Brachythecium amurense Ignatov, 2019

Ignatov, M. S., Fedorova, A. V. & Troitsky, A. V., 2019, A new Brachythecium (Brachytheciaceae Bryophyta) from the Russian Far East, Arctoa 28 (2), pp. 222-225 : 225

Brachythecium amurense Ignatov , sp. nov.

Type: Russia, Khabarovsk Territory, North Sikhote-Alin, ca. 1 km westward of Tardoki-Yani Mt. Peak, N : 48°53’16.9”, E: 138°02’52.8”, 1940 m, on soil. Coll. A. V . Ermolenko #7-4, 24.VIII.2013 ( Holotype MW9112512 , Isotype MHA) .

Diagnosis. Differs from other species in combination of (1) robust pale-stramineous plants, weakly branched stems, terete foliate shoots; (2) leaves with ovate base, subpiliferous distally, strongly concave, crumply plicate; (3) margins minutely serrulate almost all around; (4) laminal cells 65–70(–90)×7–10 µm, moderately thick-walled, porose; (5) alar cells wider, extending upwards.

Description. Plants large, light yellowish-green, glossy, soft, forming loose tufts; outermost proximal branch leaf in branch primordia in 12 o’clock position, abruptly acuminate and consistently squarrose; axillary hairs with one apical and two basal cells, 45–60 µm long. Stems to 8 cm long, simple, with few short branches or irregularly branched, terete-foliate. Leaves erect-spreading to spreading when dry, crumpled, erect-spreading to loosely appressed when moist, 2–3×1.0– 1.3 mm, ovate to ovate-triangular, widest at 1/6 the leaf length, abruptly narrowed into long filiform acumen, strongly concave (forming deep plicae in slides); margins plane or narrowly recurved at base and at the constriction to acumen, weakly serrulate in upper 3/4, subentire below; costa single, weak, quickly narrowing upwards, extending to 1/2– 3/4 the leaf length; median laminal cells linear, 65–70(–90) ×7–10 µm, slightly porose; basal laminal cells elongaterectangular, 60–75×15–20 µm, porose; alar group moderately delimited; alar cells in several submarginal rows, not extending to costa, short-rectangular, 35–50×25–30 µm, moderately thick-walled, slightly porose. Apparently dioicous. Gametangia and sporophytes unknown.

Differentiation. Robust habit, crumply plicate leaves, and pattern of basal cell differentiation of B. amurense are similar to B. garovaglioides and, partly, also to B. complanatum . However, both these species have coarsely serrate leaves, and they belong to phylogenetically distant groups (Fig.1). According to the obtained phylogeny, the closest to B. amurense are B. mildeanum (differs in entire leaf margins of rather narrowly triangular shape), B. laetum (differs in strongly plicate leaves and expand- ed group of opaque basal cells), and B. boreale (differs in medium-sized plants, rather short acumina, dense areolation throughout the leaf, except for a small group of enlarged cells in leaf corners).

Ecology. The species was collected at 1940 m a.s.l., in alpine belt, on soil on moist open slope, with Philonotis fontana, Loeskypnum badium, Campylium stellatum, and Hylocomiastrum pyrenaicum .

The finding of such large and conspicuous moss once again illustrates the poor knowledge of of high mountain diversity in Far Eastern region.