中国东南沿海四株亚历山大藻的系统发育研究

通过核糖体基因大亚基(LSU rDNA)D1-D2区以及ITS序列分析,研究了采自于中国东南沿海的4株亚历山大藻(Alexandrium Halim)的系统发育.结果显示,本地的亚历山大藻与来自日本和韩国的藻株亲缘关系很近;而且通过构建系统发育树,发现本地亚历山大藻与东亚藻株聚成一个大族.与东亚藻株在rDNA序列上的高相似性也说明本地株亚历山大藻属于温带亚洲基因型,而从欧美传入的机会较小.结果同时显示,塔玛亚历山大藻(A. tamarense)与链状亚历山大藻(A. catenella)LUS和ITS序列相近,可能在遗传学上是同一种类.

Phylogenetic relationship of four Alexandrium tamaranse/catenella isolates from Southeast Chinese costal waters using rDNA sequences

The occurrence of harmful algal blooms (HABs) has increased in the worldwide sea areas and poses a great threat to human health, fishery resources and marine ecosystems. Alexandrium is a major HABs genus of dinoflagellates. However, morphological differences among species of Alexandrium are very subtle under the microscopic observation. In this study, phylogenetic relationship of four Alexandrium strains collected from Southeast China were explored using D1-D2 regions of large subunit (LSU) and ITS-5.8S (internal transcribed spacer) rDNA sequences. Both the LSU and ITS rDNA sequences show that the local Alexandrium strains are closely related to each other and to the strains from Japan and Korea. Maximum likelihood phylogenetic analysis of D1-D2 regions of LSU and ITS-5.8S rDNA sequences established the four strains in a high bootstrap support clade with A. catanella/tamarense strains from East Asia. The homogeneity of rDNA sequences of the Chinese strains and East Asia strains indicates their close genetic relationship with the temperate Asian ribotype, implying that the Chinese A. catanella/tamarense complex is unlikely to have been introduced from Europe or the other sea areas other than Asia through ballast water or other vectors. Similarities in LSU and ITS-5.8S sequences indicate that A. catenella and A. tamarense are conspecifics rather than interspecifics.