Ignatova, E.A., V.E. Fedosov, O.I. Kuznetsova, A.V. Fedorova & M. S. Ignatov. 2024. On the genus Didymodon s. str. (Pottiaceae, Bryophyta) in Russia

Arctoa (2024) 33: 129–155

doi: 10.15298/arctoa.33.14

The present study addresses problematic groups within Didymodon s. str. occurring in Russia, mainly related to D. validus, D. icmadophilus and D. acutus. A combined morphological and molecular-phylogenetic approach revealed that D. validus is the commonest species of this group in Russia, especially in its Asian part and the Caucasus, whereas distribution of D. icmadophilus is likely restricted to the humid habitats in the Caucasus, and we failed to confirm the identity of any D. acutus specimen from the country. Didymodon cordatus is sporadically distributed in southern Siberia, Far East and the Caucasus. Four species recently described from China were revealed in Asian Russia: D. hengduanensis in Primorsky Territory and Irkutsk Province; D. daqingii in southern Siberia and Yakutia; D. tibeticus in Zabaikalsky Territory, and D. mongolicus in southern Siberia, Yakutia and the Caucasus. However, we failed to find D. schensianus which is widespread in neighboring territories of China and Japan. Six species are described as new for science: D. baicalensis (Irkutsk Province, Buryatia, Zabaikalsky Territory, Khakassia, Altai Republic), D. borealis (Yakutia, Perm Territory, Sverdlovsk Province, Finland), D. cherdantsevae (Primorsky Territory), D. calciphilus (Primorsky Territory, Dagestan), D. abramovae (Tyva, Ingushetia, and Dagestan), and D. truncatus (Altai Republic). Descriptions, illustrations and ecological data are provided for newly described species and newly found in Russia D. hengduanensis and D. daqingii; for D. mongolicus an emended description, illustrations and a comparison with Chinese and Mongolian plants are given. Sporophytes are described for the first time for Didymodon validus; its morphological circumscription and variability are discussed.