Strong genetic differentiation of the clam Meretrix lamarckii in the China Sea revealed by mitochondrial DNA marker.

The hard clam Meretrix lamarckii is ecologically and economically important in the coastal regions of China. In this study, we evaluated the genetic diversity and population structure of six M. lamarckii populations in the East China Sea and the South China Sea using mitochondrial cytochrome c oxidase subunit 1 (COI) and cytochrome b (Cytb) genes. We obtained 582 bp of partly sequences comprising 28 novel haplotypes of COI gene from 138 specimens and 1168 bp of partly sequences comprising 22 novel haplotypes of Cytb gene from 125 specimens. The haplotype diversity of COI and Cytb genes ranged from 0.606 to 0.862 and 0.562 to 0.863, respectively. The nucleotide diversity ranged from 0.0015 to 0.0038 in COI gene and ranged from 0.0007 to 0.0032 in Cytb gene. Thus, there is moderate-level genetic diversity in M. lamarckii in the China Sea. The F-statistics showed that the Zhoushan (ZS) and Xiangshan (XS) populations were significantly (P < 0.01) differed from the populations of Wenzhou (WZ), Zhangpu (ZP), Shantou (ST), and Zhanjiang (ZJ) in both COI and Cytb genes. Both haplotypes network and plot of STRUCTURE analysis suggested obviously genetic divergence between East China Sea and South China Sea regions. Knowledge on genetic variation and population structure of M. lamarckii populations along the Southeast China Sea obtained from this study will support the aquaculture management and conservation of M. lamarckii in China.