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 inthe southern Atlantic, and harbour endemic lineages that presumably evolvedafter sea-level rise, associated with glacial periods, isolated ancestral popula-tions. We investigate the role of the MFI in isolating populations from conti-nental counterparts of two highly vagile species: the sheldgeese Chloephagapicta 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 geneticdifferentiation 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 andC. rubidiceps, which diverged from their continental counterparts during theMiddle-Late Pleistocene and have since experienced negligible gene flow.Main conclusions The c. 450 km that separate the archipelago from thecontinent are sufficient to isolate populations of these putatively highly vagilespecies. Ancestral lineages may have reached the MFI refugium during glacialcycles. Without conservation measures, the drastic decline of the morphologi-cally, behaviourally and ecologically distinct continental population ofC. rubidiceps,to< 1000 individuals, may lead to the extinction of an indepen-dently evolving taxon. Fil: Kopuchian, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina Fil: Campagna, Leonardo. Cornell University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Di Giacomo, Adrian Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina Fil: Wilson, Robert E.. University Of Alaska; Estados Unidos Fil: Bulgarella, Mariana. University of Minnesota; Estados Unidos Fil: Petracci, Pablo. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Grupo de Estudios en Conservación y Manejo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Mazar Barnett, Juan. Asociación de Ornitología del Plata; Argentina Fil: Matus, Ricardo. Centro de Rehabilitación de aves Leñadura; Chile Fil: Blank, Olivia. Centro de Rehabilitación de aves Leñadura; Chile Fil: McCracken, Kevin G.. University Of Alaska; Estados Unidos