Joint study on the biogeography around the Tsushima Current Regions

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Numerical model used for understanding the origin of the Tsushima current suggests that the currents is basically driven by geostrophic adjustment under the barotropic study. The water mass distribution around Cheju Island is as follows ; In winter Yellow Sea Warm Water flows into the Yellow Sea through the southern sea of Sohuksando, and Yellow Sea Cold Water flows southward through Taehuksando are between Sohuksando and the Korean Peninsula, otherwise in summer Yellow Sea Bottom Cold Water flow southward to the southern sea of Sohukusando and Yellow Sea Warm Water flows into the Yellow Sea through Taehukusando.77 pelagic copepods were found around the coast of Cheju Island, and 7 species of them which have been also observed in Kuroshio are predominant. Paracalanus indicus shows three peaks in abundance in early spring, early summer and early winter, Calanus sinicus, Acartia steuteri, Corycaeus affinis and Oncaea plumifera did two peaks in summer and winter, and A.omorii had a single … More peak in autumn.Modern dinoflagellate cysts in surface sediments of Aso Bay of Tsushima Island and southern coast of the Korean Peninsula consists of more than 25 species of gymnodinioid, gonyaulacoid, tuberculodinioid and peridinioid groups, and also the strongly positive relation was observed between their alpha diversities and surface water temperatures.Boring core sediments were collected from two points in Cheju island ; Mt.Tong Su Ak and west of Sogwipo. The former sediments contained Kikai-Akahoya volcanic ash layr near the base, and the latter probably record the palaeoenvironmental change since the last glacial time.According to palynological analysis for sediments collected from the Danjo Basin, the Japanese laurel forest was distributed along the coastal area of South Kyushu in the last maximum glacial time.One-hundred and twenty-nine species of laurel-leaved trees and shrubs were found in the Tsushima Current regions ; of which 53 species were restricted to Japanese islands and only 4 to Korean satellites. In studies of rock outcrop vegetation, Rhododendron yedoense var. poukhanense is distributed on those habitat of rocky ridges and gorge wall. A new plant association, Adino-Rhododendretum poukhanense, we first described from Cheju Island. Another out crop plant, Carypters incana, was found on such habitat with thin vegetation cover.A result of starch gel electtrophorensis for an amphidromous fish, Plecogloss altivelis collected from Korean Peninsula, Cheju, Goto, Tsushima, Oki and Kagoshima suggests that these population do not show any significant difference in gene frequency except for the populations of Fukue and Oki which probably established by the artificial founder effect.There are no significant differences in gene composition of Phxinus oxcephalus jouyi collected in Nagasaki, Coto, Tsushima and southeastern part of the Korean Peninsula, and this suggests that these populations are still uniform. However, the populations in Shimo-Tsushima and Nakadouri-jima have a distinct gene composition probably given by a genetic random drift.Phylogenetical investigation on native horses in Tsushima and Cheju by using electrophoresis for protein in blood and mitcondrian DNA-analysis revealed that these horses have closely relationship in phylogeney and also suggested that their ancestor may be Equus przewalskii, a native horse in Mongolia.Acrida lata, Atractomorpha bedeli and Gonista bicor populations in the Korean Peninsula, Cheju, Tsushima, Iki, Goto and Kyushu possessed supernumerary chromosomes (B-chromosomes), and A.bedeli populations in the Korean Peninsula and Kyushu showed a chromosomal polymorphism for a supernumerary segment. These facts support that Kyushu was connected with the Korean Peninsula before the last glacial age.A karyomorph analysis for Crocothemis cervilia suggests that a type of 2n*=24 (n=12) is endemic only for the population of the Japanese Island, and its boundaries are located between Amami Island and Yaku Island in the north-to-south, and between Tsushima and the Korean Peninsula in the east-to-west. Less