Bromus pinetorum Swallen (1943: 77)

Saarela, Jeffery M., Peterson, Paul M. & Valdés-Reyna, Jesus, 2014, A taxonomic revision of Bromus (Poaceae: Pooideae: Bromeae) in México and Central America, Phytotaxa 185 (1), pp. 1-147 : 108-109

17. Bromus pinetorum Swallen (1943: 77) . Fig. 56 .

Bromopsis pinetorum (Swallen) Holub (1973: 168) . Type:— MÉXICO. Coahuila: Sierra del Pino : vicinity of La Noria, 20–26 August 1940, I.M. Johnston & C.H. Mueller 497 (holotype US-2209362 !, isotypes US-1981050 ! fragm., GH-00023262!).

Plants perennial, not rhizomatous. Culms 80–120 cm tall, 2.5–3 mm wide at base, erect or ascending; nodes 3–7, moderately to densely pubescescent. Leaf sheaths densely pubescent, hairs up to 1.5 mm long; auricles absent; ligules 1.5–4 mm long, lacerate, glabrous, sometimes with a few hairs along the margins; blades 14.5–32 cm × 5–10 mm, flat, firm, abaxial and adaxial surfaces sparsely to densely pubescent, sometimes glabrous, margins serrulate. Panicles 16.5–22 cm long, open, nodding, branches erect to ascending, stiff, scabrous, 1–2(–3) spikelets per branch, lower branches longer than spikelets, upper branches shorter or longer than spikelets. Spikelets 2.5–3 cm long, 7–9-flowered, elliptic to lanceolate, terete to morderately laterally compressed; glumes pubescent, hairs up to 0.5 mm long, green to purplish green, margins narrowly hyaline, midnerves glabrous proximally, scabrous to pubescent distally; lower glumes 7.5–9 mm long, narrowly lanceolate, 1-nerved, apices acute; upper glumes 9.5–11 mm long, obovate-lanceolate, 3-nerved, apices mucronate, mucros up to 1.5 mm long; lemmas 10–11 mm long, elliptic to lanceolate, rounded over the backs, apices obtuse to truncate, 7-nerved, pubescent across the backs and margins, hairs up to 0.5 mm long; awns (6–) 6.5–8 mm long, inserted up to 0.5 mm below lemma apex, straight; paleas shorter than the lemmas, backs pubescent, keels ciliate, cilia 0.1–0.2 mm long; anthers (3–) 3.5–4 mm long; caryopses 8.5−9.5 mm long, light brown. 2 n = unknown.

Distribution:—Native. Endemic to Coahuila, where it is known only from Sierra de la Madera and Sierra del Pino in western Coahuila ( Fig. 57 ).

Ecology: —Pine-oak forests in rocky arroyos derived from calcareous parent materials; associated with Juniperus deppeana , Quercus gravesii Sudworth (1927: 86) , Q. intricata Trel. in Standley (1922: 185), Pinus arizonica , Prunus serotina , Arbutus xalapensis and Fallugia paradoxa . Elevation: 1615–1980 m.

Common Names: —Unknown.

Comments: — Bromus pinetorum is a poorly understood taxon, known from only a few collections. Johnston (1943) considered the material here included in B. pinetorum to be a hairy robust form of B. anomalus . Described by Swallen (1943), the species was recognized by Wagnon (1952), but most other authors have included B. pinetorum in B. lanatipes ( Soderstrom & Beaman 1968, Beetle 1977, Espejo-Serna et al. 2000, Pavlick et al. 2003). Beetle (1987) did not mention the taxon. We experienced difficulty placing plants included here into B. lanatipes , from which it differs by its longer awns [(6–) 6.5–8 mm vs. 2–6.5 mm], longer lemmas [10–11 mm vs. 8–10 mm], longer glumes [lower glumes 7.5–9 mm vs. 4–6 mm, upper glumes 9.5–11 mm vs. 6.5–8 mm], pubescent leaf sheaths [vs. lanate leaf sheaths], stiffer inflorescence branches [vs. laxer inflorescence branches] and stiffer and generally wider leaf blades [5–10 mm wide vs. laxer and 4–7 mm wide]. Bromus pinetorum differs from B. richardsonii by its longer anthers [(3–) 3.5–4 mm vs. 1–2.6(–3.4) mm], longer awns [(6–) 6.5–8 mm vs. 3.1–6.5 mm], panicle branches that are stiff and erect to ascending [vs. lax and ascending to nodding] and stiff leaf blades [vs. lax].

The stiffly erect to nodding panicles of B.pinetorum are similar to those of B. pumpellianus Scribner (1888: 9) , a widespread western North American species of sect. Bromopsis that does not occur in México. The known southernmost distribution of B. pumpellianus is in northern New Mexico ( Pavlick & Anderton 2007). Bromus pinetorum differs from B. pumpellianus in lacking rhizomes [vs. rhizomatous], lemma apices obtuse to truncate [vs. subulate to acute], shorter anthers [(3–) 3.5–4 mm vs. 3.5–7 mm], and longer lemmatal awns [(6–) 6.5–8 mm vs. 1–4.5(–5) mm]. Pavlick & Anderton (2007) reported lemmatal awns up to 7.5 mm long in B. pumpellianus , whereas in other treatments the awns of this species are reported as 1.5–5 mm ( Tzvelev 1976), 1–4.5(–5) mm ( Saarela 2008), 2–3 mm ( Allred 1993) and <3 mm (Weber & Wittmann 2001). The measurements in Pavlick & Anderton (2007) may have included specimens of B. riparius Rehmann (1872: 10) , a closely-related Old World species ( Saarela et al. 2007) used in North America as forage, which has awns (3–) 4–7.1 mm long ( Saarela 2008). Peterson & Annable 10676 is placed here even though it has short-awns (2−3.5 mm long); in other respects it agrees with characteristics of B. pinetorum . Bromus pinetorum is unique in sect. Bromopsis in México in having firm leaf blades and stiff inflorescence branches. However, these characters are described only from a few herbarium specimens. This curious taxon should be studied more closely in the field.

Specimens Examined:— MÉXICO. Coahuila: vicinity of La Noria, a broad valley in the calcareous Sierra del Pino , [28.23°N, 102.87°W], 28 August 1941, R. M . Stewart 1213 ( GH); Sierra El Pino, 39.5 km Wof Rancho El Cimarron, 15 Sep 1991, P. M . Peterson & C. R . Annable 10676 ( US) ; W Coahuila, Sierra de la Madera, vicinity of La Cueva in Corte Blanco fork of Charretera Canyon , 27.14°N, 102.53°W, 1615–1981 m, 11–15 September 1941, I. M . Johnston 8926 ( GH, US-90887 , US-1817802 ) .

108 Phytotaxa 185 (1) © 2014 Magnolia Press

SAARELA ET AL. ATAXONOMIC REVISION OF BROMUS (POACEAE)

Phytotaxa 185 (1) © 2014 Magnolia Press 109

Figures

FIGURE 56. Holotype of Bromus pinetorum (Johnston & C.H. Mueller 497, US-2209362).

FIGURE 57. Geographical distribution of Bromus pinetorum in México.