Morphological
differences between two arcto-alpine species of Oligotrichum, O. hercynicum and
O. falcatum (Polytrichaceae) are rather few, overlapping and not always
expressed, thus problems with their distribution in Asia remain. In the present
study we found that morphology of these species corresponds well with the six
characteristic substitutions in nrITS1, providing more robust ground for
delimitation of these two species. Oligotrichum hercynicum occurs in
relatively oceanic climates in Northern Europe, mountains of Central Europe,
Caucasus, Kuznetskij Alatau in South Siberia, Kamchatka, Chukotka, and northern
North America. Contrary to that, Oligotrichum falcatum has the Beringian
distribution, in a broad sense. It is known from mountains of South Siberia
(westwards to Altai), Yakutia, xeric regions of North-East Asia and Arctic
North America, including Western Greenland, and also reported from Tibet.