Study Of Genetic Diversity In Pen Shell (Atrina Pectinata) And Ark Shell (Scapharca Broughtonii)

Atrina pectinata is a large marine mollusc widely distributed in the coast of China waters. It is known well by the big and delicious posterior adductor muscle with high economical values. Scapharca broughtonii, a cold-temperate mollusc with its delicacy and high economic value, is a kind of famous aquatic production for export. However, the wild stocks of A. pectinata and S. broughtonii have been declining dramatically in these years due to over-exploitation and the deterioration of environmental conditions in China. Given their important economic value and descending tendency, the knowledge on population genetic structure and genetic diversity of the populations is of significant in developing effective strategy for fishery propagation and management.In this paper, two mitochondrial genes (Cyt b and 16S rRNA) are used to investigate the genetic variation, population genetic structure and phylogeny of A. pectinata along the coast of China. In total, 135 samples are sampled from six populations (Rizhao (RZ), Weihai (WH), Lianyungang (LYG), Xiamen (XM), Beihai (BH), Haikou (HK)), and 62 and 34 haplotypes are detected based on 346bp segment of Cyt b and 392bp segment of 16S rRNA, respectively. Moderately high haplotype diversity (Hd= 0.918±0.020 for Cyt b; Hd= 0.880±0.017 for 16S rRNA) and relatively low nucleotide diversity (π= 0.069±0.0097 for Cyt b;π= 0.0636±0.0039 for 16S rRNA) are detected among the six populations. Neither the neighbor-joining tree nor minimum spanning network based on the haplotype data exhibit clear geographical patterns of the six populations. Analyses of molecular variance and Fst statistics reveal significant genetic differentiation between XM and the other populations, especially based on Cyt b gene. Fst statistics also show that the RZ, WH and LYG populations could be considered as a Northern group. The neutrality test and mismatch distribution analysis indicate that sudden population expansion might have occurred in XM population and the Northern group, and the approximate expansion time would be 0.278 mya and 0.401 mya, respectively.Mitochondrial COI gene and ribosomal ITS-1 gene are used to study the genetic variance and population genetic structure of wild S. broughtonii from Rongcheng (RC) and Jimo (JM), and Jimo's artificially propagated progenies (JZ). The feasibility of sowing the Jimo progenies to Rongcheng water for the enhancement of S. broughtonii is discussed. Analyses of molecular variance and Fst statistics reveal that moderately genetic differentiation exists among the populations. The Jimo's artificially propagated progenies have lower genetic diversity than the wild populations. And the genetic divergence between Rongcheng and Jimo's progenies populations is larger than the divergence between wild populations of Rongcheng and Jimo. The population genetic structure of S. broughtonii in Rongcheng will be seriously affected, if the Jimo's artificially propagated progenies are sowed into Rongcheng water. Thus, sowing the Jimo progenies to Rongcheng water for the enhancement of S. broughtonii needs to be carried out very cautiously, and the parental population size should be as large as possible.