イワベンケイ属の生物地理

抄録

The genus Rhodiola, consisting of 49 species, is one of the representative genera dominating in the high altitudes of the region from Pamir-Alai to SW China (mainly Yunnan and Szechuan) trough Himalaya, Tibet and N Burma. Actually excepting 6, the remaining 43 species of Rhodiola are distributed in that region (Fig. 2-13). I noticed three remarkable distribution patterns common among Rhodiola. These were named as Aa, Bb and c, tentatively. The Aa pattern is characterized by the shape that is along the east or the west margin of the Central Asiatic highland. In the Ice Ages the flora of circum boreal or arctic regions might migrate southward (A) to the Himalayan-Tibetan-SW Chinese high altitudes through these margins and vice versa (a). So that these margins of the Central Asiatic highland are regarded as corridors of both boreal or arctic and Himalayan-Tibetan-SW Chinese floras in the past. I have named the Central Asiatic highland corridor to it (OHBA in press). In the case of Rhodiola, the Aa pattern is found in the species of the subgenera Clementsia, Crassipedes and two sections, Rhodiola and Chamarehodiola. It might be considered that the Aa pattern is given rise by the causes such as continentral drift or climatic changes in global level. The Bb pattern can be defined as the east-west extention limited in the region from Pamir-Alai to SW China through Himalaya, Tibet and N Burma. This pattern is characterized by the migration from west to east (B) and vice versa (b). The c pattern is related to the migration and remnant during the Ice Ages.