Impatiens agastyamalayensis (Bhaskar) A.Joe, V.Bhaskar & M.Sabu, 2017

Joe, Alfred, Bhaskar, V. & Sabu, Mamiyil, 2017, Impatiens agastyamalayensis stat. nov. (Balsaminaceae) - A reassessment of Impatiens rufescens var. agastyamalayensis and rediscovery of the plant from the Western Ghats, India, Phytotaxa 326 (2), pp. 144-150 : 145-148

Impatiens agastyamalayensis (Bhaskar) A.Joe, V.Bhaskar & M.Sabu stat. nov.

Impatiens rufescens var. agastyamalayensis Bhaskar , Taxonomic Monograph on Impatiens of Western Ghats 171,

2012.

Type:— Exsiccatum, sin.num. Agastyamalai (Acc. No. 7488 MH!), Aghasteer Mallay, Tinnevelli, (erstwhile Madras state, presently in Trivandrum district, Kerala) May 1901, C.A. Barber 2923 (MH!) ( FIGURES 1 , 2 )

Branched, erect perennial herbs up to 30 cm tall; stem 4-angled, glabrous except at upper reddish nodes, green or green with purple tinge; internodes 1.5–8 cm long. Leaves opposite, decussate, crowded at apex, 2.7–3.5 × 1.1–1.3 cm, oblong, acute at apex, base rounded, margin serrate, spinose, upper surface green, puberulous, lower surface pale greenish or whitish, veins 3 on each side, hairy at midrib and veins; petiole 1–2 mm long, glabrous, pale green or whitish. Flowers solitary on leaf axils, 16–18 × 12–15 mm, purple or pale purple with 2 red spots at the throat and whitish towards base; pedicel 18–22 mm long, whitish or pale purple, densely villous, hairs white. Lateral sepals ovate-lanceolate, 8–9 × 2–3 mm, villous, pale green with purple apex. Lower sepals 7–8 × 4–5 mm, saccate, villous, white with few reddish honey guides towards margin, spur ca. 2 mm long, cylindrical, stout, straight, villous, purple. Dorsal petal 7–8 × 4–5 mm, broadly ovate, white, glabrous except hairy keel, keel green, apex mucronate. Lateral united petals 2-lobed; distal lobe 9–11 × 5–6 mm, ovate with obtuse apex, purple; basal lobe ca. 6 × 2 mm, pale purple or whitish, orbicular or obovate, apex acute or rounded; dorsal auricle 2–3 × 2 mm, cream with reddish honey guides. Stamens 5–6 × 2 mm; filaments 3–4 mm long, glabrous, white, anthers 2–3 × 2–3 mm, glabrous, white, pollen white. Pistil 3–4 × 1 mm; ovary oblongoblanceolate, green, glabrous. Capsule 12–14 mm long, ellipsoid or oblanceolate, glabrous, ridged, stalk 2–3 cm long, purple; seeds 1–3 per capsule, 6–7 × 3–4 mm, oblong, almond-shaped, brown, villous.

Micro-morphological characters:—

Pollen morphology:— 4-colpate, rectangular, bilateral, pollen greatly vary in size, ranging from 32 × 19 μm to 43 × 25 μm, exine finely reticulate, reticulations small; lumen ca. 2–3 × 2–3 μm, muri thin, ca. 0.5 μm, duplibaculate, apo- and meso-colpium slightly differentiated.

Seed trichome morphology:— Trichomes bi-morphic, trichomes near hilum in a white sticky bunch, long and slender, with double helical banding pattern, trichomes away from hilum stiff with reticulate banding pattern. Trichomes with reticulate banding arise from a dark brown base and the apices without reticulate banding. There are also dwarf trichomes all over the seed in between long stiff trichomes and they are also reticulately banded and bands brownish.

Phenology:— This plant was collected with both flowers and fruits during February by Udayan and during March by the first author, while the specimen collected by C.A. Barber during May 1901 bears only flowers. From its occurrence during summer months like February and March (the northeast monsoon often extends up to these months in this part of the Western Ghats) it appears that this species is perennial in nature and its life cycle is adopted to both southwest and northeast monsoon seasons.

Distribution:— This species is narrowly endemic and so far known only from Pongalapara of Agastyamala,

Western Ghats of Kerala.

Conservation Status:— Ever since the type specimen was collected by C.A. Barber in 1901, there have been no collections of this balsam from either the type locality or from any other part of the Western Ghats. Its first collection was by Udayan and others during 2009 from the same locality (CMPR!) and the present one by the first author during 2016 (CALI!). Further, it is known to exist only in a single location, i.e., Pongalapara of Agastyamala and the geographic range or area of occupancy is estimated to be less than 10 km 2. Therefore, this species is classified as Critically Endangered [CR B1ab(ii, iii)+B2ab(i,ii)] ( IUCN 2012).

Note:— Impatiens agastyamalayensis is a very interesting species as it resembles I. tomentosa and I. rufescens on one hand with its tomentose nature of leaves and floral parts and bearing opposite-decussate leaves, but differs from them in having glabrous stems except at nodes, ovate-lanceolate lateral sepals, straight short spur 2 mm long, and capsule enclosing 1–3 large brown seeds which are oblong and hairy. On the other hand, this species resembles I. gardneriana in having ovate-lanceolate lateral sepals, brown seeds and bimorphic hairs on seeds but differs from it in not having a verticillate leaf arrangement, long slender spur and 3-colpate pollen grains. Further, the seed size (6–7 × 3–4 mm) is unusually big and not encountered in any brown-seeded species of Impatiens known so far in the Western Ghats. Bhaskar (2012) had formed two new subsections under section ‘ Annuae’, viz. ‘ Verticillatae’ placing I. gardneriana under it, while the rest of the species were under ‘ Oppositifoliae’. Incidentally, I. gardneriana was the only species exhibiting brown hairy seeds and 3-colpate pollen grains and the grouping hitherto looked natural, but now with the discovery of I. agastyamalayensis having similar seed (except the size) and seed hair characters but with opposite leaf arrangement and 4-colpate pollen morphology and also being the only perennial balsam in the whole of Section ‘ Annuae’, it has become difficult to place it either under subsection ‘ Verticillatae’ or under subsection ‘ Oppositifoliae’ although it has opposite-decussate leaf arrangement and 4-colpate pollen. This is additional evidence that active speciation is under progress among the species of Impatiens in the Western Ghats. Thus, presently it is assumed that it forms an intermediate position between these two subsections and further DNA studies of these related species would resolve its exact taxonomic position and relationships.

Additional Specimens examined: — INDIA. Kerala: Thiruvanthapuram District, Agastyamala, near Pongalapara , 15 March 2016, A. Joe 148725 ( CALI!) ; Pongalapara , 13 February 2009, Udayan P. S. et al. 05632 ( CMPR!) .

Figures

FIGURE 1. Impatiens agastyamalayensis. A. Twig showing branching pattern; B-C. Leaf-adaxial and abaxial surfaces; D. Flowering twig; E. Portion of plant showing red ring and long hairs at nodal region; F. Flower-front view; G. Lateral united petal; H. Lateral sepals; I-K. Dorsal petal; I. Side view; J. Abaxial view; K.Adaxial view; L. Lower sepal; M. Stamen; N. Ovary with pedicel; O. Mature fruit with pedicel; P. Dehisced fruit; Q. Seed; R. Seed attached to the placenta with aborted ovule. (Photos by Alfred Joe).

FIGURE 2. Seed trichomes and pollen morphology of Impatiens agastyamalayensis. A–D. Hilum part of seed showing whitish bunch of trichomes which have double helical banding pattern; E–I. Seed trichomes away from hilum showing reticulate banding pattern; E–F. Dark brown base of the trichomes and dwarf trichomes with reticulate banding pattern ad-pressed to testa; J. Brownish bands in dwarf trichomes; K–O. Pollen morphology showing 4-colpate nature, variation in pollen size, finely reticulate exine, intraluminar bacules and colpus. (Micro-photographs by V. Bhaskar).