Distribution and genetic diversity of the toxic benthic dinoflagellate genus Ostreopsis in Korea.

Species belonging to the toxic dinoflagellate genus Ostreopsis are widespread, occurring from tropical to temperate waters. As mainly benthic/epiphytic species, they would be expected to show distinct geographical patterns. In this study, ribosomal DNA (rDNA) sequences from partial nuclear LSU D8-D10, 5.8S, and ITS regions were determined for 169 isolates of Ostreopsis species collected from three coastal sites (i.e., Jeju Island, Chuja Island, and Pohang) within Korea. The phylogenetic tree inferred from the LSU rDNA D8-D10 sequences showed that Korean Ostreopsis species corresponded to either Ostreopsis sp. 1 or sp. 6, with Ostreopsis sp. 1 being relatively predominant regarding their distribution. While Ostreopsis sp. 1 occurred throughout all the three sampling sites within Korea, Ostreopsis sp. 6 was confined to the northern part of Jeju Island. When further investigated, the genetic diversity of Ostreopsis sp. 1 in Korea based on ITS sequences showed a total of 21 haplotypes. The presumed ancestral haplotype H3, was also present in the Japanese and Russian populations of Ostreopsis sp. 1. Although the overall demographic history of all the Korean populations of Ostreopsis sp. 1 could not be clearly identified, probably due to a mixture of different regional demographic patterns within Korea, each Ostreopsis sp. 1 population showed a characteristic demographic pattern at a regional scale. While the Jeju Island Ostreopsis sp. 1 population showed a signal in agreement with population equilibrium, the Chuja Island and Pohang Ostreopsis sp. 1 populations showed distribution patterns that are expected in a sudden population expansion model. The results from this study provide a basis for a better understanding of the distribution and genetic structure of the Asian Ostreopsis sp. 1 populations.