Laboratori de Genètica, Universitat de les Illes Balears, 07122, Palma de Mallorca, Spain.
Mol Ecol. 2013 Oct;22(19):4829-41. doi: 10.1111/mec.12443. Epub 2013 Aug 21.
Two monophyletic sister species of wall lizards inhabit the two main groups of Balearic Islands: Podarcis lilfordi from islets and small islands around Mallorca and Menorca and Podarcis pityusensis from Ibiza, Formentera and associated islets. Genetic diversity within the endangered P. lilfordi has been well characterized, but P. pityusensis has not been studied in depth. Here, 2430 bp of mtDNA and 15 microsatellite loci were analysed from P. pityusensis populations from across its natural range. Two main genetic groupings were identified, although geographical structuring differed slightly between the mtDNA and the nuclear loci. In general, individuals from islets/islands adjacent to the main island of Ibiza were genetically distinct from those from Formentera and the associated Freus islands for both mtDNA and the nuclear loci. However, most individuals from the island of Ibiza were grouped with neighbouring islets/islands for nuclear loci, but with Formentera and Freus islands for the mitochondrial locus. A time-calibrated Bayesian tree was constructed for the principal mitochondrial lineages within the Balearics, using the multispecies coalescent model, and provided statistical support for divergence of the two main P. pityusensis lineages 0.111-0.295 Ma. This suggests a mid-late Pleistocene intraspecific divergence, compared with an early Pleistocene divergence in P. lilfordi, and postdates some major increases in sea level between 0.4 and 0.6 Ma, which may have flooded Formentera. The program IMa2 provided a posterior divergence time of 0.089-0.221 Ma, which was similar to the multispecies coalescent tree estimate. More significantly, it indicated low but asymmetric effective gene copy migration rates, with higher migration from Formentera to Ibiza populations. Our findings suggest that much of the present-day diversity may have originated from a late Pleistocene colonization of one island group from the other, followed by allopatric divergence of these populations. Subsequent gene flow between these insular groups seems likely to be explained by recent human introductions. Two evolutionary significant units can be defined for P. pityusensis but these units would need to exclude the populations that have been the subjects of recent admixture.
一种是来自马略卡岛和梅诺卡岛周围小岛和小岛上的 Podarcis lilfordi，另一种是来自伊比萨岛、福门特拉岛和相关小岛的 Podarcis pityusensis。濒危物种 P. lilfordi 的遗传多样性已经得到了很好的描述，但 P. pityusensis 并没有被深入研究。在这里，对来自其自然分布范围内的 P. pityusensis 种群的线粒体 DNA 的 2430bp 和 15 个微卫星位点进行了分析。虽然 mtDNA 和核基因座的地理结构略有不同，但鉴定出了两个主要的遗传群体。一般来说，与伊比萨岛主要岛屿相邻的小岛/岛屿上的个体在 mtDNA 和核基因座上与福门特拉岛和相关的弗雷乌斯岛的个体明显不同。然而，对于核基因座来说，伊比萨岛上的大多数个体与邻近的小岛/岛屿聚集在一起，但对于线粒体基因座来说，它们与福门特拉岛和弗雷乌斯岛聚集在一起。使用多物种合并模型，为巴利阿里群岛内的主要线粒体谱系构建了一个时间校准的贝叶斯树，并为两个主要的 P. pityusensis 谱系的分化提供了统计支持，分化时间为 0.111-0.295Ma。这表明与 P. lilfordi 的早更新世分化相比，这是一次中更新世的种内分化，并且发生在 0.4 至 0.6Ma 之间的几次海平面大幅上升之后，海平面上升可能淹没了福门特拉岛。IMa2 程序提供了 0.089-0.221Ma 的后向分化时间，这与多物种合并树的估计相似。更重要的是，它表明存在低但不对称的有效基因拷贝迁移率，从福门特拉岛到伊比萨岛的种群的迁移率更高。我们的研究结果表明，当今的大部分多样性可能起源于一个岛屿群从另一个岛屿群的晚更新世殖民，然后这些种群发生了地理隔离分化。这些岛屿群体之间的随后的基因流可能是由最近的人类引入解释的。可以为 P. pityusensis 定义两个具有进化意义的单位，但这些单位需要排除最近发生混合的种群。
