Data from: Footprints of selection in wild populations of Bicyclus anynana along a latitudinal cline

One of the major questions in ecology and evolutionary biology is how variation in the genome enables species to adapt to divergent environments. Here, we study footprints of thermal selection in candidate genes in six wild populations of the afrotropical butterfly Bicyclus anynana, sampled along a ~3,000 km latitudinal cline. We sequenced coding regions of 31 selected genes with known functions in metabolism, pigment production, development, and heat shock responses. These include genes for which we expect a priori a role in thermal adaptation and, thus, varying selection pressures along a latitudinal cline, and genes we do not expect to vary clinally and can be used as controls. We identified amino-acid substitution polymorphisms in 13 genes and tested these for clinal variation by correlation analysis of allele frequencies with latitude. In addition, we used two FST-based outlier methods to identify loci with higher population differentiation than expected under neutral evolution, while accounting for potentially confounding effects of population structure and demographic history. Two metabolic enzymes of the glycolytic pathway, UGP and Treh, showed clinal variation. The same loci showed elevated population differentiation and were identified as significant outliers. We found no evidence of clines in the pigmentation genes, heat shock proteins and developmental genes. However, we identified outlier loci in more localized parts of the range in the pigmentation genes yellow and black. We discuss that the observed clinal variation and elevated population divergence in UGP and Treh may reflect adaptation to a geographic thermal gradient.生态学与进化生物学领域的核心议题之一，是基因组变异如何助力物种适应异质性环境。本研究以沿约3000公里纬度渐变群采样的6个野生安氏眼蝶（Bicyclus anynana）种群为对象，解析其候选基因中的热选择印迹。我们对31个功能明确的候选基因的编码区进行了测序，这些基因涉及代谢、色素生成、发育以及热激响应过程。其中既包含我们预先推测可能参与热适应、因此会沿纬度渐变群呈现选择压力差异的基因，也包含我们预期不会随纬度渐变群发生变异、可作为对照的基因。我们在13个基因中鉴定到了氨基酸替换多态性，并通过等位基因频率与纬度的相关性分析，检验这些多态性是否存在渐变群变异。此外，我们采用两种基于FST的离群位点检测方法，筛选出在中性进化预期下群体分化程度高于预期的基因座，同时校正了群体结构与种群历史可能带来的混杂效应。糖酵解通路中的两种代谢酶UGP与Treh呈现出渐变群变异，这两个基因座同时表现出升高的群体分化程度，被鉴定为显著的离群位点。我们未在色素生成相关基因、热激蛋白基因以及发育相关基因中检测到渐变群变异的信号。不过，我们在该物种分布区的局部区域内，于色素生成基因yellow与black中鉴定到了离群位点。我们讨论认为，UGP与Treh中观测到的渐变群变异及升高的群体分化，可能反映了物种对地理热梯度的适应性进化。