Hylophila vietnamensis Aver. & V.C.Nguyen, 2024

Averyanov, Leonid V., Nguyen, Van Canh, Le, Tuan Anh, Vuong, Truong Ba, Nuraliev, Maxim S., Maisak, Tatiana V., Yudova, Daria A., Nguyen, Cuong Huu & Nong, Duy Van, 2024, New orchids in the flora of Vietnam IX (Orchidaceae: Orchidoideae, tribes Cranichideae and Orchideae), Phytotaxa 664 (4), pp. 229-248 : 242-244

Hylophila vietnamensis Aver. & V.C.Nguyen , sp. nov.

( Fig. 8 )

Diagnosis: —The new species differs from the morphologically most similar Hylophila mollis in distant leaves, ovary spreading almost horizontally or at an obtuse angle to the rachis, tubular (hardly opening) flowers twice longer than wide, narrowly ovate sepals 4.4–5.3 mm long, lip with semi-ovoid hypochile and forward directed epichile, disk of hypochile with glabrous longitudinal callosity, entire rostellum shorter than anther cap, and entire circular stigma.

Type: — VIETNAM. Dak Lak Province: Chu Yang Sin Mountains, lithophytic, creeping and ascending herb in mossy place along stream in evergreen broad-leaved forest, very rare, 07 August 2022, Nguyen Van Canh, AL 2459 (holotype LE LE 01254638 https:// en.herbariumle.ru/?t=occ&id=218339, drawing LE LE 01124836 https://en.herbariumle.ru/?t=occ&id=220670).

Description: —Perennial sympodial terrestrial creeping herb with ascending erect floriferous stem; stem, peduncle, rachis, floral bracts (outside), pedicel, ovary, sepals (outside) and fruit densely covered with long multicellular glandular hairs. Floriferous stem terete, longitudinally finely ribbed, (14)16–24(26) cm tall, (3)3.2–3.8(4) mm in diameter, with 3–5(6) distant, spirally arranged leaves. Leaves sheathed, sessile or subsessile; leaf sheath scarious, tubular, (5)7– 12(14) mm long, (4.5)5–6(7) mm in diameter, shortly hairy outside; leaf blade oblong narrowly obovate, leathery, with 1 main vein, obtuse, (2.5)4–8(9) cm long, (1)1.1–1.5(1.6) cm wide, almost glabrous. Inflorescence a dense, slightly secund raceme with numerous spirally arranged flowers. Peduncle and rachis erect, straight; peduncle (4.5)5–7(8) cm long, with 2–3(4) sterile bracts; sterile bracts leaf-like, narrowly triangular, acute to acuminate, (1.2)1–1.5(1.7) cm long, (2)3–5(5.5) mm wide (when flattened), almost glabrous (except for sheath); rachis (4.5)5–8(10) cm long. Floral bracts narrowly ovate to narrowly triangular ovate, cymbiform, acuminate, (4.5)5–9(10) mm long, (1.2)1.5–2(2.2) mm wide (when flat), glandular ciliate along margin, inside (adaxially) almost glabrous. Pedicel terete, (1)1.2–1.7(1.8) mm long. Ovary spreading almost horizontally or at an obtuse angle to the rachis, fusiform, terete, slightly grooved, (2.2)2.5–3.5(3.8) mm long, (0.6)0.8–1.5(1.7) mm in diameter, twisted at 180°. Flowers hardly opening, tubular, (3.5)3.7–4(4.2) mm long, (1)1.2–1.6(1.7) mm in diameter. Sepals free, 1-veined, narrowly ovate, concave, straight, slightly cucullate at obtuse or shortly acuminate apex, (4.4)4.6–5.1(5.3) long, (1.6)1.7–2(2.1) mm wide, adaxially glabrous; lateral sepals slightly oblique at base, slightly larger than median sepal. Petals 1-veined, straight, strongly oblique, obscurely rhomboid, narrowing to apex, as long as median sepal, (1.15)1.2–1.4(1.45) mm wide, glabrous, fused together in apical half into a sympetalum connivent with the median sepal to form a narrow hood. Lip (4.9)5– 5.2(5.3) mm long, (2.5)2.6–3(3.1) mm wide, glabrous, distinctly divided into hypochile and epichile. Hypochile somewhat fleshy, deeply saccate, semi-ovoid, (2.4)2.6–2.8(3) mm long, (1.9)2(2.1) mm wide, with slightly involute margins, entirely enclosed by lateral sepals; disk adaxially with simple, elongate, glabrous longitudinal callosity at center. Epichile simple, slender, straight, forward directed, oblong narrowly triangular to subulate, cymbiform, obtuse, 1.5–1.6 mm long, about 0.3 mm wide. Column slender, shortly cylindrical, (2.2)2.4–2.6(2.8) mm tall, 0.3–0.35 mm in diameter, wingless, somewhat bent forward; stigma entire, circular, finely tuberculate, placed at front in apical part of column, as wide as column; rostellum entire, narrowly triangular to triangular, erect or somewhat bent forward, (0.5)0.6–0.8(0.9) mm long, (0.45)0.5–0.6(0.65) mm wide; anther broadly semi-ovoid, cordate at base, acute or shortly acuminate at apex, 1–1.2 mm long, as wide as rostellum. Fruit a narrowly ellipsoid capsule, (3.6)3.8–4(4.2) mm long, (1.8)2–2.2(2.4) mm in diameter.

Etymology: —The species name refers the country of the species origin.

Habitat and phenology: —Primary and secondary mountain evergreen broad-leaved forests, commonly in mossy places along streams, very rare. Flowers in July–August.

Distribution: — Vietnam (Dak Lak Province: Chu Yang Sin Mountains).

Conservation status: — Hylophila vietnamensis is known from a single location within the territory of the Chu Yang Sin Mountains in the limits of Dak Lak Province. This location is likely to be within the borders of the Chu Yang Sin National Park. Information on the size and geographical extension of the only known population is currently unavailable. Hence, we estimate the conservation status of H. vietnamensis as Data Deficient (DD). Additional field studies are necessary to comprehensively establish the status of the species.

Notes: —The finding reported here represents the first record of the genus Hylophila in the flora of Vietnam.

Prior to this study, the genus Hylophila included five species widely distributed in Southeast Asia and Australasia, from Thailand and Taiwan to the Philippines, Indonesia and the Pacific Islands ( Pridgeon et al. 2003, Pedersen et al. 2011b, Lin & Wang 2014, Rojchana-Umpawan et al. 2015). Four of them ( H. cheangii Holttum , H. lanceolata (Blume) Miq. , H. nipponica (Fukuy.) T.P.Lin , and H. rubra Ames ) were segregated by some taxonomists ( Fukuyama 1936, Seidenfaden 1976, 1978, Dressler 1981, 1993) into a separate genus Dicerostylis Blume (1859: 116) , or at least were discussed to belong to this genus. Dicerostylis was distinguished from Hylophila s.str. by its bilobed stigma, V-shaped or bearing at front a pair of conspicuous finger-like stigma lobes. The only remaining species ( H. mollis Lindley (1840: 490) , the type species of Hylophila ) is characterized by an entire stigma lacking any appendages or callosities.

Hylophila vietnamensis corresponds in its overall morphology, and particularly in the stigma structure, to Hylophila s.str. It differs from H. mollis in a series of significant morphological characters, as outlined in Table 2.

taken from its protologue and from Holttum (1964), Seidenfaden & Wood (1992), Comber (2001) and Rojchana-Umpawan et al. (2015).

Both species of Hylophila s.str. ( H. mollis and H. vietnamensis ) are very close in their general appearance to the genus Goodyera R.Br. in Aiton (1813: 197), but differ mainly in the hypochile that bears neither hairs nor glands. At the same time, the shape of the flower lip in H. vietnamensis is very similar to that of some species of Goodyera .

Figures

FIGURE 8. Hylophila vietnamensis. A. Flowering plant. B. Leaf, adaxial side. C. Portion of rachis, floral bract and flower, side view. D. Floral bract, abaxial side. E. Flattened sepals and petals, adaxial view (petals artificially separated). F. Median sepal and sympetalum, adaxial view. G. Apical part of ovary, lateral sepal, lip, and column, side view. H. Apical part of ovary, column and sagittally dissected lip, side view. I, J. Distal part of column and lip, view from above and half-side view. K. Distal part of column and lip, partially dissected and flattened, showing callus on disk, view from above. L. Column, front, half-side and side views. M. Anther, view from below. N. Pedicel and ripening fruit. O. Typical glandular hairs of plant indumentum. Drawn from the holotype specimen Nguyen Van Canh, AL2459 by L. Averyanov.