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）是一种岛屿蜥蜴，甚至可在栖息地面积不足0.5公顷的极小岛屿上被发现。本研究提出假说：该岛屿种群要么通过岛屿间频繁的基因交流得以存续，要么彼此间相互独立。为验证上述假说，本研究对11处末次冰期时期曾为陆桥岛屿（land-bridge islands）的区域以及4处孤立岛屿的21个种群的遗传结构展开了调查。通过对67条线粒体细胞色素b基因序列（mitochondrial cytochrome b gene sequence）以及235个样本的10个微卫星位点（microsatellite loci）进行分析，本研究发现：种群间存在中等到较高水平的遗传分化，多数岛屿中存在大量私有等位基因（private alleles）/单倍型（haplotypes），当代基因流水平极低；遗传多样性与岛屿面积呈正相关，而亲缘关系与岛屿面积呈负相关。上述结果表明，独立遗传漂变而非基因交流对种群分化起到了主导作用，支持了即使是极小岛屿种群也存在隔离分化的假说。本研究证实了距离隔离效应（isolation-by-distance effect）的存在，且在排除4处孤立岛屿后该效应更为显著，表明该遗传格局是陆桥时期遗留的特征。但在少数岛屿种群中，偶发跨海扩散的可能性得到了部分支持，因此无法完全排除该情况。