基于3种线粒体基因的珠母贝属系统进化关系

摘要

为了研究珠母贝属的分类地位和系统演化情况,通过聚合酶链式反应技术(PCR)扩增并直接测序出雷州半岛珠母贝属中的马氏珠母贝、大珠母贝、珠母贝、斑珠母贝和黑珠母贝的3种线粒体基因(12S rRNA、16S rRNA和COⅠ)部分序列,分析其碱基组成和种间遗传距离.同时结合GenBank上发表的白珠母贝序列,构建珠母贝属的分子系统树.结果显示,5种珍珠贝的3种基因部分序列碱基AT含量大于GC含量,与其他无脊椎动物线粒体DNA序列基本一致,序列都处于高度饱和的状态.系统分析显示,构建的分子系统树与传统的形态分类基本一致.在黑珠母贝和白珠母贝亲缘关系上,3种线粒体DNA片段在碱基组成、种间遗传距离和系统进化树上都显示黑珠母贝和白珠母贝非常相近,可以认为是同一种中的2个亚种.在斑珠母贝的亲缘关系上,系统分析显示斑珠母贝与黑珠母贝和白珠母贝更为接近.研究表明,大珠母贝和珠母贝在系统进化中较早的分离出来,是一个比较原始的种类.3种分子标记对马氏珠母贝亲缘关系分析上存在一定差异,根据现有的数据尚不足以得出结论,需进一步做分子系统研究并结合形态特征和解剖结构进行分析.%In oder to reconstruct the molecular phylogeny of Pinctada,partial sequences of 3 mtDNA fragments (12S rRNA,16S rRNA,COⅠ)from 5 species of Pinctada(P.martensii,P.maxima,P.margaritifera,P.maculata, P.nigra)were amplified by polymerase chain reaction(PCR)and directly sequenced,and the samples were collec-ted from Leizhou Peninsula. Base ratio and genetic distances were analyzed. At the same time, these sequences were compared with the published sequence of P.albina.Results showed that A+T contents of 3 mtDNA frag-ments from 5 species were higher than G+C obviously, in accordance with the other invertebrate mtDNA se-quences. Data showed that the sequences of 3 mtDNA fragments had a high degree of saturation. Analysis showed that the molecular phylogenetic trees were basically constructed and well supported the traditional morphological taxonomy.In the relations of P.nigra and P.albina,3 mtDNA fragments were very similar in nucleotide composi-tion,genetic variability,genetic distance and molecular phylogenetic trees.So this suggests that P.nigra and P.al-bina represented two subspecies in the same species.About the taxonomy of P.maculata,the molecular phylogen-etic trees showed that P.maculata was close to P.nigra and P.albina.Moreover,it revealed P.margaritifera and P.maxima were more primitive than the others.There was a little difference on the genetic relationship analysis about P.martensii by 3 mtDNA fragments,and no conclusion could be drawn from the existing data.It is neces-sary to do more study of molecular systems and morphological and anatomical structure.