Pleione arunachalensis Hareesh, Kumar & M.Sabu, 2017

Hareesh, Vadakkoot Sankaran, Kumar, Pankaj & Sabu, Mamiyil, 2017, Pleione arunachalensis (Orchidaceae: Epidendroideae: Arethuseae: Coelogyninae), a new species from North-East India, Phytotaxa 291 (4), pp. 294-298 : 294-298

Pleione arunachalensis Hareesh, Kumar & M.Sabu sp. nov. ( Fig. 1 & 2 )

Type:— INDIA . Arunachal Pradesh: Lower Dibang Valley district, Mayodia , 2100m, 06 May 2016, V. S.Hareesh 143761 holotype: CALI !; isotypes: CAL!, CALI !)

Diagnosis: Pleione arunachalensis sp. nov. shows affinity with P. chunii and P. hookeriana but differs from the latter two in having broadly ovate lip with obtuse apex and minutely undulate margin; lip purple with brownish yellow towards the apex; 4 rows of papillae on the disc and column apex truncate.

Description: Lithophytic herb up to 11–15 cm long. Pseudobulbs 28–32 × 14–16 mm, ovoid-conical with an elongated neck, glabrous, green or greenish black, covered with remains papery brown sheaths. Leaf solitary, plicate, lamina 4.5–5 × 1.3–1.5 cm, oblanceolate, acuminate, glabrous, pale green or greenish black. Inflorescence erect, 1-flowered; peduncle 5.5–5.7 cm long, slender, glabrous, deep pink; bract 15–18 × 6–7 mm, obovate to oblanceolate, obtuse, cymbiform and embracing the ovary, glabrous, pinkish brown; pedicel c. 4–5 mm long, pale pink, glabrous. Flower 5–5.5 cm across, deep pink; dorsal sepal 30–33 × 4–5 mm, oblanceolate, subacute, 5-nerved, glabrous, deep pink; lateral sepals 30–32 × 7–8 mm, oblanceolate, acuminate at apex, glabrous, deep pink; petals spreading, 35–36 × 4–5 mm linear-oblanceolate, obtuse or sub-acute at apex, glabrous, deep pink; lip 33–35 × 25–27 mm, obscurely 3-lobed towards the apex, broadly ovate when flattened, obtuse at apex, margin minutely undulate; callus of 4 lines of long papillae 14 mm apart from the base and extends towards the apex. Column sub-clavate, 15–16 mm long, winged along both sides, wings broadened upward, truncate at apex, glabrous, white with purple shade towards the wings. Ovary 8–10 mm long, glabrous, pinkish brown. Anther cap 5–6 × 4 mm. Pollinia 1.7 mm long, oblong.

Phenology: Late April–June.

Etymology: Named after the state of Arunachal Pradesh in India where this species was discovered.

Distribution and Ecology: The new species known only from Mayodia pass, Lower Dibang Valley district of Arunachal Pradesh, North-East India . The new species grows in the moist rocky areas in association with moss at an elevation varies from 2000 to 2100 m. The area characterised by heavy snowfall in January and February, snowfall starts in November and continues occasionally till April.

Conservation status: The new species has so far only been collected from the type locality. The area of occupancy is estimated to be less than 4km 2 and the known populations contain a maximum of 20–50 plants. The new species perceive serious threat of existence due to widening of the roads, and other developmental activities which may lead to loss of its natural habitat. Based on these information the new species has been assessed as Critically Endangered [ B2 ab(iii,iv,v);D] based on IUCN (2013). This is a provisional threat assessment ; more field studies are needed to confirm the status. For the time being, we are trying to grow the plants for conservation at Calicut University Botanical Garden ( CUBG) .

Key to Indian species of Pleione :

- Lip lacking purple dark blotches, elliptic in shape, lip base saccate ................................................................................ P. praecox 4. Callus on the lip with 3 entire undulate lamellae ............................................................................................................. P. saxicola - Callus on the lip 4 to 7, lacerate or erose or papillose or hair-like.................................................................................................... 5 5. Petals and sepals white ....................................................................................................................................................... P. humilis - Petals and sepals pink or dark pink...................................................................................................................................................6 6. Callus on lip composed of lacerate lamellae ............................................................................................................... P. grandiflora - Callus on lip composed of rows of individual papillae .................................................................................................................... 7 7. Callus with 7 rows of hair or papillae ......................................................................................................................... P. hookeriana - Callus with 4 rows of hair or papillae ................................................................................................................... P. arunachalensis

Figures

FIGURE 1. Pleione arunachalensis. A. Plant with flower. B. Flower—front view. C. Floral bract. D—G. Dissected flower. D. Dorsal sepal. E. Lateral sepals. F. Lateral petals. G. Labellum. H. Labellum—spread opened. I. Column with ovary. J. Column—front view. K. Column—wings spread up. L. Pollinia. (Photos by V.S. Hareesh)

FIGURE 2. Pleione arunachalensis. A. Plant with flower. B. Flower—front view. C. Floral bract. D–G. Dissected flower. D. Dorsal sepal. E. Lateral sepals. F. Lateral petals. G. Labellum. H. Column with ovary. I. Column—front view. J. Column—wings spread up. K. Pollinia. (Illustrations by V.S. Hareesh).