Bulbophylum thangii Vuong, Aver. & R.Amsler, 2023

Truong, Ba Vuong, Averyanov, Leonid V., Maisak, Tatiana V., Dang, Minh Quan, Nguyen, Van Canh, Amlser, Roland, Nguyen, Quoc Bao & Dang, Van Son, 2023, Bulbophylum sect. Cirhopetallum s. str. (Orchidaceae) in Vietnam with the description of a new species, B. thangii, and a new national record, B. fenestratum, Phytotaxa 625 (2), pp. 201-210 : 207-209

4. Bulbophylum thangii Vuong, Aver. & R.Amsler sp. nov.

( Fig. 4 )

Type: — VIETNAM. Khanh Hoa Province: Van Ninh District, Van Phu Commune , 4 July 2023, Truong Ba Vuong, Nguyen Van Canh, Phan Trong Quyet & Phan Dai Thang BV 1775 (holotype VNM 00063955 !, analytical photos LE01124297 https://en.herbariumle. ru/?t=occ&id=186069) .

Diagnosis: —The new species differs from all known members of Bulbophyllum sect. Cirrhopetallum s. str. by its warty or colliculate sepals and lip. It has a hairy base of the lip, as observed also in B. annamense but not in other species of the section.

Etymology:—The species is named after Mr. Phan Dai Thang, who kindly provided materials for this study.

Description:—Lithophytic or epiphytic herb. Pseudobulbs 1-leaved, green, narrowly ovoid to ovoid, 0.5–2.5 cm tall, distant on a woody brown rhizome, 2–5 mm in diameter, covered by brownish bracts. Leaves shortly petiolate; petiole ca. 0.5 mm long; leaf blade green, elliptic, glossy, leathery, 5.5–8.5 cm long, 1.5–2 cm wide, acute. Inflorescence arising from the base of the pseudobulb, ascending to erect, terete, glabrous; peduncle ca. 10 cm long, with 2–3(4) sterile brown tubular bracts at the base and one near the middle; rachis ca. 1 mm long, bearing 2–4 flowers, opening simultaneously; floral bracts narrowly triangular, pale yellow green with unclear purple spots, 7–8 mm long, tapering, acute; pedicel and ovary yellow, with many red dots, 9–10 mm long. Flowers red to dark red, dorsal sepal reddish with many dark red dots, lateral sepals with many red warts, lip white, with many dark red dots. Dorsal sepal almost rounded, concave, 10–11 mm long, 8.5–9 mm wide, with an entire margin and a simple seta at the apex. Lateral sepals oblong narrowly ovate, mucronate, ca. 3 cm long, 7 mm wide near base, twisted at the base, upper margin connate to each other, free at base, and apex, lower margin free. Petals narrowly ovate, slightly oblique, 6–7 mm long, 3–4 mm wide, margin entire, at apex with few dents and slender, simple seta. Lip simple, fleshy, recurved, narrowly ovate oblong, 9–10 mm long, ca. 3 mm wide at base, retuse; adaxially verrucose or colliculate, basal half densely papillose, shortly canaliculate, abaxially with prominent longitudinal keels coming from the base to apex. Column stout, erect, glossy, white with many small purple marks, 3.5–4 mm tall, at front with rounded, forward directed wings; at apex with large prominent stelidia bent forward at right angle to column, apically subulate, inner margin with large triangular rounded wing; anther cap light yellowish, obscurely rectangular, finely verruculose; column foot forward directed and incurved at apex; pollinia 4. Fruits not seen.

Habitat and phenology: —Lithophyte on granite rocks or epiphyte at elevation of about 800 m a.s.l. Flowers in July–August.

Distribution:—So far, the new species has only been found in the type locality in Khanh Hoa Province, southern Vietnam.

Conservation assessment: —Very few specimens of the new species were collected by local people in the forest near Van Phu commune in Khanh Hoa Province. The data about the natural conditions of the species’ habitat and its population size remain unclear. However, the wide collection of plants for sale provides certain evidence that the single known population is severely threatened. We infer that the Extent of Occurrence (EOO) and Area of Occurrence (AOO) are not more than 100 and 10 km 2. However, due to a lack of information, this species is assessed as Data Deficient.

Note:— Bulbophyllum thangii has warty or colliculate sepals and a lip that is unique among all species in the section. Morphologically, our plant is most similar to B. annamense , sharing similar flower coloration and a finely papillose lip at the base. However, B. annamense differs in the smooth surface of sepals, dorsal sepal and petals with three setae at the apex, and the lip with auricles at the base (while the new species has prominent warty blotches on the surface of sepals and lip, dorsal sepal and petals with a single seta at the apex, and a simple lip without auricles).

Figures

FIGURE 4. Bulbophyllum thangii. A. Flowering plant. B. Pseudobulb and leaf, abaxial side. C. Inflorescence. D. Floral bracts. E. Flowers, views from different sides. F. Proximal part of flowers, front and side view. G. Dorsal sepal, adaxial and abaxial side. H. Lateral sepals, adaxial and abaxial side. I. Petals, adaxial and abaxial side. J. Lip, views from different sides. K. Column, petals and lip, side view. L. Column and lip, side view. M. Pedicel, ovary and column. N. Column, view from back. O. Column apex, front view. P. Anther cap, view from above and from below. Q. Pollinarium. All photo by Truong Ba Vuong from the type specimen (BV 1775), photo correction and design by L. Averyanov and T. Maisak.