적조 원인 종 PROROCENTRUM MICANS 와 AKASHIWO SANGUINEA 의 분류와 집단 유전학적 연구

Abstract

For study for the morphological and genetic diversity due to geographical difference and its distribution at different spatial and temporal scales of two HAB species, Prorocentrum micans and Akashiwo sanguinea, each of 106 and 253 strains, isolated in 11 different localities in Korean and Japanese coasts from December 2006 to March 2009. These species were characterized with the use of light and scanning electron microscopy on morphology, and sequencing of the ITS and LSU rDNA on genetic diversity. Among the strains of Prorocentrum micans, no variation according to the geographical differences based on morphology and genetic analysis. Of the study on P. micans, its cryptic species, Prorocentrum cf. micans was reported which was confirmed from morphological evidence and rDNA sequence data with phylogenetic analysis. In P. cf. micans, the overall cell shape, color of chloroplast, morphology of trichocyst pores and dimensions of poroids are distinct from P. micans. ITS/5.8S rDNA sequence divergence was 9.2~9.9 % between two species. Furthermore, a phylogeny based on LSU rDNA including four strains of P. micans and three strains of P. cf. micans was branched with high support in a Prorocentrum clade, and separated each other species. In Akashiwo sanguinea, Although all of the A. sanguinea strains were morphologically identical, a new diacritical feature of an intersulcal tubular structure (STS) was verified in the sulcal area that is similar to, but distinguishable from, the intercingular structure in the other gymnodiniales species. Moreover, the presence of collared pits in the cingular region of dinoflagellates was recorded for the first time using SEM. Approximately 4000bp of ITS/5.8S and LSU rDNA were evaluated for geographical distribution among strains. This species was monophyletic in LSU rDNA phylogeny. Moreover, two rDNAs tested showed no sequence divergence among the strains. To determine the process of population expansion for these two species, firstly, I isolated eight polymorphic microsatellites from Prorocentrum micans using dual suppression PCR method. Also, 13 polymorphic microsatellites markers were isolated from Akashiwo sanguinea by compound SSR PCR method. For analysis of population structure, I isolated 106 strains of P. micans and 253 strains of A. sanguinea in Korean and Japanese coastal waters. In P. micans, analyses by nonmetric multidimensional scaling plots of pairwise FST, global AMOVA, and genetic admixture analysis identified two clusters - the western Korea (Incheon, Taean), north Japan (Okhotsk Sea) populations, and other the southern Korea (Masan) populations - indicating genetic structuring of the four samples into two distinct populations. No significant relationship of isolation-by-distance patterns and almost no genetic distance were detected although there is a maximal distance of > 1000 km between samples. This results clearly showing that a large-scale transfer from west to east has occurred via the Tushima Warm Current. On the other hand, the southern Korea population was distinguished with the western Korea population, which means fundamentally may have established own population by the restricted gene flow. A. sanguinea populations was analyzed also two cluster? the Korea, Hiroshima, Ariake, Ofuna populations, and other the Pacific Ocean (Inokushi, Kouchi, Hukura) populations. The Pacific Ocean populations are flow the Kuroshio Current, which may occur gene flow between the populations. Even if statistical test is difficult to support the possibility of gene flow across the populations, assignment test and UPGMA dendrogram showed dividing pattern of A. sanguinea population. However, further study is need in western, southern Korea coastal population and Southeast Asian populations for reveal the genetic structure in Kuroshio Current.