Demographic history inferred from genome-wide data reveals two lineages of sheldgeese endemic to a glacial refugium in the southern Atlantic

Aim: The Malvinas/Falkland Islands (MFI) constitute the largest archipelago in the southern Atlantic, and harbour endemic lineages that presumably evolved after sea-level rise, associated with glacial periods, isolated ancestral populations. We investigate the role of the MFI in isolating populations from continental counterparts of two highly vagile species: the sheldgeese Chloephaga picta and Chloephaga rubidiceps. Location: Patagonia and the Malvinas/Falkland Islands. Methods: We sampled C. picta and C. rubidiceps on the continent and MFI. Using a reduced-representation genomic approach, we quantified the genetic differentiation between insular and continental populations of both species, and used coalescent-based analyses to model their demography. Results: The MFI harbour independently evolving lineages of C. picta and C. rubidiceps, which diverged from their continental counterparts during the Middle-Late Pleistocene and have since experienced negligible gene flow. Main conclusion...