Didymoplexiella ornata (Ridl.) Garay (1954: 33)

Nuraliev, Maxim S., Averyanov, Leonid V., Nguyen, Khang Sinh, Nguyen, Cuong Huu, Le, Tuan Anh, Maisak, Tatiana V., Lyskov, Dmitry F., Kuznetsov, Andrey N. & Kuznetsova, Svetlana P., 2023, The mycoheterotrophic genus Didymoplexiella (Orchidaceae) in Cambodia, Laos and Vietnam, Phytotaxa 620 (1), pp. 18-32 : 24-25

2. Didymoplexiella ornata (Ridl.) Garay (1954: 33) ( Fig. 4 )

Seidenfaden (1975: 75, Fig. 9, 1978: 175, Fig. 108), Seidenfaden & Wood (1992: 138, Fig. 57a), Averyanov (2012: 132, Fig. 5h , 2013: 158, Fig. 81c), Suddee (2014: 480, Fig. 266), Lindsay et al. (2022: 551).

≡ Leucolena ornata Ridley (1891: 340 , Pl. 43). Ridley (1924: 207).

≡ Didymoplexis ornata (Ridl.) J.J. Smith (1920: 20) . Holttum (1964: 108).

TYPE: — MALAYSIA. Malacca, Bukit Sadanen, Derry s.n. (fide Seidenfaden 1975, 1978) .

= Leucolena ornata var. singapurensis Ridley (1908: 143) . Ridley (1924: 207).

TYPE: — SINGAPORE. Stagmount, damp sandy woods on a stream bank, April 1907, Ridley s.n. (fide Seidenfaden 1975, 1978).

Ecology and phenology: —The species inhabits primary and secondary tropical evergreen broad-leaved forests at elevations from sea level to 400 m. Flowers from April to July.

Distribution in the region of study: — Vietnam: Quang Ninh Province (Ha Long Bay).

Distribution worldwide: —S Thailand: Phang Nga Province (Takua Pa), Nakhon Si Thammarat Province (Khao Nan), Trang Province (Khao Soi Dao), Yala province (Betong), Narathiwat province (Hala-Bala). Malaysia: Peninsular Malaysia (Negeri Sembilan: Bukit Tangga; Johor: Sedenak; Bukit Sadanen), Borneo. Singapore. Indonesia: Sumatra (South Sumatra Province: Bukit Besar).

Conservation status in the region of study: —The species is known in Vietnam from a single location, where a few mature individuals were observed (and unknown in Cambodia and Laos). Following the formal criteria of the IUCN Red List (2023), we tentatively assess the conservation status in the study area as Critically Endangered (CR) meeting the following conditions: A1a,c+2a,c, B1a,b(i,ii,iii,v)+2a,b(i,ii,iii,v), C1a(i,ii)+2a(i,ii), D. Outside the study area, the conservation status of D. ornata has not yet been assessed by the IUCN criteria and remains as Not Evaluated (NE).

Notes:

1. The limits of morphological variation of D. ornata , as well as the morphological and geographical delimitation of this species from some of its congeners, are not fully resolved. For example, Seidenfaden (1975, 1978) pointed that the Thai specimens assigned by him to D. ornata are quite similar to D. trichechus . Seidenfaden stressed that his identifications are questionable, and were partly induced by the geographical proximity of the Thai specimens to the type locality of D. ornata .

Then, the drawing of a labellum of D. ornata provided by Kumar et al. (2020: Fig. 3F ) and stated to be “drawn from colour photographs of plants in Malaysia provided by Ong Poh Teck and from original description ( Ridley 1891)” in fact differs significantly from the drawing included in the species protologue ( Ridley 1891: Pl. 43-4). The protologue depicts a labellum with side lobes much longer and wider than the median lobe; the side lobes are forward directed at a sharp angle with the median lobe and therefore far project beyond it. The side lobes projecting beyond the median lobe make the drawing from Ridley’s work quite similar to the labellum shape of D. laosensis . Therefore, distinctness of D. laosensis from D. ornata is not completely clear. Unfortunately, Ridley (1891) has neither described nor depicted labellum ornamentation of D. ornata . Recollection of D. ornata from type locality is required for clarification of these uncertainties.

2. The Vietnamese specimen cited here is the only known record of D. ornata outside Malesia and Peninsular Thailand. Given its rather isolated geographical position and the uncertainties in species delimitation outlined here, we consider our identification of the specimen Hiep NTH 6271 as tentative. The labellum shape in this specimen is somewhat intermediate between the shapes depicted in the protologue of D. ornata and by Kumar et al. (2020): the side lobes are nearly of the same length and width as the median lobe, forward directed at a sharp angle with the median lobe but not projecting beyond it.

3. The specimens Averyanov et al. AL 891, Averyanov et al. AL 1086 ( Averyanov et al. 2019b) and Nuraliev 1781 ( Nuraliev et al. 2019), which were earlier assigned to D. ornata , are identified here as D. laosensis (see note under the latter species). The third specimen cited by Averyanov et al. (2019b), Averyanov et al. AL 995, bears only immature flower buds, and its identification remains uncertain. Thus, no occurrences of D. ornata are known from Laos after re-consideration of these collections.

Additional specimens examined:— VIETNAM. Quang Ninh Province: Ha Long Bay, Cong Do Island, around point 20°52’371’’N 107°11’748’’E, 9 May 2011, N. T. Hiep NTH 6271 (CPC Herbarium, LE: LE 01067822 https:// en.herbariumle.ru/?t=occ&id=17411, photos LE 01089024 https://en.herbariumle.ru/?t=occ&id=65553).

Figures

FIGURE 3. Didymoplexiella laosensis. A. Habit. B–H. Flowers in different views. I. Column (semi-adaxial view).A–C: Averyanov et al. AL 1086; D, E. Nguyen S.K. et al. 001; F, G: Averyanov et al. AL 891; H, I: Nguyen H.C. et al. CHKH 202206243073. Photos A–C, F, G by L.V. Averyanov; D, E. by S.K. Nguyen; H, I by H.C. Nguyen.

FIGURE 4. Didymoplexiella ornata, dried material. A. Flower with labellum removed. B. Sepals and petals. C, D. Labella (adaxial view). E. Column (adaxial view). F. Flower. Hiep NTH 6271. Photos by L.V. Averyanov from LE01067822.

FIGURE 5. Didymoplexiella siamensis. A. Inflorescence. B–E. Flowers in different views. F. Labellum and column (semi-side view). G. Labellum (side view). H. Labellum and column (top view). I. Column (adaxial view). J. Rhizome.A–I: Nuraliev et al. NUR 3557; J: Nuraliev et al. NUR 3540. Photos by M.S. Nuraliev.