Populations along steep environmental gradients are subject to differentiating selection that can result in local adaptation, despite countervailing gene flow, and genetic drift. In montane systems, where species are often restricted to narrow ranges of elevation, it is unclear whether the selection is strong enough to influence functional differentiation of subpopulations differing by a few hundred meters in elevation. We used targeted capture of 12 501 exons from across the genome, including 271 genes previously implicated in altitude adaptation, to test for adaptation to local elevations for 2 highland hummingbird species, Coeligena violifer (n = 62) and Colibri coruscans (n = 101). For each species, we described population genetic structure across the complex geography of the Peruvian Andes and, while accounting for this structure, we tested whether elevational allele frequency clines in single nucleotide polymorphisms (SNPs) showed evidence for local adaptation to elevation. Although the 2 species exhibited contrasting population genetic structures, we found signatures of clinal genetic variation with shifts in elevation in both. The genes with SNP-elevation associations included candidate genes previously discovered for high-elevation adaptation as well as others not previously identified, with cellular functions related to hypoxia response, energy metabolism, and immune function, among others. Despite the homogenizing effects of gene flow and genetic drift, natural selection on parts of the genome evidently optimizes elevation-specific cellular function even within elevation range-restricted montane populations. Consequently, our results suggest local adaptation occurring in narrow elevation bands in tropical mountains, such as the Andes, may effectively make them “taller” biogeographic barriers.

中文翻译：

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高地专家安第斯蜂鸟种群对海拔高度的局部适应的普遍基因组特征

沿陡峭环境梯度的种群受到差异化选择的影响，这可能导致局部适应，尽管有抵消基因流动和遗传漂变。在山地系统中，物种通常被限制在狭窄的海拔范围内，目前尚不清楚这种选择是否足以影响海拔相差几百米的亚群的功能分化。我们使用了来自整个基因组的 12 501 个外显子的靶向捕获，包括以前与海拔适应有关的 271 个基因，以测试 2 种高地蜂鸟 Coeligena violifer (n = 62) 和 Colibri coruscans (n = 101) 对当地海拔的适应. 对于每个物种，我们描述了秘鲁安第斯山脉复杂地理中的种群遗传结构，并且在考虑这种结构的同时，我们测试了单核苷酸多态性（SNP）中的海拔等位基因频率是否显示出局部适应海拔的证据。尽管这 2 个物种表现出截然不同的种群遗传结构，但我们发现了临床遗传变异的特征，两者均随海拔的变化而变化。与 SNP 海拔相关的基因包括先前发现的用于高海拔适应的候选基因以及其他先前未发现的基因，其细胞功能与缺氧反应、能量代谢和免疫功能等有关。尽管基因流动和遗传漂变的同质化效应，对部分基因组的自然选择明显优化了海拔特定的细胞功能，即使在海拔范围受限的山地种群中也是如此。最后，