Data from: Influence of ecological and geological features on rangewide patterns of genetic structure in a widespread passerine.

Geological and ecological features restrict dispersal and gene flow, leading to isolated populations. Dispersal barriers can be obvious physical structures in the landscape; however microgeographic differences can also lead to genetic isolation. Our study examined dispersal barriers at both macro- and micro-geographical scales in the black-capped chickadee, a resident North American songbird. Although birds have high dispersal potential, evidence suggests dispersal is restricted by barriers. The chickadee’s range encompasses a number of physiological features which may impede movement and lead to divergence. Analyses of 913 individuals from 34 sampling sites across the entire range using 11 microsatellite loci revealed as many as 13 genetic clusters. Populations in the east were largely panmictic whereas populations in the western portion of the range showed significant genetic structure, which often coincided with large mountain ranges, such as the Cascade and Rocky Mountains, as well as areas of unsuitable habitat. Unlike populations in the central and southern Rockies, populations on either side of the northern Rockies were not genetically distinct. Furthermore, Northeast Oregon represents a forested island within the Great Basin; genetically isolated from all other populations. Substructuring at the microgeographical scale was also evident within the Fraser Plateau of central British Columbia, and in the southeast Rockies where no obvious physical barriers are present, suggesting additional factors may be impeding dispersal and gene flow. Dispersal barriers are therefore not restricted to large physical structures, although mountain ranges and large water bodies do play a large role in structuring populations in this study.地质与生态特征会限制个体扩散与基因流（gene flow），进而造成种群隔离。扩散障碍既可以是景观中显著的物理结构，也可源于微地理尺度的差异，从而引发遗传隔离。本研究以北美留居鸣禽黑头山雀（black-capped chickadee）为研究对象，探究了大地理与微地理两个尺度下的扩散障碍。尽管鸟类具备较强的扩散潜力，但已有研究证据表明其扩散过程仍会受到各类障碍的限制。黑头山雀的分布范围涵盖多种可能阻碍个体移动、进而导致种群分化的生理特征。研究人员对覆盖其整个分布范围的34个采样点的913个个体，利用11个微卫星位点（microsatellite loci）开展遗传分析，结果揭示了多达13个遗传聚类簇（genetic clusters）。东部种群整体呈现泛交（panmictic）特征，而分布范围西部的种群则表现出显著的遗传结构，且这些结构往往与喀斯喀特山脉、落基山脉等大型山系，以及不适宜栖息的区域相吻合。与落基山脉中部和南部的种群不同，落基山脉北部两侧的种群并未出现遗传分化。此外，俄勒冈州东北部是大盆地（Great Basin）内的一片森林“孤岛”，其种群与其他所有种群均存在遗传隔离。微地理尺度下的种群亚结构也在不列颠哥伦比亚省中部的弗雷泽高原（Fraser Plateau），以及落基山脉东南部（该区域无明显物理障碍）被观测到，这暗示存在其他因素可能阻碍个体扩散与基因流。综上，扩散障碍并非仅局限于大型物理结构，尽管在本研究中，山系与大型水体确实在种群遗传结构的形成中发挥了重要作用。