Pylaisia bezgodovii Ignatov & Ignatova, 2020

5. Pylaisia bezgodovii Ignatov & Ignatova sp. nov.

Figs. 17, 18, 34A.

Type: “ East Siberia, Republic Sakha / Yakutia , Ust-Maya District , Yugorenok , Khlebny Creek , 59°49’N – 137°59’E, 370 m alt., at base of Salix in regularly flood- ed part of the Yudoma River Valley , 7 Sept. 2000, Ignatov 00-711 (Holotype MHA9130416). Isolates: OK212 and OK2802 GoogleMaps .

Ethymology: the species name is given in honour of Andrej Gennadievich Bezgodov, an outstanding explorer of bryophyte flora of Urals and some areas in Sibera, who collected a specimen of the new species in Perm Province.

Diagnosis: Strongly falcate-secund leaves turned to the substrate make the species habit similar to that of P. steerei , although its leaves are smaller, 0.9–1.2× 0.35– 0.45 mm vs. 1.1–1.6× 0.4–0.6 mm). Differences from P. steerei include also smaller spores (10–12 vs. 12–18 µm) and only slightly papillose endostome (vs. densely papillose in P. steerei ). Alar cells are usually larger (to 12 µm wide) and more conspicuously differentiated than in P. steerei , forming larger alar group, 12–22 cells long and 5–6 cells wide vs. 10–15 cells long and 5–10 cells wide in the latter species. The strong unique substitutions in nuclear ITS and IGS sequences suggest a separate status of this species ( Figs. 1–4 View Fig View Fig View Fig View Fig ).

Description. Plants small to medium-sized, light to whitish green, sometimes with glaucous tint. Stem and branches straight or only indistinctly curved, moderately densely foliate; leaves falcate-secund, turned towards substrate. Axillary hairs 4-celled, 70–90×9–11 µm. Proximal branch leaves triangular, irregualrly incised. Stem leaves 0.9–1.2× 0.35–0.45 mm, ovate to ovate-lanceolate, gradually narrowed into a long acumen, slightly rounded to insertion; margin serrulate above, median laminal cells 35– 70(–87)×5–6 µm, alar cells subquadrate, form elongate compact group 12–22 cells long and 5–6 cells wide; alar cells often to 12 µm wide. Branch leaves somewhat smaller. Inner perichaetial leaves erect, up 1.3× 0.55 mm, not much elongated after fertilization. Capsules cylindrical, 1.5 mm long without operculum. Operculum high conic to conic-rostrate. Annulus deciduous. Peristome forming high conus when dry. Exostome teeth 250–300 µm long above the mouth, dorsal plates smooth below, papillose above; endostome up to 325 µm above the mouth, not adherent to exostome, endostome segments narrow, not perforated along keel, moderately papillose. Spores 9–12(–13) µm.

Differentiation. Likewise P. steerei , P. bezgodovii differs from all other species of the genus in having complanate foliage and falcate leaves turned toward substrate. Differences from P. steerei are described in the diagnosis.

Variation. Contrary to P. steerei , specimens of P. bezgodovii from Yakutia and a specimen from Perm Territory show little variation in gametophyte and sporophyte characters, being easy to recognize.

Distribution. This species was revealed in the course of molecular phylogenetic studies, before is was kept just under Pylasia steerei . At the moment it is known by several specimens from eastern Yakutia and one specimen from Ural Mountains, Perm Territory. In the latter locality, Pylaisa with falcate leaves was noticed on the base of aspen tree, while average-looking Pylaisia polyantha grew on the trunk above the level of snow cover in winter, i.e. as it usually grows. We sequenced both plantsfrom that tree, confirming that the true epiphytic plants belong to the most common ITS-haplotype of European P. polyantha , while P. steerei -like plants from the trunk base were identical to Yakutian plants. Additional search of such plants in herbaria revealed several specimens of P. bezgodovii from few nearby localities in Ust-Maya District in Yakutia.

In the valley of Yudoma River where the holotype of P. bezgodovii was collected, P. steerei was also found in about the same habitats, but these two species provide no problem with identification by spore size and shape of the alar cell group, as given in the key.

Specimens examined: RUSSIA: East Siberia, Republic Sakha /Yakutia, Ust-Maya Distr., Yugorenok: Medvezhij Creek, Ignatov 00-976 (MHA9130429); same place, Shchel Creek, Ignatov 00-709 (MHA9130430).