Data from: 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 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.研究目的：马尔维纳斯群岛/福克兰群岛（Malvinas/Falkland Islands, MFI）是南大西洋规模最大的群岛，孕育了推测在与冰期伴生的海平面上升事件后演化形成、且与祖先种群相互隔离的特有演化支系。本研究旨在探究该群岛对两种高度扩散性物种——草雁属的白草雁（Chloephaga picta）与棕头草雁（Chloephaga rubidiceps）——的大陆种群的隔离作用。 研究区域：巴塔哥尼亚与马尔维纳斯群岛/福克兰群岛。 研究方法：我们在大陆及马尔维纳斯群岛/福克兰群岛采集了白草雁与棕头草雁的样本。采用简化基因组分析方法，量化了两个物种的岛屿种群与大陆种群间的遗传分化，并运用基于溯祖理论的分析方法对其种群历史动态进行建模。 研究结果：马尔维纳斯群岛/福克兰群岛拥有白草雁与棕头草雁的独立演化支系，二者在中更新世至晚更新世时期与其大陆同源种群分化，此后几乎未发生基因交流。 主要结论：分隔该群岛与大陆的约450公里海域足以隔离这些被认为具有高度扩散能力的物种种群。祖先演化支系可能在冰期循环中抵达该群岛的避难所。若未采取保护措施，棕头草雁大陆种群——其形态、行为与生态特征均具有独特性——的数量锐减至不足1000只，可能导致这一独立演化的类群走向灭绝。