Geographical Distribution of Sexual and Apogamous Types of Dryopteris formosana and Dryopteris varia (Dryopteridaceae) in Taiwan

Abstract

Cytological observations of the mitotic chromosomes of Dryopteris formosana and D. varia (Dryopteridaceae) in Taiwan are reported. Only the triploid apogamous cytotype has been reported from D. formosana. This is the first report of a diploid sexual type of D. formosana. Counts of spore numbers per sporangium of herbarium specimens to presume the reproductive mode in these two species revealed that both sexual and apogamous types of D. formosana and D. varia are widely distributed in Taiwan. Although the sexual type of D. formosana occurs at relatively lower elevations than the apogamous type, such differentiation between cytotypes was not observed in D. varia. It is important to understand diploid sexual types to be able to explain variation in apogamous species, because sexual cytotypes should be the source of the variation observed in apogamous cytotypes.