Muhlenbergia setarioides E. Fourn., Mexic. Pl. 2: 84. 1886.

Peterson, Paul M., Herrera Arrieta, Yolanda, Lobo Cabezas, Silvia & Romaschenko, Konstantin, 2023, Taxonomic revision of Muhlenbergia (Poaceae, Chloridoideae, Cynodonteae, Muhlenbergiinae) in Central America: phylogeny and classification, PhytoKeys 230, pp. 1-106 : 1

30. Muhlenbergia setarioides E. Fourn., Mexic. Pl. 2: 84. 1886.

Fig. 21F-J

= Muhlenbergia polypogonoides Hack., Ann. K. K. Naturhist. Hofmus. 17: 255. 1902. Type: México, A. Schmitz 862 (holotype: W-18890124080!; isotypes: US-3412356! fragm. ex W, W-19160029073!

Type.

México, Orizaba , Borrego, 14 Nov 1865 -1866, M. Bourgeau 3362 (lectotype, designated here: MPU-026952 [image!]; isolectotypes: G-00099164 [image!], GH-0024047 [image!] ex P, K-000308906 [image!], MO-2974294!, US-0091990! ex P & ex LE, S-14-29487 [image!]. ≡ Muhlenbergia sylvatica var. setarioides (E. Fourn.) Beal, Grass. N. Amer. 2: 249. 1896.

Description.

Sprawling perennials, rooting at the lower nodes. Culms 30-70(-100) cm tall, geniculate, usually glabrous, with many branches, about 1.5 mm thick near base. Leaf sheaths shorter or longer than internodes, terete, striate, glabrous or scaberulous; ligules 1.5-3.5 mm long, hyaline, becoming yellowish-brown or brownish, erose; blades 4-12(-17) cm long, 3-6(-9) mm wide, flat, thin, dark green, scaberulous above, narrowing to the base, central vein whitish, prominent. Panicles 6-13.5(-15) cm long, 1-2 cm wide, yellowish-brown to greenish, densely flowered, interrupted below; primary branches 1-3.5 cm long, appressed or ascending, flowered to the base; pedicels 0.2-1.7 mm long, shorter than the spikelets, hispidulous. Spikelets (2-)2.5-3 mm long; glumes 1-2(-2.5) mm long, unequal, 1-veined, green and prominent, apex acute to acuminate; lower glumes 1-1.5 mm long; upper glumes 1.5-2(-2.5) mm long; lemmas (2-)2.5-3 mm long, lanceolate, pale, awned, mottled with dark green spots, the 3-veins green and prominent, scabrous along the veins, pilose over the central vein and margins on the lower 1/3-1/2, the awns 5-14 mm long, somewhat flexuous, purplish; paleas about as long as the lemma, pilose between the veins on lower ½; anthers 1-1.2 mm long, yellowish. Caryopses 1.3-1.5 mm long, narrowly-ellipsoid, dark reddish-brown. 2 n = 40.

Distribution.

Muhlenbergia setarioides ranges from Puebla, Oaxaca (Peterson & Annable 9897, 1.4 mi E of Ayutla on Mex 179), Tlaxcala,Veracruz, and Chiapas in México to Central America from Guatemala to Panama ( Sanchez-Ken 2018).

Ecology.

This species is found in tropical-wet forests, shaded banks, near cornfields, and along barrancas; 1500-2400 m.

Comments.

Morphologically, M. setarioides resembles M. spiciformis but differs from the latter in having wider leaf blades 3-6(-9) mm wide (1-3 mm wide in M. spiciformis ), shorter spikelets (2-)2.5-3 mm long (versus 3-4 mm long), acute to acuminate (obtuse to acute in M. spiciformis ) glumes, upper glumes 1.5-2(-2.5) mm long (versus ≤ 1mm long), and lemmas with awns 5-14 mm long [versus (10-)20-40 mm].

Muhlenbergia setarioides is a member of M. subg. Muhlenbergia and is sister to all remaining species in the subgenus (Fig. 1 ; Peterson et al. 2021).

Specimens examined.

Costa Rica. Alajuela: along road below Los Cartagos, 5 km above Carrizal, wet bank of roadside, in shade of herbs, R.W. Pohl & G. Davidse 11735 (CR, US). Cartago: River crossing of Río Reventado between Llano Grande and Tierra Blanca, R.W. Pohl & M. Lucas 13097 (MO, CR); Cerro de La Carpintera, in potrero, P.C. Standley 34502 ( US). San José: along Rio Maria Aguilar, near San José, P.C. Standley 38976 ( US); Vazquez de Coronado, Quebrada Corralillo, 2 km E of Rancho Redondo, moist mossy canyon walls in shade and along roadsides, R.W. Pohl & G. Davidse 11701 (CR, MO, US); La Palma, wet forest, P.C. Standley 33006 ( US); San Gabriel, orillas de un arroyo, O. Jiménez 173 ( US). El Salvador. La Libertad: Volcan San Salvador, near bottom of crater of Volcán San Salvador, N.C. Fassett 28595 (MO, ITIC, US); Volcan San Salvador, Boquerón de San Salvador, L.E. González 1852 (MO, ITIC). San Salvador: San Salvador, A.S. Hitchcock 8927 ( US). Sonsonate: A. R. Molina et al. 21747 (LAGU). Guatemala. Escuintla: San José, W. A. Kellerman 5115 (MO, US). Guatemala: Near San Rafael, W.A. Kellerman 6239 ( US). Huehuetenango: Thickets and forest in deep canyon of tributary of Rio Blanco, about 5 km W of Aguacatán, L.O. Williams, A. Molina R. & T.P. Williams 22329 ( US). Quetzaltenango: Mountains near Santa Maria, just S of Quetzaltenango, Weatherwax 161 (1679) ( US); Region of Las Nubes, south of San Martin Chile Verde, densely forested barranco, P.C. Standley 83711 ( US); Ravine below Fuentes Georginas, just above Zunil, J.A. Steyermark 34480 ( US); Retalhuleu, M. De Koninck 226 ( US); Mountains above Rio Samala, Sierra Madre Mountains, 2 km west of Zunil, L. O. Williams, A. Molina R. & T.P. Williams 22987 ( US). Sacatepequez: near Pastores, damp ravine, P.C. Standley 59936 ( US); Volcano Agua, near Antigua, shady bank, A.S. Hitchcock 9134 ( US); Nacimiento del Cangrejal, cuesta de Las Cañas, A. Molina R. 15439 ( US). San Marcos: Barrancos 6 mi south and west of town of Tajumulco, northwestern slopes of Volcan Tajumulco, moist thickets in quebrada, J.A. Steyermark 36594 ( US); Barranco Eminencia, above San Rafael Pie de la Cuesta, wet meadow, P.C. Standley 68464 ( US). Solola: Mixed forest area, mountains slopes above Lake Atitlan, about 3-5 km west of Panajachel, L.O. Williams, A. Molina R. & T.P. Williams 25264 ( US). Mexico. Chiapas. Motozintla: along road from Toilman to Niquivil, near Ojo de Agua, D.E. Breedlove 42616 (MO). Siltepec: On the ridge above Siltepec on the road to Huixtla, D.E. Breedlove & Almeda 58258 (CAS, MO). Tenejapa: along trail from Tenejapa center to San Cristóbal de las Casas, in the paraje of Balum K’ anal, D.E. Breedlove 9350 (ENCB, DS, US); La Punta del Cerro Cruz Ch’en, A. Shilom Méndez Ton 5088 (MEXU, MO). Unión Juárez: En el volcán Tacaná a 500 m al E de Talquián, E.M. Martínez S. & A Reyes-García 20293 (MO). Panama. Chiriquí: Rio Caldera, 1-2 mi above El Boquete, E.P. Killip 4513 ( US).

Figures

Figure 1. A, B Bayesian tree inferred from combined plastid (ndhA intron, rps 16 - trnK, rps 16 intron, rps 3, and rpl 32 - trnL) and ITS sequences. Thick branches indicate posterior probabilities of 0.95 - 1; species in bold occur in Central America; Scale bar: 2 %.

Figure 21. A-E Muhlenbergia spiciformis Trin. A habit B ligule C glumes D floret E stamens, pistil, and lodicules F-J Muhlenbergia setarioides E. Fourn. F habit G ligule H glumes I floret J stamens, pistil, and lodicules. A-E drawn from P. M. Peterson & C. R. Annable 8361 (US) F-J drawn from D. E. Breedlove 9350 (US).