Muhlenbergia vaginata Swallen, Contr. U.S. Natl. Herb. 29(9): 406. 1950.

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

36. Muhlenbergia vaginata Swallen, Contr. U.S. Natl. Herb. 29(9): 406. 1950.

Type.

Guatemala, San Marcos, road between San Sebastián and San Marcos, 2700-3800 m, 15 Feb 1940, J.A. Steyermark 35598 (holotype: F-1046643!; isotypes: US-2240531!, US-2236472!) .

Description.

Annuals or short-lived perennials. Culms 16-40 cm tall, lax, slender, glabrous, decumbent, rooting at the lower nodes. Leaf sheaths 0.7-1.6 cm long, shorter than the internodes, glabrous; ligules 1.3-3 mm long, hyaline, apex acute to obtuse, decurrent; blades 0.5-3.5 (-4) cm long, 0.6-1.8 (-2) mm wide, mostly cauline, flatted or folded, with navicular apex, glabrous to scabrous. Panicles 0.5-3 cm long, 3-7 mm wide, frequently partially included in the upper sheath; primary branches 3-10 mm long, ascending or appressed; pedicels 0.5-3 mm long, appressed, scabrous. Spikelets 1.6-2.5 mm long; glumes 0.6-1 mm long, subequal, glabrous, 1-veined, oblong to ovate, light green to green-grayish, apex obtuse, rounded to subacute, occasionally erose; lower glumes 0.6-0.8 mm long; upper glumes 0.6-1 mm long; lemmas 1.6-2.5 mm long, lanceolate, sparsely pubescent below and along the midvein and margins, mottled with olive-green spots, often purplish, apex scabrous, acuminate, sometimes mucronate, the mucro 0.2 mm long; paleas 1.5-2.5 mm long, lanceolate, glabrous or with a few hairs between the veins; anthers 0.5-0.8 mm long, purplish. Caryopses 1-1.2 mm long, ellipsoid to fusiform, brown. n = 9.

Distribution.

Muhlenbergia vaginata ranges from México to Guatemala in Central America (In México it is found in Chiapas, Chihuahua, Ciudad de México, Durango, Hidalgo, Jalisco, México, Michoacán, Morelos, Puebla, Querétaro, Sinaloa, Tlaxcala, and Veracruz ( Peterson and Annable 1991).

Ecology.

This species is found in wet meadows, wet depressions, open flats, sandy flats along creeks, and rivers in pine or pine-oak woodlands; 1500-3800 m.

Comments.

Morphologically, M. vaginata can be separated from M. ligularis in having contracted, narrow panicles up to 0.7 cm wide (0.4-1.5 cm wide in M. ligularis ) and culms often rooting at the lower nodes (not rooting at lower nodes in M. ligularis ) [ Peterson and Annable 1991]. Muhlenbergia ligularis can be separated morphologically from M. filiformis in having inconspicuous panicles partly enclosed in the sheath (conspicuous, long-exerted panicles in M. filiformis ) and leaf blades that are well developed along the entire length of the culm (versus leaf blades most numerous near the base of the culm) [ Peterson and Annable 1991].

Based on DNA sequence analysis, Muhlenbergia vaginata is in M. subg. Bealia and forms a clade with M. filiformis and M. ligularis (Fig. 1 ; Peterson et al. 2021).

Specimens examined.

Guatemala. Huehuetenango: La Capellania, Sierra de los Cuchumatanes, 3.3 mi NW of La Capellania on hwy 9N and 14.6 mi N of Huehuetenango, P.M. Peterson & C.R. Annable 4685 (GH, MO, NY, RSA, UC, US, WS); El Mirador, at the summit of the road leading from Huehuetenango to Sierra de los Cuchumatanes, P.C. Standley 81872 ( US); Sierra de los Cuchumatanes. 1.1 mi E of Santa Eulalia on road to San Sebastian Coatan, P.M. Peterson & C.R. Annable 4690 ( US, WS); meadow at Tojah on hwy 9N, P.M. Peterson & C.R. Annable 4697 ( US, WS). Quetzaltenango: along eastern side of Rio Somala opposite Santa Maria de Jesus, J.A. Steyermark 35049 ( US). San Marcos: San Sebastian, along road between San Sebastian at km 21 and km 8, 8- 18 mi NW of San Marcos, 4 km from San Sebastián, NW of San Marcos, J.A. Steyermark 35598 (MO). Zinacantán: near Paraje Nachij, D.E. Breedlove & G. Davidse 53877 (CAS, MO). Mexico. Chiapas: Chamula: large sphagnum bog at Paraje Muk’in ha, D.E. Breedlove & B. Bartholomew 55504 (SLPM, CAS, MO). Chenalhó: edge of pasture 1 mile south of Chenalho Center, D.E. Breedlove & P.H. Raven 8254 (DS). Huixtán: Chilil, SE de San Cristóbal de Las Casas, M. González et al. 405 (SLPM); 10.5 mi SE of San Cristobal de las Casas, P.M. Peterson & C.R. Annable 4723 (GH, MO, NY, US, WS).

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 %.