Muhlenbergia distichophylla (J. Presl) Kunth, Enum. Pl. 1: 202. 1833.

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

7. Muhlenbergia distichophylla (J. Presl) Kunth, Enum. Pl. 1: 202. 1833.

Fig. 7F-I

Podosemum distichophyllum J. Presl, Reliq. Haenk. 1(4-5): 231. 1830. Type: México, 1831, T.P.X. Haenke s.n. (holotype: PRC-450429 [image!]; isotypes: MO-1837831!, US-90711 fragm ex PR!, W-0002571!). ≡ Epicampes stricta var. distichophylla (J. Presl) M.E. Jones, Contr.W. Bot. 14: 6. 1912. Basionym.

= Muhlenbergia angustifolia Swallen, N. Amer. Fl. 17(6): 457. 1935. Type: México, near Guadalajara, on rocky hills, 11 Nov 1889, C.G. Pringle 2346 (holotype: US-822822!; isotypes: BR-0000006863357 [image!], BR-0000006884116 [image!], CM-2819 [image!], KFTA-0002830 [image!], LE!, MEXU-00005188 [image!], MO-1837815!, UC-122455 [image!], US-995828!, US-3274342!, W-18900000582 [image!], W-19160027683 [image!]).

Description.

Caespitose perennials. Culms 100-180 cm tall, erect, glabrous to pubescent below the nodes; internodes glabrous. Leaf sheaths 8-42 cm long, longer than basal internodes, glabrous, the keels prominent, sometimes coiled to shredded below, basal sheaths compressed-keeled; sheath auricles 6-26 mm long, on lower portions and to 6.4 cm above, apex acuminate; ligules 4-15 mm long, membranous, apex finely lacerate sometimes almost to the base; blades 18-90 cm long, 2-7 mm wide, flat or folded, scaberulous to scabrous on both sides, the margins and keel saw-toothed. Panicles 35-70 cm long, 4-15 cm wide, densely-flowered, oblong, sometimes lax near apex, greenish-brown, sometimes reddish-purple; primary branches 2-15 cm long, without spikelets near the base, appressed to loosely spreading up to 60° from the rachises; pedicels 0.2-4 mm long, glabrous to scaberulous. Spikelets 1.5-2.8(-3) mm long, erect, greenish-brown, to reddish-purple; glumes 1.2-2.8 mm long, longer, as long or a little shorter than the lemma, subequal, oblong to narrowly-oblong, faintly 1-veined, hyaline, glabrous to scaberulous, usually with faint, widely scattered hairs, the hairs less than 0.1 mm long, apex acute to acuminate; upper glumes rarely mucronate, the mucro to 0.4 mm long; lemmas 1.4-2.7 mm long, lanceolate to linear-lanceolate, awned, glabrous or sometimes the margins on the lower 1/3 pubescent, the hairs to 0.2 mm long, rarely the lower 1/3 with scattered hairs, apex acute, minutely bifid, the teeth to 0.5 mm long, the awn 4-16 mm long, flexuous, often reddish-purple near base; callus usually short pilose; paleas 1.3-2.7 mm long, glabrous or with few hairs between the veins on the lower 1/3, apex acute; anthers 1.2-1.5 mm long, yellowish, sometimes reddish tinged. Caryopses not seen.

Distribution.

The species ranges from central México in Jalisco, Guerrero, México, Oaxaca, and Chiapas to Guatemala ( Peterson et al. 2001).

Ecology.

Muhlenbergia distichophylla occurs in open pine-oak forests and tropical deciduous forests on rocky slopes, canyons, and ravines; 400-2000 m.

Comments.

This species can be separated from other members of M. subg. Trichochloa in having long, acuminate sheath auricles up to 6.4 cm long on the culm, usually greater than 2 cm long on the lower innovations (Herrera Arrieta and Peterson 2018). Muhlenbergia distichophylla , a member of M. subg. Trichochloa , has been found in an unsupported clade with nine other species, distributed in North America (Eastern USA, western USA, México) and Central America [ M. lindheimeri Hitchc., M. setifolia Vasey, M. dubia E. Fourn., M. gypsophila Reeder & C. Reeder, M. x Muhlenbergia involuta Swallen, M. reverchonii Vasey & Scribn., M. sericia (Michx.) P.M. Peterson, M. expansa (Poir.) Trin. and M. capillaris ] (Fig. 1 ; Peterson et al. 2021).

Specimens examined.

Guatemala. Escuintla: Rio Coyolate, near Highway CA-2, thickets on banks of Río Coyolate, W.E. Harrmon & J.A. Fuentes 4721 (MO). Huehuetenango: On dry bank about 5 km. west of Huehuetenango, L.O. Williams, A. Molina R. & T.P. Williams 22309 ( US); Sierra de los Cuchumatanes, P.C. Standley 81480 ( US). Mexico. Chiapas: Escuintla, E. Matuda 319 (MEXU); Monte Ovando, E. Matuda 322 (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 7. A-E Muhlenbergia macroura (Kunth) Hitchc. A habit B ligule C glumes D floret E stamens, pistil, and lodicules F-I Muhlenbergia distichophylla (J. Presl) Kunth F ligule G glumes H floret I stamens pistil, and lodicules. A-E drawn from P. M. Peterson & C. R. Annable 5970 (US) F-I drawn from L. O. Williams, A. Molina R. & T. P. Williams 22309 (US) and F. W. Gould 12666 (US).