Oberonia Lindley (1830: 15)

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 : 29-30

Oberonia Lindley (1830: 15)

Oberonia maxima C.S.P.Parish ex Hooker (1888: 677) , Seidenfaden (1968: 21, 1975b: 79, 1978: 13), Ansari & Balakrishnan (1990: 22), Pearce & Cribb (2002: 233), Averyanov et al. (2016: 29), Geiger (2016: 391) pro parte, Averyanov & Gruss (2017: 28), Bunpha et al. (2019: 121) pro parte, Kaliamoorthy & Saravanan (2019: 319), Aung et al. (2020: 92), Ormerod et al. (2021: 175), Bunpha & Pedersen (2022: 887) pro parte.

( Fig. 12D–F )

Lectotype (designated by Seidenfaden (1978: 13)):— MYANMAR. Mon State: Mawlamyine District, C. S. P. Parish 287 ( K K000387694 photo!).

Ecology and phenology in Vietnam: —Clustering epiphyte. Primary and old secondary humid evergreen broad-leaved submontane forests on granite and sandstone at elevations of 700–1500 m a.s.l. Rare. Flowers in September–October.

Distribution: — Vietnam: provinces Dien Bien (Muong Nhe District) and Lam Dong (Lac Duong District). NE India , Myanmar, Thailand, Laos.

Conservation status in Vietnam: —Two localities of Oberonia maxima , which are more than 1100 km apart from each other, are known in the country. Available information on the species populations in both locations is very scarce. However, wide deforestation and land exploitation for agriculture in both areas surely lead to a dramatic decrease in the possible extent of the species habitats and their quality. Based on these observations, we estimate the national conservation status of the species as Near Threatened (NT). The conservation status of this species outside Vietnam has never been evaluated. Meanwhile, in a locality in Laos documented by Averyanov et al. (2016), this species was observed to be fairly common, which points to a Least Concern (LC) status.

Notes: — Oberonia maxima is remarkable within the genus in its unusually large habit. It distinctly differs from the morphologically close O. integerrima Guillaumin (1955: 692) also occurring in Eastern Indochina ( Chen et al. 2009, Averyanov 2013, Jin et al. 2023) in commonly twice longer leaves (usually longer than 7–8 cm vs. 5–21 cm long), in less dense inflorescence appearance with sepals and petals partially exposed, being only partially overlapped by lips of more basal flowers (vs. inflorescence very dense, with sepals and petals entirely obscured by the overlapping lips) and lip orbicular to orbicular triangular, emarginate at apex and erose-denticulate along the margin (vs. lip reniform to broadly reniform, round at apex, with entire straight to inconspicuously erose margin). Taking these differences into account, we treat O. integerrima as a distinct species, despite it was synonymized with O. maxima by Geiger (2016), Bunpha et al. (2019) and Bunpha & Pedersen (2022).

Studied specimens:— VIETNAM. Dien Bien Province: Muong Nhe District, Muong Nhe Natural Reserve, Sin Thau Municipality, A Pa Chai Village, around point about 22º22’50’’N 102º14’18”E, old humid secondary evergreen broad-leaved submontane forest on steep mountain slopes composed with sandstone at elevations of 750–820 m a.s.l. along small stream, epiphyte on tall tree, occasional, 16 May 2022, herbarium prepared on 4 October 2022, flowers uniform light green, L. Averyanov, T. Maisak, VR1681 (LE LE01169539 https://en.herbariumle.ru/?t=occ&id=144129, photos LE LE01123561 https://en.herbariumle.ru/?t=occ&id=143254). VIETNAM. Lam Dong Province: Lac Duong District, forest around Da Nhim, flowers green, median lobe almost rounded, apex rounded or slightly retuse, margin dentate, 6 October 2020, Truong Ba Vuong, Ngo Quang Dang, BV889 (photos LE LE01088171 http://en.herbariumle. ru/?t=occ&id=43686).

Figures

FIGURE 12. A–C. Dendrobium deltatum. Photos by L.Averyanov from the specimen L. Averyanov, T. Maisak, AL2825. D–F. Oberonia maxima. Photos by Truong Ba Vuong from the specimen Truong Ba Vuong, Ngo Quang Dang, BV889. Photo correction and design by L. Averyanov.