Data from: Reconstruction of caribou evolutionary history in Western North America and its implications for conservation

The role of Beringia as a refugium and route for trans-continental exchange of fauna during glacial cycles of the past 2 million years are well documented; less apparent is its contribution as a significant reservoir of genetic diversity. Using mitochondrial DNA sequences and 14 microsatellite loci, we investigate the phylogeographic history of caribou (Rangifer tarandus) in western North America. Patterns of genetic diversity reveal two distinct groups of caribou. Caribou classified as a Northern group, of Beringian origin, exhibited greater number and variability in mtDNA haplotypes compared to a Southern group originating from refugia south of glacial ice. Results indicate that subspecies R. t. granti of Alaska and R. t. groenlandicus of northern Canada do not constitute distinguishable units at mtDNA or microsatellites, belying their current status as separate subspecies. Additionally, the Northern Mountain ecotype of woodland caribou (presently R. t. caribou) has closer kinship to caribou classified as granti or groenlandicus. Comparisons of mtDNA and microsatellite data suggest that behavioural and ecological specialization is a more recently derived life history characteristic. Notably, microsatellite differentiation among Southern herds is significantly greater, most likely as a result of human-induced landscape fragmentation and genetic drift due to smaller population sizes. These results not only provide important insight into the evolutionary history of northern species such as caribou, but also are important indicators for managers evaluating conservation measures for this threatened species.

白令陆桥（Beringia）在过去200万年冰期循环中作为冰期动物群跨大陆交流的避难所与迁移通道的作用已得到充分研究与证实，但其作为重要遗传多样性储存库的贡献却鲜为人知。本研究借助线粒体DNA（mtDNA）序列与14个微卫星位点（microsatellite loci），对北美西部驯鹿（*Rangifer tarandus*）的系统地理学历史展开探究。遗传多样性分布模式显示，北美西部驯鹿可划分为两个显著分化的种群：源自白令陆桥的北部种群，其线粒体DNA单倍型的数量与变异程度均高于起源于冰盖以南冰期避难所的南部种群。研究结果显示，阿拉斯加的R. t. granti亚种与加拿大北部的R. t. groenlandicus亚种在线粒体DNA与微卫星位点上均未表现出显著分化，这与二者当前的独立亚种分类地位相悖。此外，目前归类为R. t. caribou的林地驯鹿北部山地生态型，与granti或groenlandicus种群的亲缘关系更为密切。对线粒体DNA与微卫星数据的对比分析显示，行为与生态特化是一类较晚演化形成的生活史特征。值得注意的是，南部种群间的微卫星分化程度显著更高，这一现象极有可能源于人类活动诱发的景观破碎化，以及种群规模缩减所引发的遗传漂变。本研究结果不仅为驯鹿等北方物种的演化历史提供了重要科学认知，同时也可为管理者评估该受胁物种的保护策略提供关键参考依据。