Pronounced population genetic differentiation in the rock bream Oplegnathus fasciatus inferred from mitochondrial DNA sequences

The population genetic structure of the rock bream (Oplegnathus fasciatus) along the coastal waters of China was estimated based on three mtDNA fragments (D-loop, COI, and Cytb). A total of 112 polymorphic sites were checked, which defined 63 haplotypes. A pattern with high levels of haplotype diversity (h(COI) = 0.886 +/- 0.034, h(Cytb) = 0.874 +/- 0.023) and low levels of nucleotide diversity (pi(COI) = 0.009 +/- 0.005, pi(Cytb) = 0.006 +/- 0.003) was detected based on the COI and Cytb fragments, and high levels of genetic diversity (h(D-loop) = 0.995 +/- 0.007, pi(D-loop) = 0.021 +/- 0.011) were detected from the mtDNA D-loop. The population genetic diversity of O. fasciatus in south China was significantly higher than those of north China. Three genealogical clades were checked in the O. fasciatus populations based on the NJ and MST analyses of mtDNA COI gene sequence, and the genetic distances among the clades ranged from 0.018 to 0.025. Significant population genetic differentiation was also checked based on the Fst (0.331, p = 0.000) and exact p (0.000) test analyses. No significant population differentiations were checked based on mtDNA D-loop and Cytb fragments. Using a variety of phylogenetic methods, coalescent reasoning, and molecular dating interpreted in conjunction with paleoclimatic and physiographic evidences, we inferred that the genetic make-up of extant populations of O. fasciatus was shaped by Pleistocene environmental impacts on the historical demography of this species. Coalescent analyses (neutrality tests, mismatch distribution analysis, and Bayesian skyline analyses) showed that the species along coastline of China has experienced population expansions originated in its most recent history at about 169-175 kya before present.