10.13 JARAVA Ruiz & Pav.
Mirta O. Arriaga
MODIFIED August, 2008 by removal of Jarava speciosa to Pappostipa
Plants perennial; cespitose, sometimes rhizomatous, rhizomes forming knotted bases. Culms 15–200 cm, not branching at the upper nodes; basal branching intravaginal or extravaginal; prophylls not evident, shorter than the leaf sheaths. Leaves mostly basal, not overwintering; sheaths open to the base; cleistogenes not present; collars with tufts of hair on either side; auricles absent; ligules membranous, truncate or shortest in the center and rounded, edges usually ciliate, hairs at the outer edges often longer than the central membranous portion, ligules of the lower leaves glabrous or hairy, sometimes densely hairy, those of the upper leaves glabrous or sparsely hairy; blades usually convolute, apices narrowly pointed, flag leaves longer than 10 mm. Inflorescences panicles, often partially included in the upper leaf sheath; branches straight. Spikelets 5.5–24 mm, with 1 floret; rachillas not prolonged beyond the floret; disarticulation above the glumes, beneath the floret. Glumes unequal, usually longer than the floret, sometimes shorter, hyaline, 0–5-veined; florets narrowly lanceoloid, terete; calluses 0.2–1.6(3) mm, acute, less than or equaling the floret diameter, antrorsely strigose distally, hairs white; lemmas thickly membranous, basal 2/3 scabrous or shortly pubescent, distal 1/3 often bearing a pappus of ascending to strongly divergent 3–8 mm hairs, sometimes glabrous or with appressed hairs shorter than 1 mm, margins not or only slightly overlapping at maturity, apices not fused into a crown, lobes to 0.2 mm, with a single, terminal awn, awn-lemma junction conspicuous; awns 9–45(80) mm, persistent or deciduous, scabrous, weakly once- or twice-geniculate, first segment scabrous or pilose, terminal segment glabrous or pilose, smooth or scabrous; paleas 1/3–1/2 as long as the lemmas, flat between the veins, membranous to hyaline, glabrous or sparsely pubescent, 2-veined, veins poorly developed, apices rounded to irregular; lodicules 2–3, the third, if present, reduced; anthers 3. Caryopses fusiform, not ribbed; hila linear. x = unknown.
Jarava is a South American genus that used to be included in Stipa. Its limits are currently under study. As treated here, it is a genus of approximately 35 species, all of which are native to South America. It includes two groups that have been recognized as subgenera within Stipa sensu lato: Jarava (Ruiz. & Pav.) Trin. & Rupr. and Ptilostipa Speg. Jacobs and Everett (1997) recommended including only the approximately 14 species of Stipa subg. Jarava in Jarava. This treatment adopts a somewhat broader interpretation including the members of the subgenus Ptilostipa, pending more detailed study of relationships among the American Stipeae. In both FNA 24 and the Manual of Grasses for North America, Stipa subg. Pappostipa was included in Jarava. Romaschenko et al. (2008) promoted it to generic level in July 2008.
Two species, J. ichu and J. plumosa, both members of Jarava sensu stricto, have been found as escapes from cultivation in California. Many species of Jarava have conspicuous hairs on the distal portion of the lemma, termed a pappus, or on the first and/or second segment of the awn. These are an adaptation to wind dispersal. Jarava sensu stricto shows an even stronger adaptation to wind dispersal, usually combining a well-developed pappus with light florets less than 5 mm long and 1 mm wide.
SELECTED REFERENCES Arriaga, M.O. 1983. Anatomía foliar de las especies de Stipa del subgénero Pappostipa (Stipeae-Poaceae) de Argentina. Revista Mus. Argent. Ci. Nat., Bernardino Rivadavia Inst. Nac. Invest. Ci. Nat., Bot. 6:89–141; Caro, J.A. and E. Sánchez. 1973. Las especies de Stipa (Gramineae) del subgénero Jarava. Kurtziana 7:61–116; Jacobs, S.W.L. and J. Everett. 1997. Jarava plumosa (Gramineae), a new combination for the species formerly known as Stipa papposa. Telopea 7:301–302; Matthei, O. 1965. Estudio crítico de las gramíneas del género Stipa en Chile. Gayana, Bot. 13:1–137; Peñailillo, P. 2002. El género Jarava Ruiz et Pavon (Stipeae-Poaceae): Delimitacion y nuevas combinaciones. Gayana, Bot. 59:27–34. Romaschenko, K., P.M. Peterson, R.J. Soreng, N. Garcia-Jacas, O. Futorna, and A. Susanna. 2008. Molecular phylogenetic analysis of the American Stiepeae (Poaceae) resolves Jarava sensu lato polyphyletic: evidene for a new genus, Pappostipa. Journal of the Botanical Research Institute of Texas 2: 165-192.
1. Jarava ichu Ruiz & Pav.
Plants densely cespitose, not rhizomatous. Culms (15)30–100 cm, bases dull brown, glabrous; nodes 2–4; branching intravaginal. Sheaths mostly glabrous, scabridulous, basal sheaths dull brown; ligules 0.3–1 mm, truncate, erose, abaxial surfaces glabrous or almost so, ciliate, hairs longest (to 2 mm) towards the sides of the leaves, at the top of the sheaths; blades (3)10–40 cm long, 0.5–1 mm wide, all alike, straight, erect, convolute, apices sharp. Panicles (3)10–25(30) cm, narrow, cylindrical to lanceoloid, dense, from partially to wholly exserted at anthesis, erect or nodding distally; branches strongly ascending. Spikelets 5.5–11 mm. Glumes subequal, clearly exceeding the florets, linear-lanceolate, tapering to attenuate apices; lower glumes 5.5–11 mm, 1–3-veined; upper glumes 5–10.5 mm, 3-veined; florets 2.3–3 mm, cylindrical to fusiform; calluses 0.2–0.4 mm, acute to broadly acute, strigose; lemmas hairy throughout, hairs on the lower portion about 0.15 mm, sparse, appressed, pappus hairs 3–4 mm; awns 9–15 mm, twice-geniculate, first 2 segments twisted, scabridulous; paleas 1–1.5 mm, sparsely pubescent, 2-veined, apices rounded; lodicules 2, 0.6–1 mm; anthers about 0.8 mm. Caryopses 1.8–2.2 mm long, 0.6–0.7 mm thick, cylindrical.
Jarava ichu is native to Mexico, Costa Rica, Venezuela, Colombia, Ecuador, Peru, Bolivia, and Argentina. It is abundant in much of this range. In the Flora region, it is sold as an attractive ornamental. The species could become a problem, because it is self-compatible and produces a large quantity of wind-dispersed seeds. In parts of its native range, J. ichu is highly valued for its ability to prevent soil erosion, and for its use in thatch, mats, and basketry. “Ichu” is a term used to describe any bunchgrass in some parts of South America.
2. Jarava plumosa (Spreng.) S.W.L. Jacobs & J. Everett
Plants cespitose, shortly rhi-zomatous, rhizomes forming knotted bases. Culms 15–85 cm, glabrous, bases dull gray-brown; nodes 2–6; basal branching mostly extravaginal, lower nodes sometimes with intravaginal branches. Sheaths glabrous, basal sheaths dull gray-brown; ligules 0.1–0.2 mm, truncate, abaxial surfaces puberulent, ciliolate to ciliate, hairs longest (1.5–4 mm) towards the sides of the leaves, at the top of the sheaths; blades 1–9(25) cm long, those of the innovations the longest, 1–1.5 mm wide and flat or conduplicate, or to 0.5 mm in diameter and convolute, straight to almost falcate, abaxial surfaces of the innovation leaves glabrous or pubescent, adaxial surfaces usually glabrous, sometimes slightly scabrous. Panicles 3–20 cm, ovoid, lax, partially included in the upper leaf sheaths; branches ascending to divergent; pedicels 1–1.5 mm. Spikelets 5–8 mm. Glumes from shorter than to subequal to the florets, linear-lanceolate, hyaline, smooth, ecostate or with 1 inconspicuous vein, apices attenuate; lower glumes 2.5–5 mm; upper glumes 4.5–6.5 mm; florets (4)5–7.5 mm; calluses 1–1.5 mm, strigose, hairs white; lemmas about 0.3 mm thick, mostly scabrous, strigose over the midvein, tapering to the apices, pappus hairs 5–8 mm; awns 15–30 mm, scabrous, weakly geniculate; paleas 1–2.5 mm, from 1/3–1/2 the length of the lemmas, hyaline, glabrous, weakly 2-veined; lodicules 2, 0.8–1 mm, linear. Caryopses 4–5 mm, narrowly lanceoloid. 2n = 40.
A native of Argentina, Chile, and Uruguay, Jarava plumosa was collected in Berkeley, California in 1983. It is not known to be established in the Flora region. In its native range, it often grows on poor, unstable soils. Matthei (1965) stated that it is a valuable forage species when young, but that it should not be overgrazed because of its value in preventing soil degradation.