Muhlenbergia diversiglumis Trin., Mem . Acad. Imp. Sci. Saint-Petersbourg , Ser . 6, Sci. Math., Seconde Pt. Sci. Nat. 6,4(3-4):298. 1841.

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 : 148-150

8. Muhlenbergia diversiglumis Trin., Mem. Acad. Imp. Sci. Saint-Petersbourg, Ser. 6, Sci. Math., Seconde Pt. Sci. Nat. 6,4(3-4):298. 1841. Fig. 7A-D

Type.

Mexico, Porto Pedro, Karwinsky 1393 (holotype: LE-TRIN-1497.01!; isotypes: US-84831! fragm. ex LE-TRIN-1497.02, W!).

Description.

Sprawling annuals. Culms 16-50 cm tall, decumbent, rooting at the lower nodes; nodes retrorsely pilose; internodes smooth or scabridulous. Leaf sheaths 1.5-8.5 cm long, sparsely or densely pilose, hairs to 3 mm long, papillose-based; ligules 0.5-0.8 mm long, membranous, apex truncate, erose; blades 2-6 cm long, 1.5-4 mm wide, flat, bases distinctly narrowed to the junction with the sheath, surfaces scabridulous and sparsely pilose, hairs papillose-based. Panicles 6-10.5 cm long, 2.0-4.5 cm wide, secund, open; primary branches 0.8-3.5 cm long, secund, spreading at right angles or somewhat reflexed usually lying to one side with 2-5 spikelets; secondary branches not developed; pedicels 1-5 mm long, scabrous or shortly pilose, hairs papillose-based; disarticulation at the base of the primary branches where there is a weak and contorted stipe. Spikelets 4-8 mm long, dimorphic with respect to the glumes, proximal spikelets on each branch almost sessile; glumes of proximal spikelets on each branch subequal, 0.2-0.7 mm long, orbicular, truncate, often erose or irregularly toothed, unawned; glumes of distal spikelets on each branch markedly unequal; lower glumes to 8 mm long, 1-veined, acute, usually awned, awns 0.5-3 mm; upper glumes orbicular, acute, sometimes awn-tipped; lemmas 4.0-7.6 mm long, linear to broadly lanceolate, light greenish, smooth or scabrous, usually with greenish veins, apices acuminate, awned, awns 6-19 mm long, usually straight, scabrous; paleas 3.7-6.8 mm long, narrowly lanceolate, coarsely papillate or almost smooth, 2-keeled, the veins prominent, scabrous, greenish, sometimes extending as minute awns, acuminate; anthers 0.4-0.8 mm long, yellowish. Caryopses 1.8-3 mm long, oblong-ovoid, flattened, brownish. 2 n = 20.

Distribution.

The species is native to North America, Central America, Colombia, Venezuela, Ecuador, Peru, and Argentina.

Ecology.

Muhlenbergia diversiglumis grows on moist cliffs, along water courses, sandy slopes, and road cuts, primarily in moist shaded environments of broadleaf evergreen forests and pine-oak forests, at elevations of 600-2500 m.

Comments.

Muhlenbergia diversiglumis can be differentiated from M. ciliata , M. microsperma , and M. romaschenkoi in having secund panicles (versus not secund in the latter three species) with each primary branch consisting of 2-5 dimorphic spikelets where the proximal spikelets have short orbicular glumes less than 1 mm long, and the distal spikelets have glumes up to 8 mm long ( Peterson and Annable 1991; Giraldo-Cañas and Peterson 2009).

Muhlenbergia diversiglumis is a member of M. subg. Muhlenbergia and is sister to M. alamosae Vasey and together they are sister to the M. tarahumara - M. cenchroides - M. bryophilus - M. uniseta clade (Fig. 1B ).

Specimens examined.

Peru. Amazonas: Dist. Vista Alegre, Puente sobre el Río Salas, 1525 m, 30 Jun 1998, I.M. Sánchez Vega, M.O. Dillon & M. Zapata 9580 (HAO, MO). Ayacucho: Naranjayoc, entre Ayna y el Río Apurimac, 900 m, 16 May 1969, O. Tovar 6136 (USM); Ayna, cerca entre Tambo y San Francisco, Jan 1969, L. Aucasime 428 (USM); Province La Mar, Machente, entre Yanamonte y Ayna, 1200 m, 16 May 1969, O. Tovar 6126 (USM); Province La Mar, entre Ayna & Río Apurimac, 900 m, 16 May 1969, O. Tovar 6136 (USM); Ayna, between Huanta and Río Apurimac, 750 m, 7 May 1929, E.P. Killip & A.C. Smith 23127 (US). Cusco: Urubamba Valley, San Miguel, 1800 m, 28 May 1913, O.F. Cook & G.B. Gilbert 958 (US); Urubamba, Ciudadela Macchu Picchu, 2300 m, 11 Apr 1963, C. Vargas C. 2159 (US), 14355 (US, USM); Urubamba, Macchu Picchu, 2040 m, Mar 1949, F. Marin 1381 (US); Urubamba, 110 km de Cusco en el camino y atrás de las aguas termales con plantaciones de palta, Macchu Picchu, 2050 m, 21 May 1988; G. Valencia & R. Ochoa 9147 (MO, US). Huánuco: Province Leoncio Prado, La Divisoria, carretera a Pucallpa, 1600 m, 21 Apr 1989, J. Schunke Vigo 11349 (MO, US, USM). Piura: Huancabamba, Porculla, 1770 m, 6 Mar 1989, S. Llatas Quiroz 2431 (CPUN, HAO, 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 7. A-D Muhlenbergia diversiglumis Trin A habit B ligule C glumes D floret E-H Muhlenbergia microsperma (DC.) Kunth E habit F ligule G glumes H lemma. Drawings from Peterson and Annable (1991) A-D drawn from P. M. Peterson & C. R. Annable 4158 (WS) F-H drawn from P. M. Peterson & C. R. Annable 4185 (WS).