Gastrochilus dresslerii Vuong, Aver. & V.S.Dang, 2021

Nguyen, Dinh Hiep, Averyanov, Leonid V., Dang, Van Son, Bui, Van Huong, Maisak, Tatiana & Truong, Ba Vuong, 2021, Gastrochilus dresslerii (Orchidaceae), a new species from northern Vietnam, Phytotaxa 498 (2), pp. 145-149 : 146-148

Gastrochilus dresslerii Vuong, Aver. & V.S.Dang , sp. nov. ( Fig 1 )

Type:— VIETNAM, described from northern Vietnam: Ha Giang Province, Quang Ba District, Thai An Commune , forest near Thai An Village , 1 January 2020, Truong Ba Vuong, Dang Van Son, Bui Van Huong, Vang Di Thao , BV 471 (holotype VNM VNM00024327 , analytical photos LE LE01089446 http://en.herbariumle.ru/?t=occ&id=74194) .

Paratype:— VIETNAM, Ha Giang Province, Quang Ba District, Thai An Commune, forest near Thai An Village , 3 January 2020, Truong Ba Vuong, Dang Van Son, Bui Van Huong, Vang Di Thao , BV 472 ( VNM VNM00024328 ) .

Etymology:—The species epithet honors Robert L. Dressler for his outstanding contribution to the global orchidology.

Description:— Miniature twig epiphyte. Stems spreading horizontally or pendulous, simple, 3.5–5 cm long, leafy on apical half, covered by leaf sheaths, dull brownish purple or green with sparse purple blotches, glabrous, stout and semi-woody at base, somewhat fleshy toward the apex, rooting from nodes; roots vermiform, glossy, ca. 1 mm in diameter, white or greenish. Leaves distichous, glabrous, broadly lanceolate to narrowly ovate, 8–13 mm long, 4–6 mm wide, adaxially green or dark green with irregular dull purple spots, abaxially greenish, glossy with less dull purple blotches; leaf apex with 2 lateral acute teeth and 1 median seta. Inflorescence lateral, arising from node of apical half of stem, racemose, ca. 9 mm long, with 3–4 simultaneously opening flowers; peduncle slender, ca. 2 mm long, green with small purple dots, with 1–2 brownish bracts at base; rachis fleshier than peduncle, ca. 7 mm long, green with purple blotches, base with 1 acute tubular bract, ca. 1 mm long; floral bracts triangular, acute, ca. 2 mm long, 0.5 mm wide, green with purple blotches; pedicel and ovary green with purple dots, ca. 6.5 mm long. Flower s not widely opening, sepals and petals green with few purple dots abaxially, sepals with purple mid vein, abaxially rugose; lip white with greenish tint, epichile central callus dull yellowish-green with purple-brownish dots, margin of hypochile pinkish, inside with few purple dots. Dorsal sepals obovate, ca. 4 mm long, 2 mm wide, concave, apex rounded. Lateral sepals narrowly ovate, oblique, concave, ca. 4 mm long, 2 mm wide, acute. Petals broadly elliptic, ca. 4 mm long, 3 mm wide, slightly concave, obtuse. Lip spurred, divided into hypochile and epichile; hypochile saccate to almost globular, outside glossy, at right angle to epichile, ca. 4.3 mm long, 3.5–4 mm wide, apex rounded, slightly retuse, densely hairy on front-wall, with low median keel inside, epichile reniform to half-circular, ca. 2.5 mm long, 6 mm wide, margin somewhat upcurved, central callus with sparse short hairs, side lobes glabrous. Colum short, rectangular at front, ca. 2 mm long. 2.5 mm wide, with shortly cylindrical down directed fleshy lateral wings, without column foot; rostellum prominent, down directed, furcate, hanging above stigma; stigma cordate, concave; anther cap helmet shaped, ca. 2 mm long, with elongate triangular beak ca. 0.8 mm long; pollinia subglobose, entire, attached to a slender, filiform, stipe ca. 2 mm long, viscidium narrowly elliptic ca. 1.5 mm long. Fruits not seen.

Habitat and Phenology:—The plant grows on mosses twigs in marginal canopy zone of large trees. Flowers in December – January.

Proposed conservation status:—According to present observations the species is locally very rare and can be overlooked easily due to its miniature habit the character of habitat. More field studies are needed for acceptable identification of its current conservation status. According to the IUCN criteria ( IUCN, 2019) it may be tentatively assessed at present as “Data Deficient” (DD).

Distribution:— Vietnam (Ha Giang Province). Endemic.

Additional specimens studied: — Gastrochilus matsudae : TAIWAN, Pingtung, Peitawushan (Daibuzan), 20 November 1918, E. Matsuda s.n. (isotype TAI TAI032825, photo!), E. Matuda s.n. (holotype, TAI T01205, photo!). Gastrochilus hoi : TAIWAN, Hualien County, Yunlong, 19 January 2001, Ching-Kuoh Liou 1460 (TAIF TAIF126532, photo!).

Notes:—The newly described species resembles Gastrochilus setosus morphologically, but differs in lax 2–4 flowered inflorescence (vs. inflorescence dense, with 10 or more flowers), glabrous side lobes of epichile (vs. side lobes of epichile with sparse hairs), and saccate to subglobular hypochile placed at right angle to the epichile (vs. hypochile shortly cylindrical at obtuse angle to epichile). Our plant also somewhat similar to G. hoi and G. matsudae , but can be easily recognized by the morphological characters presented in Table 1.

Figures

FIGURE 1. Gastrochilus dresslerii. A. Plant in natural habitat. B. Flattened flowering plans. C.Apical portion of stem with inflorescence. D. Leaves, adaxial and abaxial surfaces. E. Leaves apex, frontal and side views. F. Flower, side, half-side and frontal views. G. Dorsal sepal. H. Lateral sepals. I. Petals. J, K. Lip, frontal views. L. Lip, view from below. M. Column, frontal view and view from behind. N. Anther cap, frontal view and view from behind. O. Pollinaria. Photos by Truong Ba Vuong from holotype BV 471. Images correction and design by L. Averyanov and T. Maisak.