Spathoglottis arunachalensis J. Tsering & K. Prasad, 2020

Tsering, Jambey & Prasad, Kothareddy, 2020, Spathoglottis arunachalensis (Orchidaceae), a new species from Arunachal Pradesh, India, Phytotaxa 432 (3), pp. 289-295 : 289-293

Spathoglottis arunachalensis J. Tsering & K. Prasad sp. nov. ( Fig. 1 & 2 )

Diagnosis:— The new species differs from its closely allied taxon, Spathoglottis ixioides (D. Don 1825: 36) Lindley (1831: 120) by means of its 20–30 cm long inflorescence (vs. 8–16 cm long), 1.8–2 cm across flowers (vs. 2–3 cm across), presence of sparse minute hairs on inner surface of sepals, petals and midlobe of lip (vs. glabrous on inner surface), 9–10 mm long, 3-veined sepals (vs. 16–22 mm long, 5–6-veined), 10–11 mm long petals (vs. 16–19 mm long), petals rounded at apex (vs. obtuse at apex), 7.5–8 mm long lip (vs. 14–18 mm long), lateral lobes yellow and with reddish-purple markings inside (vs. yellow with small purple spots at base), claw of midlobe without auricles (vs. claw of midlobe with 2 acute auricles at base), reniform or reniform to flabellate midlobe (vs. obcordate or obovate), midlobe undulate along margins (vs. entire margins), raised ridges of lip spreading, white, narrowly long rectangular, upper surface verrucose (vs. ridges erect, yellow, elongate, rounded-obtuse, not verrucose).

Type: — INDIA . Arunachal Pradesh: West Kameng district, Sessa Orchid Sanctuary, 27° 6’ 9.30” N, 92° 31’ 47.23” E, 1235 m, 4 th October 2016, J. Tsering 40642 (holotype: OHT, isotypes: CAL, OHT).

Description:— Terrestrial herbs. Pseudobulbs c. 2.5 × 3 cm, subterranean, ovoid-conic, covered with ridged fibrous-sheathed. Leaves 2 to 4, plicate; lamina 8–35 × 1–1.5 cm, linear or linear-lanceolate, acuminate at apex, entire along margins, sheathing and petiole-like stalk at base, glabrous, 2–4 strongly nerved; leaf base usually forming a pseudostem. Inflorescence 20–30 cm long, lateral, simple raceme; peduncle 15–22 cm long, slender, pubescent, lower part covered with 1 to 4 amplexicaul tubular sheaths; rachis 5–8 cm long, pubescent, laxly 2 to 6-flowered (rarely 9-flowered). Flowers yellow, 1.8–2 cm across; pedicel 2–3 cm long, densely pubescent, pale greenish-yellow; floral bracts 5–6 × 2–2.5 mm, much shorter than the ovary, ovate-lanceolate or lanceolate, acute or acuminate at apex, sheathing at base, pubescent, persistent, 3-veined. Sepals 3, similar, spreading, 9–10 × 5.4–6 mm, ovate-elliptic or ovate-oblong, obtuse to subacute at apex, outer surface densely pubescent, inner surface sparsely with minute hairs, 3- veined; dorsal sepal slightly hooded towards the apex. Petals 10–11 × 6–7 mm, spreading, slightly broader than sepals, ovate-elliptic or broadly elliptic, rounded at apex, inner surface sparsely with minute hairs, outer surface glabrous, 5 to 7-veined. Lip subsaccate or saccate at base, 7.5–8 × 6.7–7 mm when flattened, 3-lobed; lateral lobes c. 5 × 3 mm, sub-erect, diverging, falcately triangular or ovate-triangular, obtuse at apex, reddish-purple markings inside; midlobe spreading, clawed at base, reniform or reniform to flabellate, c. 5 × 5 mm, obtusely 2-lobed or rounded at apex, undulate along margins, upper surface sparsely covered with minute hairs; disk between the side lobes is pubescent, low central ridge running from middle of claw to near apex of midlobe, two lateral raised ridges running from claw of midlobe to just above the base of midlobe; raised ridges c. 2.5 × 0.6 mm, fleshy, distinctive, spreading, white, narrowly long rectangular, upper surface verrucose. Column 5–6 mm long, elongated, curved, clavate, narrowly winged throughout and becoming broader towards apex, without foot, yellow with white shade near base. Pollinia 8, in 2 groups (4+4), yellow, subequal in size, clavate, commonly attached to a solitary viscidium. Ovary 5–8 mm long, narrowly clavate, ribbed, densely pubescent, pale greenish-yellow. Capsule not seen.

Phenology:— Flowering in September-October and fruiting not seen.

Habitat:— Generally grows on moist moss covered hill slopes in open forest, wet banks along road sides at about 1200–1250 m. a.s.l. elevation and in close association with Anthogonium gracile Wallich ex Lindley (1840: 426) .

Distribution:— It is presently known only from the type locality, Sessa Orchid Sanctuary, West Kameng, Arunachal Pradesh.

Etymology:— The new species is named after the state, Arunachal Pradesh, where this novelty occurs.

Conservation status:— Spathoglottis arunachalensis is known only from the type locality which has about 200 individuals in single location. However, the present habitat is now disturbed due to construction of Trans-Arunachal Highway. Few explorations were made in the adjacent habitat but could not locate the species. Based on ‘Extent of Occurrence’ (Criterion B1: EOO <100 km 2) and ‘Area of Occupancy (Criterion B2: AOO <10 km 2) together with the number of locations – 1 (subcriterion ‘a’) and projected decline in area, extent and/or quality of habitat (subcriterion ‘b(iii)’), the new species is assessed here as ‘Critically Endangered [CR B1 B2 a, b(iii)]’ ( IUCN 2014).

Figures

FIGURE 1. Spathoglottis arunachalensis sp. nov.A. Habit; B. Flower; C. Dorsal sepal; D. Lateral sepals; E. Petals; F. Lip; G. Pedicel with ovary, floral bract and column side view; H. Column front view; I. Pollinia.

FIGURE 2. Spathoglottis arunachalensis sp. nov. A. Habit; B. Pseudobulb; C. Inflorescence; D. Pedicel with ovary; E.–G. Flower front, side and top view.