Habenaria Willdenow (1805: 44)

Averyanov, Leonid V., Nguyen, Van Canh, Le, Tuan Anh, Vuong, Truong Ba, Nuraliev, Maxim S., Maisak, Tatiana V., Yudova, Daria A., Nguyen, Cuong Huu & Nong, Duy Van, 2024, New orchids in the flora of Vietnam IX (Orchidaceae: Orchidoideae, tribes Cranichideae and Orchideae), Phytotaxa 664 (4), pp. 229-248 : 235-238

Habenaria Willdenow (1805: 44)

Habenaria siamensis Schlechter (1906: 82) , Gagnepain & Guillaumin (1934: 607), Seidenfaden & Smitinand (1959: 30) pro parte, Seidenfaden (1977: 130, fig. 82), Chen et al. (2009b: 148, fig. 191 (4–6)), Kurzweil (2009: 87, 2011: 141, fig. 81), Zhou et al. (2016: 72).

( Fig. 5 )

Type: — THAILAND. [Tak Province:] Wang-Djao [Wang Chao], 160 m, 5 October 1904, C. C. Hosseus 52 (lectotype, designated by Kurzweil (2009: 87): K K000364316 photo! https://data.kew.org/records/occurrences/b3d7c20d-c0c7-4ba5-9b27-e7787d81cf54; isolectotypes: AMES 00100091 photo! https://kiki.huh.harvard.edu/databases/specimen_search.php?barcode=00100091, BM 000033435 photo! https://data.nhm.ac.uk/object/9f0deb6f-e533-4263-b8ba-3a7461ac76db, L L0061377 photo! https://bioportal. naturalis.nl/en/specimen/ L __0061377, M M0168795 photo! https://pictures.snsb.info/BSMvplantscoll/web/M-0168/M-0168795_ 20120402_122714.jpg, P P00439796 photo! http://coldb.mnhn.fr/catalognumber/mnhn/p/p00439796). Citation of protologue: — “Siam: Auf dem Gipfel des Porphyrhügels, Wang Djao, c. 160 m ü. d. M.- C. Hosseus no. 52, blühend am 5. Oktober 1904 ” .

Habitat and phenology in Vietnam: —Evergreen broad-leaved lowland forests and scrub on limestone at elevations of about 600–700 m a.s.l., very rare. Flowers in August.

Distribution: — Vietnam (Son La Province: Thuan Chau District). S China (Guizhou), N Thailand.

Conservation status in Vietnam: — Habenaria siamensis is known in the country by a single collection originated from a limestone area in Son La Province. This area is highly affected by agricultural activities.Taking into consideration the widescale land transformation for the crop fields, we preliminarily estimate the national conservation status of the species as Near Threatened (NT). Kurzweil (2009) assessed the status of this species as Endangered (EN).

Notes: — Habenaria siamensis is reported here as a new record for the flora of Vietnam. The Vietnamese population of H. siamensis is situated geographically almost between the known locations of the species in southern China and in northern and northeastern Thailand. Since H. siamensis is a rather unattractive ephemeroid that flowers in the rainy season, it is likely to be easily overlooked during botanical surveys. Hence, we suppose the distribution of this species to be significantly broader than currently documented.

Studied specimens:— VIETNAM. Son La Province, Thuan Chau District: forest near Chieng Pac Commune, terrestrial orchid in limestone area, 12August 2023, Truong Ba Vuong, BV1819 (LE LE01253840 https://en.herbariumle. ru/?t=occ&id=213820, VNM 00060083, photos LE LE01124301 https://en.herbariumle.ru/?t=occ&id=186706).

Figures

FIGURE 5. Habenaria siamensis. A. Flowering plant in natural habitat. B. Flattened flowering plants. C. Floral bract, adaxial and abaxial side. D. Flower, half-side view. E–G. Flowers, front views from different angles. H. Median sepal, adaxial and abaxial side. I. Petals, adaxial side. J. Lateral sepals, adaxial side. K. Ovary, column, and lip with spur, side view. L. Column, side and half-side views. M. Pollinaria, side view. Photos by Truong Ba Vuong from living plant prior to the preparation of the voucher herbarium specimen Truong Ba Vuong, BV1819. Photo correction and design by L. Averyanov and T. Maisak.