Demographic history inferred from genome-wide data together with morphological analyses reveals two lineages of sheldgeese endemic to a glacial refugium in the southern Atlantic: Taxonomic and Conservation Implications

KOPUCHIAN, CECILIA; CAMPAGNA, LEONARDO; ADRIAN S. DI GIACOMO; WILSON, ROBERT E.; PETRACCI, PABLO; BULGARELLA, MARIANA; MAZAR BARNETT, J.; MACCKRAKEN K

Washington DC

Congreso; VI North American Ornithological Conference; 2016

Smithsonian Institution

Species endemic to archipelagos worldwide illustrate the importance of geographic isolation in the process of speciation. The Malvinas/Falkland Islands (MFI) constitute the largest archipelago in the Southern Atlantic, located ~450 km east of Tierra del Fuego (Patagonia); and harbor endemic lineages that evolved after ancestral populations became isolated during the Pleistocene glaciations. Various bird species have populations on the continent and the MFI that are not genetically differentiated, suggesting geographic isolation may not be enough to reduce gene flow, and thus allow diversification. Two species of sheldgeese, Chloephaga picta and Chloephaga rubidiceps, have populations that are codistributed between the MFI and Patagonia and show opposing demographic trends: while insular populations are increasing in size, continental ones are in sharp decline, due mainly to anthropogenic causes. We combined a genomic approach with analysis of morphological data to quantify differentiation among insular and continental populations of both species, and used coalescent-based analyses to model their demographic history. Our results show that the MFI harbor independently evolving lineages of C. picta and C. rubidiceps,which diverged from their continental counterparts during the Pleistocene and have since experienced negligible gene flow. We conclude that the distance that separate the archipelago from the continent is sufficient to isolate populations of these vagile species. This implies that without appropriate conservation measures, the drastic decline of the morphologically, behaviorally and ecologically distinct continental population of C. rubidiceps, may lead to the extinction of an independently evolving taxon.