Systematic study on the process of diversity and distribution of higher plants in the Northern Hemisphere with special reference to the Sino-Japanese region in eastern Asia

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We investigated phylogeography on the genus of Hydrangea, Coptis, Pieris, Cymbidium, Tricyrtis and Lagerstroemia and discussed on the historical biogeographical implications for angiosperms in the Northern hemisphere. Results indicate the same biogeographic pattern, i.e., origin and speciation in eastern Asia with subsequent expansion into North America. Therefore the all taxa examined in the present study showed asymmetrical disparsal from the Old World to the New World via Bering Land bridge during the Miocene (ca. 10 Ma) to the early Pliocene (ca. 5 Ma). The noteworthy finding was the general biogeograhic pattern in plant taxa restricted to the Sino-Japanese region that all lineages have been restricted ancestrally to the Yunnan & Sichuan Province in China and secondarily expanded their ranges via dispersal. The lineages distributed from the Ryukyu and Japanese Archipelagos are monophyletic with few DNA sequence divergences.