Data from: Evolutionary reconstruction supports the presence of a Pleistocene Arctic refugium for a large mammal species

Aim: The presence of refugia in the Canadian High Arctic has been subject to debate for decades. We investigated the potential existence of Arctic refugia during the Pleistocene for a large mammal species in the Canadian Archipelago because if these refugia were present, reconsideration of the evolutionary histories of North American fauna and flora beyond the major refugia of Beringia and south of the Laurentide and Cordilleran Ice Sheets would be required. Peary caribou (Rangifer tarandus pearyi), identified as a subspecies based on morphological characteristics, inhabits the Canadian Arctic Islands and Boothia Peninsula. Previous studies demonstrated incomplete lineage sorting of mitochondrial DNA interpreted as a Beringian origin but were based on small sample sizes. Location: Canadian Arctic. Major taxa studied: Mammals: caribou (Rangifer tarandus). Methods: We used two molecular markers (microsatellites and mitochondrial DNA) and approximate Bayesian computations (ABC) testing the hypotheses of colonization out of Beringia into the Arctic Islands following the Last Glacial Maximum (LGM) or a divergence from Beringia significantly before the end of the LGM within a different refugium. Results: The coalescent-based analyses rejected a recent Beringian origin with subsequent colonization, instead supporting a divergence of Peary caribou from Beringia ~100,000 years ago linking it to the last interglacial/early Wisconsin Glacial Stage (125,000–75,000 years ago). Admixture on Banks Island with Beringian-derived barren-ground caribou is indicative of post-Pleistocene secondary contact; further supporting a divergent history of Peary caribou within a separated Arctic refugium. Main conclusions: Our results offer support for the existence of an Arctic refugium for large mammal species and add to the increasing evidence of such refugia in North America. This has significant implications on understanding the evolution and conservation of Arctic species, particularly in light of sensitivities and adaptive potential to a rapidly changing climate.研究目的：加拿大大高北极地区是否存在冰期避难所（refugia）这一议题已争论数十年。本研究针对加拿大北极群岛中的大型哺乳动物类群，探究更新世（Pleistocene）北极冰期避难所的潜在存在性——若此类避难切实存在，则需重新审视白令陆桥（Beringia）以外、劳伦泰德与科迪勒拉冰盖（Laurentide and Cordilleran Ice Sheets）以南区域的北美动植物演化历史。基于形态特征被定为亚种的皮尔里驯鹿（Rangifer tarandus pearyi）栖息于加拿大北极群岛与布西亚半岛。既往研究基于较小样本量，将线粒体DNA（mitochondrial DNA）的不完全谱系分选现象解读为其起源于白令陆桥，但该结论受限于样本规模。 研究区域：加拿大北极地区。 研究类群：哺乳动物：驯鹿（Rangifer tarandus）。 研究方法：本研究采用两种分子标记（微卫星与线粒体DNA）结合近似贝叶斯计算（approximate Bayesian computations, ABC），对两种假说进行验证：一是末次盛冰期（Last Glacial Maximum, LGM）后从白令陆桥扩散至北极群岛；二是在末次盛冰期末期之前的另一独立避难所中，与白令陆桥类群发生分化。 研究结果：基于溯祖理论的分析结果不支持“近期起源于白令陆桥并随后扩散”的假说，反而证实皮尔里驯鹿约于10万年前与白令陆桥类群发生分化，该分化时间对应末次间冰期/早威斯康星冰期（125,000–75,000年前）。班克斯岛（Banks Island）上皮尔里驯鹿与源自白令陆桥的贫瘠地驯鹿存在基因渐渗现象，这表明更新世后发生了二次接触，进一步佐证了皮尔里驯鹿在独立北极避难所中发生分化的演化历史。 主要结论：本研究结果为大型哺乳动物在北极存在冰期避难所提供了支撑，同时进一步补充了北美地区此类避难所的相关证据。鉴于北极物种对快速变化的气候具有敏感性与适应潜力，该研究结果对理解北极物种的演化与保护工作具有重要意义。