Platanthera dambungensis K.Prasad, 2023

Abstract, Prasad K. & Rich., Platanthera, 2023, The genus Platanthera (Orchidaceae) in India with two new species, Rheedea 33 (2), pp. 31-52 : 35-38

Platanthera dambungensis K.Prasad , sp. nov. Figs. 1 & 2

Platanthera dambungensis is closely allied to P. yadongensis X.H.Jin & W.T.Jin but differs by having non-stoloniferous tuberoids (vs. stoloniferous), rachis with dentate ribs (vs. not dentate), ovate-lanceolate or narrowly lanceolate, 8–20 mm long floral bracts, with dentate margins (vs. linear-lanceolate, about 30 mm long with ciliate margins), ribs of pedicels and ovary dentate (vs. ribs not dentate), lateral sepals 3.8–4.4 mm long (vs. 3.5 mm long), lip distinctly arching with sub-entire margins, slightly longer than the sepals, 3.9–4.6 mm long (vs. slightly arching and entire, shorter than the sepals, c. 3 mm) and rostellar arms shallowly concave (vs. deeply concave).

Type: INDIA , Sikkim, North Sikkim district, Lachung, way to Dambung from Lachung , N 27°43’41”, E 88°45’22”, 2987 m, 01.08.2019, K . Prasad 86540 (holo CAL!; iso CAL!) .

Terrestrial herbs, 25–45 cm high. Tuberoids not stoloniferous, narrowly fusiform, fleshy, gradually tapering from base to tip, 1–6 cm long, 1–3 mm thick. Stem erect, cylindric, with c. 1 cm long solitary tubular sheath at base. Leaves 3–5, alternate, scattered, unequal, sessile; lower largest leaf situated below the middle of stem, broadly oblanceolate or elliptic-oblanceolate, 4.5–10.5 × 0.8–3.5 cm, sheathing at base, entire along margins, acute at apex; upper leaves 2 or 4, gradually becoming smaller, uppermost bract-like, lanceolate or linear-lanceolate or oblong-lanceolate, 1.5–8.6 × 0.5–1.5 cm, acute or acuminate at apex. Racemes 8–12 cm long; rachis laxly 15–25-flowered, ribbed; ribs dentate. Flowers small, green or greenish-yellow, not fully opening. Pedicels with ovary narrowly cylindric-fusiform, 8–14 mm long, beaked and curved at tip, ribbed, ribs dentate. Floral bracts ovate-lanceolate or narrowly lanceolate, 8–20 × 2–5 mm, dentate along margins, acuminate at apex, 3-veined, lateral veins branched, lower ones longer than flowers, upper ones longer or as long as flowers. Sepals subequal, margins sub-equal, to minutely dentate, 3-veined, lateral veins branched or not; dorsal sepal oblong or ovate-oblong, 3.7–4.2 × 1.8–2.2 mm, apex obtuse, forming a hood with petals; lateral sepals obliquely oblong-lanceolate or oblong-elliptic, 3.8–4.4 × 1.2–1.6 mm, spreading, falcate, apex acute or obtuse. Petals obliquely ovate or ovate-elliptic to oblong, 3.2–3.7 × 1.1–1.8 mm, apex acute, with branched vein. Lip slightly longer than sepals, distinctly arching, oblong-lanceolate or narrowly lanceolate, 3.9–4.6 × 1–1.1 mm, base shortly clawed, minutely saccate, margins sub-entire, curved in the middle, apex obtuse; spur shorter than the ovary, slender, cylindrical, 4–5 mm long, slightly curved near the base, directed downwards. Column short, c. 1.3 mm high; rostellum erect, prominent; rostellar arms concave; anther thecae slightly divergent towards base, connective rather narrow; pollinia obovoid, caudicle short; viscidium sub-orbicular when spread out, margins more or less involute like a semi-circular tube; staminodes sub-globose; stigma with 2 lateral lobes and a small median lobe; lateral stigmatic lobes spreading on each side of base of lip, broadly oblong or sub-orbicular. Capsules obovoid.

Flowering & fruiting: July to September Habitat: It grows in open alpine pasture within grassy slopes at 2800–3300 m elevation.

Etymology: The specific epithet is chosen after the type locality, Dambung in North Sikkim.

Distribution: Hitherto known only from the type locality, Shingba Rhododendron Sanctuary and Dambung (Lachung), North Sikkim, India .

Specimenexamined (paratype): INDIA , Sikkim, North Sikkim district, Lachung, Shingba Rhododendron Sanctuary , N 27°43’47”, E 88°44’21”, 3211 m, 21.08.2018, K . Prasad 86525 ( CAL) .

Conservation status: Platanthera dambungensis is known only from the type locality (North Sikkim, Lachung) which in 2018 and 2019 had about 150 individuals in two adjacent locations. All the individuals were observed in an area around 2 km 2. North Sikkim area is highly species-rich and threatened by human activity. The type locality is similarly exposed to grazing and other anthropogenic activities. Further rigorous survey should be carried out in this region to determine the actual population status of the new species; hence it is assessed here as ‘ Data Deficient’ ( DD) ( IUCN, 2022) .

Notes: Platanthera dambungensis is close to P. yadongensis in having a similar habit, two long and outstretching stigmatic lobes, and naked and involute viscidium. However, it is easy to distinguish the new species from the latter by the characters discussed in the diagnosis.

Figures

Fig. 1. Platanthera dambungensis K. Prasad sp. nov.: a. Habit;b. Raceme;c–e. Flowers in different view (photos by K.Prasad).

Fig. 2. Platanthera dambungensis K.Prasad sp. nov.: a. Habit; b. Flower;c. Floral bract; d. Dorsal sepal;e. Lateral sepals; f. Petals; g. Lip with spur and pedicel with ovary; h. Lip; i & j. Column front and side views (from K. Prasad 86540; photos by K. Prasad).