Muhlenbergia beyrichiana Kunth, Enum. Pl. 1: 200. 1833.

Peterson, Paul M., Vega, Isidoro Sanchez, Romaschenko, Konstantin, Giraldo-Canas, Diego & Rodriguez, Nancy F. Refulio, 2018, Revision of Muhlenbergia (Poaceae, Chloridoideae, Cynodonteae, Muhlenbergiinae) in Peru: classification, phylogeny, and a new species, M. romaschenkoi, PhytoKeys 114, pp. 123-206 : 134-135

1. Muhlenbergia beyrichiana Kunth, Enum. Pl. 1: 200. 1833. Fig. 2A-F

Pereilema beyrichianum (Kunth) Hitchc., Contr. U.S. Natl. Herb. 24(8): 385. 1927. Type: Brazil, Province de Saint-Paul, Voyage d’Auguste de Saint-Hilaire de 1816 a 1821, Saint-Hilare Cat. B #1028 (lectotype, designated here: P-00751689!; isolectotype: US-1645654! ex P).

Description.

Caespitose annuals. Culms 30-80 cm tall, slender, terete, glabrous, often branching from the aereal nodes below, usually with stilt-roots from lower nodes. Leaf sheaths usually shorter than the internodes, furrowed, scabrous; ligules 0.5-0.7 mm long, membranous; auricles 1-2 mm long, ciliate, sometimes cauducous at maturity, the cilia about 1 mm long; blades 8-20 cm long, 3-6 (-8) mm wide, flat, scabrous, apex attenuate. Panicles 5-16 (-20) cm long, 1-2.5 cm wide, contracted, spike-like, interrupted, the branches widely spaced along the rachis; primary branches 1-3 cm long, appressed, ascending or divergent and spreading. Spikelets in dense clusters of 2-4 subtended by 10-15 bristles, the bristles 1-5 mm long; glumes 0.7-1 mm long, ovate, membranous, 1-veined, apex awned, bidentate, the awns 3.5-5 mm long; lemmas (1.2-) 2-2.2 mm long, lanceolate, 3-veined, cartilaginous, scaberulous, awned, the awns 10-16 (-20) mm long, straight; callus short, the hairs 0.2-0.4 mm long; paleas as long as the lemmas, 2-veined, these often extending into mucros 0.1-0.3 mm long; stamens 3, anthers 0.7-1 mm long, purplish. Caryopses 1-1.3 mm long, ellipsoid.

Distribution.

Muhlenbergia beyrichiana is known to occur in Brazil, Ecuador and Peru. Earlier, it was reported in Mexico and Central America but these are probably an error for Muhlenbergia diandra (R.W. Pohl) Columbus, a more recently described species that superficially resembles M. beyrichiana (Espejo Serna et al. 2000; Lægaard and Peterson 2001; Peterson et al. 2001).

Ecology.

This species occurs in xerophilic savannahs with Cactaceae , roadsides and along moist ravines; 150-2000 m ( Lægaard and Peterson 2001).

Comments.

Muhlenbergia beyrichiana is morphologically similar to M. pereilema P.M. Peterson, which does not occur in Peru, but can be separated from the latter in having interrupted panicles with divergent primary branches (versus uninterruped panicles with tightly appressed primary branches in M. pereilema ), straight lemma awns (versus flexuous or wavy), wide leaf blades 3-6 (-8) mm (versus 2-3 mm) and ciliate auricles (versus not ciliate) [ Lægaard and Peterson 2001].

Muhlenbergia beyrichiana is in a clade with M. pereilema and M. plumiseta and is sister to M. flexuosa Hitchc. in M. subg. Muhlenbergia (Fig. 1B ; Peterson et al. 2010b).

Specimens examined.

Peru. Junín: Huancayo, abajo de Pariahuanca, 2000 m, 5 May 1979, Tovar 7880 (US, USM), Tovar 7901 (USM).

Figures

Figure 1. A, B Maximum-likelihood 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 red occur in South America; scale bar = 2 %.

Figure 2. A-E Muhlenbergia beyrichiana Kunth A habit B ligule with auricles C glumes D floret E stamens and pistil F-H Muhlenbergia maxima Laegaard & Sanchez Vega F habit G end of panicle branch H floret. A-E drawn from A. S. Hitchcock 20635 (US) F-H drawings from Laegaard & Sanchez Vega (1990) drawn from the holotype collection Sanchez Vega & Ruiz Vigo 3561.