Data from: Population structure over a broad spatial scale driven by non-anthropogenic factors in a wide-ranging migratory mammal, Alaskan caribou

Wide-ranging mammals face significant conservation threats, and knowledge of the spatial scale of population structure and its drivers is needed to understand processes that maintain diversity in these species. We analysed DNA from 655 Alaskan caribou (Rangifer tarandus granti) from 20 herds that vary in population size, used 19 microsatellite loci to document genetic diversity and differentiation in Alaskan caribou, and examined the extent to which genetic differentiation was associated with hypothesized drivers of population subdivision including landscape features, population size and ecotype. We found that Alaskan caribou are subdivided into two hierarchically structured clusters: one group on the Alaska Peninsula containing discrete herds and one large group on the Mainland lacking differentiation between many herds. Population size, geographic distance, migratory ecotype and the Kvichak River at the nexus of the Alaska Peninsula were associated with genetic differentiation. Contrary to previous hypotheses, small Mainland herds were often differentiated genetically from large interconnected herds nearby, and genetic drift coupled with reduced gene flow may explain this pattern. Our results raise the possibility that behaviour helps to maintain genetic differentiation between some herds of different ecotypes. Alaskan caribou show remarkably high diversity and low differentiation over a broad geographic scale. These results increase information for the conservation of caribou and other migratory mammals threatened by population reductions and landscape barriers and may be broadly applicable to understanding the spatial scale and ecological drivers of population structure in widespread species.

广泛分布的哺乳动物面临着严峻的保护威胁，若要阐明维持这些物种多样性的核心过程，亟需掌握种群结构的空间尺度及其驱动机制。本研究采集并分析了来自20个种群（种群大小各不相同）的655头阿拉斯加驯鹿（Rangifer tarandus granti）的DNA样本，利用19个微卫星基因座（microsatellite loci）解析了阿拉斯加驯鹿的遗传多样性与遗传分化特征，并探究了遗传分化与种群分化的假设驱动因子——包括景观特征、种群大小与生态型——之间的关联程度。研究发现，阿拉斯加驯鹿可划分为两个层级结构化的遗传聚类群：其一为分布于阿拉斯加半岛的离散种群群，其二为分布于阿拉斯加大陆地区、多数种群间无显著遗传分化的大型连通种群群。种群大小、地理距离、迁徙生态型以及位于阿拉斯加半岛枢纽地带的克维查克河，均与遗传分化存在显著关联。与此前的研究假说相悖的是，大陆地区的小型种群往往与附近的大型连通种群存在显著遗传分化，遗传漂变（genetic drift）与基因流（gene flow）水平降低或许可以解释这一现象。本研究结果还提示，行为模式或许有助于维持不同生态型的部分种群之间的遗传分化。整体而言，阿拉斯加驯鹿在广阔的地理范围内展现出极高的遗传多样性与较低的遗传分化水平。本研究结果为受种群缩减与景观阻隔威胁的驯鹿及其他迁徙哺乳动物的保护工作提供了更为详实的科学依据，同时也可为广泛分布物种的种群结构空间尺度与生态驱动因子研究提供普适性参考。