Ophiopogon muongnhensis K.S.Nguyen, N.Tanaka & Aver., 2023

Pham, Van The, Tanaka, Noriyuki, Averyanov, Leonid V., Maisak, Tatiana V., Tran, Huy Thai, Nguyen, Huu Cuong & Nguyen, Khang Sinh, 2023, Ophiopogon muongnhensis (Asparagaceae, Convallarioideae), a new species from northwest Vietnam, Phytotaxa 591 (2), pp. 171-176 : 172-175

Ophiopogon muongnhensis K.S.Nguyen, N.Tanaka & Aver. , sp. nov. ( Figs. 1 , 2 )

Type: — VIETNAM. Dien Bien Province: Muong Nhe Distr., Muong Nhe Natural Reserve, Sin Thau Municipality , A Pa Chai Village , remnants of primary evergreen broad-leaved submontane forest on steep slopes of sandstone mountain, alt. 700–800 m a.s.l., humid and shady areas along streams, around point N22º22’51’’ E102º14’26”, terrestrial herb, flowers light lilac to almost white, seeds glossy blue, common, 15 May 2022, L . Averyanov , H . T . Tran , K . S . Nguyen , H . C . Nguyen , T . Maisak & B . C . Khoa , VR 1660 (holotype: HN, isotypes: LE, HN)

Diagnosis: —In having slenderly petioled clavate leaves, this new species is most similar to O. griffithii , but is clearly distinguishable mainly by the wider (1.8–2.9 vs. 0.3–1.9 cm) leaf blades, wider (3.5–7.5 vs. 2–2.8 mm), obliquely (vs. explanately) expanded perianth lobes, and free narrowly deltoid (vs. laterally connate, linear-lanceolate) anthers.

Description: —Herb terrestrial, rhizomatous, tufted, glabrous, evergreen, perennial. Rhizome subterranean, horizontal, simple or branched, knobby, flexuose, (3–)5–7(–8.5) cm long, (6–)7–9(–11) mm in diameter, robust, brown; knobs (tubers) (5–)7–9(–11), subglobose or ovoid, erect or suberect, 9–14 mm high, producing (2–)3–4(–5) roots, apically covered with cataphylls and bases of leaves. Roots proximally cordlike, somewhat straight, semi-ligneous, (1–)1.5– 2.2(–2.5) mm in diameter, brown, puberulent when young. Cataphylls several, imbricate, the innermost linear-lanceolate or ensiform, (5–)7–9(–11) cm long, (8–)10–16(–18) mm wide (when flattened), subacute or obtuse, longitudinally concave or convolute, chartaceous, margins winged and scarious, soon disintegrated into fibrous remains. Leaves (20–)30–45(–50) per plant, 4–5 per shoot, tufted, sub-erect or slightly arching, (41–)65–80(–83) cm long, distinctly petiolate; petiole linear, (5–)20–38(–40) cm long, (2.5–)3–3.5(–4) mm wide, triangular to semi-circular in cross section, grooved adaxially, basally brown to brownish yellow, light green upward; blade linear-oblanceolate (or narrowly clavate), (35–)40–50(–52) cm long, (1.8–)2–2.7(–2.9) cm wide, acute to subacute at apex, attenuate at base, leathery, slightly oblique, adaxial surface glossy, light green when young, becoming darker green with age, abaxially silverglaucous; longitudinal veins 21–30 including midrib which is raised on both surfaces, pale light green; transversal veinlets numerous, strongly oblique, spaced at intervals of 5–6 mm, indistinct (detectable only on dried blades by a magnifier); leaf margins finely serrulate distally, with white scarious wings 2–4(–5) mm wide from base to petiole. Flowering stem (including peduncle and rachis) sub-erect to ascending, nearly straight, with 2 prominent and 15–19 slightly raised longitudinal ridges, broadly elliptic or nearly circular in cross section, whitish green tinged with purple, base sometimes almost purple; peduncle subterete, slightly flattened, (6–)8–10(–12) cm long, (3–)3.5–4(4.5) mm in diameter, basally covered with several imbricate sterile bracts 1.8–2.5 cm long, 1.2–1.5 cm wide, in the middle part usually with 1 (rarely 0) sterile bract which is ascending, broadly ovate to deltoid-ovate, 16–22(–25) mm long, 14–18(–20) mm wide, acute to obtuse, concave, abaxially greenish white tinged with purple, or almost purple to black purple, margins white, membranous. Inflorescence racemose with (5–)9–12(–15) fascicles of (1–)2(–3) flowers; rachis (5–)9–12(–17) cm long; pedicels much shorter than basal stalky part of perianth, (2.8–)3–4(–4.2) mm long, (0.7–)0.8–0.9(–1) mm in diameter, terete or sub-triangular in cross section, greenish white, sometimes tinged with purple; floral bracts in tufts of (2–)3, cymbiform, broadly acute to obtuse, abaxially dirty bluish purple to almost black purple, adaxially dull white, margins membranous to scarious; the outermost bract broadly ovate to ovate, becoming smaller upward, (7–)9–13(–15) mm long, (5–)6–9(–10) mm wide, with three longitudinal veins; the second outermost bract (bracteole), if present, ovate to narrowly ovate, (3.5–)4–6(–7) mm long, (2–)2.5–3.5(–4) mm wide; the third bract (innermost bracteole), ovate to subulate, 1.5–2(–2.5) mm long, 1–1.5 mm wide. Flowers secund, cernuous, broadly campanulate, (15–)17–19(20) mm across when fully expanded, odorless, enectariferous. Perianth proximally syntepalous, distally 6-cleft, fleshy; syntepalous part (including basal stalky part) infundibuliform, (9–)10–13(–14) mm long, (4–)5–7(–8) mm in diameter at summit, 1.2–1.5 mm in diameter at base, white, glossy; lobes 6 in 2 whorls, abaxially white, pinkish white, or white tinged with purple or maroon along margins, adaxially white, often distally pinkish, or purple in large part, broadly acute to obtuse, slightly recurved at apex, almost entire; outer 3 lobes oblong, (9.5–)10–12 (–12.5) mm long, (3.5–)4–5(–5.5) mm wide; inner 3 lobes deltoid-ovate, shorter and slightly wider than outer ones, (9–)9.5–11(–11.5) mm long, (5–)5.5–6.5(–7.5) mm wide. Stamens 6, free, inserted at base of each perianth lobe; filaments trapezoidal, 0.5–0.6 mm long, 1.4–2 mm wide, ca. 0.6–0.8 mm thick, greenish white to light green; connective dorsally incrassate, subulate, greenish; anthers connivent distally, distinct, narrowly hastate-deltoid (lateral sides slightly concave and dilated toward base), (4.8–)5–5.8(–6) mm long, 2–2.4 mm wide at base, 0.7–0.9 (–1) mm thick, introrse, apical portion of each theca dehiscent, light pale yellowish white. Pistil 1, tricarpellate, white; ovary inferior, obconoid or nearly obovoid, apex subtruncate, slightly convex above, but somewhat concave around base of style, 3-locular; each locule with 2 ovoid to subglobose ovules on basal part of ovary central axis; style (acicular-)subulate, erect, straight or slightly curved distally, (9–)10–12(–13) mm long, 0.8–1 mm in diameter at base; stigmatic portion minute, subacute to obtuse. Seeds ellipsoid or ovoid, (11–)12–15(–16) mm long, (8.5–)9–11(–11.5) mm in diameter, glossy, sarcotesta externally cobalt blue, sparsely dispersed with minute white dots.

Etymology: —The specific epithet refers to the type locality (Muong Nhe, NW Vietnam).

Phenology: —Flowering in May, probably also in June. Seed ripening in May. It takes about 1 year from flowering to seed ripening.

Habitat and conservation status:― Ophiopogon muongnhensis grows in humid and shady areas along streams of sandstone mountains covered by remnants of primary evergreen broad-leaved forest, alt. 700–800 m a.s.l. It was not rare in the surveyed area. We estimated approximately 80–150 mature plants occurring in the area of about 1000 m 2. The habitat in the Muong Nhe Nature Reserve is protected by regional authorities from any artificial disturbance. More populations of this species may also be found in other sandstone mountains of Muong Nhe District , northwestern Vietnam, the southwestern areas (e.g. Pu’er, Honghe and Xishuangbanna Counties) of Yunnan Province, China, and in the northeastern regions of Phongsali Province, Laos. According to the IUCN Red List categories and criteria (2019), O. muongnhensis is tentatively assessed here as “data deficient” (DD).

Distribution: ―Currently known only from the type locality, NW Vietnam.

Taxonomic relationships: ―In having slenderly petioled clavate leaves Ophiopogon muongnhensis appears most similar to O. griffithii ( Baker 1875: 502) Hooker (1892: 270) originally described from NE India. According to Tanaka (1999), O. griffithii is distributed also in Myanmar, N. Thailand, and SW China (SW Yunnan). The new species is distinguishable from O. griffithii mainly by the characters mentioned in the above diagnosis. The anthers of O. muongnhensis are free, whereas those of O. griffithii are laterally connate. In this respect O. muongnhensis is plesiomorphic.

The new species also shares slenderly petioled leaves with O. corifolius F.T.Wang & L.K.Dai in Wang and Tang (1978: 253) distributed in SW Guizhou, SW China, but differs chiefly by the wider (1.8–2.9 vs. 1–1.5 cm) leaf blades with more longitudinal veins (21–30 vs. 9), shorter peduncle (6–12 vs. ca. 24 cm), and shorter (4.8–6 vs. ca. 8 mm) narrowly deltoid (vs. linear) anthers.

In general appearance, the new species somewhat resembles both O. intermedius and O. megalanthus , but readily distinguishable from them mainly by the distinctly petiolate, wider (1.8–2.9 vs. 0.2–0.8 cm in O. intermedius and 0.8–1.5 cm in O. megalanthus ) clavate (vs. linear) leaves, shorter peduncle (6–12 vs. 20–50 cm in O. intermedius and 30–35 cm in O. megalanthus ), ovate (vs. lanceolate) floral bracts, and longer style (9–13 vs. 5.8 mm in O. intermedius and ca. 8 mm in O. megalanthus ) (data from Wang and Tang 1978 for O. intermedius and O. megalanthus , and Tanaka 2001 for the style length of O. intermedius ).

Figures

FIGURE 1. Ophiopogon muongnhensis. A. Plant in natural habitat. B. Inflorescence. C. Portion of inflorescence. D. Infructescence with ripe seeds. E. Habit (pressed specimen). F. Rhizome. G. Portion of leaf blade, adaxial surface (above) and abaxial surface (below). H. Leaf apex, abaxial (left) and adaxial (right) surface. I. Floral bracts and pedicels. Photos and design by K.S. Nguyen.

FIGURE 2. Ophiopogon muongnhensis. A. Distal portion of inflorescence. B. Flower, rear view. C. Flower, showing its interior. D. Flower, front view. E. Dissected flower. F. Portion of flower longitudinally cut, showing pistil and stamens. G. Stamens, abaxial view (left) and adaxial view (right). Photos and design by K.S. Nguyen.