Impatiens megamalayana Ramasubbu, 2017

Ramasubbu, R., Divya, C., Kala, N. Sasi, Surendran, Anjana & Sreekala, A. K., 2017, Impatiens megamalayana, a new species of Impatiens from the Western Ghats, Tamil Nadu, India, Phytotaxa 302 (2), pp. 193-197 : 193-196

Impatiens megamalayana Ramasubbu sp. nov. ( Fig. 1 , 2 )

Type:─ INDIA. Tamil Nadu: Theni District, Megamalai Hills way to Highwavies, 09 º 39′06.36″N, 77 º 21′05.08″E, 1451 m a.s.l, 11 September 2015, R. Ramasubbu 609 (holotype MH!, isotype Gandhigram University Herbarium!).

Diagnosis: This species is closely allied to Impatiens herbicola Hook.f.(1911:354) and I. inconspicua Benth. in Wall. (1831:4741), the latter with three varieties, but it differs by its ridged stem, ensiform and villous leaves, a wrinkled boat-shaped lower sepal with outwardly curved tip, ornamented seeds and strictly ovate pollen grains.

Annual, succulent, erect, glabrous herbs 28–42 cm tall; stem purplish, cylindrical with 3–5 ridges, often branched, branches erect, nodes slightly swollen, internode elongate, 5–5.5 cm. Leaves in a pair, opposite decussate, shortly petiolate, petiole 0.5 mm, densely hairy, ensiform, acuminate, entire, base truncate, slightly cordate, reflexed upwards, 2.5–3.5 × 1–1.5 cm, densely hairy above, smooth below, completely purplish at base when mature, lower part of main nerve densely hairy, leaf margin distinctly serrate, leaf blade teeth 1–2 mm, extra petiolar glands present. Inflorescence 1–2 per angle (4 per node), flowers simple, axillary, 3.8–4.7 mm wide, pale purple with deep reddish-yellow spot at base; pedicellate, pedicel 1.3–1.8 cm at anthesis, 1.7–2.3 cm in fruit, with one row of long hairs. Sepals: lateral sepals 2, sickle-shaped, apex acuminate, 1.8–2.6 mm long, 1–2 nerved, upwardly curved, purplish, densely hairy. Petals: dorsal petal orbicular, 2–2.3 × 3.2–3.8 mm, recurved, dorsally keeled, apiculate, keel densely covered with singlecelled hairs, lateral united petals oblong-spherical, deeply clawed, 2-lobed, 2.6–3.1× 3.6–4.3 mm, basal lobe small, oblong, distal lobe round or spherical, pale orange with deep reddish-yellow spot, dorsal auricle prominent, obtuse; lower sepal boat-shaped, 3.2–4.3 × 0.8–1.6 mm, with 4–7 wrinkles, tip of lower sepal outwardly curved, horizontal, spur absent, densely hairy, purple. Ovary elongate, 1.6–2.3 mm long. Fruit a capsule, ovoid, turgid, 11–13 × 3–5 mm, acute, beaked, 5–9-seeded. Seed round with prominent caruncle, compressed, 0.8–1.3 × 0.2–0.4 mm, ornamented, black, shining.

Flowering and fruiting —July to October.

Conservation status — Impatiens megamalayana is assessed as Critically Endangered (CR B1ab(i,ii,v); 2ab(i,ii,iv); D) in accordance with the IUCN guidelines( IUCN 2016).However, more field studies are required to observe details as to the extent of decline. The habitat of the species is severely affected by landslides.

Etymology —The species for its occurrence in the Megamalai Wildlife Sanctuary, a part of Western Ghats, Tamil Nadu.

Distribution —Rare on hill tops at 1451 m a.s.l., only found on the way to Highwavies, Megamalai Hills, Theni District, Tamil Nadu, India.

Additional specimens examined (paratypes) — INDIA, Tamil Nadu, Theni District, Megamalai Hills way to Highwavies , 09 º 39′06.36″N, 77 º 21′05.08″E, 1451 m a.s.l., 16 October 2016, G. Manikandan & Anjana Surendran GU 627 (Gandhigram University Herbarium) ; ibid., 09 º 39′06.39″N, 77 º 21′05.13″E, 1451 m a.s.l., 8 November 2016, C. Divya & N. Sasi Kala GU 636 (Gandhigram University Herbarium) .

Notes— Impatiens megamalayana grows on rocky slopes and in grasslands near streams and marshy areas. This species is associated with Habenaria longicorniculata J. Graham , Cynotis villosa (Spreng.) Schult. & Schult. f. , Drosera peltata Thunb. , Eulalia phaeothrix (Hack.) Kuntze , Isachne kunthiana (Wight & Arn. ex Steud.) Miq. , and Oplismenus undulatifolius (Ard.) P. Beauv. ex Roem. & Schult. In general floral structure, I. megamalayana is closely allied to I. herbicola but it differs by its ridged stem, ensiform and villous leaves, a wrinkled boat-shaped lower sepal with outwardly curved tip, ornamented seeds and strictly ovate pollen grains. Impatiens megamalayana is phenotypically similar to I. inconspicua , the latter with three varieties ( Bhaskar 2012) but vary from characteristic sickle shaped lateral sepals, densely hairy, wrinkled boat-shaped lower sepals, ornamented seeds and 3-colpate, ovate pollen grains ( Table 1).

Figures

FIGURE 1. Impatiens megamalayana Ramasubbu sp. nov. A. Upper portion of adult plant, B. Leaves, adaxial view, C. Petiole with pairs of extra-petiolar glands, D. Leaf, lateral view, showing hairs, E. Leaves, adaxial view, showing main nerve with single-celled hairs, F. Flower, ventral view, G. Flower lateral view, H. Lower sepal, ventral view, I. SEM of pollen grain, J. Ovary, K. Fruit, L. Seeds, M. Ornamentation of seed coat. (Photographs by R. Ramasubbu).

FIGURE 2. Impatiens megamalayana Ramasubbu sp. nov.A. Habit, B. Leaf blade, lateral (top) view and adaxial (bottom) view, C. Stem and leaves showing pairs of extra-petiolar glands, D. Flower, ventral view, E. Flower, lateral view, F. Lateral view of lower sepal, G. dorsal view of lateral sepals, H. Adaxial view of dorsal petal, I. Top view of lateral petals, J. Androecium, K. Ovary, L. Seed. (Illustrated by Dr. D. Felix Irudhyaraj based on fresh specimens).