Muhlenbergia utilis (Torr.) Hitchc., J. Wash. Acad. Sci. 23(10): 453. 1933.

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

35. Muhlenbergia utilis (Torr.) Hitchc., J. Wash. Acad. Sci. 23(10): 453. 1933.

Fig. 18 F-K

Vilfa utilis Torr., Pacif. Railr. Rep. 5(2):365-366. 1857. Type: U.S.A., California, Lost Mountain Spring, from Tejon to the Lost Hills, in stony places, W.P. Blake s.n. (holotype: NY-00431757 [image!]; isotypes: GH-00023997 [image!], MO-992072!). ≡ Sporobolus utilis (Torr.) Scribn., Bull. Div. Agrostol., U.S.D.A. 17:171, f. 467. 1899. Basionym.

Description.

Perennials; with slender, scaly rhizomes. Culms 7-30 cm tall, erect to decumbent, older plants trailing, up to 1 m long, minutely pubescent to glabrous below the nodes; internodes mostly smooth to lightly nodulose roughened. Leaf sheaths 0.3-2.4 cm long, shorter or longer than the internodes, glabrous, margins hyaline; ligules 0.2-0.8 mm long, membranous, decurrent, apex truncate; blades 0.5-4.7 cm long, 0.2-1.8 mm wide, involute, sometimes flat, straight or arcuate-spreading, the blades often at right angles to culms, mostly glabrous abaxially and hirsutulous adaxially. Panicles 1-5 cm long, 0.1-0.4 cm wide, narrow, contracted, interrupted between each branch, partially included in the upper sheaths; primary branches 0.2-1.2 cm long, appressed, rarely ascending to spreading 30° from the rachises; rachises usually visible between the branches; pedicels 0.1-1.1 mm long, glabrous. Spikelets 1.4-2.4 mm long, erect; glumes 0.5-1.4 mm long, ⅓ to as long as the lemma, subequal, unawned, glabrous, 1-veined, occasionally 2-to 3-veined, yellowish to light green, apex acute; lemmas 1.3-2.4 mm long, lanceolate, unawned, glabrous or with minute appressed pubescence along the margins and the base, the hairs about 0.1 mm long, green or purplish, apex acute; paleas 1-2 mm long, lanceolate, glabrous, apex acute; anthers 0.7-1.4 mm long, yellow to purplish. Caryopses 0.7-1.2 mm long, ellipsoid to ovoid, brown. 2 n = 20.

Distribution.

Muhlenbergia utilis ranges from the southern United States to México in Chiapas, Chihuahua, Durango, Guanajuato, Hidalgo, Jalisco, México, Ciudad de México, Michoacán, Puebla, Querétaro, Sonora, Veracruz, and Zacatecas, and Central America (Guatemala and México) [Herrera Arrieta and Peterson 2018].

Ecology.

This species occurs in wet soils along streams, ponds, depressions in grasslands, and alkaline or gypsiferous plains associated with Quercus spp.; 200-2500 m.

Comments.

Morphologically, Muhlenbergia utilis can be confused with M. vaginata but the former differs in having slender, scaly rhizomes, ( M. vaginata without rhizomes but culms decumbent and rooting below can sometimes be mistaken for rhizomes) and unawned lemmas (mucronate in M. vaginata ).

Muhlenbergia utilis is a member of M. subg. Pseudosporobolus and forms a clade with M. repens and M. villiflora Hitchc. (Fig. 1 ; Peterson et al. 2021).

Specimens examined.

Mexico. Chiapas: San Cristóbal de las Casas: Marsh at S end of San Cristóbal de las Casas, D.E. Breedlove 54373 (ENCB, SLPM, CAS, MO).

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 18. A-E Muhlenbergia plumbea (Trin.) Hitchc. A habit B ligule C glumes D floret E stamens and lodicules F-L Muhlenbergia utilis (Torr.) Hitchc. F habit G rhizome H ligule I glumes J floret K stamens, pistil, and lodicules. A-E drawn from C. G. Pringle 9581 (US- 396634) F-L drawn from A, S. Hitchcock 5652 (US).