Dimeria raviana Kiran Raj & Sivadasan, 2015

Raj, M. S. Kiran, Sivadasan, M., Alfarhan, A. H. & Veldkamp, J. F., 2015, Dimeria raviana (Poaceae: Panicoideae), a new species from Southern Western Ghats, India, Phytotaxa 195 (2), pp. 193-196 : 193-195

Dimeria raviana Kiran Raj & Sivadasan , sp. nov. ( Fig. 1 )

Type:— INDIA. Kerala: Idukki District, Periyar Tiger Reserve, s.d., 9° 18´– 9° 41´N, 76° 55´– 77° 25´E, ± 950 m elevation, Jomy s.n. (holotype CALI!, isotypes KFRI!).

Dimeria raviana closely resembles D. fuscescens , but differs in having a flattened and winged raceme rachis of 1.0– 1.25 mm in width, with smooth margins.

Perennials. Culms robust, erect or geniculate from base, up to 70 cm long, sometimes rooting at the lower nodes; nodes shortly bearded. Leaves all along the culm; sheath much longer than internodes, very loose, keeled, smooth, pilose in the upper third with bulbous-based hairs; blade linear-acute, 4.0–15.0 × 0.2–0.4 cm, rounded at base, acuminate at apex, keeled on midrib below, keel continuous with that of the sheath, coarsely scabrid on nerves on both surfaces and margins, with bulbous-based hairs on upper surface and margins; ligule membranous, up to 1 mm long, ciliate on the truncate apex. Peduncle long-exserted. Racemes 5–12 cm long; rachis flattened, 1.0– 1.25 mm wide, margins broadly winged, straight, carrying alternately arranged pedicellate spikelets; pedicels ca. 0.5 mm long, compressed, concave above, sparely hairy. Spikelets linear oblong, 4.5–5.0 mm long, closely appressed to rachis with the lower glume widely spreading at anthesis; callus ca. 0.5 mm long, bearded on the lower edge. Lower glume coriaceous, 4.2–4.5 mm long, linear-oblong, acuminate at apex, straight on back and keeled towards apex, thin to hyaline at sides, scabrid all along the back. Upper glume coriaceous, 4.7–5.0 mm long, oblong-elliptic, acute at apex, strongly compressed, straight on the back, keeled, broadly winged on the upper half. Lower floret empty. Lower lemma thinly hyaline, oblanceolate, 1.5–2.0 mm long, acute at apex, 1-nerved, ciliate on margins towards apex. Palea absent. Upper floret complete, bisexual. Upper lemma hyaline, elliptic-obtuse, 2.6–3.0 mm long, bifid at apex with acute lobes, awned from the sinus; awn 12–14 mm long with a dark twisted 3 mm long column. Palea absent. Lodicules 2, small. Stamens 2, anthers 2.5–3.0 mm long. Styles 2, short; stigma plumose.

Phenology:—September–December.

Habitat:—Margins of evergreen forests.

Distribution and conservation status:—Known only from the type locality which is on the Southern Western Ghats in Kerala state, India. No earlier or later collections of the species are available, and hence it is considered to be very rare. Further explorations are to be made for collection of specimens and to assess status as per IUCN guidelines and criteria ( IUCN 2012, 2014). As it has not been evaluated against the criteria, it is categorized as ‘Not Evaluated’ (NE).

Etymology:—The species is named in honour of Prof. N. Ravi, formerly the Head of the Department of Botany, Sree Narayana College, Kollam, Kerala and a well-known agrostologist of South India, who stimulated the revision of Dimeria in peninsular India. He was a source of inspiration for several of his students to pursue plant taxonomy as a field of specialization.

Notes:— Dimeria raviana resembles D. fuscescens Trinius (1832: 335) of Dimeria sect. Dimeria and both species have stoloniferous rhizomes. However, D. fuscescens has an angular or trigonous rachis of ca. 0.5 mm width with ciliate margins. All the specimens studied showed consistency in their vegetative and reproductive characteristic features. A comparison of distinguishing features of D. raviana and D. fuscescens is given in Table 1.

Figures

FIGURE 1. Dimeria raviana A. Habit with inflorescence. B. Leaf-sheath mouth portion with ligule. C. A portion of raceme-rachis with pedicels. D. Spikelet. E. Lower glume. F. Upper glume. G. Lower lemma. H. Upper lemma with awn. I. Lodicules, stamens & pistil. J. Grain. Drawings by M. S. Kiran Raj from Jomy s.n. (holotype CALI).