Data from: Divergence in coloration and the evolution of reproductive isolation in the Anolis marmoratus species complex

Adaptive divergence in coloration is expected to produce reproductive isolation in species that use colorful signals in mate choice and species recognition. Indeed, many adaptive radiations are characterized by differentiation in colorful signals, suggesting that divergent selection acting on coloration may be an important component of speciation. Populations in the Anolis marmoratus species complex from the Caribbean island of Guadeloupe display striking divergence in adult male color and pattern that occurs over small geographic distances, suggesting strong divergent selection. Here we test the hypothesis that coloration is locally adaptive and is linked to reduced gene flow among populations. We quantify variation in adult male coloration across a habitat gradient between mesic and xeric habitats, use a multilocus coalescent approach to infer historical demographic parameters of divergence, and examine gene flow and population structure using microsatellite variation. We find that color variation evolved without geographic isolation and in the face of rampant gene flow, consistent with strong divergent selection, and that both ecological and sexual selection are implicated. However, we find no significant differentiation at microsatellite loci across populations, suggesting little reproductive isolation and high levels of contemporary gene exchange. Strong divergent selection on loci affecting coloration likely maintains clinal phenotypic variation despite high gene flow at neutral loci, supporting the notion of a porous genome in which adaptive portions of the genome remain fixed while neutral portions are homogenized by gene flow and recombination. We discuss the impact of these findings for studies of color evolution and ecological speciation.

体色的适应性分化，在那些通过色彩信号进行配偶选择与物种识别的类群中，被认为会促成生殖隔离的形成。事实上，诸多适应性辐射类群均以色彩信号的分化为典型特征，这表明作用于体色的歧化选择或许是物种形成过程中的关键环节。分布于加勒比海瓜德罗普岛的斑安乐蜥（Anolis marmoratus）物种复合体的种群，在成体雄性的体色与斑纹上呈现出显著的地理分化，且这种分化发生在极小的地理尺度内，这暗示了极强的歧化选择作用。本研究旨在验证如下假说：体色具有局域适应性，且与种群间基因流的降低存在关联。我们量化了湿润生境与旱生生境之间的生境梯度上的成体雄性体色变异，采用多位点溯祖方法推断分化的历史种群动态参数，并利用微卫星（microsatellite）变异分析种群的基因流与群体结构。研究结果表明，体色变异是在无地理隔离且面临大量基因流的情况下演化而来的，这与强歧化选择的预期相符，同时暗示生态选择与性选择均参与其中。然而，我们未在种群间的微卫星位点上发现显著的遗传分化，这表明种群间生殖隔离程度极低，且当代基因交流水平较高。尽管中性位点存在高水平基因流，但作用于体色相关位点的强歧化选择或许维持了表型的渐变式变异，这支持了“多孔基因组”的概念：即基因组中的适应性区域得以保留分化，而中性区域则因基因流与重组作用趋于同质化。我们还讨论了本研究结果对体色演化与生态物种形成研究的启示。