Ivanova, E.I., N.E. Bell, O.I. Kuznetsova, H. Lee, M. Park, M.S. Ignatov. The genus Polytrichastrum (Polytrichaceae) in Russia
Arctoa (2014) 23: 164-184
Revision of herbarium collections and sequence study of rps4 and trnL-F resulted in recognition in Russia of 7 species of the genus Polytrichastrum sensu stricto, i.e., excluding sect. Aporotheca. The status of Polytrichastrum sphaerothecium is confirmed, and this species turns out to be the most isolated in the genus, not closely related to P. sexangulare. A group of rather closely related species is formed by P. alpinum, P. fragile, P. septentrionale (Brid) E.I. Ivanova, N.E. Bell & Ignatov comb. nov., and P. altaicum. Their morphological differentiation corresponds with sequence level characters, supporting their taxonomic recognition. One specimen from Chukotka has some characters of P. papillatum and is tentatively referred to this species, despite incomplete morphological and molecular congruence with the Himalayan material.