Extensive gene flow among populations of the cavernicolous shrimp at the northernmost distribution margin in the Ryukyu Islands, Japan.

Takefumi Yorisue,Nina Yasuda,Akira Iguchi,Masaru Mizuyama,Aika Miyagi,Yoshihisa Fujita,Yuki Yoshioka

doi:10.1098/rsos.191731

Abstract

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.

Highlights

Populations of coastal organisms have declined due to recent anthropogenic pressures such as coastal development, pollution and over-harvesting (e.g. [1,2,3])
We detected 5454 loci that matched to the catalogue, which resulted in 62 single-nucleotide polymorphisms (SNPs) markers from filtering method (i) and (ii), respectively
We detected 5454 loci that matched to the catalogue, which resulted in 62 SNPs that are available for the population genetic analyses

Summary

Introduction

Populations of coastal organisms have declined due to recent anthropogenic pressures such as coastal development, pollution and over-harvesting (e.g. [1,2,3]). Marine cave environments have restricted exposure to the open sea and are sometimes connected to anchialine environments, which are defined as tidally influenced subterranean estuaries [6,7]. Such marine cave environments are often characterized by highly discrete species distributions [8,9]. Marine cave environments provide habitats for cavernicolous fauna that are dominated by stygobitic crustaceans [10,11,12]. Considering the unique environments and isolated species distributions of marine caves, it is expected that connectivity between populations of stygobitic species is restricted

Methods

Results

Conclusion