Marine cave habitats in the Ryukyu Islands, Indo-West Pacific, are located at the northern edge of the distribution of many cave-dwelling species. At distribution margins, gene flow is often more restricted than that among core populations due to the smaller effective population size. Here, we used high-throughput sequencing technology to investigate the gene flow pattern among three sampling sites of a marine cave-dwelling species at the margin of its distribution range. We collected individuals of the barbouriid shrimp Parhippolyte misticia from three marine caves in the Ryukyu Islands and performed population genetic analyses by means of multiplexed inter-simple sequence repeat genotyping by sequencing. Based on 62 single-nucleotide polymorphism markers, no clear population structure or directional gene flow pattern was found among the three sites. These results were unexpected because previous studies of other stygobitic shrimps in this region did find significant population genetic structures and northward directional gene flow patterns. Together, these inconsistent findings imply that marine cave-dwelling species in the region have different mechanisms of larval dispersal. Future studies on larval ecology and the biotic and abiotic factors influencing gene flow patterns are needed to clarify the mechanisms underlying the population dynamics of marine cave-dwelling species.

印度洋-西太平洋琉球群岛的海洋洞穴栖息地位于许多洞穴居住物种分布的北部边缘。在分布边缘，由于有效种群较小，基因流通常比核心种群受更多限制。在这里，我们使用高通量测序技术研究了一个海洋洞穴栖居物种在其分布范围边缘的三个采样点之间的基因流动模式。我们收集了Barbouriid虾Parhippolyte misticia的个体从琉球群岛的三个海蚀洞中提取，并通过多重简单序列间重复序列基因分型进行测序，进行种群遗传分析。基于62个单核苷酸多态性标记，在这三个位点之间未发现清晰的种群结构或定向基因流型。这些结果是出乎意料的，因为先前对该区域其他定尾虾的研究确实发现了重要的种群遗传结构和北向基因流型。总之，这些不一致的发现暗示该地区的海洋洞穴居民物种具有不同的幼虫扩散机制。需要进一步研究幼虫生态学以及影响基因流动模式的生物和非生物因素，以阐明潜在的海洋洞穴动物种群动态的机制。