Dryopteris protobissetiana (Dryopteridaceae), a New Diploid Sexual Species of the Dryopteris varia Complex (Subg. Erythrovariae, Sect. Variae) from Yakushima, Kagoshima, Japan

抄録

The Dryopteris varia complex (subg. Erythrovariae, sect. Variae Fraser-Jenk.) is an apogamous fern complex. Most species of the complex are apogamous triploids; Dryopteris saxifraga and D. varia, the only known diploid sexual cytotypes in the complex, are insufficient to account for the morphological and genetic variation within the complex. In this study, we describe a new diploid sexual species, Dryopteris protobissetiana K. Hori et N. Murak., from southern Yakushima, and discuss its morphological characteristics, reproductive mode, and chromosome number. Dryopteris protobissetiana is similar to D. bissetiana in having slightly bullate scales and a dark green lamina surface, but it differs in having flat, serrate margins at the apex of the upper pinnae. Dryopteris protobissetiana is a sexual diploid with 2n=82, and may be a source of the genetic variation in the apogamous complex.