Rotala dhaneshiana Sunil, Ratheesh & Sivadasan, 2014

Ratheesh Narayanan, M. K., Sunil, C. N., Shaju, T., Nandakumar, M. K., Sivadasan, M. & Alfarhan, A. H., 2014, Rotala dhaneshiana, a new species of Lythraceae from India, Phytotaxa 188 (4), pp. 227-232 : 227-230

Rotala dhaneshiana Sunil, Ratheesh & Sivadasan , sp. nov.

Type: — INDIA. Kerala: Wayanad District, Muthanga Range of Wayanad Wildlife Sanctuary, Maragadha , semi-marshy area, 900 m, 18 September 2012, Sunil & Ratheesh Narayanan 2211 (holotype CAL! , isotypes MH! , TBGT! ). Figures 1 & 2 .

Rotala dhaneshiana resembles R. malampuzhensis in having decussate leaves and usually trimerous flowers, but differs in having 4-angled stems, prominent long epicalyx lobes, obovate, apiculate petals, and absence of nectar scales.

Erect marshy-terrestrial annuals, growing singly, not in tufts. Stems single, branched, up to 50 cm high, rooting from nodes below, branches erect, inconspicuously 4-angled, obscurely ribbed, often narrowly winged on younger branches, up to 4 mm diam., internodes slightly swollen, floral branches 2–16 cm long, rarely branched. Leaves simple, decussate, sessile, reddish-tinged when mature, 1.5–3.5 × 0.3–0.6 cm, linear-lanceolate to oblong, base slightly cordate to semi-amplexicaule, margin entire, apex acute, midrib prominent below, canaliculate above. Flowers solitary in axils, sessile, monomorphic, usually trimerous, occasionally tetramerous, 2.0– 2.5 mm long and 1.0– 1.5 mm diam.; bracts dimorphic, resembling foliage leaves, those on main stem larger, those on floral branches smaller, 2–6 × 0.5–2.0 mm, ovate or elliptic, usually red-tinged; bracteoles 2, reddish, 1.5–2.0 mm long, linear-lanceolate, tip acuminate, sometimes curved, equal to or exceeding floral tubes; epicalyx lobes narrowly triangular, tip acuminate, 0.75–1.0 mm long, longer and alternating with sepals; floral tube campanulate, reddish, glabrous, 1.5–2.0 mm long, sepals 3 or 4, each ca. 0.25 mm long, very shallowly-triangular; nectar scales absent; petals 3 or 4, persistent, obovate, apiculate at apex, rose to white in colour, ca. 0.25 × 0.2 mm long; stamens 3 or 4, inserted above the base of the floral tube, equaling to the level of floral tube, filaments white, 0.75–1.0 mm long, anthers globose, 2-celled, dehiscence introrse; ovary globose, sessile, 3-locular, slightly trilobed, 0.5–0.75 × 0.4–0.5 mm, style very short, ca. 0.25 mm long, stigma capitate. Capsule globose, 3-valved, equal to or slightly exceeding floral tube, ca. 1.5 mm long and ca. 1 mm diam., reddish; seeds numerous, plano-convex, 0.25–0.3 mm long, bright red.

Flowering & Fruiting: —October–December.

Ecology: — Rotala dhaneshiana was collected from an open semi-marshy area in moist deciduous forest.

Etymology: —The specific epithet is in honour of Mr. P. Dhanesh Kumar, Divisional Forest Officer, South Wayanad Forest Division, Kerala who received the ‘Sanctuary Wildlife Award - 2012’, instituted by the Sanctuary Asia Magazine for his valuable and tireless efforts in protecting the forest of the State. He is a courageous forest officer and a visionary environmentalist who has undertaken herculean tasks to protect the wilderness in various parts of India.

Affinities: — Rotala dhaneshiana is allied to R. malampuzhensis in having decussate leaves and usually trimerous flowers, but differs by 4-angled, ribbed, narrowly winged stems, long epicalyx lobes alternating with sepals, and obovate, apiculate petals. Presence of three linear nectar scales alternating with stamens in R. malampuzhensis is a distinguishing character which is absent in R. dhaneshiana . Nectar scales have been reported in species like R. cookii , R. malabarica , R. malampuzhensis , R. mexicana Schlechtendal & Chamisso (1830: 567) , and R. vasudevanii of Peninsular India. In R. malampuzhensis epicalyx lobes are minute or sometimes absent in contrast to the long and very prominent lobes of R. dhaneshiana . The new species also resembles the African Rotala juniperina Fernandes (1974: 126) in having dimorphic bracts, usually trimerous flowers, long epicalyx lobes alternating with sepals and absence of nectar scales, but differs in having sessile leaves with a decurrent base, reddish when mature, occasional tetramerous flowers, obovate rose to white petals, stamens inserted near base of the floral tube, sessile pistil and reddish seeds, while in R. juniperina leaves are petiolate with rounded base, green when mature, flowers consistently trimerous, petals elliptic and red, stamens attached slightly below the middle of the floral-tube, pistil stipitate and seeds white.

Comparison of characters of Rotala dhaneshiana with R. juniperina and the closely similar species R. malampuzhensis is provided in Table 1 .

Distribution: — Rotala dhaneshiana is restricted to semi-marshy areas in the moist deciduous forests at elevations of ca. 800– 900 m. inside the Wayanad Wildlife Sanctuary. It is usually seen near temporary water bodies in the area and grows in association with Eriocaulon quinquangulare Linnaeus (1753: 87) , Fimbristylis dichotoma ( Linnaeus 1753: 50) Vahl (1805: 287) , Imperata cylindrica ( Linnaeus 1759: 878) Beauvois 1812: 165 ), Lindernia anagallis (Burman filius 1768: 135) Pennell (1943: 252), Cyperus tenuispica Steudel (1854: 11) , Centranthera indica ( Linnaeus 1753: 603) Gamble (1924: 971) and Arundinella leptochloa (Nees ex Steudel 1853: 62) Hooker filius (1896: 76).

Conservation: —In both the locations of collections, populations of this new species are small. Our observations showed that there were less than hundred mature individuals in a 1 km 2 area each in Margadha and Nallorvayal, and the populations are highly fragmented. More field explorations are essential to assess a conservation status through IUCN guidelines and criteria ( IUCN 2012, 2014); since it has not been evaluated until now, Rotala dhaneshiana is now categorized as ‘Not Evaluated’ (NE).

Paratype: — INDIA. Kerala: Wayanad District, Nallorvayal , 12 September 2013, Sunil & Ratheesh Narayanan MSSH 4212 (Community Agrobiodiversity Centre (CAbC)-MS Swaminathan Research Foundation Herbarium, Wayanad!) .

Figures

FIGURE 1. Rotala dhaneshiana A. Habit. B. A portion of flowering twig. C. Bract. D. Single flower. E. Floral tube cut-opened showing pistil, stamens, petals and epicalyx-lobes. F. Stamens—abaxial and adaxial views. G. Mature fruit enclosed in floral tube. H. Capsule. I. Seeds. Drawings by T. Shaju from live specimens.

FIGURE 2. Rotala dhaneshiana A. Habit. B. A portion of twig. C. Single flower. D. A portion of twig with mature fruits.