Fedosov, V.E., A.V. Fedorova & E.A. Ignatova. On the two
poorly known Orthotrichum species from north Asia
Arctoa (2017) 26: 144–153
doi: 10.15298/arctoa.26.14
Recent revision of Asiatic specimens
of the genus
Orthotrichum s. str. revealed two
species widely distributed and rather frequent in northern Asia,
which however differ from all
currently recognized species. One of them includes plants growing on silted
bases of willows and fallen
trees in flood valleys; its specimens were
previously referred to O. holmenii, but in fact
it fits O. sibiricum, a species described from the lower
course of Yenisei River in
1890, but later reduced to the
synonymy of O. pallens. However, O.
sibiricum differs from European O. pallens in high, branched papillae and pointed,
not blunt, leaf apex, and
they are also clearly distinct
in ITS sequences.
Orthotrichum sibiricum
occurs in Nenets Autonomous disctict in NE
European Russia, the Polar and
Subpolar Urals, the lower course
of the Yenisei
River, on the Anabar Plateau,
Orulgan Range and in Transbaikalia.
The second species is also
superficially somewhat similar to O. pallens, at least most its
collections were so named in
herbaria. However, it is characterized by having hyaline cells at
leaf apices, and usually 1–2 teeth nearby it,
as well as
branched papillae on laminal cells,
immersed to emergent capsules with 8 ribs at
entire urn length, stomata half-covered by subsidiary cells, exostome teeth in pairs,
8 or 16 endostome segments, and smooth,
hairless calyptra. This species grows
mostly on siliceous rocks in cold areas
of Siberia, both in northern
regions and in high mountains.
It is described
as a new
species, O. hyperboreum;
its range includes Polar Urals, Byrranga Mts. in Taimyr,
Anabar Plateau, Orulgan Range in
the lower course of Lena
River, and Chukotka.