Muhlenbergia nigra Hitchc., N. Amer. Fl. 17(6): 468. 1935.

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

19. Muhlenbergia nigra Hitchc., N. Amer. Fl. 17(6): 468. 1935.

Fig. 3F-J

Type.

México, México, Nevado de Toluca , cool slopes under pines, 2 Sep 1892, C.G. Pringle 4211 (holotype: US-746689!; isotypes, F!, MO-2974170!, MSC, US-821929!) .

Description.

Caespitose perennials. Culms 45-110 cm tall, erect, rounded near base, pubescent below the nodes, internodes glabrous to scaberulous. Leaf sheaths 3-17 cm long, shorter than the internodes, glabrous to scaberulous, the basal persistent, papery and flattened with age; ligules (5-)8-20 mm long, strongly decurrent, occasionally splitting into auricles, membranous to chartaceous above, firmer below near margins, apex truncate to obtuse; blades 5-25(-35) cm long, 2-3 mm wide, involute, scabrous and short pubescent above and mostly glabrous below. Panicles 6-15(-17) cm long, 5-10 mm wide, dense, spikelike, erect, exserted and surpassing the blades in height, plumbeous with a hint of green; primary branches 1-6 mm long, tightly appressed and ascending, imbricate, unexposed; pedicels 0.1-1.3 mm long, densely hispidulous. Spikelets (5.3-)6-8 mm long, erect, laterally compressed, plumbeous with a hint of green; glumes (5.3-)6-8 mm long, linear-elliptic to linear-ovate, usually longer than the lemma, 1-veined, sometimes mucronate or awn-tipped, scabrous along the keel, subequal; apex acuminate, scabrous, the awn up to 1.8 mm long; lemmas 5-6.5 mm long, broadly lanceolate, the margins involute, scabrous, unawned, mucronate or awned greenish-gray; apex acute, sometimes awn-tipped, the awn up to 1.3 mm long sometimes borne between two minute lobes, the lobes 0.1-0.3 mm long; callus sparingly pilose, the hairs 0.1-0.3 mm long; paleas 4.5-6 mm long, shorter than the lemma, scabrous; apex acute; anthers 2.5-3.2 mm long, grayish-green to whitish-gray. Caryopses 3-3.5 mm long, fusiform, brownish. Chromosome number unknown.

Distribution.

Muhlenbergia nigra occurs in central México south to Guatemala and Costa Rica ( Peterson et al. 2001).

Ecology.

This species is found in mountain meadows, lava fields, and open pine forests; 2300-4000m.

Comments.

Muhlenbergia coerulea (Griseb.) Mez from the Cordillera de los Andes in South America is morphologically similar to M. nigra . However, in recent molecular studies M. nigra and M. coerulea , both members of M. subg. Trichochloa , do not share an immediate common ancestor but lie in a poorly resolved clade with 10 other species in the subgenus (Fig. 1 ; Peterson et al. 2018, 2021).

Specimens examined.

Costa Rica. San José: Sabana, south fork of Rio Talarí, A.S. Weston 12372 (CR, ISC); Pérez Zeledón, sendero a la Sabana los Leones, 700m. S del Puesto, A. Rodríguez 6461 (INB); Pérez Zeledón, P.N. Parque Nacional Chirripó, Cuenca Chirripó, Cuenca Terraba-Sierpe, sendero a Valle Los Leones, E. Alfaro 1770 (INB, MO); Pérez Zeledón, Paramo en Las Sabanas Chirrido, E. Alfaro 424 (INB, MO); Pérez Zeledón: bosques quemados y bosque enano camino al Rio Terbi y Sabana de Los Leones, J.F. Morales 5174 (INB); Pérez Zeledón, Parque Nacional Chirripó. Del Puesto Los Crestones, 2.5 km al Sur, camino a Sabana Leones, R. Robles 1784 (INB, MO); Rivas. P.N. Chirripó. Sabana de los Leones, J. Sánchez el al. 2870 (MO); P.N. Chirripó, Valle de los Conejos, R. Ocampo 1492 (CR); Parque Nacional Chirripó, Frente a refugio Los Crestones, G. Vargas et al. 540 (USJ); P.N. Chirripó, Sabana de los Leones, A. Weston 10114 (CR). Guatemala. Huehuetenango: Todos Santos, Cuchumatan, Tuicoy, R. Flores & M. Véliz 94.4308 (MO); Todos Santos Cuchumatan, camino a la Torre, M. Véliz et al. 14030 (MO); Sierra de los Cuchumatanes, ca. 28 mi from Huehuetenango, slopes of Cerro Chemal, J.G. Hanokes 1453 ( US); Cerro Chémal, J.A. Steyermark 50305 (US-1935065, US-2208671). Quetzaltenango: Volcan Santa Maria, near summit of mtn., in open somewhat weedy and disturbed meadow above timberline, J.H. Beaman 4119 ( US). Sacatepequez: Volcano Agua, open pine woodland on steep northern slopes, W.E. Harmon 3595 (MO); Santa Maria de Jesús, M. Véliz et al. 2M. 8512 (MO); Acatenango, Volcán de Acatenango, M. Véliz et al. 10351 (MO); Volcan de Agua, summit of south rim of crater. In open, gravelly soil, J.H. Beaman 2931 ( US); Volcano Agua, A.S. Hitchcock 9117 ( US); Volcan de Agua, W.A. Kellerman 7416 ( US); Antigua, Volcan de Agua, W.A. Kellerman s.n. ( US); Volcan de Agua, G. Salas 538 ( US).

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 3. A-E Muhlenbergia breviligula Hitchc. A habit B ligule with auricles C glumes D floret E stamens and lodicules F-J Muhlenbergia nigra Hitchc. F habit G ligule H glumes I floret J stamens, pistil, and lodicules. A-E drawn from A. Molina R. 25227 (US- 2942492) F-J drawn from S. D. Koch 76255 (US- 2824590).