Aira (Poaceae): a new generic record for Nicobar Islands, India

Genus Aira L. belongs to the tribe Aveneae (Poaceae: Pooideae) and comprises ca. eight species worldwide. It is distributed from Europe to the Mediterranian region; but widely spread as a weed (Mabberly 2008). Bor (1960) reported a single species of the genus from India i.e. Aira caryophyllea L.

During plant exploration expeditions of the Andaman & Nicobar islands in 2014, we collected some interesting grass specimens from the Camorta Island of Nicobar. After critical study and taxonomic analysis the unidentified grass species has been identified as an Aira caryophyllea L. Perusal of relevant literature (Bor 1960; Clayton & Renvoize 1986; Rao 1986; Hajra et al. 1999; Pandey & Diwakar 2008) revealed that the genus Aira L. has so far not been reported from the Andaman & Nicobar Islands. Hence, it is reported in the present communication as a new record to the Nicobar Islands.

Aira caryophyllea L., Sp. Pl. ed. 1, 66 (1753); Bor, Grass. Bur. Cey. Ind. Pak. 430. 1960 (Image 1).

Perennial; Culm 50–60 cm tall, stout, branched from base, terete, glabrous, ridges and furrows on internodes, nodes glabrous. Leaf sheath 2–3 cm long, terete to sub-compressed, loosely arranged, hairy at margin, ciliate towards the mouth, cilia 2–3 mm long; ligule up to 0.5mm long, membranous, hairy; leaf blade 3–10 cm long, elliptic, acuminate, coriaceous, involute, tubercled based hairs on both surface, margin scabrous.

Panicle 3–5 cm long, lax. Spikelets 3.5–4 × 1.5–2 mm (excluding awn), elliptic to obovate, laterally compressed. Lower glume 3.5–4 × 1.2 mm, ovate to lanceolate, acute to acuminate, tip laterally compressed, membranous, glabrous, 9-nerved, margin hyaline. Upper glume 3.5–4 × 1–1.5 mm, elliptic to ovate, acute to acuminate, tip laterally compressed, 9-nerved, margin broadly hyaline. Florets 2, hermaphrodite, aristate, sub-equal to equal, 3–3.5 × 1 mm long, lanceolate, callus acute, ca. 0.4mm long. Lemmas 3×1 mm, lanceolate, 3-nerved, hairy at back, cartilaginous, aristate; arista ca. 3mm long, scabrous. Palea 2.5–3 × 0.8 mm, lanceolate, hairy, cartilaginous, apex notched. Stamens 2; anthers 0.2mm long. Pistil 1, ca. 1mm long. Caryopsis 1.2mm long, oblong; hilum scared.

Specimen examined: 32184 (PBL!, SUK!), 10.xii.2014, Camorta Island, Nicobar, Andaman & Nicobar, India, elevation 36m, coll. M.Y. Kamble (Fig. 1; Image 2).

Flowering and fruiting: September–January.

Note on distribution in India: Bor (1961) reported Aira caryophyllea L. from India in a cultivated condition without the locality’s name. However in the present work, we have collected it in a wild condition a long distance away from the mainland of India, i.e., the Camorta Islands of Nicobar.

Habitat and ecology: Rare, Grows on hill tops in open grasslands with associate Dimeria ornithopoda Trin., Heteropogon contortus (L.) P. Beauv.ex Roem. & Schult., Ischaemum indicum (Houtt.) Merr. Ischaemum thomsonianum Stapf. Ex C.E.C. Fisch., Ischaemum sp., Pennisetum pedicellatum Trin., Sorghum nitidum (Vahl) Pers., Themeda sp., etc., at Kamorta Islands.

Distribution: The species is widely distributed in Africa, Asia and Europe and introduced in Antarctica, Asia, Australia, America and Pacific (eMonocot 2010). Bor (1961) reported Aira caryophyllea L. from India in cultivated condition without localities name. However in present work, we have collected it in wild condition from long distance of mainland of India, i.e., Camorta Island of Nicobar.

Taxonomic note: The genus Aira L. is easily distinguished from the other members of the tribe Aveneae by spikelets consisting of hermaphrodite, aristate, equal two florets without rachilla.

References

Bor, N.L. (1960). The Grasses of Burma, Ceylon, India, and Pakistan (excluding Bambuseae). Pergamon Press, London, 430pp.

Clayton, W.D. & S.A. Renvoize (1986). Genera Graminum: Grasses of the World. [Kew Bulletin, Additional Series 13]. Her Majesty’s Stationery Office, London, 131pp.

eMonocot (2010). http://e-monocot.org/taxon/urn:kew.org:wcs: taxon:390804 accessed 22nd June 2016

Hajra, P.K., P.S.N. Rao & B.K. Sinha (1999). Flora of Great Nicobar Islands. Botanical Survey of India, Culcutta.

Mabberley, D.J. (2008) Mabberley’s Plant Book: A Portable Dictionary of Plants, their Classification and Uses (3rd Edition). Cambridge: Cambridge University Press, 23pp.

Pandey, R.P. & P.G. Diwakar (2008). An integrated checklist of flora of Andaman and Nicobar Islands, India. Journal of Economic and Taxonomic Botany 32: 403–500.

Rao, M.K.V. (1986). A preliminary report on the angiosperms of Andaman and Nicobar Islands. Journal of Economic and Taxonomic Botany 8(1): 107–184.