【摘要】 为探讨双壳贝类主要类群间的系统发生关系,测定了魁蚶中国群体的ND1、COX1和Cytb基因,从Gen Bank中检索下载了双壳纲65个种类的同源序列进行分析,并用邻接法和最大似然法构建系统发育树,研究双壳纲贝类线粒体基因变异规律及其分子系统进化关系.结果显示双壳贝类的ND1、COX1和Cytb序列有插入/缺失序列,存在明显的长度多态性,A+T含量均明显高于G+C含量,具有明显的AT偏好.目内科间遗传距离为0.169~0.468,目间遗传距离在0.323~2.557之间.NJ树和ML树显示所有双壳纲的种类构成了单系发生的进化枝,不同基因构建的进化树中翼形亚纲的系统发生关系不一致,异齿亚纲是单系发生,帘蛤目和海螂目的种类没能完全聚到所属支系,彼此嵌套,缝栖蛤科的种类从海螂目中分离出来.蛏螂目位于进化树的基部,古异齿亚纲和古列齿亚纲聚为一支,二者可能具有较近的亲缘关系.更多还原

【Abstract】 In order to investigate the phylogenetic relationships among main groups of bivalve molluscs,mitochondrial genomic ND1,COX1 and Cytb sequences of the Chinese population of Scapharca broughtonii were determined by PCR amplification and sequencing. The homologous sequences of 56 species,which belong to 11 orders and 20 families,were selected from Genbank,and the phylogenetic tree was constructed by Neighbor-Joining( NJ) method and maximum likelihood( ML) method. The mitochondrial gene variation and the evolutionary relationship of the molecular system were studied. The results showed that many indels( insertions/deletions) of the ND1,COX1 and Cytb sequences of bivalve molluscs were observed,so there is polymorphism in sequence length of these sequences. The A+T content was significantly higher than that of G+C,indicating an obvious AT preference. Genetic distances among families and orders were from 0.169 to 0.468 and 0. 323 to 2.557,respectively. NJ and ML trees showed that all bivalve species formed a monophyletic branch. The phylogenetic relationship of Pteriomorphia was different in the phylogenetic tree constructed by different genes. The Heterodonta was clustered as a monophyletic glade,and species of Veneroida and Myoida were not completely gathered to their branches,but nested with each other. Species of the family Hiatellidae were separated from the order Myoida. The Solemyoida( Cryptodonta) located at the base of the phylogenetic tree,and the Palaeotaxodonta and Palaeoheterodonta were clustered together,implying that they may have a close genetic relationship.更多还原