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

Abstract

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 conclusions The c. 450 km that separate the archipelago from the continent are sufficient to isolate populations of these putatively highly vagile species. Ancestral lineages may have reached the MFI refugium during glacial cycles. Without conservation measures, the drastic decline of the morphologically, behaviourally and ecologically distinct continental population of C. rubidiceps, to < 1000 individuals, may lead to the extinction of an independently evolving taxon.

Migration Routes and Stopover Sites of Upland Geese Chloephaga Picta in South America

“…This phenomenon is apparent in the Malvinas (Falkland) Islands, where both, Upland and Ruddy-headed Goose populations, remain within the islands year round, since they encounter sufficient resources around their breeding territories (Summers and McAdam, 1993). However, evidence of genome-wide differentiation confirmed that the Upland Goose found in Argentina and Chile are not only morphologically (Summers and McAdam, 1993) but also genetically different from the Malvinas subspecies (Bulgarella et al, 2014;Kopuchian et al, 2016), which might impact on their migratory behaviour. In addition, some authors described that while most sheldgeese in southern Patagonia start their northward migration around the end of April, there are a few individuals that may overwinter on the breeding grounds (Martin et al, 1986;Summers and McAdam, 1993).…”

La conservación de las aves en la era de la genómica

“…A pesar de que en la lista roja de especies amenazadas de la Unión Internacional para la Conservación de la Naturaleza la especie figura en la categoría de Preocupación menor (IUCN 2018), la declinación de la población continental ha sido drástica en las últimas décadas, con menos de 1000 individuos en la actualidad, en contraposición a los más de 40000 individuos presentes en Islas Malvinas. La designación de la población continental como un taxón independiente es una acción crítica para redefinir su categoría de conservación y tomar medidas para recuperarla (Kopuchian et al 2016). En otro estudio reciente basado en SNPs, Andersen et al ( 2017) mostraron la divergencia genética que existe entre las poblaciones de aves que habitan distintas islas del archipiélago de Fiji, en el sudeste asiático, y propusieron cambios en su estatus taxonómico, así como la necesidad de generar planes de conservación independientes para cada una de ellas.…”

Spatial and temporal variation in the migration of Ruddy-headed Goose in southern South America using satellite tagging

“…This species has two separate populations: one sedentary, which resides in the Malvinas/Falkland Islands and one migratory population (the mainland South American population) that overwinters mainly in Southern Buenos Aires province (Pampas region, Central Argentina) and breeds in Southern Patagonia (Argentina and Chile). Recently, new findings postulated that these two populations are genetically isolated as they do not share mtDNA haplotypes (Bulgarella et al 2014) and have dissimilarities based on their nuclear DNA (Kopuchian et al 2016). However the latest IUCN Red List considered this species as 'Least Concern' (BirdLife International 2016).…”