Schoenorchis hangianae Aver. et N.V.Duy., 2015

Duy, Nong Van & Averyanov, Leonid V., 2015, Bulbophyllum bidoupense and Schoenorchis hangianae-new species of orchids (Orchidaceae) from southern Vietnam, Phytotaxa 213 (2), pp. 113-121 : 117-119

Schoenorchis hangianae Aver. et N.V.Duy. , sp.nov. Figs 1A, H–N , 3

Short-creeping epiphyte; stem simple or branching, creeping, to 18 cm long, 3 – 5 mm wide with internodes to 12 mm long; leaves distichous, narrowly ovate, fleshy, broadly crescent in cross section, 1 – 1.8 cm long, 5 – 10 mm wide, oblique bilobe at apex, finely pustulate-verruculose; inflorescence lateral, raceme, to 6 cm long, with few distant flowers; flowers 3 – 3.5 mm across, sepals, lip and spur white sometimes with purple tint; petals, column and anther cap yellow; median sepal broadly ovate, 1.8 – 2 mm long; lateral sepals oblique, semicircular, 2.5 – 3 mm long; petals oblong narrowly obovate, 1.6 – 2 mm long; lip spurred, 4 – 5 mm long, 3-lobed; side lobes rectangular, erect, 1.5 – 2 mm tall, median lobe narrowly ovate, 2.5 – 3 mm long, with large bilobulate callus at middle and thin up-curved lamellate apex, with bilobulate callus at the base of median lip lobe and large entire callus at the lip base, spur saccate, at right angle, (2 –)2.5(– 3) mm long, with incomplete longitudinal septum; column small, at front with 2 large, acute, protruding rostellum arms; anther cap in form of twin hemispheres, with large, S-curved beak; viscidium very large, boat-shaped, forward protruding, 1.4 – 1.6 mm long, 0.5 – 0.6 mm wide; pollinia 2, each half-split into 2 unequal hemi-obovoid portions. Type: — VIETNAM. Herbarium type specimen collected from cultivated plant. 7 July 2014, Nong Van Duy, VTN 984 (holotype, Herbarium of Tay Nguyen Institute of Scientific Research of Vietnamese Academy of Science and Technology !; isotype, LE!). Living plant originated from southern Vietnam , Khanh Hoa province, Khanh Vinh district , Hon Giao Ridge , Khanh Vinh Pass. , canopy epiphyte in broad-leaved, evergreen, humid forest at elevation about 1000 m a.s.l., around point 12°12’50’’N 108°45’09’’E. 1 November 2013, Nong Van Duy, (cultivated in the Garden of Tay Nguyen Institute of Scientific Research of Vietnamese Academy of Science and Technology) .

Perennial short-creeping monopodial epiphytic herb. Stem simple or branching, rigid, creeping, often curved or flexuose, slightly laterally compressed, (3 –)4 – 14(– 18) cm long, 3 – 4.5(5) mm wide, with distichous leaves and wiry flexuose roots arising from internode opposite leaf axil, internodes (2 –)3 – 12(– 14) mm. Leaves narrowly ovate, straight, fleshy, succulent, indistinctly conduplicate, broadly crescent in cross section, (1 –)1.2 – 1.6(– 1.8) cm long, (5 –)6 – 8(– 10) mm wide, 1.5 – 2(– 2.5) mm thick, blunt and oblique bilobe at apex, finely alveolate-verruculose, dark green, often with purple tint; leaf sheath of young leaves smooth to finely verruculose, light green with purple marks, old sheaths green-purple or purple-brown, transversally finely wrinkled. Inflorescence lateral, straight raceme, (2 –)3 – 5(– 6) cm long, arising from stem opposite leaf axil, scape and rachis dull purple; scape (1 –)1.5 – 2.5(– 3) cm long, with 1–3 small distant, ovate, sterile bracts; rachis (1 –)1.5 – 5(– 6) cm long, slightly zig-zag curved, with few lax, spirally arranged flowers distant on (3 –)4 – 5(– 6) mm. Floral bracts dark purple, minute, triangular, acute, 0.8 – 1.2 mm long and wide. Pedicel and ovary cylindric, 4 – 5 mm long, 0.5 – 0.8 mm in diam., dull purple to dark purple-violet, slightly broadening and curved toward the apex. Flowers broadly campanulate, 3 – 4(– 5) mm across; sepals, lip and spur white, sometime tinged with purple; petals, column and anther cap yellow. Median sepal erect, broadly ovate, 1.8 – 2 mm long, 1.5 – 1.8 mm wide; lateral sepals reflexed, very oblique, semicircular, 2.5 – 3 mm long, 1.6 – 1.8(– 2) mm wide. Petals oblong narrowly obovate, slightly reflexed, 1.6 – 2 mm long, 0.8 – 1 mm wide, undulate and finely erose dentate along margin. Lip spurred, 4 – 5 mm long and wide being flattened, 3-lobed; side lobes rectangular, erect, fleshy, 1.5 – 2 mm tall, 2.2 – 2.4 mm wide; median lobe narrowly ovate, 2.5 – 3 mm long, 0.8 – 1 mm wide, with large bilobulate callus at middle and thin up-curved lamellate apex finely erose or notched at apex; disk fleshy, with twin-tops bilobulate callus at the base of median lip lobe and large entire callus at the lip base at spur entrance; spur narrowly obovoid, saccate, slightly dorso-ventrally flattened, down curved at right angle, (2 –)2.5(– 3) mm long, 1.2 – 1.5 mm broad, at apex round and slightly notched, inside with incomplete short longitudinal septum. Column small, about 0.5 mm high and wide, at front with 2 large, acute, knife-shaped parallel, forward directed rostellum arms, 1 – 1.2 mm long, 0.3 mm wide at the base. Anther cap in form of twin hemispheres, finely papillose, 1 – 1.2 mm wide and 0.5–0.6 mm tall, with large, oblong triangular, scarious, S-curved beak 0.6 – 0.8 mm wide, 0.8 – 1 mm long. Stipe (tegula) simple, small, in form of flat, erect triangular plate, 0.2 – 0.3 mm long and wide; viscidium very large, concave at apex from below, boat-shaped, forward protruding, 1.4 – 1.6 mm long, 0.5 – 0.6 mm wide. Pollinia 2, each half-split into 2 unequal hemi-obovoid portions, 0.3 – 0.4 mm long. Fruits narrowly ellipsoid capsule 0.8 – 1.2 cm long, 3.5 – 4.5(– 5) mm in diam., placed more or less horizontally on straight rigid stalk 2 – 3 mm long.

Etymology: —Species epithet refers to the name of Mrs. Nguyen Thi Thanh Hang, wife of the species discoverer, co-author of this paper — Dr. Nong Van Duy.

Ecology: —Creeping epiphyte; primary broad-leaved, evergreen, humid, submontane forests on granite. 1000 m a.s.l. Fl. May–July. Very rare. Estimated IUCN Red List status—CR.

Distribution: — Vietnam: Khanh Hoa (Khanh Vinh district). Endemic.

Notes: — Schoenorchis hangianae is obviously related to S. scolopendria Averyanov (2012: 134) having certain similarities both in plant growth habit and in floral morphology. However, it distinctly differs in having large, distant, obtuse leaves and a long inflorescence. Both species are unique among their congeners for their plagiotropic creeping shoot, forming distinctly isolated group inside the genus. In lip structure, both species of this group resemble S. fragrans , S. seidenfadenii Pradhan (1978: 912) and S. tixieri ( Guillaumin 1958: 462) Seidenfaden (1975: 102) (sect. Pumila Aver.). At the same time, their relationship with species of other sections of the genus is very problematic.

Schoenorchis hangianae is probably a local endemic of Hon Giao Range—the chain of high mountains spreading along the border between Lam Dong and Khanh Hoa provinces in southern Vietnam. In this region, the species is part of the very rich orchid flora of these mountains and occurs there with such typical local endemics of high taxonomical rank as Arachnis annamensis ( Rolfe 1905: 391) Smith (1912: 73) , Ascocentrum christensonianum Haager (1993: 39) , Bulbophyllum clipeibulbum Vermeulen (2001: 51) and Paphiopedilum delenatii Guillaumin (1924: 554) . The described plant grows as a miniature branch epiphyte in the canopies of high trees of primary forest and is therefore difficult to observe and collect without cutting of host trees. It is very rare and known until now by single collection. It is noteworthy that the lone locality of primary forest habitat for this plant is presently being destroyed due to road construction, forest logging and anthropogenic transformation of landscape. For this reason, this new species is tentatively assessed as critically endangered (CR) due to fatal decline of its habitat area.

Figures

FIGURE 1. A. Habitat of Bulbophyllum bidoupense Aver. & N.V.Duy and Schoenorchis hangianae Aver. & N.V.Duy, primary broadleaved evergreen forest on slopes of Hon Giao Range in Bidoup Mountains. Bulbophyllum bidoupense. B, C. Flowering plants in nature habitat. D, E. Inflorescence of plants from different populations. F, G. Flowers, half-side and side views (B—type specimen, VTV 1030; C, E–G—specimen L.Averyanov s.n. April 2010; D—specimen Nguyen Van Canh s.n. 8 March 2013). Schoenorchis hangianae. H–K. Flowering and fruiting plants. L. Portion of inflorescence. M, N. Flowers (type specimen VTN 984). [Photos of Nong Van Duy, L. Averyanov and Nguyen Van Canh, correction and design by L. Averyanov].

FIGURE 3. Schoenorchis hangianae. A. Flowering and fruiting plant. B. Leaf and leaf cross section. C. Portion of inflorescence. D. Flower, frontal and half-side views. E. Flowers and portion of the rachis, side view. F. Flower, view from above and from below. G. Flattened sepals and petals, adaxial surface. H. Flattened lip and spur longitudinal section. I. Lip, side view and lip sagittal section. J. Column, frontal and half-side views. K.Anther cap, frontal view, side view and view from below. L. Pollinarium, view from above, view from below and half-side view. [All drawn from the type-VTN 984 by L. Averyanov and T. Maisak].