Bulbophyllum spathulatum (Orchidaceae), a new record for Bhutan

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PLATINUM OPEN ACCESS
Bulbophyllum Thouars (1822) is one of the largest genera in family Orchidaceae comprising approximately 2,200 species, distributed in the tropical and subtropical regions of the world with the richest diversity in the tropics of Africa and Asia (Pearce & Cribb 2002;Chen & Vermeulen 2009;Chase et al. 2015;Gyeltshen et al. 2020). In Bhutan, the genus is represented by 57 species from 13 sections distributed mostly in eastern, western, and southern parts of Bhutan (Gurung 2006;Dalstrom et al. 2017;Gyeltshen et al. 2020).
During a recent floristic exploration in the Subrang and Pantang under Zhemgang District in 2019, the first author encountered a small population of an unfamiliar orchid growing on a tree. For initial examination sufficient photographs were taken.
Originally described as Cirrhopetalum spathulatum Rolfe ex E.W.Cooper, this species was circumscribed under the genus Bulbophyllum by Seidenfaden (1970) as Bulbophyllum spathulatum. Alternatively, Garay et al. (1994) described a new genus as Rhytionanthos where based on fusion of lateral sepals to form a synsepal by inward twisting and connation of their edges and included Bulbophyllum spathulatum as Rhytionanthos spathulata, however, this concept has changed. The genus Rhytionanthos has now been merged under Bulbophyllum (Pridgeon et al. 2014) and accordingly followed thereafter (Govaerts et al. 2020).
Bulbophyllum spathulatum had been included in the Orchids of Bhutan by Pearce & Cribb (2002) based on its occurrence in adjacent areas in India, however, it was never collected from within the political boundaries of Bhutan. Hence, the present collection of the species from Zhemgang District, Bhutan stands as a new record for Bhutan. Later, plants were also discovered at one more area in Zhemgang District followed by two sites in Wangduephodrang District, however, no voucher specimens were collected due to the rarity of the species. Detailed morphological descriptions, updated distribution, phenology, and ecology along with distribution map and colour photographs are provided based on the collected specimens. Type: Thailand, Bangkok, Roebelen 292-12 (K000829943) (K!-Holotype).
Phenology: Flowers from mid-February to end of March, fruits mature from May to September.
Habitat: Bulbophyllum spathulatum was found growing as epiphyte on the tree trunks of Canarium strictum in the subtropical forest at around 350m along the river bank. Other associated trees and shrubs in its habitat comprises of Tetrameles nudiflora R.Br.,