Toliara arenacea Judziewicz, 2009

Judziewicz, Emmet J., 2009, Toliara (Poaceae, Chloridoideae, Cynodonteae), a new grass genus endemic to southern Madagascar, Adansonia (3) 31 (2), pp. 273-277 : 274-276

Toliara arenacea Judziewicz , sp. nov.

( Fig. 1 )

TYPUS. — Madagascar. Toliara Province, 35 km N of Toliara on road to Morombe, forest dominated by Colvillea racemosa Bojer [ Fabaceae ] and Didierea madagascariensis Baill. [ Didiereaceae ] and 5 km E by road, 23°05’05”S, 43°38’45”E, elev. 50 m, tufted annual grass, common in open places, inflorescence green, 21.II.1993, Peter B. Phillipson 4117, with J.R. Raharilala (holo-, P!; iso-, GRA, TAN!).

OTHER MATERIAL EXAMINED. — Madagascar. Environs de Tuléar, bush à Didierea sur sable, XI.1956, J. Bosser 10364 (P [2 sheets]; TAN). — Bush à Didierea sur sable, P.K. 15 Route Tuléar-Morombe, III.1960, J. Bosser 14975 (P).

DESCRIPTION

Cespitose, somewhat sprawling, annual grass 10- 35 cm tall.Culms unbranched or branching, geniculate, both the culms and the open sheaths glabrous; ligule 0.3-0.4 mm long, membranous, delicate, eciliate.Leaves with blades lanceolate to lanceolate-ovate, 8-40 × 2-6 mm, somewhat coriaceous, antrorselyciliolate on margins (especially near base), the cilia 0.2-0.3 mm long, otherwise glabrous, clasping at the base, acute at the apex. Inflorescence terminal, 4-20 cm long, 1-1.5 mm wide, a delicate, spicate, densely-flowered, erect, straight to slightly arching raceme, its base enclosed in the uppermost leaf sheath; spikelets subsessile, produced spirally all around the rachis, their pedicels 0.2-0.3 mm long, cupulate, decurrent on the rachis as minute, antrorsely scabrous ridges. Spikelets appressed, 1.3-1.8 mm long, falling entire (the inflorescence shattering basipetally), laterally compressed, 1-flowered with no extension of the rachilla; glumes as long as spikelet, narrowly elliptical, membranous, rounded at base, obtuse to acute at apex, awnless,covered with minute antrorsely scabrous spicules (especially on the midnerve) 15- 30 µm long; lower glume slightly wider, longer and more arcuate than the upper glume, when in flower each glume stramineous with a prominent green midnerve (no lateral nerves present), slightly gaping but soon closing so that the glumes enfold each other, the spikelet thus appears narrowly elliptical; glumes becoming firmly membranous and brownish, gaping again when in fruit to expose the upper half the caryopsis. Floret solitary; lemma lanceolate, 0.5-0.9 mm long, 1-nerved, weakly keeled, hyalinediaphanous, tapering to an attenuate apex; palea 0.5-0.7 mm long, slenderly lanceolate, evidently nerveless, hyaline-diaphanous. Flower with lodicules not evident; stamens evidently 2, the anthers orange-brown, 0.3-0.4 mm long; ovary hairy at base, c. 0.4 mm long, the stigmas 2, hispid. Fruit a caryopsis 1.3-1.4 mm long, slenderly ellipsoidal, brown, laterally compressed by a ratio of about 1.25:1, its width 0.4 mm dorsally and 0.3 mm laterally; embryo basal, dark brown, 0.5-0.6 mm long; hilum basal, punctate. Chromosome number unknown.

REMARKS

Toliara arenacea grows only on sand dunes near the coast of southwestern Madagascar. The genus name is derived from the city near which it grows, and the specific epithet from the sandy soil it prefers to grow in. Using the latitude and longitude provided by the collectors and inserting these coordinates into the Google Earth website, the type locality was found to be located in a forested area approximately 30 km by air north of the city of Toliara , and approximately 5 km inland (east) of the Mozambique Channel .

Toliara arenacea is assessed as Critically Endangered because its EOO (extent of occupancy) is less than 100 km 2, it is only known to occur at a single location outside a protected area, and there is both current and predicted decline from human pressure, thus the criteria CR B1ab(i,ii,iii) of the IUCN (2001) apply.

Figures

FIG. 1. — Toliara arenacea Judziewicz, P.B. Phillipson 4117 (P): A, habit of plant; B, base of leaf showing blade clasping culm; C, apex of inflorescence showing basipetally deciduous spikelets and persistent spikelet pedicels; D, spikelet, lateral view just after flowering showing “closed” glumes; E, fruiting spikelet, lateral view showing gaping glumes and protruding caryopsis; F, lemma, dorsal view; G, palea, dorsal view; H, caryopsis, lateral view showing basal embryo. Illustration by Eva Hathaway. Scale bars: A, 2 cm; B, 2 mm; C, 1 mm; D-H, 0.25 mm