Bulbophyllum reflexipetalum (Orchidaceae, Epidendroideae, Malaxideae), a new species from Xizang, China

Abstract Bulbophyllum reflexipetalum, a new species from Motuo County, Southeast Xizang, China, is described and illustrated here. This new species belongs to Bulbophyllum sect. Umbellata Bentham & J. D. Hooker, and it is morphologically similar to B. umbellatum Lindley, B. guttulatum (J. D. Hooker) N. P. Balakrishnan and B. salweenensis X.H. Jin, but is distinguished from them by having reflexed petals, base of dorsal sepal with 1 dentate on each side, lip with significantly revolute margin, adaxially with dark brown spots or patches and one longitudinal groove.


Introduction
Bulbophyllum Thouarm (Orchidaceae) is one of the three largest genera in the orchid family, comprising about 2200 species widely distributed in tropical Africa, Asia and America (Lang andTsi 1987, Pridgeon et al. 2014). There are about 105 species in China (Chen and Vermeulen 2009), with several new species described in recent years (Zhou and Jin 2015, Liu et al. 2016, Zhai et al. 2017. Motuo is an important area in the eastern Himalaya biodiversity hotspot, but the species diversity in this region is poorly known, and some new taxa are discovered and described in recent years (Lai and Jin 2012, Huang et al. 2013, Raskoti et al. 2017). More conservation efforts are needed in this region to counteract the increasing anthropogenic disturbance and destruction. During our field survey in Motuo County, Xizang Autonomous Region, a new Bulbophyllum species of sect. Umbellata Bentham & J. D. Hooker was found in the subtropical broad-leaved forest and described below.

Materials and methods
Type specimens were collected in Motuo County, Xizang Autonomous Region, China, during a field expedition in 2016. Photographs were taken in field. Shapes, colors and other details given in the description were based on living materials (five individuals). The column and pollinia morphological photographs were taken using an Olympus SZX16. Voucher specimens were deposited at the herbarium of Kunming Institute of Botany, Chinese Academy of Sciences (KUN). The conservation status of the new species was evaluated based on the guidelines of the International Union for Conservation of Nature (IUCN 2012). Description. Epiphytic herbs. Rhizome creeping and rooting, 3-4 mm in diam. Roots arising from the nodes, 0.5-1.5 mm in diam. Pseudobulbs often 1-2 cm apart on rhizome, flattened ovoid or ovoid-conic, ca. 10-16 × 8-15 mm, with a terminal leaf. Leaf blade oblong, 50-65 × 15-20 mm, leathery, apex obtuse and emarginate, base narrowing into a petiole; petiole 10-20 mm. Scape arising from the base of pseudobulb, 13-20 cm long, longer than leaf; umbellate, often 3-4-flowered; peduncle ca. 1.5 mm in diam, with 3 tubular sheaths; floral bract lanceolate, acuminate, concave, ca. 6.3 × 2.0 mm; peduncle and ovary ca. 10-15 mm long. Flowers greenish yellow, sepals and petals with dark brown spots; lip greenish yellow, adaxially with dark brown spots or patches. Dorsal sepal ovate, concave, apex obtuse, base with 1 dentate on each side, ca.   Etymology. The specific epithet "reflexipetalum" refers to reflexed petals of this new species. Vernacular name. Fan Ban Juan Ban Lan (Chinese pronunciation); 反瓣卷瓣兰 (Chinese name).
Distribution and habitat. Bulbophyllum reflexipetalum is currently known only from the type locality of Motuo, Southeast Xizang, China. It is a predominantly epiphytic species that grows on tree trunks, under broadleaf evergreen forest at the elevation between 1300 m and 1400 m.
Conservation status. During our 2-weeks field survey, only 2 populations were found. As this new species may also grow in the broadleaf evergreen forest of vicinity region, we regard its status as Data Deficient (IUCN 2012).

Discussion
Bulbophyllum reflexipetalum belongs to sect. Umbellata based on the umbellate inflorescence (Chen and Vermeulen 2009). Morphologically, this new species is similar to B. salweenensis, B. umbellatum and B. guttulatum in terms of vegetative morphology and shape of the flowers (Figure 3), but is easily recognized by its reflexed petals, the dentate of dorsal sepal and the revolute margin of lip ( Table  1). Beyond that, B. reflexipetalum can be distinguished from B. salweenensis by the absence of sheaths on the pseudobulbs and rhizome (vs. pseudobulbs and rhizome with sheaths), scape longer than leaf and petals apex mucronate (vs. the scape shorter than leaf ); it differs from B. umbellatum with smaller and flattened void or ovoidconic pseudobulbs, shorter leaf blade, petals apex caudate (vs. obtuse-rounded petals)  ; and it differs from B. guttulatum with leaf blade oblong and apex emarginated (vs. leaf blade elliptic-oblong and apex rounded), shorter pedicel and ovary, lip papillae with a single longitudinal ridge (lip with three ridges in B. guttulatum) Vermeulen 2009, Zhou andJin 2015).