Holcoglossum nagalandense (Phukan & Odyuo) X.H.Jin

Averyanov, Leonid V., Nguyen, Van Canh, Truong, Ba Vuong, Nguyen, Khang Sinh, Nguyen, Cuong Huu, Maisak, Tatiana V., Doan, Nga Thi, Nguyen, Tuan Hoang, Pham, Van The, Dat, Pham Thi Thanh, Thai, Tran Huy, Nguyen, Van Khuong & Trinh, Ngoc Bon, 2023, New orchids in the flora of Vietnam VI (Orchidaceae, tribes Arethuseae, Cymbidieae, Diurideae, Epidendreae, Vandeae, and Vanilleae), Phytotaxa 597 (2), pp. 87-110 : 101-104

Holcoglossum nagalandense (Phukan & Odyuo) X.H.Jin in Xiang (2012: 8). ( Fig. 8 )

≡ Penkimia nagalandensis Phukan & Odyuo (2006: 331) , Chen et al. (2009: 503), Zhou et al. (2016: 105). Type: — INDIA. Nagaland, Odyuo 102808A (holotype CAL).

Ecology and phenology:—Miniature epiphyte on tall mossy trees. Primary humid evergreen broad-leaved montane forest on granite at an elevation of about 1600 m a.s.l. Very rare. Flowers in January.

Distribution:— VIETNAM, Lam Dong Province (Lac Duong District). NE India, SW China.

Conservation status:—Before our study, this species was known from one location in Assam (NE India) and two close locations in W Yunnan (SW China). Its somewhat surprising discovery in southern Vietnam expands the formal species area to the SE and SSE directions on more than 2200 km. Meanwhile, in Vietnam, a few plants of the species were collected from felled trees in logging areas where plants have no chance of surviving. Following our observation, the species stands on the verge of full extinction in Vietnam with the current national conservation status, nationally Extinct (EX).

Notes:—This rare species is superficially similar to Taiwanese H. pumilum ( Hayata 1906: 77) X.H.Jin in Xiang (2012: 8). However, it distinctly differs in light yellowish to almost white flowers with tepals having a reddish brown tint outside (vs. flowers entirely pink purple except for the bright yellow base of the lip), sepals and petals almost flat or slightly concave, blunt or roundish at the apex (vs. sepals and petals acute and slightly conduplicate), a bailer-shaped lip with an ovate median lobe having a roundish apex (vs. lip almost flat or slightly conduplicate, its median lobe rhomboid, with an acute apex), and side lobes as large as the median lobe (vs. side lobes much smaller than the median lobe, having the form of small auricles).

Studied specimen:— VIETNAM, Lam Dong Province, Lac Duong District, Dung K’No Commune , around point 12.08N 108.23E, humid dense primary evergreen montane broad-leaved forest on granite at elevation of about 1600 m a.s.l., miniature epiphyte on tall mossy trees, very rare, 3 December 2022, L. Averyanov, Nguyen Van Canh, T. Maisak, Truong Ba Vuong, Nguyen Quoc Bao, Nong Van Duy, Nguyen Phi Tam, AL 2032, fl. and coll. in cult., 08.01.202 3, Truong Ba Vuong, AL 2032 (photo LE01123793 https://en.herbariumle.ru/?t=occ&id=160775) .

Figures

FIGURE 8. Holcoglossum nagalandense (Phukan & Odyuo) X.H.Jin. A. Flattened flowering plant. B. Stem and base of leaves. C, D. Leaves. E. Intact inflorescence. F. Apical part of inflorescence. G. Intact flowers, view from below. H. Floral bracts, adaxial and abaxial side. I. Flowers, view from different sides. J. Flower with sepals and petals removed. K. Median sepal, abaxial and adaxial side. L. Lateral sepals, adaxial and abaxial side. M. Petals, adaxial and abaxial side. N. Lips, view from different sides. O. Spur, frontal wall removed. P. Column, view from different sides. Q. Anther cap, view from different sides. R. Pollinarium, view from different sides. All photos were made by B.V. Truong from the specimen, Truong Ba Vuong, AL 2032, with photo correction and design by L. Averyanov and T. Maisak.