Mawenzhangia thamnobryoides Enroth, Shevock & Ignatov, 2018

Enroth, Johannes, Shevock, James R. & Ignatov, Michael S., 2018, Mawenzhangia thamnobryoides (Bryophyta, Lembophyllaceae), a new moss genus and species from the Shangri-la region of Yunnan Province, China, Phytotaxa 346 (3), pp. 237-246 : 238-242

Mawenzhangia thamnobryoides Enroth, Shevock & Ignatov , sp. nov. ( Figs. 2 , 3 )

Type:— CHINA. YUNNAN PROVINCE: Shangri-la County, along the trail about 5 km from the upper end of Niru Village to Colorful Rainbow Waterfall, slopes of the Pielong Shan above the Niru River, on base of Picea trunk, 27°57’42”N, 100°02’11”E, 3170 m, 29 August 2017, W. Z. Ma 17-9217 (holotype KUN!, isotypes CAS!, E!, H!, KRAM!, MHA!, MO!, NY!, PE!, SZG!, TAIE!, TNS!).

Plants gregarious, stipitate-frondose, to ca. 5 cm tall, yellowish green or partly brownish-gray, somewhat glossy. Stolons creeping, tiny-leaved, bearing tufts of intensely reddish-brown, verruculose, sparsely branching rhizoids. Fronds rather complanate, subpinnately to irregularly but densely branched above stipe, branches variously curved and with secondary branches, tapering towards tip, tips sometimes flagelliform and microphyllous; flagelliform, axillary, microphyllous branchlets often present, sometimes very abundant especially in older, more or less withered fronds, making them appear broom- or tassel-like. Stipe in cross-section elliptical, with small, thick-walled epidermal cells and 4 or 5 layers of small, thick-walled cortical cells, medullary cells just inside cortex thicker-walled and smaller than inner medullary cells, central strand small but distinct, consisting of cells clearly smaller than surrounding medullary cells. Stipe leaves not overlapping, patent, to 1 mm long and 0.6 mm wide, apex narrowly acute to acuminate; costa absent or ill-defined and short; margins plane, entire. Branch primordia tightly covered by tiny, wide, arching embryonic leaves forming a dome-shaped structure; pseudoparaphyllia absent. Axillary hairs 5–8 -celled, c. 140 μm long, other cells thin-walled and hyaline except 1–2 basal cells brownish but translucent, and shorter than upper cells. Stem leaves ca. 1.6 × 0.8 mm, elliptical or nearly oblong, concave, loosely appressed when dry, patent to spreading when wet, leaf apices acute. Branch leaves similar but smaller, sometimes nearly ovate and more strongly narrowed toward base; ultimate branch leaves sometimes ecostate or nearly so. Costa single but often spurred or bifurcate near base, tapering upwards, reaching to ½–⅔ of leaf length; margins plane, serrate by uni- to tri-cellular teeth in upper parts of leaves, these teeth often reflexed, serrate to serrulate at midleaf, entire near leaf base. Leaf cells fairly thin-walled, with blunt ends, often prorate in median and upper parts of leaves, smooth or nearly so at apex and near base; apical cells somewhat sinuous, oblong to sub-rhomboid or vaguely penta- to hexagonal, 20–40 × 8–10 μm, median laminal cells oblong to linear, slightly sinuous, 40–60 × 6–8 μm, basal laminal cells similar to median cells in shape but to ca. 80 μm long, marginal cells on both sides of leaves shorter than corresponding laminal cells; alar cells forming distinct groups, small, thick-walled, short-rectangular to isodiametric and quadrate or roundish, heavily chlorophyllose in fresh plants. Dioicous. Perichaetia and perigonia uncommon, scattered in upper parts of fronds. Perigonia bud-shaped, c. 1 mm tall; perigonial leaves ovate-lanceolate or oblong-lanceolate, ecostate, margins entire throughout or with few indistinct teeth near apex. Inner perichaetial leaves ca. 1 mm long, from an ovate base at ca. midleaf narrowed to a lanceolatelingulate acumen, ecostate; margins entire below, with scattered but prominent and somewhat reflexed teeth in acumen; laminal cells fairly firm-walled, smooth, linear elsewhere but rectangular to oblong near leaf base, a discontinuous row of (long-)rectangular cells present along both leaf margins; archegonia ca. 0.35 mm long, intermixed with hyaline, filiform paraphyses with elongate, narrow upper cells and wider, thinner-walled basal cells. Sporophytes unknown.

Paratypes:— CHINA. YUNNAN PROVINCE: Shangri-la County, along the banks of the Niru River, 0.25 km from the upper end of Niru Village , slopes of the Pielong Shan , 27°57’16.4”N, 100°03’39.8”E, 2770 m, 18 September 2016, Shevock & W. Z. Ma 48904 ( CAS!, H!, KUN!, MO!, MHA!) ; Niru River , 27°57’13”N, 100°03’41”E, 2750 m, 27 August 2017, Shevock & W. Z. Ma 50590 ( CAS!, E!, H!, KRAM!, KUN!, MO!) ; Niru River , 27°57’14”N, 100°03’42”E, 2790 m, 27 August 2017, W. Z. Ma & Shevock 17-9184 ( CAS!, H!, KRAM!, KUN!, NY!) and 100°57’18”N, 100°03’37”E, 2820 m, 27 August 2017, 17-9192 ( CAS!, H!, KUN!, PE!, SZG!) .

Etymology:—The genus is named after bryologist Dr. Wen Zhang Ma (1981–), curator of bryophytes, Kunming Institute of Botany, Chinese Academy of Sciences (KUN). The species epithet refers to the appearance of the thickened dendroid erect shoots and branches of younger plants.

Distribution and Habitat:—At present, Mawenzhangia thamnobryoide s is known only from the Niru River watershed within Shangri-la County of De-qin Prefecture. All occurrences lie within the broader Hengduan Mountains, the easternmost extension of the Himalayas comprising large areas of both Sichuan and Yunnan provinces. Mawenzhangia apparently prefers boulders just above the high water zone although it can also be seasonally inundated. The forest cover along the river corridor likely provides both filtered light to shade and more mesic conditions than the drier upland slopes. Mawenzhangia thamnobryoides also occurs on the base of large Picea Dietrich (1824:794) trunks in steeper shaded canyons within the river corridor. Populations are mixed among other mosses, particularly species of Plagiomnium Koponen (1968:145) and Thuidium Schimper (1852:157) . However, these habitat parameters are based on only two separate encounters in a rather limited geographical area, and therefore, should be viewed as preliminary observations. The likelihood of discovering additional populations of Mawenzhangia is relatively high. Much of the surrounding area of the type locality is rugged mountainous terrain above 3000 m and comprised of natural pristineappearing forests with few roads or trail access.

Figures

FIGURE 2. Mawenzhangia thamnobryoides. 1−2. Habit. 3. Portion of flagelliform branch. 4. Portion of leafy flagella. 5. Portion of leaf stipe. 6−8. Main branch leaves. 9−10. Secondary branch leaves. 11−12. Stipe leaves. 13. Perichaetium. 14. Inner perichaetial leaf. 15. Innermost perichaetial leaf with archegonia.16. Perigonium. 17. Inner perigonial bract. 18. Innermost perigonial bract with antheridia. 1−5, 8, 13−15 from Ma 17-9217 (KRAM, isotype); 6−7, 10−12, 16−18 from Ma 17-9184 (KRAM, paratype). Scale bars: a − 0.5 cm (3); b − 1 mm (14−15, 17−18); c − 1 mm (11−12); d − 1 cm (1−2) and 1 mm (13, 16); e − 1 mm (6−10); f − 1 mm (5); g − 100 μm (4).

FIGURE 3. Mawenzhangia thamnobryoides. 1. Leaf apex. 2. Upper marginal cells. 3. Mid-leaf cells. 4. Basal cells. 5. Apex of innermost perichaetial leaf. 1−2, 5 from Ma 17-9217 (KRAM, isotype); 3−4 from Ma 17-9184 (KRAM, paratype). Scale bar 100 μm.