アポイ岳超塩基性岩フロラの特異性(<特集1>アポイ岳の植物群落-アポイ岳の高山植物群落の現状と将来について-)

抄録

The geology of Mt. Apoi (42°6'20" N and 143°1'40" E ; 810.6 m above sea level) consists of peridotite, on which an ultrabasicosaxicolous flora has developed. On September 7, 1939, 300 hectares of an area with this ultrabasicosaxicolous flora was designated as a natural monument of Japan with the title Mt. Apoi Alpine Vegetation, and on March 29, 1952, was further designated as a special natural monument. The most characteristic features of the flora of Mt. Apoi are that the proportions of endemic species, endemic varieties, and endemic forms are probably the highest in the world due to the effect of the bedrock, despite the relatively low altitude and the small size of the mountain mass, and that succession of vegetation to forest has not occurred over the last 10,000 postglacial years. We therefore compared the flora of Mt. Apoi with other ultrabasicosaxicolous floras such as that of Mt. Yubari, distinguished neoendemic species and paleoendemic species among the endemic species of the ultrabasicosaxicolous flora and, selecting genealogically close ecological equivalent species in the ultrabasicosaxicolous floras of various regions, analyzed the percentages of modified species. It was found that (1) many of the plants endemic to Mt. Apoi were neoendemic species, which were newly developed ultrabasic modified elements, (2) many of the species distributed to two or more ultrabasic rock areas were paleoendemic, being ultrabasic relic elements existing from older times, and (3) the percentage of species modified in the ultrabasic rock areas was higher on Mt. Apoi than in other ultrabasic rock areas. In addition, (4) the finding that none of the ultrabasic plants that constituted the peridotite flora located in the northern part of the Hidaka Range were restricted to that region highlighted the characteristically high proportion of endemic species on Mt. Apoi, which is a similar peridotite area.