Dimeria andamanica Gosavi, M.Y. Kamble, Chandore & S.R. Yadav, 2016

Gosavi, K. V. C., Kamble, M. Y., Chandore, A. N. & Yadav, S. R., 2016, A new species of Dimeria (Poaceae) from Andaman and Nicobar Islands, India, Phytotaxa 270 (4), pp. 295-300 : 296-299

Dimeria andamanica Gosavi, M.Y. Kamble, Chandore & S.R. Yadav , sp. nov. ( Figs. 1 , 2 )

TYPE: — INDIA, Andaman and Nicobar Islands, South Andaman, Chidiya Tapu, 11°28’51.55”N, 92°42’37.85”E, 28 m, 12 December 2014, M. Y. Kamble 32185 (holotype CAL!, isotypes PBL!, SUK!).

It is closely related to Dimeria fischeri but differs in its lower glume 5–5.5 mm long (vs. 3.5 mm long), upper glume 5–6 mm long (vs. 3–4 mm long), palea present in upper floret (vs. absent) and anthers 1.5–2 mm long (vs. 0.8 mm long).

Annuals. Culm 10–30 cm tall, erect or decumbent, slender, branched, terete, nodes bearded. Leaf sheath 2–6 cm long, compressed, glabrous, loose, margins hyaline, midrib very prominent; keeled near mouth; ligule ca. 0.7 mm long, membranous, ciliate at apex; leaf blade 2–10 × 0.2–0.4 cm, linear elliptic to linear lanceolate, acute, glabrous, long tubercle based hairs on near either side of margin. Raceme solitary, terminal, 2–5 cm long, distinctly excerted with 2 to 6 cm long peduncle; raceme-rachis 1.5–2 mm wide, flat, winged, margin ciliate, distinctly zigzag, turns brown after shedding of spikelet; spikelets secund, alternate, with 0.5 mm long pedicels; pedicel flat, thick, ciliate on either sides at tip, lip concave; spikelets 6–7 × 1–2 mm, awned, lanceolate to oblong, callus ca. 1 mm long; acute at apex, margin ciliate; lower glume 5–5.5 × 1 mm, elliptic to lanceolate, tip acute, coriaceous, margins hyaline, narrowly winged at back from base to apex; wing densely ciliate; upper glume 5–6 × 2 mm, oblong, tip acute, coriaceous, margins hyaline, sparsely ciliate, ca. 0.7 mm broad distinctly winged at back from base to apex; wing densely ciliate; lower floret empty, incomplete; lemma 3.5–4 × 1 mm, narrowly oblanceolate, acute, hyaline, membranous, 1-nerved, margin fimbriate; palea absent; upper floret complete, bisexual; lemma 4–5 × 1 mm, oblong to lanceolate, bifid at apex, hyaline, membranous, strongly 1 nerved; nerve converted into definite geniculate awn; awn ca. 12 mm long with a dark twisted 4 mm long column and antrorsely barbed 8–9 mm long bristle; palea 1 mm long, lanceolate, hyaline, apex acute, few hairs at apex; lodicules 2, ca. 0.5 mm long, papery, notched at apex; stamens 2, anthers 1.5–2 mm long. Pistil 1, 2.5 mm long. Caryopsis 3.5–4 × 1 mm, laterally compressed, oblong, embryo ca. 2 mm long.

Etymology:— The specific epithet ‘ andamanica ’ is given after the area of occurrence, i.e. Andaman Islands, of the species.

Morphological comments: — Dimeria andamanica falls under D. sect. Loriformes by the characters of racemes one, spikelets shed at maturity, compactly arranged, easily disarticulating with the pedicels; raceme-rachis flat, 1.5–2 mm wide, distinctly winged, glabrous to ciliate along margins; glumes coriaceaeous (Kiran Raj 2008).

The new species is closely related to Dimeria fischeri by the characters of annuals habit; raceme always one; upper glume without an apical arista or awn, winged all along the keel, from base to apex, coriaceous. Therefore, it differs in many discontinuous characters such as raceme-rachis 1.5–2 mm wide (as against 0.75–1 mm wide), spikelets 6–7 mm long (as against 3.5–4 mm long), lower glume 5–5.5 mm long (as against 2–3.5 mm long), upper glume 5–6 mm long (as against 3–4 mm long), lower lemma 3.5–4 mm long (as against 1.5–2 mm long), upper lemma 4–5 mm long (as against 2–3 mm long), upper florets palea present (as against absent), anthers 1.5–2 mm long (as against 0.8–1 mm long).

So, after addition of the present new species, Dimeria sect. Loriformes is comprised by 18 species in India.

Distribution and Habitat:— This is rare grass species, which grows on alluvial soil at open place on hill top at Chidiya Tapu (28 m) in South Andaman in association with Bridelia ovata Decaisne (1834: 484) , Hemidesmus indicus ( Linnaeus 1753: 211) Brown ex Schultes (1820: 126) , Ischaemum thomsonianum Stapf ex Fischer (1934: 1722) , Jasminum andamanicum Balakrishnan & Nair (1981: 215) , and Porana spectabilis Kurz (1873: 136) .

Phenology:— Flowering and fruiting for this species was observed in September–December.

Additional specimens examined (Paratypes):— INDIA, Andaman and Nicobar Islands, South Andaman, Chidiya Tapu , 18 August 2013, K. V. C. Gosavi 102 ( SUK!) ; Chidiya Tapu , 18 August 2013, A. N. Chandore 1847 ( SUK!) .

Figures

FIGURE 1. Dimeria andamanica (Kamble 32185) A. Habit. B. Apical portion of leaf-sheath showing ligule. C. A portion of raceme– rachis. D. Spikelet. E. Lower glume. F. Upper glume. G. Lower lemma. H. Upper lemma. I. Palea. J. Stamens. K. Lodicules and pistil. L. Caryopsis. Illustration drawn from the isotype (SUK) by K.V.C. Gosavi.

FIGURE 2. Dimeria andamanica Gosavi, M.Y. Kamble, Chandore & S.R. Yadav, A. Habit. B. Raceme. C. Raceme–rachis. D. Spikelets. Photos by K.V.C. Gosavi.