Bidoupia micrantha Aver., V.C.Nguyen & Duy, 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 : 238-241

Bidoupia micrantha Aver., V.C.Nguyen & Duy , sp. nov.

( Fig. 6 & 7 )

Diagnosis: —The new species differs from the morphologically closest Bidoupia phongii mainly in green, distinctly petiolate distantly arranged leaves, smaller floral bracts 6–10 × 1.8–3.5 mm, twice smaller flowers 7–9 mm across, glabrous ovary, concave stigma, straight triangular rostellum 0.5–0.6 mm long, the presence of auricles, and smaller pollinia 1.6–1.7 mm long.

Type: — VIETNAM. Lam Dong Province: the border of Lac Duong and Dam Rong districts, Bidoup Nui Ba National Park, mountain evergreen broad-leaved and mixed forest (with Pinus kesiya ) at elevation of 1600–1800 m a.s.l., terrestrial creeping herb in shady place along rocky mountain stream, leaves dark velvety green with whitish median stripe, common, 21 February 2023, L. Averyanov, Nguyen Van Canh, Nong Van Duy, plant flowered under cultivation on 28 September 2023, L. Averyanov, T. Maisak, AL 2172 (holotype LE LE 01233987 https://en.herbariumle.ru/?t=occ&id=196234, photos of plant used for preparation of the type herbarium specimen LE LE 01124365 https://en.herbariumle.ru/?t=occ&id=193723).

Description: —Perennial sympodial terrestrial creeping herb with ascending erect floriferous stem. Stem brownish purple, terete, somewhat fleshy, (2.5)3–3.5(4) mm in diameter; plagiotropic part epigeous, leafless, rooting at nodes, (8)10–16(20) cm long, glabrous; ascending part with peduncle and inflorescence (20)25–30(35) cm tall, glabrous, leafy at lower third, with (2)3–4(5) distant, spirally arranged leaves, terminated by erect inflorescence. Leaves shortly sheathed, petiolate, glabrous; leaf sheath scarious, tubular, (4)5–9(11) mm long, (3.5)4–6(7) mm in diameter; petiole (0.8)1.2–2.8(3.2) cm long, 1.8–2.4 mm wide, reddish to white; leaf blade narrowly ovate to ovate, slightly oblique, acute to shortly acuminate, (3.5)4–7.5(8) cm long, (1.8)2–3(3.4) cm wide, with 1 main vein, adaxially dark velvety green with indistinct white median stripe, abaxially uniformly glossy light green. Inflorescence a lax spike with (6)7–12(14) spirally arranged flowers, flowers distant with internodes (1)1.5–2(3) cm. Peduncle and rachis erect, straight, pale yellowish pink to dull olive, more or less densely hairy with very short, stiff hairs; peduncle (8)10–12(14) cm long, with 2–3 sterile bracts; sterile bracts narrowly triangular, acute to acuminate, (8)10–15(17) mm long, (2)2.5– 3(4) mm wide (when flattened), glabrous, ciliate along the margin; rachis (6)8–10(12) cm long. Floral bracts dull purple brown, narrowly triangular ovate, acuminate, densely enveloping ovary, (6)7–9(10) mm long, (1.8)2.2–3(3.5) mm wide (when flattened), outside (abaxially) sparsely hairy, inside (adaxially) glabrous, finely ciliate along margin. Ovary fusiform, dull reddish brown to pale brown, (6)7–11(12) mm long, (2)2.2–2.4(2.6) mm in diameter, glabrous, narrowing towards apex that is bent downwards, twisted. Flowers sessile, widely opening, 7–9 mm in diameter; sepals pale brownish purple; petals pure white; lip white with reddish purple saccate part of hypochile (margin of hypochile white); column white, anther cap pale pink, auricles and stigma yellow, column wings pink. Sepals free, 1-veined, glabrous; median sepal narrowly ovate, concave, straight, erect, slightly cucullate at obtuse or shortly acuminate apex, (4.3)4.5–4.8(5) long, (2.2)2.4–2.6(2.8) mm wide; lateral sepals obliquely ovate rectangular, (5.2)5.4–5.6(5.8) long, (2.6)2.8–3.2(3.4) mm wide, slightly concave to almost flat, horizontally spreading, apiculate and obtuse at apex. Petals straight, strongly oblique, semicircular, narrowing to base and apex, as long as median sepal, (1.7)1.8–2.2(2.3) mm wide, glabrous, without distinct veins, connivent with the median sepal forming a broad hood. Lip asymmetrically bent to right or left side, distinctly divided into hypochile, mesochile (claw) and epichile, 5–5.2 mm long, 2–2.2 mm wide, glabrous. Hypochile concave, broadly saccate or hemispheric, 2.4–2.6 mm long, 2–2.2 mm wide, closed by short and broad incurved side lobes firmly appressed to each other, outside longitudinally shallowly grooved and slightly notched at apex, covered by concave bases of lateral sepals; hypochile outside, on each side near the base of side lobe with low fleshy, crenulate longitudinal keel; hypochile inside with low median longitudinal keel rising near apex of hypochile into prominent flat dent 0.8–0.9 mm tall, near base bearing 2 massive, fleshy, stalked, flat flabellate glands 0.7–0.8 mm tall and wide with finely erose apical margin. Mesochile (claw) with strongly involute margins in form of subterete tube, (1.6)1.7–1.8(2) mm long, (0.2)0.3(0.4) mm in diameter, adaxially grooved. Epichile in form of 2-lobuled plate; lobules spreading, narrowly rhomboid, curved, wing-shaped, (1.6)1.8–2(2.2) mm long, (0.35)0.4–0.5(0.55) mm wide, finely papillose, acute at apex, joined to each other by a small neck recurved to the abaxial side. Column short and broad, (1.9)2–2.2(2.3) mm tall, long and wide, glabrous, bearing near the base at front 2 flat subquadrate pink keels; keels 0.5–0.6 mm long and wide, placed parallel to each other, down directed; stigma large, yellow, as wide as column, placed at front of column, entire, concave with forward rising lateral sides; rostellum triangular, longitudinally concave, straight and forward directed, 0.5–0.6 mm long and wide; column at apex on each side of rostellum with yellow glossy convex auricle; anther cap semi-ovoid, 1.7–1.9 mm long and wide, with short, straight, triangular beak shorter than clinandrium; viscidium very small, lanceolate. Pollinarium 1, with 2 pollinia; pollinium white, stalked, broadly clavate, sectile, 1.6–1.7 mm long, 0.5–0.6 mm in diameter, consisting of 2 hemipollinia. Fruit unknown.

Etymology: —The species name refers to its small flowers in relation to those of its congeners.

Habitat and phenology: —Primary and secondary mountain evergreen broad-leaved and mixed forests (with Pinus kesiya ) at elevation of 1600–1800 m a.s.l., usually in shady places along rocky streams, locally common. Flowers under cultivation in September–October.

Distribution: — Vietnam (Lam Dong Province: Bidoup Nui Ba National Park).

Conservation status: — Bidoupia micrantha is known from a single location within the territory of Bidoup Nui Ba National Park. The assessment of the population characteristics of this species is problematic, because B. micrantha when not flowering can hardly be distinguished from many other orchid species in the area, whereas it apparently rarely blossoms in nature. Formally, the species may tentatively be assessed as Vulnerable (VU) following the IUCN criterion D1, as the observed population contains surely less than 1000 mature individuals. However, additional field studies are necessary to comprehensively establish the status of the species.

Notes: —Prior to this study, the genus Bidoupia was known to comprise two species, B. khangii Aver. in Averyanov et al. (2016b: 320) and B. phongii Aver., Ormerod & Duy in Averyanov et al. (2016a: 290). The newly discovered species almost completely fits the generic characters of Bidoupia reported in its protologue ( Averyanov et al. 2016a). Morphologically, B. micrantha is very similar to B. phongii , the type species of the genus. Both species are known to be local endemics of Langbian plateau within the area known as the Central Highlands of Vietnam. The new species differs from B. phongii in a series of morphological characters, as outlined in Table 1.

Figures

FIGURE 6. Bidoupia micrantha. A. Flattened flowering plants. B. Portion of inflorescence. C. Portion of rachis, floral bract, and flower, side view. D. Portion of rachis. E. Floral bracts. F. Portion of floral bract, abaxial surface. G. Ovaries, side view. H. Flowers with floral bracts, view from different sides. I. Flowers, front, half-side, and rear views. Photos by L. Averyanov from living plant prior to the preparation of the holotype herbarium specimen L. Averyanov, T. Maisak, AL2172. Photo correction and design by L. Averyanov and T. Maisak.

FIGURE 7. Bidoupia micrantha. A. Central part of flower, front view. B. Column and lip, front view. C. Median sepal connivent with petals, adaxial view. D, E. Flattened sepals and petals, adaxial (D) and abaxial (E) side. F. Column and lip, side view. G, H. Column and tangentially dissected lip. I. Lip, sagittal section. J. Sagittal section of lip hypochile showing gland. K. Column, front view. L, M. Column, view from below and half-side view from below. N. Column, view from above. O, P. Column, side and front views (anther artificially recurved). Q, R. Column, view from above and side view (anther removed). S. Anther cap with pollinarium, view from below. T, U. Anther cap with pollinarium, half-side views. Photos by L.Averyanov from living plant prior to the preparation of the holotype herbarium specimen L. Averyanov, T. Maisak, AL2172. Photo correction and design by L. Averyanov and T. Maisak.