A taxonomic revision of Oligotrichum Lam. & DC. (Polytrichaceae) in the Sino-Himalaya

Abstract

A taxonomic revision of the moss genus Oligotrichum Lam. & DC. (Polytrichaceae) is provided for the Sino-Himalayan region. This area includes the Himalaya and the Hengduan Mountains of south-western China (Yunnan, Sichuan, and Xizang [Tibet] Provinces). Field work in recent decades has resulted in much new material for taxonomic revision. Light microscopy was used to distinguish seven species from the study area: O. aligerum Mitt., O. crossidioides P.C.Chen & T.L.Wan ex W.X.Xu & R.L.Xiong, O. falcatum Steere, O. falcifolium (Griff.) G.L.Sm., O. nepalense G.L.Sm., O. obtusatum Broth., and O. semilamellatum (Hook.f.) Mitt. Two species are excluded: O. hercynicum (Hedw.) Lam. & DC., as no specimens of this European and North American species have yet been found from the Sino-Himalayan region, and O. glaciale C.C.Towns., which has been transferred to a recently established genus Delongia N.E.Bell, Kariyawasam, Hedd. & Hyvönen, described elsewhere. The material now available has facilitated new observations on important characters such as the structures of the leaf lamellae and sporophytes. A key to accepted species is provided, as well as descriptions, synonymy, typification, line drawings, an ecological summary, and biogeographical information including distribution maps for all species. Oligotrichum falcatum is reported as new to India and Nepal, and O. obtusatum new to India and the Sichuan Province of China. Two varieties (O. semilamellatum var. darjeelingense Gangulee and var. edentatum Gangulee) are newly synonymised with O. semilamellatum. Finally, some observations on the regional ecology and phytogeography of the species are made and a list of specimens studied is appended.