the phylogeography and population genetics of the Talas?s tuco-tuco (Ctenomys talarum) from the Argentinean Pampas.

MATÍAS S. MORA

Goa (Dona Paula, Paijim)

Congreso; PAGES 2nd Young Scientists Meeting 2013; 2013

The National Centre for Antarctic and Ocean Research (an autonomous research centre under the Ministry of Earth Sciences, Government of India), and the PAGES International Project Office

We examined the phylogeography of the South American subterranean rodent Ctenomys talarum (Talas?s tuco-tucos) using mitochondrial DNA (mtDNA) control region (D-loop) sequences. This species is an herbivorous rodent endemic to the Province of Buenos Aires, Argentina, that lives in natural grasslands in coastal sand dune habitats and in some fragmented inland populations. Currently, this species has changed from Least Concern to Vulnerable by IUCN, considering its highly habitat fragmentation and population declining in the last decade. In this study, we 1) assessed the genetic relationship among populations of C. talarum across the entire distributional range of this species, 2) analyzed how the geological history of the habitat has affected the genetic structure and demographic history of these populations, and 3) used powerful statistical tools in phylogeography and paleoclimatology to evaluate in what way the Pleistocene and Holocene climatic changes had affected the effective population sizes in this species. Pairwise FST values showed significant differentiation among all populations studied. A complex network of haplotypes in conjunction with the AMOVA results showed high genetic subdivision and a strong phylogeographic pattern among populations of C. talarum. The overall pattern was similar to that expected under the isolation-by-distance model, suggesting equilibrium between gene flow and local genetic drift. Major geographic barriers (e.g. rivers and unsuitable habitat) in the area, in conjunction with population isolation, appeared to be associated with strong genetic differentiation among the different geographical groups. Local mismatch distributions and tests of neutrality suggest contrasting histories for different groups of populations; while some populations appeared to be characterized by demographic stability and no significant departures from neutrality, others showed departures from strict neutrality consistent with a recent demographic expansion. Finally, a close association seems to exist between the major climatic changes that occurred during the Late Pleistocene and Holocene in the central region of Argentina and the main historical demographic changes inferred from C. talarum. Bayesian Skyline Plots (BSP) showed a constant population size from mid-late Pleistocene to early Holocene; effective population sizes seem to have remained constant until an increase in population size approximately 8,000 years BP. This overall change in historical effective population size coincides with this important geological event of sand dune formation and a cycle of climatic amelioration in Argentinean Pampas. Current populations of C. talarum appear to be relicts of a more extended historical distribution along the Argentinean pampas. These historical extinctions, however, have not erased the signature of long-term stability and geographic structure of this species along the coastal and inland distribution ranges.