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，在那些利用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（reproductive isolation）。事实上，诸多适应性辐射（adaptive radiation）类群均以色彩信号的分化为特征，这表明作用于体色的歧化选择（divergent selection）或许是物种形成（speciation）的重要驱动组分。来自加勒比海瓜德罗普岛（Guadeloupe）的变色安乐蜥（Anolis marmoratus）物种复合群（species complex）的种群，在成年雄性的体色与斑纹上呈现出显著分化，且这种分化仅发生在极小的地理尺度内，暗示存在强烈的歧化选择。本研究旨在验证如下假说：体色具有局域适应性，且与种群间的基因流（gene flow）水平降低存在关联。我们量化了湿润生境（mesic habitat）与旱生生境（xeric habitat）之间的生境梯度上的成年雄性体色变异，采用多位点溯祖分析方法（multilocus coalescent approach）推断分化过程的历史种群动态参数，并利用微卫星标记（microsatellite）变异分析基因流与种群结构。研究结果显示，体色变异在未发生地理隔离且面临频发基因流的情况下演化，这与强烈歧化选择的预期相符，同时表明生态选择与性选择（sexual selection）均参与其中。然而，我们未在种群间的微卫星位点（microsatellite loci）上检测到显著分化，这表明种群间生殖隔离程度极低，且当代基因交流（gene exchange）水平较高。尽管中性位点（neutral loci）上存在高水平基因流，但作用于体色相关位点的强烈歧化选择，或许维持了渐变表型变异（clinal phenotypic variation），这支持了“多孔基因组（porous genome）”的概念：即基因组中受选择的适应性区段得以保留分化，而中性区段则因基因流与重组（recombination）趋于均一化。我们还讨论了本研究结果对体色演化与生态物种形成（ecological speciation）研究的启示。