Data from: Ecological divergence combined with ancient allopatry in lizard populations from a small volcanic island

Population divergence and speciation are often explained by geographical isolation, but may also be possible under high gene flow due to strong ecology-related differences in selection pressures. This study combines coalescent analyses of genetic data (11 microsatellite loci and 1 Kbp of mtDNA) and ecological modelling to examine the relative contributions of isolation and ecology to incipient speciation in the scincid lizard Chalcides sexlineatus within the volcanic island of Gran Canaria. Bayesian multispecies coalescent dating of within-island genetic divergence of northern and southern populations showed correspondence with the timing of volcanic activity in the north of the island 1.5-3.0 Ma ago. Coalescent estimates of demographic changes reveal historical size increases in northern populations, consistent with expansions from a volcanic refuge. Nevertheless, ecological divergence is also supported. First, species distribution modelling shows that the northern morph is associated with mesic habitat types and the southern morph with xeric habitat types. It seems likely that the colour morphs are associated with different anti-predator strategies in the different habitats. Second, coalescent estimation of gene copy migration (based on microsatellites and mtDNA) suggest high rates from northern to southern morphs demonstrating the strength of ecology-mediated selection pressures that maintain the divergent southern morph. Together, these findings underline the complexity of the speciation process by providing evidence for the combined effects of ecological divergence and ancient divergence in allopatry.

种群分化与物种形成通常以地理隔离作为主流解释，但在高基因流情境下，若选择压力存在与生态紧密相关的显著差异，该演化过程同样可能发生。本研究结合遗传数据（11个微卫星位点（microsatellite loci）与1千碱基对线粒体DNA（mtDNA））的溯祖分析（coalescent analyses）与生态建模，旨在探究隔离与生态因子对火山岛大加纳利岛（Gran Canaria）内石龙子科蜥蜴三线石龙子（Chalcides sexlineatus）初期物种形成的相对贡献。对该岛南北种群的岛内遗传分化开展的贝叶斯多物种溯祖定年分析显示，其分化时间与该岛北部1.5~3.0百万年前（Ma）的火山活动时段相吻合。种群动态的溯祖估计结果显示，北部种群历史上曾经历种群规模扩张，这与从火山避难所扩散的假说相符。尽管如此，生态分化的证据同样得到支持：其一，物种分布模型（species distribution modelling）结果表明，北部形态型与湿润生境类型相关，南部形态型则对应干旱生境类型，颜色形态型似乎与不同生境下的差异化反捕食策略（anti-predator strategies）存在关联；其二，基于微卫星与线粒体DNA的基因拷贝迁移溯祖估计结果显示，从北部形态型向南部形态型的基因流速率极高，这印证了维持南部分化形态型的生态介导选择压力之强。综上，本研究通过提供生态分化与异域古分化联合作用的证据，凸显了物种形成过程的复杂性。