Bulbopyllum sect. Sestochilus

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 : 16-18

Bulbopyllum sect. Sestochilus

Bulbophyllum siamense Reichenbach (1867: 572) , Ridley (1924: 60), Seidenfaden (1997: 40), Ormerod et al. (2021: 48).

( Fig. 8 )

≡ B. lobbii var. siamense (Rchb.f.) Rchb.f. in Saunders (1872: t. 116).

≡ B. lobbii subsp. siamense (Rchb.f.) Mangal, F.Velazquez & J.J.Verm. in Vermeulen et al. (2015: 40).

Type: — MYANMAR. Mon State: collected in Mawlamyine District by Parish s.n., sent to Low, cult. Day s.n. (holotype W-R 52449 fide Seidenfaden 1997 and Ormerod et al. 2021).

= B. lobbii Lindley (1847a : sub pl. 29) pro parte: Holttum (1964: 424), Seidenfaden (1979: 21), Vermeulen (1991: 259), Seidenfaden & Wood (1992: 481), Wood & Cribb (1994: 298), Augustine et al. (2001: 10), Schuiteman et al. (2008: 268).

Habitat and phenology in Vietnam: —Creeping epiphyte. Lowland evergreen broad-leaved forests.Very rare. Flowers in December–January.

Distribution: — Vietnam: Dak Lak Province (sine loc.). NE India (Assam) ?, Myanmar, Thailand, Laos?, Cambodia?, Peninsular Malaysia?, the Philippines.

Conservation status: —Conservation assessment of Bulbophyllum siamense either at a global scale or within Vietnam is impossible due to the lack of relevant data. Until comprehensive taxonomic and field studies are conducted, it is to be estimated as Data Deficient (DD).

Notes: —Although the type of B. siamense was earlier believed to originate from Thailand ( Vermeulen et al. 2015), we here follow Ormerod et al. (2021) who found it to be collected in Myanmar (see also comments by Seidenfaden 1997).

Bulbophyllum siamense is reported here as a new record for the flora of Vietnam. This species belongs to the B. lobbii species complex, which inhabits a vast area across Asia including NE India , Bangladesh, Myanmar, Thailand, Cambodia, Peninsular Malaysia, the Greater Sunda Islands and the Philippines ( Seidenfaden 1979, Vermeulen et al. 2015). This complex is treated by some authors as a single morphologically variable species, B. lobbii s.l. (see references above). The complex includes several more or less allopatric species quite different in morphology and distribution. In particular, the species found in mainland Asia ( B. coweniorum Vermeulen & O’Byrne (2003: 150) , B. orectopetalum Garay, Hamer & Siegerist (1992: 141) , B. siamense ) demonstrate rather small flowers and relatively short pedicel, distinctly differing in this respect from B. lobbii s.str. that is restricted to the islands of Malesia. Details of distribution of B. siamense in Indochina remain somewhat unclear, as some authors regarded this surely distinct taxon as a synonym of B. lobbii and therefore reported the distribution of the latter species in a wide sense ( Seidenfaden 1979, Seidenfaden & Wood 1992, Schuiteman et al. 2008). According to Seidenfaden (1979, 1995a, 1997) and Seidenfaden & Wood (1992), the form corresponding to B. siamense surely occurs in Myanmar and Thailand and may also be found in NE India , Bangladesh and Cambodia (see also Vermeulen et al. 2015). An extensive overview of the B. lobbii species complex with an emphasis on the mainland taxa and forms is provided by Seidenfaden (1997).

In some areas of its distribution, B. siamense probably occurs sympatrically with another “small-flowered” species of the B. lobbii complex, B. orectopetalum (see also Teoh 2021). Bulbophyllum siamense differs from the latter species in sepals and petals speckled with purple, narrowly ovate, blunt or roundish at apex (vs. sepals and petals with purple veins, broadly lanceolate to narrowly triangular, acute to somewhat acuminate at apex), blunt or roundish (vs. distinctly subacute to acute) lip apex, and lip disk with three separate small calli (vs. lip with a single large callus in the disk center).

Studied specimen:— VIETNAM. Dak Lak Province: sine loc., 23 December 2020, Truong Ba Vuong, BV945 (photos LE LE01123775 https://en.herbariumle.ru/?t=occ&id=157911).

Figures

FIGURE 8. Bulbophyllum siamense. A. Flowering plant. B. Leaf apex, adaxial side. C. Base of pedicel. D. Pedicel, ovary and flower, side view. E–I. Flower, view from different sides. J. Median sepal, adaxial and abaxial side. K. Lateral sepal, adaxial and abaxial side. L. Petal, adaxial and abaxial side. M. Lip, views from different sides. N. Ovary, petal, column foot and lip, side view. O. Ovary, column and column foot. P. Column, view from above. Q. Anther cap, view from below and from above. R. Pollinia, view from different sides. Photos by Truong Ba Vuong from living plant prior to the preparation of the voucher herbarium specimen Truong Ba Vuong BV945. Photo correction and design by L. Averyanov.