Bryum glacierum Y.Y. Liu & Y.H. Wu, 2021

Liu, Yong-Ying, Quan, Yu-Ping & Wu, Yu-Huan, 2021, A new moss species from northwestern China: Bryum glacierum (Bryaceae), Phytotaxa 510 (2), pp. 148-154 : 148-151

Bryum glacierum Y.Y. Liu & Y.H. Wu , sp. nov. Figures 1–2

Diagnosis: Bryum glacierum is characterized by (1) dark red-brown, obconic or ovate bulbils with peg-like leaf primordia, densely clustered in the leaf axils of sterile shoots, (2) broadly ovate unbordered leaves, with rhombic to rhomboidal distal medial cells, and (3) gemmiform to rounded-julaceous stems with imbricate leaves.

Type:— CHINA. Xinjiang Uyghur Autonomous Region: the Tianshan Mountain , forefield of Urumqi Glacier No. 1, elev. 3733 m, 43°07′34.59″N, 86°49′05.77″E, on soil, 21 August 2016, Y. H . Wu 201608210086 [holotype JZNC (Herbarium of Jiaozuo Normal College)!, isotype HTC ( Herbarium of Hangzhou Normal University )]!, PE !].

Plants yellow-green, 3–5 mm high, forming compact turfs. Stems erect, simple or branched, gemmiform to julaceous, nearly round in transverse section, central strand present; rhizoids branched or unbranched, light brown, lightly papillose to smooth, usually abundant especially near the base. Leaves imbricate when dry and wet, broadly ovate, strongly concave, 0.6–0.9 × 0.4–0.7 mm, apex obtuse to acuminate, slightly decurrent or not; margins plane, smooth, unbordered; distal and mid-laminal cells rhombic to rhomboidal, with slightly thickened walls, 28–45 (50) × (8) 11–14 μm, proximal cells short- or long-rectangular, 33–50 (60) × 11–14 μm, gradually differentiated; costa single, percurrent or excurrent, 36–44 μm wide at the base, smooth, in cross-section guide cells 2–3 in 1 layer, adaxial stereid band absent, abaxial stereid band present. Bulbils densely clustered in leaf axils of the sterile plant, obconic, ovate, or ellipsoidal, the bodies of propagules (86) 120–155 × 57–93 (104) μm, mainly dark red-brown, occasionally lightbrown, consisting of several roughly isodiametric cells; leaf primordia (0) 1–3 (4), peg-like, composed with a single row of long cells or occasionally more than two rows at the base, straight to flexuose, usually equal to the length of the body or short, at most two lengths of the body, rarely protuberances, mainly less than 5, restricted to the apex; the bulbils total length (140) 211–300 μm. Sporophyte not seen.

Etymology:—The specific epithet glacierum was selected since this type grows on ground exposed by retreating glaciers.

Paratype:— CHINA. Xinjiang Uyghur Autonomous Region: the Tianshan Mountain , forefield of Urumqi Glacier No. 1, elev. 3620 m, 43°07′12.32″N, 86°50′00.77″E, on wet land soil, 22 August 2016, Y. H . Wu 20160822218 (JZNC!, HTC!)

Distribution, habitat, and ecology

Bryum glacierum is known from the Urumqi Glacier No. 1, Tianshan Mountain, which is the source region of the Urumqi River, within the Tianshan Mountain Range, China. As a reference glacier in the World Glacier Monitoring Service, Urumqi Glacier No. 1 is the best-observed glacier in China. As currently known localities of the new species are characterized by an elevation above 3600 m, it is very frigid and dry in the winter. Warm weather can send melting water to the retreat range of the glacier in the summer. In this rather extreme unstable habitat, B. glacierum is a rather fragile and ephemeral plant. The deeply concave shape of the leaves may be related to covering and protecting the mature bulbils, allowing the leaves to remain imbricate as the bulbils grow to maturity (Koeckinger et al. 2013). While inhabiting unpredictably varying environments, production of gemma by B. glacierum can be interpreted as a strategy to use available resources effectively and enhance its survival, and it can be an effective way to maintain and enlarge populations ( Newton & Mishler 1994). The most frequently associated bryophytes in this habitat are Tortula mucronifolia Schwägrichen (1811: 136) and Barbula unguiculata Hedwig (1801: 118) .

Figures

FIGURE 1. Bryum glacierum. A. Plant. B. Leaves. C. Upper leaf cells. D. Middle leaf cells. E. Basal leaf cells. F. Bulbils. G. Crosssections of the leaf, from the upper part to the basal part. H. Cross-section of the stem. All from the holotype.

FIGURE 2. Bryum glacierum. A. Plants. B. Leaf apex. C. Basal leaf cells. D. Middle leaf cells. E–F. Leaves. G. Cross-section of the stem. H–Q. Bulbils. All from the holotype.