Ophiopogon dolichocaulis K.S.Nguyen, N.Tanaka & Aver., 2021

Nguyen, Khang Sinh, Tanaka, Noriyuki, Averyanov, Leonid V., Maisak, Tatiana V., Nguyen, Phuong Hanh & Tran, Duc Binh, 2021, Two new species, Ophiopogon dolichocaulis and O. trigonantherus (Asparagaceae), from northern Vietnam, Phytotaxa 523 (4), pp. 291-298 : 291-295

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

Most similar to O. chingii , but distinguished by a combination of several traits such as thick rigid prop roots, numerous acute, often longer leaves with a midrib raised abaxially, comparatively short floral stalks (pedicel and basal stalky part of flower), and slightly larger flowers with greenish narrowly hastate-deltoid anthers.

Type: — VIETNAM. Son La Province: Muong La District, Muong La Nature Reserve, Ngoc Chien Commune , remnant primary evergreen broad-leaved forest on sandstone mountains, along ridge or on slopes at elevation of 1300 m a.s.l., around point 21.60240°N 104.10882°E, terrestrial erect to suberect perennial herb, 40–60 cm tall, flowers abaxially white with purplish violet smears and dots, adaxially almost white, locally not rare, August 2020, Nguyen Sinh Khang & Lo Van Chieu, NSK 1348 (holotype HN!, isotype HN!) .

Description: —Herb terrestrial, glabrous, evergreen, perennial. Stem simple, usually decumbent and flexuous in proximal part, erect to suberect in distal part, (5)10–35(40) cm tall, (0.5)0.6–0.8(1) cm in diameter., densely covered with leaf sheaths, proximally with 3–5 semi-woody prop roots; prop roots rigid, fleshy, greenish to brown, (2.5)3–4(4.5) mm in diameter. Leaves 50–60, spirally, consecutively and densely scattered over aerial part of stem, arching, linear, slightly falcate, attenuate at base and apex, (15)20–35(40) cm long, (7)8–11(13) mm wide, leathery, glabrous, adaxial surface glossy, uniformly light grass-green when young, becoming darker green with age; abaxial longitudinal veins 11–18 (including marginal ones), light pale green, midrib (midvein) somewhat raised, intervein regions paler; leaf margin finely serrulate; proximal part with white scarious wings (3)4–5(6) mm wide and transversely minutely plicate. Flowering stem (including peduncle and rachis) geniculately bent proximally, ascending or horizontally spreading, flexuose, fleshy, somewhat twisted, with 15–20 prominent longitudinal ridges, nearly tetragonal in cross section, green tinged with dirty bluish violet; peduncle (1.5)2–3(3.5) cm long, (3)3.2–3.8(4) mm in diameter, ebracteate; inflorescence a lax raceme with 10–16 distant fascicles of (1)2–3(4) flowers; rachis (5)6–7(8) cm long; pedicels arising from axils of bracts, acroscopic, terete, usually dirty bluish violet, (1.5)2–4(4.5) mm long, (0.4)0.5–0.6(0.7) mm in diameter, distally slightly narrowed, forming a distinct articulation to basal stalky part of perianth; floral bracts fasciculate, outermost bract acroscopic, glabrous, lanceolate to narrowly triangular, (7)9–13(15) mm long, (2.5)3–4(4.5) mm wide, acute, cymbiform, light pale green to dirty bluish violet on both surfaces, margin scarious, more or less irregularly undulate; inner bracts (bracteoles) similar to outermost bract in texture, shape and color, but much smaller, (1.5)2– 4.5(5) mm long, (0.8)1–1.5(2) mm wide. Flowers cernuous, campanulate, (7.5)8–9(9.5) mm long, (7)7.5–8.5(9) mm across, odorless, enectariferous. Perianth fleshy, glabrous, proximally syntepalous, distally 6-cleft; syntepalous part (including basal stalky part 1–2 mm long) funnel-form, purplish violet, (3)3.2–3.8(4) mm long, (2)2.2–2.8(3) mm in diameter at summit; lobes 6, ovate to narrowly ovate, outer 3 slightly wider than inner 3, (5.2)5.5–6.5(6.8) mm long, (2.3)2.5–3(3.2) mm wide, white tinged with purplish violet, margins entire, somewhat undulate, revolute, apex subacute to obtuse, recurved. Stamens 6, free, inserted at base of each perianth lobe; filaments trapezoidal, 0.3–0.4 mm long, 0.8–1 mm wide, ca. 0.2 mm thick, greenish white to white; anthers slightly connivent distally, dorsi-basifixed, subsessile, narrowly hastate-deltoid (lateral sides somewhat concave and dilated toward base), (2.9)3–3.2(3.3) mm long, (1.2)1.3–1.4(1.5) mm wide at base, 0.6–0.8 mm thick, introrse, apical portion of each theca dehiscing earlier, light pale yellowish green. Pistil 1, tricarpellate, white; ovary inferior, nearly obovoid, apex subtruncate, slightly convex above, but somewhat concave in center around base of style, 3-locular; each locule with 2 ovules on basal part of ovary central axis, obovoid to subglobose; style awl-shaped, erect, straight or slightly curved distally, (5)5.2– 5.5(5.7) mm long, 0.5–0.7 mm in diameter, longitudinally slightly 3-sulcate; stigma minute, subacute to obtuse. Seeds ellipsoid, (9)10–12(13) mm long, (6)6.5–8(8.5) mm in diameter, sarcotesta externally cobalt blue at maturity, glossy, albumen white.

Paratype: — VIETNAM. Son La Province: Muong La District, Muong La Nature Reserve, Ngoc Chien Commune , remnant primary evergreen broad-leaved forest on sandstone mountains, from foot to middle of slopes at elevation of 1000–1350 m a.s.l., around point 21.60356°N 104.10543°E, terrestrial perennial herb erect to suberect, 45–60 cm tall, fruits glossy, cobalt blue, locally not rare, March 2019, Nguyen Sinh Khang, Nguyen Phuong Hanh, Tran Duc Binh, Nguyen Duc Thang & Lo Van Chieu, NSK 1155 ( HN!) .

Etymology: —The specific epithet is a Greek-derived adjectival compound, referring to the comparatively ‘long stem’ of the new species.

Habitat and conservation status: ― Ophiopogon dolichocaulis grows as undergrowth in the humid or wet locations of the primary evergreen broad-leaved forest covering the foot to middle part of sandstone mountains at elevation of 1000–1350 m a.s.l. It was not rare in the surveyed area; in our estimation, approximately 100 to 200 mature plants occur in the area of about 2000 m 2. The habitat has been protected by regional authorities from any artificial disturbance such as deforestation and exploitation for timber and non-timber forest products. Since several other provinces in northwestern Vietnam, such as Lai Chau, Lao Cai and Yen Bai, also have sandstone mountains, it is highly probable that more populations of the new species are present in other locations similar in habitat condition to the type locality. Ophiopogon dolichocaulis is tentatively assessed here as “data deficient” (DD) in accordance with the IUCN Red List categories and criteria (2019).

Phenology: —Flowers in August–September, fruits in February–March.

Distribution: ―NW Vietnam (Son La Province, Muong La District, Muong La Nature Reserve).

Taxonomic relationships: ―Sharing leaves scattered over an elongate aerial stem, leaf basal wings that are white, scarious and transversely minutely plicate, and campanulate flowers, Ophiopogon dolichocaulis is apparently morphologically closest to O. chingii Wang & Tang (1937: 282) . Ophiopogon chingii is distributed widely in Vietnam and southwestern China and morphologically highly variable ( Tanaka 2000a). In particular, O. chingii var. glaucifolius F.T.Wang & L.K.Dai in Wang & Tang (1978: 252) with broader glaucous leaves was once segregated, but later it was reduced to a synonym of O. chingii ( Chen and Tamura 2000, Tanaka 2000a) due to the existence of intermediate forms. The new species is distinguished from O. chingii by a combination of the following traits: thick (2.5–4.5 vs. often less than 2.5 mm in diameter) rigid (vs. soft) roots, acute (vs. often obtuse or subobtuse) leaves 15–40 (vs. 7–28) cm long with a more prominent midrib raised abaxially, somewhat thicker (nearly tetragonal in cross section vs. complanate), prominently (vs. often scarcely) ridged peduncle and rachis, slightly larger flowers (e.g. perianth lobes 5.2–6.8 × 2.3–3.2 vs. 4.3–5.8 × 1.5–2.1 mm), pedicel and basal stalky part of flower up to 6.5 (vs. 9.5) mm long, and narrowly hastate-deltoid (vs. lanceolate) anthers (numerical data on O. chingii is taken from Tanaka 2000a).

In its scattered leaves and thick rigid prop roots, the new species is also similar to Ophiopogon fruticulosus Aver., N.Tanaka & K.S.Nguyen in Averyanov et al. (2015: 28) known from Tuyen Quang Province in northern Vietnam, but is readily distinguished mainly by the shorter aerial stem (up to 0.4 vs. 0.6–1.5 m tall), campanulate (vs. sub-urceolate) flowers, thinner perianth lobes and thinner (vs. strongly incrassate) anther connectives.

Figures

FIGURE 1. Ophiopogon dolichocaulis.A.Plant innatural habitat.B.Aerial stem with leaf bases, showing white scarious wings imbricately sheathing stem. C. Habit (pressed, dried specimen). D. Four detached leaves, adaxial (top and third from above) and abaxial sides (two others). E. Portion of leaf, abaxial surface. F. Inflorescence, side view. G. Infructescence with ripe seeds. H & I. Proximal portions of inflorescence. J. Seeds; external view (left), core (right top) and cross section (right bottom). A, B, G & J: NSK 1155, C–F, H & I: NSK 1348. Photos and layout by K.S. Nguyen.

FIGURE 2. Ophiopogon dolichocaulis. A. Distal portion of inflorescence. B. Flower, front view. C. Flower longitudinally cut into two parts. D. Perianth lobe (adaxial view) and stamen (abaxial view). E. Cross section of flower immediately above filaments, front view. F. Cross section of flower at basal part, showing ovary locules and ovules.All photos: NSK 1348. Photos and layout by K.S. Nguyen.