Ivanova, E.I., N.E. Bell, O.I. Kuznetsova, E.A. Ignatova & M.S. Ignatov. The genus Polytrichum sect. Aporotheca (Polytrichaceae) in Russia
Arctoa (2015) 24: 67-78
Revision of herbarium collections and analysis of rps4 and trnL-F molecular sequence data supports the recognition in Russia of four species of Polytrichum sect. Aporotheca. Most specimens from the territory of Russia previously named as P. formosum are transferred to P. densifolium. The species status of the latter is resurrected and the distinction of P. formosum and P. densifolium is discussed. The four species are described based on the material from Russia, their distributions are summarised, diagnostic characters are illustrated, and a key to identification is provided.