Abstract
Recently, reef-building coral populations have been decreasing worldwide due to various disturbances. Population genetic studies are helpful for estimating the genetic connectivity among populations of marine sessile organisms with metapopulation structures such as corals. Moreover, the relationship between latitude and genetic diversity is informative when evaluating the fragility of populations. In this study, using highly variable markers, we examined the population genetics of the broadcast-spawning coral Acropora digitifera at 19 sites in seven regions along the 1,000 km long island chain of Nansei Islands, Japan. This area includes both subtropical and temperate habitats. Thus, the coral populations around the Nansei Islands in Japan are northern peripheral populations that would be subjected to environmental stresses different from those in tropical areas. The existence of high genetic connectivity across this large geographic area was suggested for all sites (F ST≤0.033) although small but significant genetic differentiation was detected among populations in geographically close sites and regions. In addition, A. digitifera appears to be distributed throughout the Nansei Islands without losing genetic diversity. Therefore, A. digitifera populations in the Nansei Islands may be able to recover relatively rapidly even when high disturbances of coral communities occur locally if populations on other reefs are properly maintained.
Highlights
Coral reefs support the highest biological diversity of all marine ecosystems
Private alleles (PVA) were found at some sites: in particular, two private alleles were detected at the SNS site in the Kerama region and three were at the KRS site in the Sekisei Reef region (Table 1)
Our result is in contrast with some previous studies that showed the existence of strong genetic subdivision in some spawning corals
Summary
Coral reefs support the highest biological diversity of all marine ecosystems. Reef-building corals play an important role in structuring and maintaining coral reef ecosystems and in forming the framework of coral reefs. The larval period plays an important role in the maintenance and habitat extension of coral populations. For more detailed examinations on the genetic connectivity of corals, analyses over ecological timescales using highly variable markers (e.g., microsatellites) are required. Microsatellite markers have been developed for some corals (e.g., [16,17,18]) and have been used to investigate connectivity patterns between populations. Some such studies have shown that genetic differentiation was caused by oceanographic barriers (e.g., [19]). Using highly variable markers such as microsatellites would improve the management potential for target species [21]
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