Phytotaxa 436 (1): 085–091 ISSN 1179-3155 (print edition) https://www.mapress.com/j/pt/ PHYTOTAXA Copyright © 2020 Magnolia Press Article ISSN 1179-3163 (online edition) https://doi.org/10.11646/phytotaxa.436.1.9

Bulbophyllum trongsaense (: : ), a new from Bhutan

PHUB GYELTSHEN1*, DHAN BAHADUR GURUNG2 & PANKAJ KUMAR3* 1Department of Forest and Park Services, Ministry of Agriculture and Forests, Trongsa, Bhutan. 2College of Natural Resources, Royal University of Bhutan, Lobesa, Bhutan. 3Kadoorie Farm and Botanic Garden, Lam Kam Road, Lam Tsuen, Tai Po, New Territories, Hong Kong S.A.R., P.R. China. *For correspondence: [email protected], [email protected]

Abstract

Bulbophyllum trongsaense is described as a new species from Trongsa district of Bhutan. Detailed morphological description, distribution, phenology, ecology and colour photographs are provided along with comparison with B. amplifolium to which it shows closest affinity.

Keywords: Bulbophyllum amplifolium, B. nodosum, Endangered

Introduction

Orchidaceae is the largest and most diverse family of flowering (Pearce & Cribb 2002, Gurung 2006, Chase et al. 2015) consisting over 28,000 species in 736 genera with new species increasing day by day (Christenhusz & Byng 2016). Orchids occupy almost all habitats on earth except the glaciers; however, they show highest diversity in the tropics (Gurung 2006). Bhutan, the part of Eastern Himalayan Hotspot is home to rich flora and fauna. Pearce & Cribb (2002) recorded 369 species for Bhutan and about 579 species from other Himalayan regions, but this number is surely an underestimate and Bhutan is likely to harbor around 500 species as many parts of the country are still under surveyed (Pearce & Cribb 2002, Gurung 2006). Bulbophyllum Thouars (1822: t. 3) is one of the largest genera in the family comprising around 2,200 species distributed both in the tropics and subtropics (Pearce & Cribb 2002, Chen & Vermeulen 2009, Pridgeon et al. 2014, Chase et al. 2015, Govaerts et al. 2019). In Bhutan, the is represented by 36 species from 13 sections distributed mostly in Eastern, Western and Southern parts of Bhutan (Pearce & Cribb 2002, Gurung 2006). During the field survey for transmission line alignment at Dzongkhalum under Trongsa district on October 20, 2019, a charismatic epiphytic orchid, partially blooming on Toxicodendron succedaneum was discovered at the periphery of transmission line corridor at 2000 m elevation by the first author. After returning back to station, the photographs taken from the field were examined by using available literatures at hand and identified as an unusual Bulbophyllum species belonging to section (Garay et al. 1994). On the same day, it was uploaded in the social media forum, the ‘Orchids of Bhutan’, for identification. After detail discussion with second and third authors and consultation of available literatures (Seidenfaden 1973: 1979, Pearce & Cribb 2002, Lucksom 2007, Chen et al. 2009, Pridgeon et al. 2014), it was confirmed to be a species hitherto new to science. We describe the same here as B. trongsaense and compare it with its allied species, B. amplifolium. Voucher specimens have been deposited at THIM.

Taxonomy

Bulbophyllum trongsaense P. Gyeltshen, D.B. Gurung & Kumar sp. nov. (Figs. 1 & 2).

TYPE:—BHUTAN. Dzongkhalum Province, Trongsa District, 2000 m, 20 September 2019, P. Gyeltshen 1905 (holotype: THIM!).

Accepted by Zhong-Jian Liu: 16 Feb. 2020; published: 16 Mar. 2020 85 FIGURE 1. Bulbophyllum trongsaense P. Gyeltshen, D.B.Gurung & Kumar sp. nov. A. Habit; B. Inflorescence with flowers; C. Close-up of inflorescence. Photographs by Phub Gyeltshen, plate by Pankaj Kumar.

Diagnosis: Bulbophyllum trongsaense is similar to B. amplifolium, but differs in having with swollen nodes, up to 4.5 cm long petiole, dorsal acute bearing trifurcate apex with middle forming a long clavate setae, petals obliquely falcate bearing triangular warts on both surfaces and trifurcate apex with median point extended into an elongate-clavate setae in former; against smooth regularly terete rhizome, up to 7.0 cm long petiole, dorsal sepal sub- obtuse ending up into an apex with a long setae ending in clavate tip, petals almost triangular to slightly oblique ovate bearing glabrous surface and acute apex extended into a setae with clavate tip in latter.

86 • Phytotaxa 436 (1) © 2020 Magnolia Press GYELTSHEN et al. FIGURE 2. Bulbophyllum trongsaense P. Gyeltshen, D.B. Gurung & Kumar sp. nov. A. Habit; B. Inflorescence; C. Flowers-dorsal, ventral and side views; D. Rhizome; E. Bracts dorsal and ventral views; F. Dorsal sepal, dorsal and ventral views; G. Petals; H. Lateral -dorsal view; I. Lateral sepals-ventral view; J. with ; K. Lip-ventral view; L. Lip-side view; M. Lip-dosral view; N. Capitulum; O. Pollinia. Photographs by Phub Gyeltshen, plate by Pankaj Kumar. a new species of Bulbophyllum trongsaense Phytotaxa 436 (1) © 2020 Magnolia Press • 87 FIGURE 3. A.–B. Bulbophyllum trongsaense: A. Petal; B. Dorsal sepal. C.–D. Bulbophyllum amplifolium (redrawn from Seidenfaden 1973: fig. 63): C. Petal; D. Dorsal sepal. Illustrations by Pankaj Kumar.

Epiphytic herbs, semi-erect. Roots terete, 3–7 cm long, 0.1–0.2 cm wide, caespitose, glabrous, mainly located below the pseudobulbs. Rhizome creeping, cylindrical, 4–13 (–14) × 0.4–0.8 cm, swollen at nodes at ca. 4–8 nodes between two pseudobulbs, woody, covered by membranous sheaths; sheaths 1.5–2.0 cm long, persistent, brown in colour; internodes of rhizome 1.0–1.7 (–2) cm long. Pseudobulbs ovoid-oblong, 3.5–7.0 cm long, 1.5–2.4 cm wide, 4.0–11.0 cm apart from each other on the rhizome, glabrous, green, slightly angular with longitudinal furrows during dry seasons. Petiole terete, 2.5–4.5 cm long, 0.4–0.5 cm wide, longitudinally channeled, glabrous, obliquely notched on the pseudobulb, green with minute black spots on the surface. blade linear-oblong to oblong-elliptic, 10.5– 20.0 cm long, 2.3–6.5 cm wide, leaf apex acute, dark green on upper surface and paler underneath, glabrous, base slightly attenuate, margin entire, thick, coriaceous to leathery, a few patches of black spots near the margins and at the base. Inflorescence sub-umbellate, erect or sub-erect, arising from the base of the pseudobulb, peduncle 16.0–29.0 cm long, (3–) 4–7 flowered, green with dark brown streaks, deflexed at distal portion whilst blooming; upper sheathing bracts, glabrous, lime green with red markings; basal bracts brownish–black, new ones light green, tubular-oblong, 0.7–1.4 cm long, 0.4–0.5 cm wide. Flowers resupinate, 4.2–5.0 (–5.5) cm long. Floral bracts oblong-lanceolate, 0.8–1.2 × 0.4–0.5 cm, apex acuminate, base truncate, glabrous, pinkish-green, surface light red spotted. Pedicel and ovary yellowish green with red spots, 1.5–2.5 cm long, 0.2–0.5 cm wide. Dorsal sepal ovate, 1.4–1.6 × 0.7–1 cm when flattened, yellow with pinkish-red spots, apex dark red, apex 3-lobed with a long setae from median lobe, setae of uniform width, base truncate, glabrous, margin entire at lower 2/3rd portion and minutely denticulate to crenulate towards upper 1/3rd portion; setae slender towards lower half to clavate towards apex, 0.7–0.8 mm long, deep maroon, minutely denticulate or rough surfaced when seen under microscope. Lateral sepals obliquely ovate to falcate, 4.0–5 cm long, 0.6–0.9 cm wide, yellow with reddish-maroon spotted, lower outer margin curled upwards and lightly fused, lower inner margin curled outwards and free, margins may become free with maturity, apex acuminate; base obliquely truncate to rounded when dissected free at base and adnate to column foot, broader and slightly twisted at base. Petals obliquely ovate to obliquely falcate, 5.5–7.0× 4.0–4.5 mm, margin dentate, yellow with dark red at the apex, falcate; apex three lobed with long median setae; setae slender, ca. 9 mm long, deep maroon, base slender, gradually broadening towards apex, almost elongate-clavate. Lip thick and fleshy, ovate–oblong, 6–7 mm long, 2.5–3.0 mm wide, glabrous, side lobes absent, margin entire, mobile, recurved, adaxially deep reddish-maroon and abaxially yellow to light maroon in colour; obtuse to rounded, base broad, auriculate. Column quadrangular with tapering base,0.8–0.9 mm long, 0.3–0.45 mm wide, forwarded and incurved foot; foot rectangular with tapering base, 4.5–5.0 mm long,

88 • Phytotaxa 436 (1) © 2020 Magnolia Press GYELTSHEN et al. 1.5–2.0 mm wide, adaxially reddish-maroon and abaxially yellow, minutely wing margins with maroon lining, margin entire. Stelidia falcate, broader towards center and tapering on both sides, 3.5–4.5 cm long, 0.8–0.9 mm wide, curved, apiculate with tip curved upwards, tip reddish-maroon, ca. 1 mm long. Anther cap cucullate, 2.0 mm long, 1.0–1.5 mm wide, pale yellow, margin entire on both sides, irregularly dentate on the front, front margin drawn out, glabrous, base obtuse to rounded. Pollinia yellow, 2 in one pair, ovoid, ca. 1.5 × 1.0 mm, glaucous. Fruits yellowish-green, clavate, 6.0–6.5 cm long, 1.3–1.5 cm wide, longitudinally grooved.

FIGURE 4. Bulbophyllum amplifolium: A. Dorsal sepal; B. Petal. Photographs by Khyanjeet Gogoi from Assam (India).

Flowering:—September–November Habitat:—Bulbophyllum trongsaense is an epiphytic orchid which grows on the primary and secondary tree trunks at around 2000 m elevation on specific host trees of Cinnamomum glanduliferum, Cornus capitata, Juglans regia, Schima wallichii, Symplocos ramosissima and Toxicodendron succedaneum. The other associated trees found in its habitat are Cordia grandis, Daphniphyllum himalayense, Glochidion velutinum and Nayariophyton zizyphifolium. Etymology:—Bulbophyllum trongsaense is named after Trongsa District, the type locality, which has a profound historical significance in Bhutan. Specimens examined:—BHUTAN. Dzongkhalum Province, Trongsa District, 2000 m, 20 September 2019, P. Gyeltshen 1902 (isotype: THIM!); Dzongkhalum Province, Trongsa District, 2000 m, 20 September 2019, P. Gyeltshen 1903 (isotype: THIM!); Dzongkhalum Province, Trongsa District, 2000 m, 20 September 2019, P. Gyeltshen 1904 (isotype: THIM!); Gangur Province, Lhuentse District, 2000 m, 22 October 2019, P. Gyeltshen 1906 (THIM!); Gangur Province, Lhuentse District, 2000 m, 22 October 2019, P. Gyeltshen 1907 (THIM!). Distribution and conservation status:—Bulbophyllum trongsaense is so far only known from two locations in Bhutan namely, Trongsa District (Dzongkhalum Province) and Lhuentse District (Gangur Province) located at a new species of Bulbophyllum trongsaense Phytotaxa 436 (1) © 2020 Magnolia Press • 89 approximately 80 km apart. The newly found species is under serious threat of extinction due to clearing of forest for developmental activities in the districts. Two sub-populations were observed at Trongsa with around 100 mature individuals occurring on three host trees, namely, Cornus capitata, Symplocos ramosissima and Toxicodendron succedaneum. Three sub-populations were observed at Lhuentse with around 50 mature individuals growing on four host trees namely, Cinnamomum glanduliferum, Juglans regia, Schima wallichii and Symplocos ramosissima. It is expected that this species may occur in intermediate areas, but so far, no more populations have been observed. Electric transmission lines are going to be established in Trongsa area for which some forested habitats will be cleared. Apart from this, the region also has threats due to habitat loss by firewood and timber extraction. Major threat in Lhuentse is firewood and timber extraction which may cause habitat degradation. At both sites road broadening and other economically developmental activities are also threat to the natural habitat. The total number of mature individuals is around 150 and the Area of Occupancy (AOO) according to GeoCat (Moat 2007) is 8 km2. Based on the above knowledge and on IUCN (2019) guidelines, we assess Bulbophyllum trongsaense as Endangered [EN B2ab(iii,iv,v); C2a(i); D]. Taxonomic notes:—While revising the then recognized genus Cirrhopetalum, Seidenfaden (1973) also discussed about Bulbophyllum amplifolium (Rolfe 1913: 21) Balakrishnan & Chowdhury (1968: 89) with an illustration of the species. However, in his illustration (Fig. 3), dorsal sepal was illustrated with regularly terete setae, but Chen & Vermeulen (2009) and photo from India (Fig. 4) reveal the dorsal sepal with setae ending in a clavate tip. In B. trongsaense the setae is terete without clavate tip. Seidenfaden (1973) also had doubts about the tip of stelidia which from Assam specimen appeared to be thread like, emerging from the sides of stelidia, and, in Bhutanese specimens (of B. amplifolium) he claimed the tip to be prolongation of the stelidia itself. However, after doing detailed morphological studies on living plants of both species and existing illustrations of B. amplifolium, current authors establish that the two species can be easily differentiated on the basis of morphology as discussed in the diagnosis and Table 1.

TABLE 1. Morphological differences between Bulbophyllum trongsaense sp. nov. and Bulbophyllum amplifolium.

Parts Bulbophyllum trongsaense sp. nov. Bulbophyllum amplifolium

Rhizome With swollen nodes. With smooth terete nodes.

Petiole Up to 4.5 cm long. Up to 7.0 cm long.

Apex acute ending with trifurcate tip. Median tip Apex sub-obtuse ending up into a single tip elongated Dorsal sepal elongated into a setae without a clavate end. into setae with a clavate end.

Obliquely falcate, covered with triangular warts on Triangular to obliquely ovate with smooth surfaces. Petal both surfaces. Apex trifurcate with median point Apex elongated into a single clavate setae. elongated into clavate setae.

Bulbophyllum trongsaense also shares similar character of rhizome swollen at the nodes with B. nodosum (Rolfe 1895: 35) Smith (1912: 26), but overall morphology of the two plants is very different.

Acknowledgements

We wish to express our sincere gratitude to Director General of Department of Forest and Park Services of Bhutan; Chief Forestry staffs of Nature Conservation Division as well as Bumthang Forest Division for their constant motivation and encouragement. We would like to acknowledge Roland Amsler (Swiss Botanic Garden) and Khyanjeet Gogoi (Assam, India) for their valuable help and suggestions. We are also grateful to Mr. Gyeltshen of Mongar Forest Division for additional information on the species. Our thanks extend to Veterinary hospital, Trongsa for providing lab facilities for examining the specimens.

90 • Phytotaxa 436 (1) © 2020 Magnolia Press GYELTSHEN et al. References

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