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，下文简称MFI）是南大西洋规模最大的群岛，其孕育的特有演化支被认为是在与冰川时期相关的海平面上升事件后，因祖先种群被隔离而演化形成。本研究旨在探究MFI对两种高度漫游性物种——草雁属白腹草雁（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：我们在南美大陆巴塔哥尼亚地区及MFI境内采集了C. picta与C. rubidiceps的样本。采用简化基因组研究方法，量化了两个物种种群在岛屿种群与大陆种群间的遗传分化程度，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：MFI栖息着C. picta与C. rubidiceps的独立演化支，二者于中更新世晚期与其大陆同物种种群发生分化，且自此之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公里距离，足以隔离这两种被认为具有高度漫游性的物种种群。祖先演化支可能在冰川周期中抵达该群岛的冰期避难所。若不采取保护措施，棕头草雁（C. rubidiceps）在形态、行为与生态特征上均独具特色的大陆种群数量骤降至不足1000只，或将导致这一独立演化的分类单元走向灭绝。