Data from: An investigation for population maintenance mechanism in a miniature garden: genetic connectivity or independence of small islet populations of the Ryukyu five-lined skink

The Ryukyu five-lined skink (Plestiodon marginatus) is an island lizard that is even found in tiny islets with less than half a hectare of habitat area. We hypothesized that the island populations are maintained under frequent gene flow among the islands or independent of each other. To test our hypotheses, we investigated genetic structure of 21 populations from 11 land-bridge islands that were connected during the latest glacial age, and four isolated islands. Analyses using mitochondrial cytochrome b gene sequence (n = 67) and 10 microsatellite loci (n = 235) revealed moderate to high levels of genetic differentiation, existence of many private alleles/haplotypes in most islands, little contemporary migration, a positive correlation between genetic variability and island area, and a negative correlation between relatedness and island area. These evidences suggest a strong effect of independent genetic drift as opposed to gene flow, favoring the isolation hypothesis even in tiny islet populations. Isolation-by-distance effect was demonstrated and it became more prominent when the four isolated islands were excluded, suggesting that the pattern is a remnant of the land-bridge age. In a few island populations, however, the possibility of occasional overwater dispersals was partially supported and therefore could not be ruled out.琉球五线石龙子（Plestiodon marginatus）是一种岛栖蜥蜴，甚至可分布于面积不足0.5公顷的极小海岛生境中。我们提出假说：该岛栖种群的维持机制，要么依赖于岛间频繁的基因流，要么彼此完全独立。为验证上述假说，我们对11个末次冰期时曾相互连通的陆桥岛，以及4个孤立海岛的共计21个种群的遗传结构开展了调查分析。基于线粒体细胞色素b基因（mitochondrial cytochrome b）序列（样本量n=67）与10个微卫星位点（microsatellite loci，样本量n=235）的分析结果显示：种群间存在中等到高水平的遗传分化，多数海岛种群中存在大量私有等位基因/单倍型，当前基因交流水平极低；遗传多样性与海岛面积呈正相关，而种群亲缘关系与海岛面积呈负相关。上述结果表明，独立遗传漂变的作用远强于基因流，支持了种群彼此独立的假说，即便在极小的海岛种群中亦成立。研究还证实了距离隔离效应（Isolation-by-distance）的存在，且在排除4个孤立海岛后该效应更为显著，提示该遗传格局是末次冰期陆桥时代的遗留特征。不过，部分海岛种群的分析结果部分支持了偶发跨海扩散的可能性，因此无法完全排除该扩散机制。