Rauiella thuidioides Jan Kučera & Ignatova, 2021

Kucera, J., Ignatova, E. A., Ignatov, M. S., Fedorova, A. V., Kuznetsova, O. I. & Fedosov, V. E., 2021, Rauiella thuidioides, sp. nov. (Leskeaceae, Musci), a new species from the Russian Far East, Arctoa 30 (2), pp. 425-433 : 428-432

Rauiella thuidioides Jan Kučera & Ignatova , spec. nov. Fig. 2 , 3A–D , 4A–D.

Holotype: Russian Federation, Primorsky Territory, Lazo Distr.: Elomovsky Klyuch valley , 43°13'39.3"N, 133°45'47.6"E, 250 m a.s.l., on mossy rocks in mixed conifer-broadleaved forest, 5 September 2013, coll. Ignatov, Ignatova & Malashkina 13-1264 ( MHA9101928 ) . Isotype MW9092266 .

Paratypes: (1) Russian Federation, Primorsky Territory, Lazo Distr.: Elomovsky Klyuch valley , 43°13'10"N, 133°46'31"E, 200 m a.s.l., broad-leaved alluvial wood; on half-shaded siliceous boulder, 5 September 2019, coll. J . Kučera 21299 ( CBFS). (2) The same area, without exact coordinates, ca. 200 m a.s.l., on rocks in a mixed floodvalley forest, 6 September 2006, coll. Ignatov, Ignatova & Cherdantseva 06-2175 ( MHA9131243 , MW9092267 ) .

Etymology. The specific epithet refers to thuidioid appearance which results from the presence of sparsely bipinnate branching.

Diagnosis. The species differs from its congeners, and particularly from R. fujisana and R. scita , in its sparse branching which reveals rich paraphyllia present on stem, the occasional production of second order branches from the primary ones, and the larger stem leaves, mostly exceeding 1 mm in length and 0.5 mm in width. The differences from Thuidium species with pluripapillose cells ( T. submicropteris , T. subglaucinum , T. kanedae , T. alleniorum ) include autoicous gametangia and less regular and less dense, mostly unipinnate branching. Boulaya mittenii is more densely, unipinnately branched, has unipapillose cells and is dioicous.

Description: Plants in loose, interwoven mats, rigid, green or yellowish-green, dull but with glossy stem leaf apices. Stems to 8 cm long, 0.5–1.0 mm wide with leaves, sparsely and irregularly branched, often with secondary branchlets on primary branches; central strand absent; medullary cells firm-walled, cortical cells in 3–4 layers thick-walled, brown, hyalodermis absent; paraphyllia numerous on stems and primary branches, filamentose and foliose, branched. Stem leaves incurved when dry, widely spreading when moist, 0.9–1.2× 0.6–0.8 mm, from wide triangular or cordate-deltoid bases abruptly narrowed into long, narrow triangular acumina, with uniseriate apices 2–4 cells long, abruptly rounded to the insertion, strongly plicate; costae extending to the base or middle part of narrow acumina, gradually tapered distally; margins entire, plane or recurved at places in basal half; median laminal cells irregularly polygonal and transversely ovate, with moderately thickened walls, slightly collenchymatous, with several round and 0- shaped, low papillae over lumina mainly on dorsal side of leaf lamina, 5–12×7–10 µm; cells of acumina elongate, 25–30×5–8 µm, smooth. Primary branch leaves with ovate base and triangular acumina, 0.55–0.70× 0.3– 0.4 mm, apical cell sharp, smooth; secondary branch leaves ovate, 0.2–0.25× 0.12–0.14 mm, apical cell truncate, papillose. Autoicous. Perichaetia on stem, conspicuous. Inner perichaetial leaves narrowly lanceolate, ca. 2.5–3.0× 0.5 mm, not plicate, with long, filiform, flexuose acumina, uniseriate apices 3–4 cells long; margins plane, serrulate throughout; costa to 0.7 the leaf length, weakly delimited from adjacent cells; laminal cells oblong, smooth. Perigonia on stem close to perichaetia, small, inconspicuous. Setae 1.8–2.2 mm long, yellowish or yellow brown. Capsules inclined, cylindrical, slightly curved, 1.8–2 mm long and 0.8–0.9 mm wide. Opercula and annuli not seen. Exostome teeth ca. 500 µm long, light yellow, cross-striolate below, papillose above. Endostome with basal membrane ca. 250 µm high; segments as long as exostome, narrow, not or scarcely perforated; cilia in groups of 2–3, nodose. Spores 9–11 µm, very finely papillose. Calyptrae not seen.

Differentiation. Rauiella thuidioides can be rather easily differentiated from the co-occurring common East Asian R. fujisana by the longer, up to 8 cm long stems, much sparser branching with somewhat irregularly long primary branches and particularly by the sparse but rath- er regular appearance of short secondary branches arising from the primary ones (cf. Fig. 4C). Stem leaves are larger, 0.9–1.2× 0.6–0.8 mm vs. to 0.9× 0.45 mm (as specified by Noguchi et al., 1991), are more strongly plicate and have typically longer, piliferous apices ( Fig. 3 ), although this character is rather variable in R. fujisana . Leaf laminal cells of R. fujisana are covered by dense, coarse, forked papillae on both leaf surfaces ( Fig. 3K ), while in R. thuidioides the papillae are smaller, less massive, simple or indistinctly bifid (0-shaped), more numerous on dorsal surface of leaf lamina ( Fig. 3D ). Rauiella thuidioides also differs from R. fujisana in longer setae (1.8–2.2 vs. 1.0– 1.2 mm), longer exostome teeth (500 vs. 350 µm), and smaller, finer papillose spores (9–11 vs. 12–15 µm). Rauiella scita is presently only known from eastern North America and can also be differentiated by the absence of secondary branches and more regular and dense branching pattern ( Fig. 4G), although less regular than in R. fujisana , and with only few secondary branches. Its leaves are also much smaller than those of R. thuidioides – 0.6–0.8 mm long ( Allen, 2014). The papillae on leaf lamina of R. scita are more similar to those of R. thuidioides ; cells are described by Allen (2014) as densely pluripapillose on dorsal surface, bulging or unipapillose on ventral surface (cf. Fig. 3S ). Rauiella scita has shorter setae, 0.8–1.4 mm vs. 1.8–2.2 mm long), and its spore size is similar to R. thuidioides (8–12 µm). Rauiella thuidioides possibly most resembles members of the genus Haplocladium at casual observation with respect to similar, irregular and sparse branching pattern. In particular, stem leaves of R. thuidioides are strikingly similar in shape, size and strong plication to plants named Haplocladium microphyllum in northeastern Asia, although such plants differ from typical Central American plants representing the type of H. microphyllum . Species of Haplocladium can, however, be differentiated by the unipapillose cells, dioicous gametangia distribution and mostly sparser paraphyllia, particularly on branches, and secondary branches are also absent. Boulaya mittenii is also unipinnate, more densely and regularly branched plant with thicker primary branches, cells are weakly unipapillose and somewhat collenchymatous, the plants are also dioicous. Thuidium species are dioicous as well and mostly are more densely and regularly bi- to tripinnate, except for, e.g., T. alleniorum , which howev- er has only shortly pointed stem leaves and the branch leaves are incurved.

Ecology and Geography. Rauiella thuidioides was collected from half-shaded siliceous boulders in broad-leaved alluvial wood surrounding the brook at 200–250 m a.s.l. It is not known how typical this habitat is for the species; the co-occurring R. fujisana is mostly found epiphytically in the same environments, but occasionally is also encountered on stones or bare ground. On the other hand, the habitat of shaded siliceous boulders in humid environment is also typical for the co-occurring species of the genus Haplocladium (currently referred to H. angustifolium , H. microphyllum and H. strictulum ). The valley beneath Benevskie waterfalls has been well studied for bryophytes and contains many rare mosses of the Eastern element, including Arrhenopterum heterostichum Hedw. , Boulaya mittenii (Broth.) Cardot , Forsstroemia konoi (Broth.) Enroth, Fedosov & Ignatov , Hypopterygium flavolimbatum Müll. Hal. , Orthotrichum consobrinum Cardot , Pylaisia coreana Nog. , Rhizomnium striatulum (Mitt.) T.J. Kop. and many others. This discovery confirms that the bryoflora of the north-eastern Asia still contains unnoticed species, which might, however, prove more broadly distributed after previously unassigned material is revised. The use of molecular tools greatly enhances such efforts.

Figures

Fig. 2. Rauiella thuidioides (from holotype). A–C: habit, dry; D–E: cells of stem leaf acumina; F: cells of the apical portion of the secondary branch leaf; G: cells of the apical portion of the primary branch leaf; H–K: paraphyllia; L: median cells of stem leaf; M–O: branch leaves from secondary branches; P: inner perichaetial leaf; R–S, W: branch leaves from primary branes; T–V: stem leaves; X: basal cells of stem leaf. Scale bars: 1 cm for A; 2 mm for B; 1 mm for C; 0.5 mm for M–W; 100 µm for D–L, Х.

Fig. 3. A comparison of North Hemispheric Rauiella species. A–D: R. thuidioides (from holotype). E–K: R. fujisana (from: Russia, Primorsky Territory, Dalnegorsk District, Ignatov & Ignatova 13-1601, MHA). L–S: R. scita (from: U.S.A., Maine, Allen 28294, MHA). A, E–G, L–N: stem leaves; B, H–I, O–P: branch leaves; C, J, R: S median laminal cells; D, K, S: leaf transverse sections. Scale bars: 0.5 mm for A–B, E–I, L–P; 100 µm for C–D, J–K, R–S.