中国沿海浒苔属rbcL和ITS序列比较及系统进化分析

Phylogenetic analysis of rbcL and ITS of Enteromorpha genus from Chinese coast

为阐明中国沿海浒苔的亲缘关系及地理分布特点,采集青岛栈桥、盐城弶港、宁波象山、温州平阳四地浒苔样本,克隆测序得到ITSl、5.8S rDNA和ITS2 3种不同长度序列片段.四个地区的rbcL目的片段,长度均为1 201bp.分析核苷酸差异和遗传距离,采用邻接法建立系统发生树.结果显示,ITS序列进化速率较快,rbcL序列相当保守.ITS区较短,GC含量均在65%以上,5.8S rDNA的CG含量在50%左右,ITS1区的序列差异大于ITS2区.四个地区的浒苔存在一定的地理差异,盐城和青岛的样本间的亲缘关系较近;宁波和温州的样本间的亲缘关系较近.石莼属（Ulva）和浒苔属（Enteromorpha）的物种没有聚成各自独立的分枝,而是相互混合在一起,应是两个亲缘关系相近的属.引起青岛绿潮的海藻很可能是来自盐城海域的Enteromorphalinza或Enteromorpha prolifera.

In the present study, genetic relationship and geographic distribution of Enteromorpha genus in China coast were clarified. The samples were collected from Zhanqiao of Qingdao, Qianggang of Yancheng, Xiangshan of Ningbo and Pingyang of Wenzhou. The fragments of ITS 1, 5.8S rDNA and ITS2 were amplified, cloned and sequenced. The length of genetic fragments of rbcL from these four regions were all 1201bp. The nucleotide diversity and genetic distance were analyzed, and phylogenetic trees were constructed with neighbor-joining method. The results showed that the rate of evolution of ITS was the fastest, while rbcL was quite conservative. The region of ITS was short, with the content of GC up to over 65%, however the content of GC in 5.8S rDNA was 50%. ITS1 was more diverse than ITS2. There were geographic variations among the samples from the four sites. Genetic relationship between samples from Qingdao and Yancheng was closer, and so was that between samples from Xiangshan and Wenzhou. Ulva and Enteromorpha did not separate into an independent branch respectively, but they clustered together. So it can be concluded that genetic relationship between Ulva and Enteromorpha is close. Either Enteromorpha linza or Enteromorpha prollfera from Yaneheng may caused the green tide in Qingdao.