Studies On Genetic Diversity And Molecular Phylogeny In Alexandrium Tamarense

Alexandrium tamarense is a wide-spread species of dinoflagellate causing harmful algal blooms (HABs) and paralytic shellfish poisoning (PSP) around the world. In recent years, many molecular markers have been used to study the phylogeny and the human-assisted dispersals of A. tamarense species complex(A. tamarense, A. catenella and A. fundyense). In this study, we analyse the genetic diversity of A. tamarense with different geographical distributions, including 5 European and 6 Chinese strains using rDNA and microsatellite markers. Results from 5.8S rDNA, internal transcribed spacers (ITS) and large subunit (LSU) rDNA in 11 strains A. tamarense show that:(1) CCMP116 is more close to A. affine than A. tamarense, which should be accredited to A. affine; (2) the genetic diversity of 10 strains of A. tamarense is low. According to the 5.8S rDNA and LSU rDNA, the average genetic distances of the ten strains of A. tamarense are 0.1415 and 0.0659, repectively; (3) A. tamarense in the world can be divided into at least three lineages: Western Europe, Temperate Asia, Tropical Asia; the Chinese strains belong to the type of Tropical Asia. Microsatellite analysis reveal that:(1) the effective number of alleles are 1 to 5.3333 and the gene diversity of the ten strains of A. tamarense is 0.5125;(2) the ten strains of A. tamarense can be divided into four lineages with genetic differentiation of 0.6065, which relate to their geographic origins;(3) high genetic differentiation among the four populations from different geographic suggest the lack of gene flow. In conclusion, microsatellite markers are more sensitive and accurate for analyzing the intraspecific diversity of A. tamarense than the ribosomal operon; the A. tamarense from Chinese coastal water can be divided into three lineages. However, further studies on the genetic diversity in A. tamarense from China should be addressed in the future.