Themeda saxicola Bor (1951: 452)

Chorghe, Alok R. & Kulloli, R. N., 2022, Rediscovery and IUCN threat assessment of Themeda saxicola (Poaceae: Andropogoneae), an endemic grass from the Eastern Ghats, India, Phytotaxa 532 (2), pp. 161-168 : 162-167

Themeda saxicola Bor (1951: 452) ( Fig. 2 )

Type: — INDIA. Odisha, Koraput District, Raisili Village , alt. 1000 m, 25 October 1950, H. F. Mooney 4241 (holotype K, barcode K000245985!) .

Perennial; compact mass of dead basal sheath with dormant buds in the basal leaf axils. Culms tufted, erect to decumbent, up to 35 cm long; nodes glabrous. Leaf-sheaths keeled, glabrous; ligules membranous, ciliate at apex; leaf-blades linear-lanceolate, 5.0–6.0 × 0.2–0.3 cm; attenuate at apex, pilose above, tubercle based hairy on both the surface of the blade. Inflorescence composed of a solitary raceme, terminal, exserted, subtended by a spatheole. Raceme comprises 4 involucral spikelets i.e., 2 sessile and 2 pedicelled. Involucral spikelets inserted at different levels, elliptic-lanceolate, 13–15 mm long, staminate, pedicelled. Lower glume elliptic-lanceolate, 11–15 × 1.0– 1.3 mm long, acute at apex, 11–13-nerved, 2-keeled, glabrous, margins inflexed. Upper glume 6–7 × 0.9–1.1 mm, 3-nerved, glabrous, margins ciliate. Florets 2; lower barren, epaleate; upper staminate, epaleate. Lower lemma 5–6 × ca. 0.5 mm, hyaline, margins ciliate. Upper lemma 5.0–5.5 × 0.2–0.4 mm, hyaline, epaleate. Stamens 3; anther 3.5–4.0 mm long. Sessile spikelet elliptic-oblong, 7.5–8.0 mm long; callus pungent, 2 mm long, hairy. Lower glume elliptic-oblong, 7.5–8.0 × 0.8–1 mm long, truncate at apex, coriaceous, pilose, 5-nerved. Upper glume 4.5 – 5.0 × ca. 0.5 mm, oblong, obtuse, membranous, 3-nerved. Florets 2; lower barren, upper female. Lower lemma 3–4 × 0.3–0.5 mm, obtuse, hyaline, epaleate. Upper lemma linear, hyaline, 1-awned; awn geniculate, 2–3 cm long. Upper palea 2.0–2.5 × 0.2 mm, linear, hyaline. Style 2, stigma plumos. Pedicelled spikelets, staminate, elliptic, ca. 10 mm long; callus linear, 2.0 mm long, hairy; pedicel linear, 2.5 mm long. Lower glume elliptic, 8–10 × 1.0– 1.2 mm long, chartaceous, acute at apex, margins narrowly winged. Upper glume 5.8–6.5 × 0.8–1 mm, elliptic, acute at apex, 3-nerved, membranous, margins ciliate. Florets 2; both epaleate, upper staminate. Lower lemma 5–6 × 0.7–0.9 mm, barren, hyaline, 3-nerved. Upper lemma 5.0–5.5 × ca. 0.2 mm, linear, hyaline.

Flowering and fruiting: —October–December.

Habitat & associated species: —Rocky crevices (Granite rock). Themeda saxicola grows in association with annual grass species such as, Dimeria connivens Hackel (1889: 689) , Dimeria ornithopoda Trinius (1820: 167) and also perennial grass species like Themeda mooneyi Bor (1951: 451) and Tripogon bromoides Roemer & Schultes (1817: 600) .

Ecology:— Themeda saxicola grows in the patch of shallow soil over granite-gneiss ( Bor, 1951). For most of the year (nearly 8 months) water is scarce and plants deal with extreme summer temperature and also with surface heat generated from granite rocks. Basal old leaf sheaths forms compact mass that protects buds from desiccating during the dry season. These buds start germinating on the onset of rains. It completes flowering and fruiting (till December) before the start of the dry season.

Distribution: —Raisili (Type locality) and Deomali in Koraput District, Odisha; endemic. ( Figs. 3 & 4 )

Specimens examined: — INDIA. Koraput, Laxmipur (Raisili) 15 October 1950 H. F. Mooney 4241 (K! Digital Image); Raisili Hill, 21 November 2017, Alok R. Chorghe 206437 & Deomali 22 November 2017, Alok R. Chorghe 206438 (BSI).

Threat

1. Native habitat of Themeda saxicola is under a considerable anthropogenic pressure. The stone quarrying activities were observed in the habitat of this species; and this can become major cause for population reduction ( Fig. 5 A ).

2. The native habitat is invaded by alien invasive species such as: Ageratina ligustrina ( Candolle 1836: 181) King & Robinson (1970: 223) , Cenchrus purpureus ( Schumacher 1827: 44) Morrone (2010: 129) , Lantana camara Linnaeus (1753: 627) and Mesosphaerum suaveolens ( Linnaeus 1759: 1100) Kuntze (1891: 525) ( Fig. 5 B ). There are possibilities that these alien species can spread all over these habitats and affect these populations.

IUCN threat category assessment

Area of occupancy (AOO) was calculated using GeoCat ( Bachman et al., 2011) online software developed by Kew Botanic Gardens. GPS locations of two localities of occurrence were used as input data and grid size was kept 4 km 2. Based on GPS data of the populations in the two localities, we found AOO to be 8 km 2 and EOO to be 42 km 2 (i.e. in Deomali area is 42 km 2 and in Raisili 6 km 2). We have also observed shrinkage in the habitats due to mining activities. The EOO is <100 km 2 and AOO is <10 km 2. Thus, based on IUCN (2022) we assign this plant as Critically Endangered (CR) under B1 B2biii.

Conservation measures

The population of Themeda saxicola in Raisili hill is good and healthy. But it will be in threat if this hill is not protected from mining activity. Whereas the population of Deomali is less, with no mining activity reported. But its population growth is affected by the encroachment of alien invasive species.

1. Mining activities should be controlled and if possible, minimized.

2. Implementation of species recovery programme to protect the populations in the native habitats.

Figures

FIGURE 2. Themeda saxicola Bor: A. Habit, B. Raceme; Involucral spikelet: C. Spikelet, D. Lower glume, E. Upper glume, F. Lower lemma, G. Upper lemma; Sessile spikelet: H. Spikelet, I. Lower glume, J. Upper glume K. Upper lemma; Pedicelled spikelet: L. Spikelet, M. Lower glume, N. Upper glume, O. Lower lemma.

FIGURE 3. Distribution map of Themeda saxicola.

FIGURE 4. A. Estimation of habitat distribution from Google Earth. B. Google Earth Image of Raisili Hill.

FIGURE 5. A. Mining activity in Raisili Hill. B. Invasive alien species in Themeda saxicola habitat.