Phylogeography of the Rock Shell Thais clavigera (Mollusca): Evidence for Long-Distance Dispersal in the Northwestern Pacific.

Xiang Guo,Hyuk Je Lee,Gang Ni,Tomoyuki Nakano,Daewui Jung,Chungoo Park,Akihiko Matsukuma,Dan Zhao,Ling-Feng Kong,Qi Li,Joong-Ki Park,Sanghee Kim,Zhong-Jian Liu

doi:10.1371/journal.pone.0129715

Abstract

The present-day genetic structure of a species reflects both historical demography and patterns of contemporary gene flow among populations. To precisely understand how these factors shape current population structure of the northwestern (NW) Pacific marine gastropod, Thais clavigera, we determined the partial nucleotide sequences of the mitochondrial COI gene for 602 individuals sampled from 29 localities spanning almost the whole distribution of T. clavigera in the NW Pacific Ocean (~3,700 km). Results from population genetic and demographic analyses (AMOVA, ΦST-statistics, haplotype networks, Tajima’s D, Fu’s FS, mismatch distribution, and Bayesian skyline plots) revealed a lack of genealogical branches or geographical clusters, and a high level of genetic (haplotype) diversity within each of studied population. Nevertheless, low but significant genetic structuring was detected among some geographical populations separated by the Changjiang River, suggesting the presence of geographical barriers to larval dispersal around this region. Several lines of evidence including significant negative Tajima’s D and Fu’s FS statistics values, the unimodally shaped mismatch distribution, and Bayesian skyline plots suggest a population expansion at marine isotope stage 11 (MIS 11; 400 ka), the longest and warmest interglacial interval during the Pleistocene epoch. The lack of genetic structure among the great majority of the NW Pacific T. clavigera populations may be attributable to high gene flow by current-driven long-distance dispersal of prolonged planktonic larval phase of this species.

Highlights

The present-day genetic structure of a species reflects both historical demography and patterns of contemporary gene flow among populations [1]
A 658 bp sequence of the mt COI gene fragment was determined for 602 individuals of 29 T. clavigera populations sampled across the NW Pacific Ocean (Table 1; Fig 1)
The COI data in NW Pacific T. clavigera populations showed a high level of genetic diversity; haplotype diversity (h) for all studied populations was 0.982, ranging from 0.944 to 1.000

Summary

Introduction

The present-day genetic structure of a species reflects both historical demography (i.e., population history) and patterns of contemporary gene flow among populations [1]. Historical demographic events might have a large influence on the genetic structure if a species has not yet reached mutation-drift equilibrium owing to insufficient evolutionary time since a population expansion, which is often the case for marine organisms [2]. Marine organisms in the NW Pacific became extinct or survive only in glacial refuges [6]; rising sea levels in the interglacial period resulted in reconnection of these three marginal seas and range extension in marine organisms. Historical glaciation is one of the important factors that shaped present-day phylogeographical patterns of marine species. Compared with records of historical population fragmentation, information on how oceanographic factors influence the genetic structure and distribution of natural populations remains scarce in this region

Methods

Results

Discussion

Conclusion