6种帘蛤科贝类及4个地理种群文蛤线粒体COI基因片段序列分析

对文蛤(Meretrix meretrix L.,1758)、青蛤(Cyclina sinensis G.,1791)、硬壳蛤(Mercenaria mercenaria L.,1758)、江户布目蛤(Protothaca jedoensis L.,1874)、薄片镜蛤(Dosinia corrugata R.,1850)和菲律宾蛤仔(Ruditapes philippinarum A.,1850)6种帘蛤科贝类和4个地理种群文蛤(大连、连云港、湛江、防城港)的细胞色素c氧化酶亚基I(COI)基因片段的核苷酸序列进行了分析,以探讨这一序列在种质鉴定、种群遗传结构和分子系统发生研究中的应用价值.测序结果表明,所有物种扩增片段长度均为709 bp,序列A+T含量(62.2%~67.6%)明显高于GC含量.物种间共有变异位点311个,其中简约信息位点202个;文蛤4个地理种群间共有变异位点46个,其中简约信息位点2个.此区段共编码235个氨基酸,种间共有氨基酸变异位点85个;文蛤种群间只有1个氨基酸变异位点.以COI基因片段序列为标记,用大竹蛏(Solen grandis)作外群,构建了帘蛤科贝类的系统发生树,其拓扑结构显示4个地理种群文蛤首先聚为1个单元,然后与青蛤聚在一起,最后所有帘蛤科物种聚为一枝,与外群相区别,其结果与传统形态分类基本一致,说明COI基因适合作为该科贝类种群遗传结构和系统发生研究的分子标记.

Sequence analysis of mitochondrial COI gene fragment of six Veneridae clams(Mollusca:Bivalvia) and four populations of Meretrix meretrix

A nucleotide sequence analysis of mitochondrial cytochrome c oxidase subunit I(COI) gene fragment was conducted among six family Veneridae clams,Meretrix meretrix L.,1758,Cyclina sinensis G.,1791,Mercenaria mercenaria L.,1758,Protothaca jedoensis L.,1874,Dosinia corrugata R.,1850,Ruditapes philippinarum A.,1850 and four populations of M. meretrix to determine the utility of this regions in identifying phylogeographic and phylogenetic structure.Nucleotide sequences of 709 bp in length were obtained from the mitochondrial DNA cytochrome c oxidase subunit I(COI) gene for 18 Veneridae specimens representing six species and four geographical populations of M.meretrix,with A T contents from 62.2% to 67.6%,which higher than G C contents obviously.Analysis of sequence variation at the COI gene across six species revealed 311 variable sites,which 202 were parsim-informative sites.Translation of codons into amino acids indicated 85 varable sites.Analysis of sequence variation across four M.meretrix populations revealed 46 variable sites,which only two were parsim-informative sites.Translation of codons into amino acids indicated only one variable site.The phylogenetic tree of Veneridae clams was reconstructed by using COI gene sequences as marker,and with Solen grandis as outgroups.Tree topologies indicated that four M.meretrix populations formed a monophyletic group with its sister taxon C.sinensis,all Veneridae species form a clade,which was consistent with the tree based on morphological characters.This result reveals that the COI gene was an appropriate marker for studies of phylogeny and phylogeography of the Veneridae clams.