中文摘要：

运用PCR直接测序法,对采自爱尔兰、日本、韩国和中国的大叶藻、矮大叶藻、丛生大叶藻和红须根虾形藻及GenBank中的宽叶大叶藻5种大叶藻叶绿体的matK、rbcL和核糖体ITS的部分序列进行测定,并比较分析了5种大叶藻3个目的片段的核苷酸序列,结果发现胞嘧啶（C）在3个目的片段上的含量均较低。ITS片段检测到172处核苷酸替换,表现出丰富的遗传多态性。matK基因片段上有52处核苷酸替换,rbcL基因片段上有20处核苷酸替换,且大部分替换来自于第三密码子的同义替换,种间在氨基酸水平上产生了一定的分化。基于ITS、matK和rbcL 3个目的片段,利用邻接法、最大简约法、最大似然法和贝叶斯法构建的系统发育树结果基本一致,明显分为3大支。矮大叶藻与大叶藻属间3种大叶藻的核苷酸最小差异值为19.33%,在分子数据上达到了属的水平。基于matK和rbcL基因片段拼接序列的分析结果表明：大叶藻与丛生大叶藻的分化时间在上新世（2～2.7百万年前）,与宽叶大叶藻的分化时间在上新世（4～5.3百万年）,与矮大叶藻的分化时间在渐新世（27～36百万年前）,与红须根虾形藻的分化时间在始新世（33～44百万年前）。4个地区大叶藻的ITS片段序列完全相同,结果表明大叶藻ITS区的变异程度与地理距离不相关,其不适用于大叶藻不同地理株间的分子系统演化。该研究进一步阐述了5种大叶藻的系统发育关系,同时也为国内海草的分子系统发育研究提供重要参考。

英文摘要：

Fragments of the nuclear ribosome（ITS）and the chloroplast（matK and rbcL）regions were successfully suitable for phylogenetic relationship analysis.With sequencing by PCR amplification,the paper analyzed the phylogenetic relationship of 5 Zosteraceae species（Zostera marina,Z.japonica,Z.caespitosa,Z.asiatica and Phyllospadix iwatensis）,which were collected from Ireland,Japan,Korea,China and GenBank.Partial nucleotide sequences of matK,rbcL gene and ITS were analyzed for five Zosteraceae species,and nucleotide composition analysis indicated a strong bias against cytimidine（C）in three fragments.172 nucleotide substitutions were found in ITS fragment,showing the high genetic polymorphism.52 nucleotide substitutions were checked in matK gene and 20 nucleotide substitutions were checked in rbcL gene,most of them were synonymous transitions at the third codon positions.The five species had a certain degree of differentiation at the amino acid level.Based on partial sequences of matK,rbcL and ITS gene,phylogenetic trees were constructed by NJ,MP,ML and Bayes methods and the results were consistent and the phylogenetic trees showed three separate lineages.The minimum pairwise divergences percentage in the samples of Z.japonica and other Zostera species was 19.33% and much higher than the standard（9.60%-28.80%）among genera of most angiosperm and it would be the generic rank from the molecular data.Based on the synonymous nucleotide substitution rate of the rice chloroplast genome matK combined with rbcL gene,we estimated the divergence time between 5 Zosteraceae species approximately arranged from Eocene to Pliocene.The ITS sequences of all Z.marina samples were identical,which fell into the same cluster.It was concluded that variation within ITS region of Z.marina was not correlated to their geographical distance,and ITS region was unsuitable for identification of population groups on a regional or oceanic scale.The paper further elaborated phylogenetic relationship of 5 Zosteraceae species,and also prov