Genetic diversity and large-scale connectivity of the scleractinian coral Porites lutea in the South China Sea

Abstract

In light of recent declines in scleractinian communities worldwide, research on the genetic structure of and connectivity among coral populations has assumed importance. However, the genetic structure of corals in the South China Sea (SCS) has remained largely neglected by studies. The genetic structure of the broadcast spawning coral Porites lutea was examined using 482 specimens from 20 sites in the SCS spanning 13° of latitude. Analyses of two nuclear markers congruently revealed that genetic diversity was high in most populations, with relatively lower diversity in Daya Bay (DY). However, we identified a recent bottleneck in P. lutea populations, which may be in accordance with recent coral community declines. Pairwise FST values and principal coordinates analyses indicated large-scale (~ 1500 km) genetic homogeneity among SCS P. lutea populations, possibly attributed to their reproductive strategy (spawning vs. brooding) and historical changes in population sizes. However, populations in DY were highly differentiated from the others, which may reflect the genetic-level adaptation of corals there to lower winter temperatures. Coalescent migration analyses of ITS rDNA markers revealed high levels of gene flow (Nm > 100) among all adjacent populations except between DY and Taiwan. Additionally, universally asymmetrical northward gene flow was identified, possibly reflecting the northward migration of the species in response to global warming. We concluded that populations of P. lutea in the SCS comprise one large panmictic meta-population. However, the lower-diversity, more differentiated northern marginal populations in DY are probably more vulnerable than others to the adverse effects of anthropogenic activities.