中文摘要：

测定了采自中国胶州湾赤潮异弯藻x2藻株18srDNAITS区基因序列，结合GenBank下载的37条同源序列，分析序列特征并构建分子系统树。发现534bp序列中有可变位。16＋、简约信息位点1个，可变位点和简约信息位点分别占全序列的3．0％和0．19％，序列间相似性为97％，A＋T含量（47．8％）略小于C＋G含量（52．2％）。在分子系统树上，全部序列聚类在一起，遗传距离在O．0000～0．0242之间．说明全部赤潮异弯藻遗传多样性极低。赤潮异弯藻的生长和繁殖受到外界环境因子的较大制约，而人为因素如船只压舱水等则是其传播的主要途径。

英文摘要：

Sequences of 18s rDNA ITS region in the StrainX2 of Heterosigma akashiwo collected from Jiaozhou bay of China was determined. Combined with 37 homologous sequences downloaded from GenBank, the aligned ITS sequences of H.akashiwo were 534 bp, of which 16 sites were variable, and 1 site were parsimony-informative. Similarity between sequences was 97%. The contents of A＋T （47.8%） were less than those of G＋C （52.2%）. In the phylogenetic tree, all the algae strains were clustered ,and genetic distances among genus were between 0.0000-0.0242. Genetic diversity was very low for all the H.akashiwo. The growth and reproduction of H.akashlwo was restricted by many environment factors and antbropogenic reasons, such as ships＂ ballast water had been the main way of its transmission.