Unexpectedly complex gradation of coral population structure in the Nansei Islands, Japan.

Yuna Zayasu,Go Suzuki,Noriyuki Satoh,Yuichi Nakajima,Chuya Shinzato,Kazuhiko Sakai

doi:10.1002/ece3.2296

Abstract

To establish effective locations and sizes of potential protected areas for reef ecosystems, detailed information about source and sink relationships between populations is critical, especially in archipelagic regions. Therefore, we assessed population structure and genetic diversity of Acropora tenuis, one of the dominant stony coral species in the Pacific, using 13 microsatellite markers to investigate 298 colonies from 15 locations across the Nansei Islands in southwestern Japan. Genetic diversity was not significant among sampling locations, even in possibly peripheral locations. In addition, our results showed that there are at least two populations of A. tenuis in the study area. The level of genetic differentiation between these populations was relatively low, but significant between many pairs of sampling locations. Directions of gene flow, which were estimated using a coalescence‐based approach, suggest that gene flow not only occurs from south to north, but also from north to south in various locations. Consequently, the Yaeyama Islands and the Amami Islands are potential northern and southern sources of corals. On the other hand, the Miyako Islands and west central Okinawa Island are potential sink populations. The Kerama Islands and the vicinity of Taketomi Island are potential contact points of genetic subdivision of coral populations in the Nansei Islands. We found that genetic population structure of A. tenuis in the Nansei Islands is more complex than previously thought. These cryptic populations are very important for preserving genetic diversity and should be maintained.

Highlights

Coral reefs are highly productive ecosystems that provide habitat for a great variety of marine organisms
Genotyping of 13 microsatellite loci from 298 colonies at 15 sampling locations, revealed 298 genotypes, strongly suggesting that there are no clonal colonies of A. tenuis in the Nansei, within the region surveyed
The genetic diversity parameters, allelic richness (Ar) and He, did not differ significantly among sampling locations (Kruskal–Wallis test; Ar, P = 0.9961; He, P = 0.9990; Appendix S3). We found that this species tends to be distributed along the northwestern coasts of islands, despite the fact that other Acropora species are normally distributed along southeastern coasts (Table 1, Fig. 2B)

Summary

Introduction

Coral reefs are highly productive ecosystems that provide habitat for a great variety of marine organisms. While transplantation of coral fragments has been one of the most frequently recommended approaches to enhance coral abundance on degraded reefs (Omori and Fujiwara 2004; Rinkevich 2008; Young et al 2012), there have been concerns about adverse effects of transplantation, as there have been in regard to tree transplantation (Keller et al 2000; Edmands and Timmerman 2003), an analogous situation These concerns include reduced genetic diversity, breakdown of local genetic structure, and genetic introgression (Omori and Fujiwara 2004; Baums 2008)

Methods

Results

Conclusion