Odontochilus tonkinensis (Gagnep.) Ormerod & Aver., 2023

Averyanov, Leonid V., Nguyen, Van Canh, Vuong, Truong Ba, Nguyen, Khang Sinh, Nuraliev, Maxim S., Nguyen, Cuong Huu, Ormerod, Paul A., Maisak, Tatiana V., Diep, Dinh Quang, Lyskov, Dmitry F. & Nong, Duy Van, 2023, New orchids in the flora of Vietnam VII (Orchidaceae: tribes Cypripedieae, Cranichideae, Orchideae, and Collabieae), Phytotaxa 619 (4), pp. 255-276 : 263-264

Odontochilus tonkinensis (Gagnep.) Ormerod & Aver. , comb. nov.

≡ Anoectochilus tonkinensis Gagnepain (1931b: 679) . Type:— VIETNAM. Tonkin: environ de Cha-pa, 1500 m, Pételot, Juillet 1928 (lectotype P00341454 , designated by Seidenfaden 1992: 31) .

Ecology and phenology:—Miniature terrestrial and lithophytic creeping herb. Evergreen broad-leaved montane forests on granite at elevation of 1500 to possibly 2000 m a.s.l. Flowers in June–July.

Distribution:—Endemic to Vietnam (provinces Lao Cai: Sa Pa area; and Lam Dong: Bidoup Mountains).

Conservation status:—Two locations of this species are currently known: the type locality in northern Vietnam and Bidoup mt. in southern Vietnam where a preliminarily identified specimen was collected. These locations are about 1300 km apart from each other. The area of occurrence and the number of mature individuals currently cannot be correctly estimated; hence the conservation status is estimated here as Data Deficient (DD) according to the criteria proposed by the IUCN Red List (2023).

Notes:—The differences between Anoectochilus Blume (stigmas separate, lateral on column; labellum with more or less conical spur exserted beyond lateral sepals at base; leaves with colored reticulation when apparent) and Odontochilus Blume (stigmas ventral to frontal on column, united/confluent to separate; labellum base usually saccate to rounded and enclosed basally by lateral sepals, or sometimes exposed but not exserted; leaves when colored with stripe(s) but not with colored reticulation) are quite clear. Hence, the presented nomenclatural combination seems necessary.

In the protologue of Anoectochilus tonkinensis, Gagnepain (1931b) listed two gatherings without indication of a type. One of them was effectively chosen as a lectotype for this name by Seidenfaden (1992), who also indicated P as the place of its deposition. This gathering is represented, to our knowledge, by a single sheet, P00341454. The second gathering, Maire s.n. from China (Yunnan: vallous humides de Tchen-fong-chan, plante vivace, feuilles vineuses en dessous, fleurs blanches, E.E. Maire; studied specimen: P00341456) belongs, to our opinion, to Odontochilus elwesii C.B.Clarke ex Hooker (1890: 100) . Slightly larger measurements in the protologue of Anoectochilus tonkinensis may be due to the inclusion of a former Chinese syntype (= Odontochilus elwesii ), or part of natural variation.

Odontochilus tonkinensis was often treated as a synonym of O. brevistylis Hooker (1890: 100) (e.g. Averyanov 1990, 2008, Seidenfaden 1992). Here, we consider it a separate species, because it differs from O. brevistylis in twice smaller leaves with leaf blade 1.2–2.2 cm long (vs. 2.5–5.5 cm long) and broad short simple glands at the base of hypochile, shorter than half of hypochile diameter (vs. hypochile glands rather slender, hooked, half as long as hypochile diameter). Hence, we publish a new nomenclatural combination to accommodate this taxon in the genus Odontochilus as a species distinct from O. brevistylis s. str. widely distributed in mainland SE Asia.

Studied specimens:— VIETNAM. Lam Dong Province: Bidoup Mt. , August 2014, Phung My Trung s.n. ( LE01074323 https://en.herbariumle.ru/?t=occ&id=44113; identification remains preliminary) .