FOLIAR FLAVONOIDS OF ACER-SECT PALMATA SERIES PALMATA

Thirty-eight flavonoids were isolated from leaves of 15 species of Acer sect. Palmata series Palmata. The flavonoid data indicated the presence of three distinct chemical groups: the "palmatum" type producing flavonols, flavones, and C-glycosylflavones, the "robustum" type producing flavones and flavonols, and the "japonicum" type producing only flavonols. On the basis of available flavonoid biogenetic information, the "japonicum" type appears to be the most primitive, the "robustum" type the most advanced, and the "palmatum" type intermediate, but highly specialized. The correlation of these chemical types with morphology suggests that the presence or absence of pubensence on the ovary is the most reliable diagnostic morphological character for the delimitation of the series. Flavonoid data also assisted in clarifying the taxonomic status of several previously confusing taxa (A. duplicatoserratum complex, A. takesimense, and A. amoenum var. matsumurae). The chemical and morphological data also support a putative migratory route of these taxa from southeastern China to North America via Japan, which is consistent with modern theories of phytogeography. Additionally, a more plausible hypothesis of the phylogenetic history of these taxa can be postulated using these combined data.