Muhlenbergia flexuosa Hitchc., Contr. U.S. Natl. Herb. 24(8): 388. 1927.

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 : 152-154

10. Muhlenbergia flexuosa Hitchc., Contr. U.S. Natl. Herb. 24(8): 388. 1927. Fig. 9A-E

Type.

Peru, Huacachi Estacion near Muna, summit of rocky crest, 2000 m, 20 May-1 Jun 1923, J.F. Macbride 3874 (holotype: F-534937!; isotypes: BAA-1622!, BM-000938657 [image!], G-00099373 [image!], K!, LE!, US-1256339!).

Description.

Caespitose perennials. Culms 15-40 cm tall, slender, 0.3-0.4 mm diameter just below the panicle with 6-8 nodes per culm; internodes 1-6 cm long near base, glabrous, shiny. Leaf sheaths about as long as the internodes below, glabrous; ligules 0.3-0.5 mm long, membranous, apex truncate, lacerate; blades 2-5 cm long, 1-2.2 mm wide, flat, scaberulous, apex acuminate. Panicles 3.5-6.5 (-7) cm long, 0.5-1.5 cm wide, narrow, spiciform, sometimes interrupted below; primary branches 0.5-2.5 cm long, tightly apressed to loosely ascending or spreading, not more than 45° from the culm axis. Spikelets 2.8-4.2 mm long, yellowish to light brown, erect or drooping; glumes 2.8-4 mm long, including mucos or awns, subequal, hyaline to membranous, glabrous, 1-veined, scabrous along the midvein, apex acute, unawned, mucronate or awned, the awns up to 1.3 mm long, straight or loosely flexuous; lemmas 2.8-4.2 mm long, hyaline to membranous, 3-veined, scaberulous, lower 1/3 sparsely hairy, apically awned, the awns 14-30 mm long, flexuous, callus hairy, the hairs up to 0.4 mm long; paleas about as long as the lemmas, 2-veined, glabrous, apex acuminate, often mucronate; anthers 1.3-1.6 mm long, purple. Caryopses 1.4-1.6 mm long fusiform, light brown.

Distribution.

Muhlenbergia flexuosa endemic to Peru and is known from only a few collections from Huánuco, Pasco and San Martín departments ( Hitchcock 1927; Tovar 1993).

Ecology.

Steep talus slopes, rocky trail cuts and rock outcropts with Andropogon , Acacia , Chusquea , Baccharis , Puya , Salvia , Rubus , Muhlenbergia ciliata , M. beyrichiana , Acanthaceae and Melastomataceae ; 1200-2530 m.

Comments.

Hitchcock (1927) suggested Muhlenbergia flexuosa was allied with M. flaviseta Scribn. and M. watsoniana Hitchc. (≡ M. scabra S. Watson), since all have short flat blades, spike-like panicles and slender flexuous awns. However, Muhlenbergia flaviseta and M. watsoniana are members of the M. subg. Clomena clade while M. flexuosa is sister to M. plumiseta Columbus- M. pereilema P.M. Peterson- M. beyrichiana clade, all of which are included in M. subg. Muhlenbergi a (Fig. 1 ; Peterson et al. 2010b). Within Muhlenbergia , the derivation of a slender flexuous awn found in M. flexuosa has occurred in four of the five subgenera currently recognised within the genus and is only lacking in M. subg. Pseudosporobolus (Fig. 1B ; Peterson et al. 2010b).

Specimens examined.

Peru. Huánuco: Rio Huallaga Cañon, below Rio Santo Domingo, 1316 m, 3 Jun 1923, J.F. Macbride 4205 (US); Pachitea, Canyon of the Rio Grande, 44 air km E of Huánuco, 2 air km ESE of Estación Huacachay (Huacachi), 9°51'34.7"S, 75°50'48.1"W, 1867 m, 7 Mar 2007, P.M. Peterson, R.J. Soreng & K. Romaschenko 20358 (MO, US, USM); 1.5 air km SE of Estación Huacachay (Huacachi), 9°51'42.8"S, 75°50'23.4"W, 2383 m, 8 Mar 2007, P.M. Peterson, R.J. Soreng & K. Romaschenko 20365 (MO, US, USM); along trail 1/3 air km NW of Estación Huacachay (Huacachi), 9°51'1.4"S, 75°49'53.4"W, 2519 m, 8 Mar 2007, P.M. Peterson, R.J. Soreng & K. Romaschenko 20373 (US, USM). Junin: Cerro Taldes, Rio Huancabamba, 31 km S of Pozuzo and 3 km N of Llullitunqui, 1370 m, 1 Jun 1979, H. Teppner 79-293 (US). Pasco: Oxapampa, Pozuzo, 21 Jul 1978, Ellemberg 8934 (USM). San Martín: Mariscal Caceres, 2350 m, 13 Aug 1986, K. Young 4234 (MO).

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 9. A-E Muhlenbergia flexuosa Hitchc. A habit B ligule C glumes D floret E stamens and pistil. Drawn from H. Teppner 79 - 293 (US).