Chiloschista quangdangii Vuong & Aver., 2023

Vo, Doan Trung, Averyanov, Leonid, Maisak, Tatiana, Canh, Nguyen Van, Dang, Minh Quan, Dang, Van Son, Truong, Quang Tam & Vuong, Truong Ba, 2023, Chiloschista quangdangii, a new leafless orchid (Orchidaceae) from northern Vietnam, Phytotaxa 606 (1), pp. 79-84 : 80-83

Chiloschista quangdangii Vuong & Aver. sp. nov.

( Fig. 1 )

Type:— VIETNAM. Ha Giang Province, Quan Ba District, Quyet Tien Commune, forest around the Lung Muoi Village , 6 June 2023, Truong Ba Vuong , Ngo Quang Dang, BV 1748 (holotype VNM00063979 ) .

Paratype:— VIETNAM. Ha Giang Province, Quan Ba District, Quyet Tien Commune, forest around the Lung Muoi Village , 6 June 2023, Truong Ba Vuong , Ngo Quang Dang, BV 1749 ( VNM00063980 ) .

Diagnosis:—The newly discovered species can be distinguished from the closely related C. parishii by its narrowly saccate spur-like hypochile and the presence of a small callus on the lip disc. Additionally, it differs from the similar C. glabrisepala due to its densely hairy hypochile on the inside and the small callus on the disc.

Etymology:—The species is named after Mr. Ngo Quang Dang, who successfully cultivated the plant and kindly provided the materials for this study.

Description:— Herb leafless (during anthesis), miniature, monopodial, with an abbreviated stem ca. 3 mm long and many long, glabrous, flattened, green roots. Inflorescence green, marked with brown, up to 13 cm long, covered by short white hairs; peduncle ca. 5 cm long, with 3 distant brownish sterile bracts; rachis ca. 8 cm long, bears 2–15 flowers; floral bracts rectangular-ovate, acuminate, ca. 3.5–4 mm long, keeled and, sparsely hairy with short hairs abaxially. Pedicel and ovary ca. 3 mm long, densely white hairy. Flowers open from the base, sepals and petals yellow with many large orange blotches, lip almost white, side lobes with 2–3 orange dots outside and many orange warty streaks inside. Median sepal obovate, 6.5–7 mm long, 4–5 mm wide, rounded at the apex, slightly retuse and sparcely ciliate along the margin. Lateral sepals broadly obovate, slightly oblique, 5.5–6 mm long, ca. 3–4 mm wide, rounded or blunt at the apex and sparcely ciliate at margin. Petals obscurely rectangular, 5.5–6 mm long, ca. 4 mm wide, truncate or rounded at apex, glabrous on both surfaces and ciliate along the margin. Lip 3-lobed, narrowly saccate, spur-like; side lobes somewhat rhomboid, oblique, 2–2.5 mm long, ca. 2 mm wide, erect, forward directed, apex obtuse or truncate; median lobe very small, triangular, glabrous, ca. 1 mm long, slightly down curved, apex 2- lobed, somewhat fleshy; central callus shortly oblong, knob-like, farinose, ca. 1 mm long and wide, slightly down curved, apex 2-lobed; base of the lip spur-like, obconoid tapering to the apex; back-wall callus white, fleshy, erect, conoid, covered by short stiff white hairs except proximal part, bifid at the apex, front wall with longitudinal ridge, densely corved by short stiff white hairs. Column stout, ca. 2 mm long and wide; stigma transversely elliptic to almost circular, concave; column foot at oblique angle to column and ovary, forward directed, ca. 3.5–4 mm long; anther cap with 2 filiform lateral setae, ca. 2 mm long; pollinarium with 2 pollinia, oblong stipe slightly contracted at the base, and rectangular viscidium. Fruit not seen.

Distribution:—Northen Vietnam (Ha Giang Province). Endemic, currently known only from the type location.

Habitat and phenology:—Miniature leafless branch epiphyte. Primary broad-leaved forests. Flowers in June.

Estimated conservation status:—Five specimens of the newly discovered species were collected by local residents from the forest in the vicinity of Lung Muoi Village and subsequently offered for sale in the local plant market. Unfortunately, specific details regarding the species’ habitat, environmental conditions, and rarity remain unclear. Nevertheless, the extensive collection of these plants for commercial purposes serves as compelling evidence that the sole known population is being significantly depleted and may face imminent extinction. Considering the limited extent of occurrence (EOO) and area of occupancy (AOO) of the species, which are estimated to be less than 100 km ² and 10 km ², respectively, the preliminary conservation status of the new species can be classified as critically endangered.– CR following to formal IUCN (2022) criteria, CR A3(a,d), B1(a,bi,ii), B2(a,bi,ii), C1, C2(ai,ii).

Note:— Chiloschista quangdangii resembles both C. parishii and C. glabrisepala in plant habit and flower color scheme; as a result, it may be easily confused with these species. From C. parishii (morphological detail were compiled from Gyeltshen et al. 2019 & 2020, and Dalström & Kolanowska 2020) our plant differs in a narrowly saccate, spur-like lip (vs. a lip base broadly saccate or cup-shaped), a small farinose callus on the disc, distinctly smaller than the median lip lobe (vs. a callus densely hairy with short stiff hairs, as large as the median lip lobe or larger), and a lip glabrous inside except for the farinose callus (vs. a lip inside densely hairy). The new species shares the narrowly saccate, spur-like lip base with C. glabrisepala but differs in the densely hairy spur inside (vs. spur inside with sparce hairs) and the small farinose callus on the lip disc, which is much smaller than the lip median lobe (vs. callus as large as the lip median lobe or larger, densely covered by short dense stiff hairs) ( Fig. 2 )

In addition, the new species shared the narrowly saccate, spur-like lip to C. sweelimii Holttum (1966: 147) but it differs by the glabrous lip outside surface (vs. minutely papillose externally) the smooth hairy inside spur (vs. lip sac with jagged calli), base of callus inconspicuous calli on sides (vs. a large callus on two side, at base of mid lobe)

Figures

FIGURE 1. Chiloschista quangdangii Vuong & Aver. A. Flowering plant. B. Apical part of the inflorescence. C. Portion of rachis with fully open flowers. D. Floral bract, adaxial and abaxial side. E. Flowers, frontal and back views. F. Median sepal, abaxial and adaxial side. G. Lateral sepal, abaxial and adaxial side. H. Petal, abaxial and adaxial side. I. Lip, views from different angles. J. Lip, sagittal section. K. Ovary and column, side view. L. Column, with and without anther cap, frontal view. M. Column apex, with and without pollinarium. N. Anther cap, view from above and from below. O. Pollinarium, frontal and back view. Photos by Truong Ba Vuong from the type specimen BV 1748. Photo correction and design by L. Averyanov and T. Maisak.

FIGURE 2. Chiloschista glabrisepala. A. Flower, frontal view. B. Lip, view from above. C. Lip, sagittal section. Chiloschista quangdangii. D. Flower, frontal view. E. Lip, view from above. E. Lip, sagittal section. Photo by Truong Ba Vuong from the type of C. glabrisepala, BV 1443 (A–C) and the type of C. quangdangii BV 1748 (D–F). Photo correction and design by L. Averyanov.