A taxonomic study on <i>Saxifraga</i> ser. <i>Radioflorae</i> (Saxifragaceae) in Japan, the Kuril Islands and Kamchatka

Plants of Saxifraga ser. Radioflorae (A. M. Johnson) Zhmylev, now commonly regarded as belonging to the genus Micranthes , including Saxifraga fusca Maxim. and Saxifraga purpurascens Kom. (Saxifragaceae), distributed from Kamchatka to southern Japan through the Kuril Islands, are here taxonomically revised on the basis of floral morphology. The results suggest that the plants can be divided into three groups: 1) those from Kamchatka and the northern Kurils, 2) those from Kunashiri to the Japanese archipelago, through Hokkaido and Honshu, and 3) those from the southern Kurils from Chirpoi to Etorofu Islands. Leaf characteristics and habitat preferences also correlate with these groupings. The first group is identified as Micranthes ohwii ( = Saxifraga purpurascens Kom.), and the second group as M. fusca . The third group is similar to M. fusca in floral proportions, but has petals with non‐revolute margins, larger floral discs and disc and filaments developing throughout anthesis. The third group may be derived from M. fusca , adapted to the coastal environment.