基于16S rRNA序列初步探讨贻贝属的系统发育

Molecular phylogenetics of genus Mytilus based on the 16S rRNA sequences

通过比较贻贝属5个物种包括中国的两种贻贝的线粒体16S rRNA基因部分序列,来初步确定它们的系统发育关系和了解中国沿海两种贻贝的遗传多样性情况。以Pernaviridis为外群,采用NJ法和MP法构建分子系统树。系统发育分析表明,5种贻贝(Mytilus californianus,M.corcuscus,M.galloprovincialis,M.edulis,M.trossulus)在系统树上依次进行分叉,呈放射状。M.californianus最为原始,M.corcuscus次之。每一个贻贝物种都形成单系。其中,M.edulis和M.trossulus是非常相似的,M.corcuscus和M.cali-fornianus的亲缘关系近。同时发现,我国沿海分布的紫贻贝(M.galloprovincialis)和厚壳贻贝(M.corcus-cus)的遗传多样性都较高,但厚壳贻贝的遗传多样性要低于紫贻贝,可能是由于厚壳贻贝过度被渔民开采等导致厚壳贻贝群体大小降低的缘故。这里系统发育分析为将来进行物种进化、迁移和育种方面的比较研究提供理论基础。

In this paper we compared the partial sequences of the mitochondrial 16S ribosomal RNA of the five species of genus Mytilus including two species in China to primarily determine their phylogenetie relationships and estimate the genetic diversity of two species of Mytilus along the coast of China. The phylogenetic trees were reconstructed based on neighbor-joining and maximum parsimony methods. Perna viridis was used as an outgroup. The phylogenetic analysis revealed that five species of mussel Mytilus, M. californianus, M. corcuscus, M. galloprovincialis, M. edulis, M. trossulus, diverged in the basal polytomy at the base of the Mytilus radiation. M. californianus is the most basal among all species of genus M. ytilus, and the secondary is M. coruscus. The individuals of the each of five species solely cluster a monophyletic clade, respectively. M. edulis and M. trossuZus are the most similar to the three closely related species. M. corcuscus is a closer relative of M. californianus than of M. edulis, M. galloprovincialis, M. trossulus. And we found that while the genetic diversity of both M. corcuscus and M. galloprovincialis distributed along the coast of China was higher, the genetic diversity of M. corcuscus was lower than that of M. galloprovincialis, this may be caused by declined population size due to overexploitation and human activity. This molecular phylogeny provides the theoretic foundation for future comparative studies of species evolution, immigration and breeding strategies.