Didymodon schensianus (Pottiaceae, Bryophyta), a new combination for a widespread, but overlooked taxon in East Asia

Barbula schensiana, endemic to China is transferred to the genus Didymodon as D. schensianus. It is shown that B. schensiana and its variety longifolia has incorrectly been considered conspecific with Didymodon vinealis and D. constrictus, respectively. Examination of other type specimens from East Asia such as Didymodon guangdongensis, Barbula altipes, Barbula nipponica and B. nipponica var. gracilis revealed that are new synonyms of D. schensianus. The range of the species is extended to Japan, Taiwan and Philippines. The species is described, lectotypified, illustrated and its distribution is mapped. Its distinction from and relationships with, similar species are discussed.