Generally, the gene flow of marine organisms is well maintained, but some local populations of coastal species are genetically differentiated even on a small scale (genetic patchiness). Small-scale isolation can be crucial for understanding genetic diversity within a species. The present study examined the population genetic structure of the sand bubbler crab Scopimera ryukyuensis, which is endemic to the Ryukyu Islands in the northwestern Pacific. A total of 52 haplotypes of mitochondrial cytochrome c oxidase subunit I were recovered from 197 specimens collected from four islands. The haplotype and nucleotide diversities were relatively high in the central Ryukyus (Amami-Oshima and Okinawa Islands) with some exceptions but were low at the southern edge of the geographical distribution of the species, i.e., the southern Ryukyus (Ishigaki and Iriomote Islands). Pairwise FST analysis suggested that the gene flow of S. ryukyuensis was largely restricted. The local populations of the species are differentiated among islands, except for stations on Ishigaki Island and a station on Iriomote Island. Moreover, a clear intra-island population genetic structure was observed within Amami-Oshima and Iriomote Islands, e.g., only 20 km between stations. Small-scale isolation among local populations may be a common tendency for coastal species in the Ryukyu Islands, considering the results of previous studies on corals.

中文翻译：

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日本琉球群岛上起沙蟹Scopimera ryukyuensis的小规模种群遗传结构。

通常，海洋生物的基因流得到很好的维护，但是一些沿海物种的本地种群即使在很小的规模上也具有遗传分化（遗传斑驳）。小规模隔离对于了解物种内的遗传多样性至关重要。本研究调查了西北太平洋琉球群岛特有的沙泡蟹Scopimera ryukyuensis的种群遗传结构。从四个岛屿收集的197个标本中，共回收了52种线粒体细胞色素C氧化酶亚基I单倍型。除某些例外外，琉球中部（A美大岛和冲绳群岛）的单体型和核苷酸多样性相对较高，但在物种地理分布的南部边缘则较低。南部琉球（石垣岛和西表岛）。成对FST分析表明，琉球葡萄球菌的基因流动受到很大限制。除石垣岛上的站和西表岛上的站外，其他岛屿上该物种的当地种群有所不同。此外，在Am美大岛和西表岛内观察到清晰的岛内种群遗传结构，例如站之间仅20 km。考虑到先前对珊瑚的研究结果，在本地种群之间进行小规模隔离可能是琉球群岛沿海物种的普遍趋势。此外，在Am美大岛和西表岛内观察到清晰的岛内种群遗传结构，例如站之间仅20 km。考虑到先前对珊瑚的研究结果，在本地种群之间进行小规模隔离可能是琉球群岛沿海物种的普遍趋势。此外，在Am美大岛和西表岛内观察到清晰的岛内种群遗传结构，例如站之间仅20 km。考虑到先前对珊瑚的研究结果，本地人群之间的小规模隔离可能是琉球群岛沿海物种的普遍趋势。