A new sexual diploid of Dryopteris erythrosora complex (Dryopteridaceae)from Oki Islands, Japan

A new sexual diploid of D. erythrosora complexwas discovered from the Oki Islands in Japan. Spores of this plant were observed and the meiotic chromosome number was confirmed to be n=41II(2x). This diploid plant differs from the two other endemic sexual diploid species in the D. erythrosora complex, D. caudipinna and D. koizumiana, in having pale-green indusia. This newly reported diploid plant will help inform the origin and diversity of agamosporous species within the D. erythrosora complexin Japan.