Data from: Extensive sampling of polar bears (Ursus maritimus) in the Northwest Passage (Canadian Arctic Archipelago) reveals population differentiation across multiple spatial and temporal scales

As global warming accelerates the melting of Arctic sea ice, polar bears (Ursus maritimus) must adapt to a rapidly changing landscape. This process will necessarily alter the species distribution together with population dynamics and structure. Detailed knowledge of these changes is crucial to delineating conservation priorities. Here, we sampled 361 polar bears from across the center of the Canadian Arctic Archipelago spanning the Gulf of Boothia (GB) and M'Clintock Channel (MC). We use DNA microsatellites and mitochondrial control region sequences to quantify genetic differentiation, estimate gene flow, and infer population history. Two populations, roughly coincident with GB and MC, are significantly differentiated at both nuclear (FST = 0.01) and mitochondrial (ΦST = 0.47; FST = 0.29) loci, allowing Bayesian clustering analyses to assign individuals to either group. Our data imply that the causes of the mitochondrial and nuclear genetic patterns differ. Analysis of mtDNA reveals the matrilineal structure dates at least to the Holocene, and is common to individuals throughout the species’ range. These mtDNA differences probably reflect both genetic drift and historical colonization dynamics. In contrast, the differentiation inferred from microsatellites is only on the scale of hundreds of years, possibly reflecting contemporary impediments to gene flow. Taken together, our data suggest that gene flow is insufficient to homogenize the GB and MC populations and support the designation of GB and MC as separate polar bear conservation units. Our study also provide a striking example of how nuclear DNA and mtDNA capture different aspects of a species demographic history.

随着全球变暖加速北极海冰消融，北极熊（Ursus maritimus）亟需适应快速变化的生存环境。这一过程势必改变该物种的分布格局，同时影响其种群动态与种群结构。精准掌握此类变化，对于划定物种保护优先级至关重要。
本研究从横跨布西亚湾（Gulf of Boothia, GB）与麦克林托克海峡（M'Clintock Channel, MC）的加拿大北极群岛中部区域，采集了361头北极熊的样本。我们采用微卫星DNA（DNA microsatellites）与线粒体控制区序列，量化遗传分化程度、估算基因流水平，并推断种群历史。
研究结果显示，分别大致对应GB与MC的两个种群，在核基因座（FST=0.01）与线粒体基因座（ΦST=0.47；FST=0.29）上均存在显著分化，贝叶斯聚类分析可将个体准确归类至相应种群。
我们的数据表明，线粒体与核基因的遗传模式成因存在差异。线粒体DNA（mitochondrial DNA, mtDNA）分析显示，其母系结构至少可追溯至全新世，且覆盖该物种整个分布范围的个体均存在这一特征。此类线粒体DNA差异可能同时反映了遗传漂变与历史殖民动态。
与之相反，由微卫星DNA推断的种群分化仅发生在数百年尺度内，可能反映了当前存在的基因流阻碍因素。
综合来看，我们的数据表明基因流不足以使GB与MC种群实现遗传均质化，支持将GB和MC划定为独立的北极熊保护单元。本研究还生动展示了核DNA与线粒体DNA如何分别记录物种人口统计历史的不同维度。