Data from: Absence of population structure across elevational gradients despite large phenotypic variation in mountain chickadees (Poecile gambeli)

Montane habitats are characterized by predictably rapid heterogeneity along elevational gradients and are useful for investigating the consequences of environmental heterogeneity for local adaptation and population genetic structure. Food-caching mountain chickadees inhabit a continuous elevation gradient in the Sierra Nevada, and birds living at harsher, high elevations have better spatial memory ability and exhibit differences in male song structure and female mate preference compared to birds inhabiting milder, low elevations. While high elevation birds breed, on average, two weeks later than low elevation birds, the extent of gene flow between elevations is unknown. Despite phenotypic variation and indirect evidence for local adaptation, population genetic analyses based on 18 073 single nucleotide polymorphisms across three transects of high and low elevation populations provided no evidence for genetic differentiation. Analyses based on individual genotypes revealed no patterns of clustering, pairwise estimates of genetic differentiation (FST, Nei's D) were very low, and AMOVA revealed no evidence for genetic variation structured by transect or by low and high elevation sites within transects. In addition, we found no consistent evidence for strong parallel allele frequency divergence between low and high elevation sites within the three transects. Large elevation-related phenotypic variation may be maintained by strong selection despite gene flow and future work should focus on the mechanisms underlying such variation.山地生境以沿海拔梯度呈现可预测的快速异质性为典型特征，是探究环境异质性对局部适应及种群遗传结构影响的优质研究体系。储食性山地山雀栖息于内华达山脉的连续海拔梯度中，相较于低海拔温和生境的种群，高海拔严酷生境的个体具备更优异的空间记忆能力，且雄性鸣唱结构与雌性配偶偏好均存在显著差异。尽管高海拔种群的繁殖时间平均较低海拔种群晚两周，但不同海拔间的基因交流程度仍不明晰。尽管存在表型变异且有局部适应的间接证据，但基于三条海拔梯度样带内18073个单核苷酸多态性（single nucleotide polymorphism, SNP）位点开展的种群遗传分析，并未检测到遗传分化的相关证据。基于个体基因型的分析未呈现明显聚类模式，成对遗传分化估计值（FST、Nei's D）均处于极低水平，分子方差分析（Analysis of Molecular Variance, AMOVA）也未发现由样带划分，或样带内高低海拔位点所介导的遗传变异结构。此外，在三条样带的高低海拔位点间，未发现一致的强烈平行等位基因频率分化证据。尽管存在基因交流，但强烈的选择作用或许维持了与海拔相关的显著表型变异，未来研究应聚焦于此类变异背后的潜在作用机制。