Dendrobium naungmungense Q.Liu & X.H.Jin, 2018

Liu, Qiang, Zhou, Shi-Shun, Jin, Xiao-Hua, Pan, Bo, Maung, Kyaw Win, Zyaw, Myint, Li, Ren, Quan, Rui-Chang & Tan, Yun-Hong, 2018, Dendrobium naungmungense (Orchidaceae, Dendrobieae), a new species from Kachin State, Myanmar, PhytoKeys 94, pp. 31-38 : 32-35

Dendrobium naungmungense Q.Liu & X.H.Jin sp. nov. Figs 1 , 2

Diagnosis.

Dendrobium naungmungense is similar to D. vexabile and D. ciliatilabellum , but can be distinguished by the oblong epichile with three long-ciliate laminae and the margin crisped with hairs and the margin of column wing with significant denticulation.

Type.

MYANMAR. Kachin State. Putao County, Naungmung Town , tropical forest, 500-600 m a.s.l., epiphytic on the trunk of riparian trees, 8 Apr 2017, Qiang Liu, 430 (Holotype, HITBC!) .

Description.

Plant epiphytic, pendent, 30-50 cm long. Stems slender, branching from nodes, internodes covered by sheaths, yellowish, 1.4-2.8 cm long. Leaves anguste-ovate, acute to acuminate, entire, sessile, distichous, 3.0-4.2 × 4.0-5.5 mm. Inflorescence leaf-opposed, 1-2 flowered; peduncle short, sheathed at base, 0.7-0.9 cm long; sheaths membranous, overlapping, 2.5-3.0 mm long; floral bracts broadly lanceolate, three veined membranous, 3.0-4.5 × 2.0-2.5 mm. Flower fragrant, ca. 1.5 cm diameter when open, yellowish green, lip with sparsely purple stripe and spots. Dorsal sepals elliptic, 5-veined, 11.2-12.3 × 6.0-6.5 mm, acuminate; lateral sepals triangular, 5-veined, 12.0-13.5 × 8.0-8.5 mm, apex acuminate; mentum broad, ca. 3 mm. Petals lanceolate, 3-veined, 10.5-11.0 × 4.0-4.5 mm, acuminate. Lip 3-lobed with a short claw, obovate (when spread), 14.5-15.0 × 7.5-8.0 mm, lateral lobes elliptic, 6.0-6.5 × 2.6-3.1 mm, margin with hairs; mid-lobe oblong, 7.5-8.0 × 3.5-3.8 mm, margin crisped with hairs. A broad median band on the hypochile; disc with an ovoid cushion, three long-ciliate laminae extending from base to near apex of epichile. Column ca. 9.0 mm, stelidia falcate with significant denticulation. Operculum subglobose, with densely white crystalline papillate.

Etymology.

The new species is named after Naungmung, Kachin State, North of Myanmar, where it was discovered in a vast area of tropical rainforest.

Distribution and habitat.

Dendrobium naungmungense is only known from the type locality. It is epiphytic on the trunk of riparian trees in tropical rainforest, which is dominated by Dipterocarpus obtusifolius Teijsm. ex Miq. ( Dipterocarpaceae ).

Additional specimens examined (Paratype).

MYANMAR. Kachin State. Putao County, Naungmung Town , tropical forest, 500-600 m a.s.l., epiphyte on the trunk of riparian trees, 11 Jun 2017, Hong Jiang & Qiang Liu, 17017 (YAF!) and 8 Apr 2017, Qiang Liu, 430 (HITBC!) .

Conservation status.

Dendrobium naungmungense was collected in Naungmung Town, Kachin State, Northern Myanmar. Until now, only one population, consisting of ca. 20 mature individuals, has been discovered in 3 years of continuous field investigations (2015-2017). In addition, population growth and human activities have led to serious habitat destruction and deforestation in this region. It is also illegally collected by local people due to the highly ornamental and medicinal values. Hence, according to IUCN Red List Categories and Criteria ( IUCN Standards and Petitions Subcommittee 2017), D. naungmungense should be regarded as Critically Endangered (CR B1ab (iii, v) + 2ab (iii, v); D), which is the category for species facing the highest risk of extinction in the wild. It meets the IUCN criteria in having an extent of occurrence <100 km2, an area of occupancy <10 km2, is known from a single location and with a continuing decline inferred from the number of mature individuals, a continuing decline in the quality of habitats and a population size of less than 50 mature individuals.

Key to D. naungmungense , D. vexabile and D. ciliatilabellum

1	Mentum (1 × 3 mm), epichile (7.5-8.0 mm) longer than hypochile (6.0-6.5 mm), oblong epichile with three ciliate laminae and margin crisped with dense hairs, column wing with significant denticulation	D. naungmungense
-	Mentum (2 × 1 mm), epichile (3.5-4 mm) significantly shorter than hypochile (9-10 mm), ovate epichile without ciliate laminae and margin crisped without hairs, column wing without denticulation	2
2	Mid-lobe (2 × 2 mm), disc of lip with densely long-ciliate lamina and un-deflexed epichile	D. ciliatilabellum
-	Mid-lobe (4 × 5 mm), disc of lip with sparsely ciliate lamina and de-flexed epichile	D. vexabile

Figures

Figure 1. Dendrobium naungmungense. A Habitat B Plant C Flower D Lateral view of flower E Lateral view of labellum F Column wing G Front and lateral view of column H Abaxial and adaxial anther cap I Pollinarium J Sepals and petals K Front view of labellum. All from the type collection (Qiang Liu, 430) and drawn by Bo Pan.

Figure 2. Dendrobium naungmungense. A Habitat B Plant C Flower D Lateral view of flower E Sepals and petals F Column G Front view of labellum H Lateral view of labellum J Abaxial and adaxial anther cap K Pollinarium I Column wing (Photographed by Q. Liu).