Variations in flower morphology and pigments in Rhododendron kiusianum makino endemic to Kuju and Aso Mountains and their surrounding areas

The variations in flower morphology and flavonol pigment composition in the petals of Rhododendron kiusianum endemic to Kuju and Aso Mountains and their surrounding areas were investigated. A typical R. kiusianum plant which grows in the Kuju Mountains seems well-adapted to severe climatic conditions, such as alpine temperatures and strong winds, as well as acid soil and the presence of sulfurous acid gas. Although the species is also distributed at the top of Mt. Yufudake and Aso Mountains, the distributional areas of this species are separated from the other crosscompatible azalea species, such as R. kaempferi, by a summergreen forest or an open field, respectively. Flower colors of individuals growing on Mt. Haneyama varied widely, nearly all having prominent blotches on their petals. The composition of flavonols in their petals also ranged widely. From these findings, we conclude that the population at Mt. Haneyama seems to be the result of natural crossing between R. kiusianum and R. kaempferi.