Ophiopogon heterotepalus N.Tanaka, Vuong & Aver., 2025

Tanaka, Noriyuki, Truong, Ba Vuong, Averyanov, Leonid V. & Maisak, Tatiana V., 2025, Ophiopogon heterotepalus (Asparagaceae), a new species from north-western Vietnam, Phytotaxa 700 (2), pp. 243-250 : 244-248

Ophiopogon heterotepalus N.Tanaka, Vuong & Aver. , sp. nov. ( Fig. 1, 2)

Diagnosis: — Ophiopogon heterotepalus appears most closely related to O. peliosanthoides , but readily distinguishable chiefly in its significantly smaller, less widely open urceolate-campanulate flowers, shorter prominently dimorphic (or heteromorphic) perianth lobes differing in shape and size between the inner and the outer whorls, shorter triangular anthers, and shorter styles.

Type: — VIETNAM. Lai Chau Province: Sin Ho District, Lang Mo Commune, forest around Tu Cua Phin Village, terrestrial clustering herb, leaves green above, silvery below, flower pink to pinkish, 31 March 2022, Truong Ba Vuong & Bui Van Huong, BV 1363 (holotype: VNM VNM 00070763!).

Images of living materials examined for this identification are archived under LE LE 01123079 // Virtual herbarium of Komarov Botanical Institute of the Russian Academy of Sciences (http://re.herbariumle.ru/01123079).

Etymology: —The specific epithet refers to the heteromorphic (or dimorphic) perianth lobes differing markedly between the inner and the outer whorls, which distinguishes the new species from all other congeners.

Description:—Plant acaulescent, rhizomatous, glabrous, evergreen, perennial. Stem short, hardly defined from rhizome. Rhizome elongate, subterete, at least 3.5 cm long, 5.5–7 mm in diameter, ascending, externally pale brown, apical part covered with decayed dark brown fibrous remnants mostly of sheath leaves that are broadly ovate to linear lanceolate with scarious margins, to 4 cm long. Roots cord-like or filamentous, white to pale brown, up to 2 mm in diameter, densely covered with root hair. Foliage leaves 4–5, clustered on apical part of stem/rhizome, distinctly petiolate; petiole 11–18 cm long, 3–4 mm wide, abaxially rounded (in cross-section), adaxially somewhat flat; blade elliptic-oblong, somewhat oblique proximally, obtuse at apex, 10–12.5 cm long, 2.2–3.3 cm wide, adaxially glossy, deep green, abaxially glaucous (silvery or fairly whitish), longitudinal veins parallel, 7–9 (–13) including midvein, marginal and somewhat thinner ones, several inner lateral veins coalescent with midvein, forming a narrow bundle in basal and sub-basal region, and then diverging parallel from midvein, ribbed abaxially, transversal veinlets somewhat prominent, nearly perpendicular to longitudinal veins, spaced close to one another with intervals of 0.3–2 mm. Flowering stem (peduncle and inflorescence rachis) 17.8–18.3 cm tall, shorter than foliage leaves; peduncle terete, 10–11.5 cm long, 2 mm in diameter, tinged purple, bracteate; bracts 11 including proximal ones, denser toward base, acroscopic, narrowly triangular-lanceolate, white, membranous, 7–16 mm long, 5–6 mm wide, embracing peduncle; inflorescence racemose (reduced thyrsoid or panicle); rachis erect, almost straight, 7–9 cm long, 2 mm in diameter in middle, distally narrowing. Flower actinomorphic, bisexual, adichogamous, solitary in axils of bracts, up to 16 per rachis, urceolate-campanulate or cup-shaped, 6.5 mm high, ca. 6 mm across, usually horizontally directed, but tending to be slightly nodding in late anthesis, pedicellate; pedicels terete, 2.5–4 mm long, 1.5 mm in diameter, jointed with basal stalky part of flower (articulation formed slightly above middle of entire stalky part including pedicel), subtended at base by 2 bracts (1 outer bract and 1 inner bracteole) which are acroscopic, navicular, purplish; bract narrowly triangular, up to 7.5 mm long, 4.5 mm wide, bracteole narrowly triangular or subulate, acute, up to ca. 4 mm long. Perianth distally 6-lobed, pink-purplish; basal tubular part broadly funnel-shaped, tapering below into a short stalk ca. 2.3 mm long; lobes in 2 whorls of 3, dimorphic as to shape and size between inner and outer whorls, apex obtuse, 1-nerved; outer lobes narrowly triangular lanceolate, 5.5–5.8 mm long, 3 mm wide, usually scarcely excurved distally; inner lobes broadly triangular ovate, 6–6.5 mm long, 5–5.5 mm wide, apically recurved (inner lobes larger, paler in color, more distinctly recurved distally than outer lobes). Stamens 6, arranged almost in 1 whorl, shaped conic in assemblage (androecium); filaments proximally directed outward, distally abruptly inflexed, subterete, 0.8–1 mm long, 1–1.2 mm wide, white; anthers dorsi-basifixed, connivent distally surrounding style, valvately arranged, triangular, 2.5–3 mm long, 1.7–2 mm wide, cordate at base, apically obtuse and poricidal, (greenish) yellow, abaxial and adaxial anther sacs oblique in side view. Pistil 1, white; ovary half-inferior, apical exposed portion nearly circular, 2.8–3 mm across, slightly inflated above, radially 3-lobed, lobes 0.5–0.8 mm high, proximal sunken portion 3-locular; ovules borne on basal central placentae; style arising from apical hollow center of ovary, erect, subulate, obtusely 3- angled, 3-sulcate, 3.8–4 mm long, 0.5 mm in diameter near base; stigma 3-lobed, ca. 0.3 mm across. Fruits not seen.

Ecology and phenology:— Occurs occasionally as a terrestrial clustering herb in a shady humid rocky location in a remnant primary forest of evergreen broad-leaved trees at elevations of 1200–1500 m a.s.l. Flowers in March– April.

Conservation status:— The new species was found occasionally in a single location. The ample precise information about its populations and distribution in wider areas is currently unknown. The conservation status of this species is hence assessed here as data deficient (DD), following the guidelines of IUCN (2024).

Distribution: —The new species is currently known only from the type locality in Sin Ho District, Lai Chau Province, NW Vietnam.

Notes: —The perianth lobes (in two whorls of three) of O. heterotepalus are distinctly dimorphic (or heteromorphic) as to shape and size between the two whorls. As far as we are aware, those in other species of this genus are nearly monomorphic (or homomorphic) or less prominently dimorphic even when they exhibit some degree of dimorphism. The remarkable dimorphism in O. heterotepalus can hence be used as a good distinguishing character for this new species.

Wang & Tang (1978: 251) once classified 12 species of Ophiopogon possessing oblong or oblanceolate leaf blades with distinct petioles into O. sect. Peliosanthoides F.T.Wang & L.K.Dai in Wang & Tang (1978: 251). In this section, some species have an aerial stem as in O. dracaenoides (Baker) Hooker (1892: 268) , while others are acaulescent as in O. tonkinensis Rodriguez (1929: 998) and O. xylorrhizus Wang & Tang (1978: 252) .

Of these acaulescent species, O. heterotepalus appears most closely related to both O. peliosanthoides Wang & Tang (1978: 252) and O. pingbienensis F.T.Wang & L.K.Dai in Wang & Tang (1978: 251) each known from SW China ( Wang & Tang 1978) and N Vietnam ( Averyanov et al. 2020), for these three species lack woody prop roots and share abaxially whitish leaf blades with several inner lateral veins coalescent with the midvein in the sub-basal part; and solitary or only a few (up to 3) purplish flowers in axils of bracts. In addition, these three species occur close to one another in geographical distribution. Several characters that seem taxonomically significant of these three species are compared in Table 1.

In having petioles longer than the blades, somewhat prominent transversal veinlets on the blades, and comparatively long peduncle, O. heterotepalus may be viewed as closer to O. peliosanthoides than to O. pingbienensis .

From O. peliosanthoides , the new species differs mainly in the slightly narrower (2.2–3.3 vs. 3.2–3.8 mm wide), flat or unwrinkled (vs. often wrinkled) leaf blades with parallel (vs. slightly more like pinnate-parallel) longitudinal lateral veins and often closer transversal veinlets; significantly smaller, less widely open, solitary (vs. 1–3), urceolate-campanulate flowers in axils of bracts; shorter (5.5–6.5 vs. 10–12 mm) distinctly heteromorphic (vs. nearly homomorphic) perianth lobes; shorter (2.5–3 vs. ca. 8 mm) triangular (vs. linear lanceolate) anthers; and shorter styles (3.8–4 vs. ca. 9 mm) ( Table 1).

From O. pingbienensis , O. heterotepalus is distinguishable chiefly by the slightly wider leaf blades (2.2–3.3 vs. 1.5–2 cm) with more prominent transversal veinlets, significantly smaller, less widely expanding flowers with shorter (5.5–6.5 vs. 8–11 mm) heteromorphic (vs. nearly homomorphic) perianth lobes, shorter (2.5–3 vs. ca. 6 mm) triangular (vs. narrowly lanceolate) anthers, and shorter styles (3.8–4 vs. ca. 7 mm) ( Table 1).

In future field surveys, it is likely that O. heterotepalus will be found also in adjacent regions of Yunnan, SW China.