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.在过去200万年的冰期循环中，白令陆桥（Beringia）作为动物群跨大陆交流的避难所与通道的作用已有充分记载；但其作为重要遗传多样性储备库的贡献却尚不明确。本研究利用线粒体DNA（mitochondrial DNA）序列与14个微卫星位点，对北美西部驯鹿（Rangifer tarandus）的系统地理历史展开探究。遗传多样性的分布模式显示，驯鹿可划分为两个截然不同的类群：起源于白令陆桥的北方类群，其mtDNA单倍型的数量与变异程度均高于源自冰盖以南避难所的南方类群。研究结果表明，阿拉斯加亚种R. t. granti与加拿大北部亚种R. t. groenlandicus在mtDNA与微卫星位点上并未形成可区分的演化单元，这与当前将二者划分为独立亚种的分类地位相悖。此外，当前归类为R. t. caribou的林地驯鹿北山生态型，与granti或groenlandicus类群的亲缘关系更为密切。对mtDNA与微卫星数据的比较分析显示，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，南方种群间的微卫星分化程度显著更高，这极有可能是人类活动引发的景观破碎化，以及种群规模缩小导致的遗传漂变（genetic drift）所致。上述研究结果不仅为驯鹿等北方物种的演化历史提供了重要的认知视角，同时也可为评估该受威胁物种保护措施的管理者提供关键的参考依据。