Bulbophyllum sect. Macrocaulia

Averyanov, Leonid V., Nguyen, Van Canh, Vuong, Truong Ba, Nuraliev, Maxim S., Nguyen, Khang Sinh, Maisak, Tatiana V., Yudova, Daria A., Saidov, Nikita T., Nguyen, Cuong Huu & Nong, Duy Van, 2024, New orchids in the flora of Vietnam VIII (Orchidaceae: Epidendroideae, tribes Malaxideae, Neottieae and Podochileae), Phytotaxa 658 (1), pp. 1-49 : 12-14

Bulbophyllum sect. Macrocaulia

Bulbophyllum malleolabrum Carr (1932: 24) , Holttum (1964: 434), Seidenfaden (1986a: 170), Vermeulen (1991: 195), Seidenfaden & Wood (1992: 512), Wood & Cribb (1994: 300), Vermeulen et al. (2015: 549).

( Fig. 6 )

Type: — MALAYSIA. Pahang State: Cameron Highlands, altitude c. 4,600 feet, April, 7 1930, M. R. Henderson No. A.458 (syntype SING?) & 23474 (syntype SING?).

= B. lingii M.Z.Huang, G.S.Yang & J.M.Yin in Huang et al. (2020: 185), syn. nov. Type: — CHINA. Hainan: Lingshui City, Mount Diaoluoshan, tree trunks, 900 m, 29 May 2013, Huang 13052901 (holotype ATCH).

Habitat and phenology in Vietnam: —Creeping epiphyte. Primary and secondary evergreen broad-leaved montane forest on granite at elevation of about 1900 m a.s.l. Very rare. Flowers in May–June.

Distribution: — Vietnam: provinces Lao Cai (Bat Xat District) and Son La (sine loc.). S China (Hainan), Peninsular Malaysia, Borneo, Sulawesi.

Conservation status in Vietnam: —Both known Vietnamese populations of Bulbophyllum malleolabrum were discovered in habitats severely disturbed by forest logging. Based on the formal criteria of the IUCN, we preliminarily assess the national conservation status of the species as Critically Endangered (CR). The species meets the following conditions within the country: area of occupancy (AOO) ˂ 10 km 2; severely fragmented populations; continuing decline of quality of habitats and number of mature individuals; these conditions result in CR B2ab(i,ii,iii,v).

Notes: —In the protologue of B. malleolabrum ( Carr 1932) , two gatherings by M.R. Henderson (A.458 and 23474) are cited, but place of their deposition is not indicated and the type is not designated. Although both syntypes are stated to be housed at SING by Vermeulen (1991), Wood & Cribb (1994) and Vermeulen et al. (2015), they are in fact absent from there (Serena Lee, pers. comm.). Thus, typification of this species is currently unclear and requires special efforts.

In the original description of B. lingii, Huang et al. (2020) provided a comparison of their species with B. catenarium Ridley in Stapf (1894: 235), but have not mentioned B. malleolabrum . It is most likely that these authors overlooked B. malleolabrum while investigating their collections from Hainan. Meanwhile, B. lingii is indistinguishable from B. malleolabrum , sharing in particular all its floral features.

Bulbophyllum malleolabrum is reported here as a new record for the flora of Vietnam. It was earlier believed to be endemic to Malesia, which makes its discoveries in Hainan and northwestern Vietnam rather unexpected. Its Vietnamese populations reported here are distanced over 2200 km north from the nearest previously known locality of this species (apart from the Hainan localities) in the central part of the Malay Peninsula. Most importantly, the areas inhabited by both Vietnamese populations lie within the Sikang-Yunnan Floristic Region (belonging to Holarctic Floristic Kingdom); these areas are thus characterized by a significant portion of subtropical floristic elements, being opposed to the Paleotropical Floristic Kingdom that embraces Malesia, Hainan and the rest of Vietnam (Averyanov et al. 2003, Fu et al. 2019). Meanwhile, the Vietnamese plants, as well as the plants reported from Hainan ( Huang et al. 2020), almost completely meet morphologically the detailed drawings of the specimens from the Cameron Highlands ( Seidenfaden 1986 a, Seidenfaden & Wood 1992); in particular, their show the peculiar lip of a very characteristic structure. At the same time, the specimens of B. malleolabrum from Sabah in Malaysian Borneo ( Vermeulen 1991, Vermeulen et al. 2015) differ from the type in smooth shortly cylindrical epichile (vs. epichile globular, rough or verruculose, clavate with narrow base) and narrowly triangular (vs. subulate to linear) stelidia. Apparently, B. malleolabrum shows considerable morphological variation between its geographically separated populations.

Studied specimens:— VIETNAM. Lao Cai Province: Bat Xat District, Bat Xat Nature Reserve, 4 km SSE of Y Ty Village, disturbed forest, stream bank, epiphytic, 22°37’14’’N 103°37’21’’E, elevation 1900 m a.s.l., 9 June 2019, Nuraliev M.S. 2680 (LE LE01058754 http://en.herbariumle.ru/?t=occ&id=9407). VIETNAM. Son La Province: Chu Xuan Canh, s.n., 25 November 2010, herbarium and photos prepared from cultivated plants in May–June 2012, L. Averyanov s.n. (LE LE01055790 http://en.herbariumle.ru/?t=occ&id=7687, photos LE LE01087157 http:// en.herbariumle.ru/?t=occ&id=18681).

Figures

FIGURE 6. Bulbophyllum malleolabrum. A–D. Flowering plants. E–H. Flowers, view from different sides. I. Column and lip, view from different sides. J. Petals, lip, column, anther, and stelidia. K. Leaves, abaxial side. L. Ripening fruit. Photos by M. Nuraliev from living plant prior to the preparation of the voucher herbarium specimen Nuraliev NUR2680. Photo correction and design by L.Averyanov and T. Maisak.