Bromus madritensis Linnaeus (1755: 5)

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 : 104-107

16. Bromus madritensis Linnaeus (1755: 5) . Figs. 53 , 54 .

Anisantha madritensis (L.) Nevski (1934: 21). Festuca madritensis (L.) Desfontaines (1798: 91). Genea madritensis (L.) Dumortier (1868: 67). Zerna madritensis (L.) Gray (1821: 117). Type:— SPAIN. Manifesto prope Madritum, Loefling s.n. (neotype LINN-93.35!, designated by Smith 1985: 500).

Plants annual. Culms 10–75(–120) cm long, 0.5–1 mm wide at base, erect or ascending, glabrous below inflorescences; nodes 1–5, glabrous. Leaf sheaths glabrous or minutely pubescent, occassionally densely pubescent with hairs up to 0.5 mm long; ligules 1.5–4 mm long, glabrous, lacerate; blades 2–27 cm × 2–6 mm, flat, sometimes convolute, abaxial and adaxial surfaces glabrous to minutely pubescent, or densely pubescent, hairs up to 0.3 mm long, margins serrulate. Panicles 3–22 cm × 2.5–10 cm, loosely obovoid to oblong-ovoboid, erect, ± compact, sometimes reduced to a single spikelet, often purple, branches ascending to spreading, 0.2–5 cm long, usually shorter than spikelets, occassionally longer than spikelets, pubescent, most branches visible, shortest branch on lowest node 6–24 mm long, longest branch on lowest node branched 0–2 times, internodes reduced upwards. Spikelets 2.7–4.5 cm long (3–6.5 cm including awns), 4–13-flowered, linear-elliptic to cuneate, moderately laterally compressed, florets not overlapping at maturity; glumes glabrous, margins hyaline, 0.1–0.2

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mm wide, midnerves glabrous proximally, scabrous distally, apices acute; lower glumes 6–11 mm long, narrowly lanceolate, 1-nerved, green to purple along nerve; upper glumes 10–17 mm long, lanceolate, 3-nerved, green to purple along and between nerves; lemmas 11–23 mm long, linear-lanceolate, rounded over the backs, apices bidentate, teeth 1–3 mm long, 5–7-nerved, green to purple along and between the nerves, glabrous or scabrous, margins hyaline, 0.2–0.4 mm wide; awns 12–30 mm long, inserted 1.5–4 mm below lemma apices, straight or arcuate, scabrous; paleas shorter and narrower than lemmas, backs glabrous or pubescent, keels ciliate, cilia 0.1–0.6 mm long; anthers 0.6–1.2 mm long; caryopses 8−11 mm long. 2 n = 4 x = 28 ( Esnault 1984, Sánchez Anta et al. 1988, Sheidai & Fadaei 2005).

Distribution: ―Introduced. In México B. madritensis is known only from Baja California ( Fig. 55 ). In the United States its range includes California, southern Oregon and Arizona ( Pavlick et al. 2007). Native to the Mediterranean region and Central and Atlantic Europe ( Sales 1994).

Ecology:— Open, xeric, mostly disturbed sites. Elevation: 20– 900 m.

Common Names: ―Foxtail chess, madrid brome, Spanish brome, compact brome (English).

Comments: ― Soderstrom & Beaman (1968) did not recognize B. madritensis in México, but it was treated by Gould & Moran (1981) for Baja California.

Bromus madritensis and B. rubens (sect. Genea ) are part of the polymorphic B. madritensis complex, a group of morphologically similar taxa in which multiple taxa have been described ( Scholz 1981, Sales 1993, Sales 1994). The complex is distinguished from other taxa in sect. Genea by a combination of small lemmas and erect, contracted to somewhat contracted inflorescences during flowering ( Sales 1994). They have mostly been recognized as distinct species ( Gould & Moran 1981), although their recognition as species has been questioned on the basis of considerable morphological variation ( Esnault 1984, Esnault & Huon 1985, Sales 1993). Sales (1994) conducted a multivariate analysis of the polymorphic B. madritensis complex and accepted one species and two subspecies ( B. madritensis subsp. madritensis and B. madritensis subsp. rubens ). Some recent treatments have

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followed this circumscription ( Jones et al. 1997, Saarela & Peterson 2012), whereas others have maintained the taxa as distinct species ( Felger 2000, Aryavand 2002, Jessop et al. 2006, Pavlick & Anderton 2007).

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Molecular studies have shed independent light on the evolutionary history of these taxa, informing their classification. Isozyme evidence suggests that the taxa have independent origins, in line with their recognition as species ( Oja & Jaaska 1996, Oja 2002). Arecent study of plastid and nuclear ribosomal loci, and the Waxy gene, demonstrated that these two taxa are allopolyploids that arose independently from different diploid parental taxa: B. madritensis from a B. sterilis × B. fasciculatus Presl (1820: 39) cross, and B. rubens from a B. fasciculatus × B. tectorum cross ( Fortune et al. 2008). In both taxa the maternal genome is derived from the B. fasciculatus lineage ( Fortune et al. 2008). Given their independent origins, we treat these taxa as species, a classification that reflects their evolutionary history. The morphological variation in the complex globally may reflect multiple origins of these taxa or hybridization among them.

The character states related to pubescence of the culms, glumes and lemmas given in the key may not always distinguish B. madritensis and B. rubens , as these characters apparently vary in the complex and B. madritensis can sometimes be pubescent ( Sales 1994), but they distinguish the species in México based on the specimens examined here.

Specimens Examined:― MÉXICO. Baja California: 25 km SE of Tijuana, at bottom of Cañón la Presa , 32.3958°N, 116.8333°W, 190 m, 13 May 1982, R . Moran 30700 ( SD-111163 ); at roadside 1.5 km NE of Las Delicias , ca . 17 km Eof Ensenada , 31.9083°N, 116.425°W, 660 m, 20 May 1979, R . Moran 27265 ( SD-102443 ); between La Humarosa [Rumarosa] and Tecate , 32.53°N, 116.38°W, 27 April 1981, A. A . Beetle & R . Alcaraz M- 6745 ( ARIZ-229626 , MICH-1119160 , MEXU); Guadalupe Island , Sslope of cañon above NE Anchorage , 29.1542°N, 118.2833°W, 20 m, 14 February 1957, R . Moran 5688 ( SD-47529 ); La Flor de Sol , 32.425°N, 116.95°W, 220 m, 22 June 1977, R . Moran 24273 ( SD-97340 ); La Misión , between Ensenada and Tijuana, on steep slopes and in arroyo bottom along Sside of river, 32.0936°N, 116.8694°W, 50 m, 18 April 1998, J . Rebman , P . Flanagan & La Misión Community Group 5046 ( RSA-POM-643071 , SD-144705 , SD-144706 ); Rancho ontiveros, Sern foothills of Otay Mountain just Sof the US/MEX border between Tijuana and Tecate, along a side canyon of the Río Tecate just W of the MEX Hwy. 2 toll booth, 32.5461°N, 116.8544°W, 85 m, 26 April 2005, J . Rebman , J . Delgadillo , M . White & K . Comer 11830 ( SD-161420 ); San Carlos Canyon , Sof Ensenada , [31.87°N, 116.59°W], 29 April 1981, A. A . Beetle & R . Alcaraz M 6600 ( MEXU); San Isidoro, 30.7667°N, 115.5333°W, 900 m, 2 June 1975, R . Moran 22257 ( SD-91369 ); Descando Valley , 32.1833°N, 116.8667°W, 15 m, 29 April 1972, R . Moran 19110 ( MEXU, SD-83045 ) .

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Figures

FIGURE 53. Bromus madritensis. A. Lemma. B. Spikelet. C. Inflorescence. Illustration by C.T. Roché, reproduced from Barkworth et al. (2007) with permission.

FIGURE 54. Bromus madritensis. Moran 27265 (SD-102443).

FIGURE 55. Geographical distribution of Bromus madritensis in México.