Ophiochloa, a New Endemic Serpentine Grass Genus (Poaceae: Paniceae) from the Brazilian Cerrado Vegetation

Abstract

Ophiochloa is described and illustrated as a new, monotypic genus and new species of the Digitariinae, Paniceae, from Goias, Brazil, characterized by ligules a row of hairs, solitary, unilateral, winged racemes that end in a sterile projection, adaxial spikelets, specialized, narrow 2-nerved lower lemma with 2 prominent setae, and hyaline, free, upper lemma and palea tips. It is a C4 grass with Kranz anatomy. Its putative relationships are discussed. The new species is a narrow, serpentine endemic that grows on rocks along intermittent or permanent streams in the ultramafic rock belt of the cerrado of central Brazil. Serpentine soils occur in many parts of the world, and they often support a flora that is generally poorly diversified but highly endemic (Brooks, 1987). These soils are derived from ultramafic rocks and because they are characterized by high concentrations of magnesium, iron, nickel, chromium, and cobalt plus abnormally low levels of some plant macronutrients such as potassium, calcium, and phosphorus, they provide an unusual environment for plants (Brooks, 1987). During a recent botanical survey carried out in the municipality of Niquelandia in the Brazilian state of Goias, where previous fieldwork had detected serpentine soil and the presence of a serpentinic adapted flora (Brooks et al. 1990; Davidse & Filgueiras, 1993; Filgueiras & Davidse, in prep.), an interesting grass was collected that could not be placed in any described genera of the Poaceae (Clayton & Renvoize, 1986; Webster et al., 1989; Watson & Dallwitz, 1992). This plant is here described as a new genus and a new species. Ophiochloa hydrolithica Filgueiras, Davidse & Zuloaga, gen. et sp. nov. TYPE: Brazil. Goias: NOVON 3: 360-366. 1993. Municipio de Niquelandia, Macedo, (14018'S48?23'W), ca. 20 km N da cidade, crescendo dentro dagua, sobre pedras, em pequeno riacho temporario e brejo adjacente, unica popula5ao vista, 4 Aug. 1992, T. S. Filgueiras & R. D. Lopes 2438 (holotype, SP; isotypes, CANB, IBGE, ISC, K, L, LE, MO, PRE, RB, SI, UB, UFG, US). Figures 1-3. Leptocoryphio Nees spiculis membranaceis, flosculo superiore cuprino, lemmate superiore marginibus aplanatis apicem versus, apice hyalino et palea superiore hianti apice similis sed ligula pilis seriatis, inflorescentia racemo solitario ac axillari racemo adjecto, rhachidi alata projectura sterili in extremitate, spiculis sessilibus, gluma superiore 2-nervia, hyalina, spiculae aequanti arcte flosculum superiorem amplectanti, lemmate inferiore 2-nervio, hyalino, dense ciliato-pectinato prompter distinguitur. Densely caespitose perennial with a dense accumulation of wiry, adventitious roots and old culm bases forming a compact mass. Culms 54-78 cm tall, erect, stiff, unbranched in the vegetative portion, with 7-11 elongated internodes; internodes hollow, glabrous, stramineous; nodes dark, glabrous. Leaves basal and cauline; sheaths rounded on the back, persisting for some time, striate, glabrous, the margins free, hyaline, glabrous, the apex much broader than the base of the blade, without auricles; ligule a minute fringe of hairs, V-shaped and continuous with the hyaline shoulder of the sheath apex, the hairs to 0.5 mm long, the hairs behind the ligule to 6.5 mm long, whitish; collar undifferentiated; blades 10-19.2 cm long, 0.5-1 mm wide, setaceous, glabrous but with a few scattered, whitish hairs to 6.3 mm long, U-shaped in cross section with an adaxial groove, becoming nearly circular toward the apex, the apex subpungent, slightly scaberulous. Inflorescences solitary, unilateral, spikelike racemes, 1 terminal and usually 1 axillary per This content downloaded from 207.46.13.124 on Wed, 22 Jun 2016 06:04:13 UTC All use subject to http://about.jstor.org/terms Volume 3, Number 4 Filgueiras et al. 361 1993 Ophiochloa and the free, 2-nerved lower lemma.'-E. Upper glume, flattened. -F. Lower lemma with 2 prominent setae. iI 'B G. Apex of the lower lemma showing the prominent, pectinate-ciliate nerves with the pustulose bases of the setae. -H. Spikelet viewed from the back of the upper glume. -I. Upper floret, viewed from the palea side. J-K. Caryopsis. -J. Embryo view. -K. Hilum view. [Based on Filgueiras & Lopes 2438 (SI).] ! G _ _ . This content downloaded from 207.46.13.124 on Wed, 22 Jun 2016 06:04:13 UTC All use subject to http://about.jstor.org/terms