Muhlenbergia robusta (E. Fourn.) Hitchc., N. Amer. Fl. 17(6): 462. 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

29. Muhlenbergia robusta (E. Fourn.) Hitchc., N. Amer. Fl. 17(6): 462. 1935.

Fig. 20A-E

Epicampes robusta E. Fourn., Mexic. Pl. 2:89. 1886. Type: México, Distrito Federal, Santa Fe, 2 Oct 1865, M. Bourgeau 1153 (lectotype: P!, designated by Hitchcock, N. Amer. Fl. 17(6): 462. 1935; isolectotypes: K!, US-999036!, US-999031! fragm., US-90734! fragm.). Basionym.

= Epicampes stricta J. Presl, Reliq. Haenk. 1(4-5):235, t. 39. 1830. Type: México, T. Haenke s.n. (holotype: PRC?; isotypes: LE-TRIN-1558.01! fragm., US-865970! fragm.). ≡ Muhlenbergia presliana Hitchc., N. Amer. Fl. 17(6): 462. 1935b, nom. nov.

= Epicampes berlandieri E. Fourn., Mexic. Pl. 2:89. 1886. Type: México, México, Feb 1839, J.L. Berlandier 670 (lectotype: P! designated by Hitchcock, N. Amer. Fl. 17(6): 462. 1935; isolectotypes: BM-000938652 [image!], G-00099371 [image!], US-1127013!). ≡ Muhlenbergia fournieriana Hitchc., J. Wash. Acad. Sci. 23(10): 453. 1933.

= Epicampes macrotis Piper, Proc. Biol. Soc. Wash. 18:144. 1905. Type: México, Zacatecas, Sierra Madre Mountains, ca. 40 km W of San Juan Capistrano, 7 Aug 1897, J.N. Rose 3528 (holotype: US-302505!). ≡ Muhlenbergia macrotis (Piper) Hitchc., N. Amer. Fl. 17(6): 463. 1935.

= Epicampes minutiflora Mez, Repert. Spec. Nov. Regni Veg. 17:212. 1921. Type: México, Michoacán, near El Canizal, 600m, 15 Jan 1899, E. Langlassé 750 (isotype: US-386160!). ≡ Muhlenbergia meziana Hitchc., N. Amer. Fl. 17(6): 461. 1935, nom. nov.

Description.

Caespitose perennials. Culms 100-230(-300) cm tall, erect, compressed-keeled near base, glabrous to sometimes pubescent below the nodes; internodes glabrous. Leaf sheaths 15-70 cm long, longer than the internodes, glabrous, becoming brownish below, sometimes shredded; sheath auricles present, (1-)2-4(-10) cm long, linear subulate to broadly triangular, longer above, straight or twisted, firm below; ligules 2-10(-12) mm long, membranous, lacerate throughout; blades 40-100 cm long, 4-7 mm wide, folded sometimes involute toward tip, scaberulous above and below, the margins and keel saw-toothed. Panicles 30-80 cm long, (2-)3-8 cm wide, narrow to loosely contracted, greenish-gray to silvery gray or purplish; primary branches 1-15(-17) cm long, naked near base, ascending and closely appressed to spreading up to 40° from the rachises; pedicels 0.3-1.1 mm long, shorter than the spikelets, erect, scaberulous; central axis prominently ribbed, scabrous. Spikelets (1.8-)2-3 (-3.2) mm long, erect, greenish-gray or purplish; glumes 1.8-3.2 mm long, usually longer than the floret, subequal, narrowly oblong to elliptic, veinless to indistinctly 1-veined, hyaline to greenish-gray, glabrous to scaberulous, apex acute to obtuse occasionally erose; lemmas 1.7-2.6 mm long, linear-oblong, unawned or rarely mucronate, greenish to yellowish-brown, glabrous or pubescent with scattered hairs on lower, the hairs up to 0.3 mm long, callus glabrous or with few hairs, apex acute, the mucro when present up to 1 mm long; paleas 1.7-2.6 mm long, glabrous to sparingly pilose between the veins on lower, apex acute; anthers 1.1-2 mm long, purplish. Caryopses 1.2-1.7 mm long, fusiform, brownish. 2 n = 40.

Distribution.

Muhlenbergia robusta occurs in mountainous areas from Sinaloa and Chihuahua south to Chiapas, Guatemala, Honduras, and Nicaragua in Central America ( Peterson et al. 2001).

Ecology.

It is found on rocky slopes, along barrancas (canyons), in pine and pine-oak forests, and in tropical deciduous forests; 850-3000 m.

Comments.

Morphologically, M. robusta is similar to M. mutica but can be separated from the latter in having narrow panicles (2-)3-8 cm wide [(8-)15-30 cm wide in M. mutica ] and auriculate leaf sheaths (not auriculate in M. mutica ), the auricles 2-4(-10) mm long.

In DNA sequence studies, Muhlenbergia robusta is found to align in a large polytomy with other species in M. subg. Trichochloa (Fig. 1 ; Peterson et al. 2010b; Peterson et al. 2021).

Specimens examined.

Guatemala. Chimaltenango: near finca La Alameda, near Chimaltenango, P.C. Standley 59136 (US); Above Santa Maria, Volcano Agua, A.S. Hitchcock 9129 (US). Guatemala: Guatemala City, 21 km W of Guatemala on CA-1, along road in oak forest, W.E. Harmon& J.A. Fuentes 4865 (MO); Guatemala City, Eureka, A.S. Hitchcock 9081 (US); Guatemala City, A.S. Hitchcock 9035 (US), 9063 (1/2) (US). Huehuetenango: Barranco "Palo Negro" in oak-pine forest about 10 km west of Aguacatan, L.O. Williams et al. 21844 (US), 21848 (US); km 101 between El Mirador and Chintla, Sierra Cuchumatanes, rocky slopes, A. Molina 21176 (US). Santa Rosa: Taxisco, Naranjo, J. Donnell Smith 3932 (US, MO). Quiche: Nebaj, NE of Nebaj, M.J. Metzler 17 (MO). Sacatepequez: near Antigua, P C. Standley 61698 (US); P.C. Standley 76942 (US). Santa Rosa: Taxisco, Naranjo, Heyde & Lux 3932 (MO). Sololá: 5 km W of Patzún, collection from deep ravine covered with pine and oak, W.E. Harmon & J.D. Dwyer 2646 (MO); Cerca del Lago Atitlán, M. de Koninck 145 (US). Honduras. Intibucá: La Esperanza, Intibucá, Cerro San Cristóbal, bosque mixto premontano húmedo, T. M. Mejía O. 87 (MO). Mexico. Chiapas: Camino de San Cristobal a Ocosingo, 31 km suroeste de Ocosingo, R. Banda S. et al. 73117 (DS). Amatenango del Valle: 14 km SE of Teopisca along hwy. to Comitán, G. Davidse et al. 29800 (MO). Angel Albino Corzo: slopes of Río Cuxtepec below Finca Cuxtepec, D.E. Breedlove & G. Davidse 54699 (CAS, MO). Bochil: 5 km east of Bochil on road to Pichucalco, D.E. Breedlove & G. Davidse 55164 (CAS, MO). Comitán de Domínguez: 6 km N of Comitán along Mexican hwy 190, 1770 m, D.E. Breedelove & G. Davidse 54873 (SLPM, CAS, MO); 6 km N of Comitán along Mexican Highway 190, D.E. Breedlove & G. Davidse 54877 (CAS, MO); 6 km N of Comitán along Mexican Highway 190, D.E. Breedlove & G. Davidse 54869 (CAS, MO). Ixtapa: at Escopetazo, D.E. Breedlove & G. Davidse 53948 (CAS, MO); along Mexican Highway 190 at the Zinacantán paraje of Muctajoc, Laughlin 1559 (DS). La Independencia: above and SW of La Soledad on road to Las Margaritas, D.E. Breedlove 53126 (CAS, MO). La Trinitaria: 6-7 km S of La Trinitaria, G. Davidse et al. 29950 (MO); 10 km south of La Trinitaria on Mexican Highway 190, G. Davidse et al. 55070 (CAS, MO). Rayón: 9 miles NW of Pueblo Nuevo Solistahuacá along the road between Rincon Chamula and Rayón, H. Zuill 609 (DS). near summit of Zontehuitz, A. Shilom Ton 30 (DS). Teopizca: 7 km NW of Teopisca along hwy. to San Cristobal de las Casas, G. Davidse et al. 29829 (MO); North of Teopisca, D.E. Breedlove & G. Davidse 54765 (CAS, MO). Tuxtla Gutiérrez: 31 km al W de Tuxtla Gtz y 13 km NE de Chiapa de Corzo, 1050 m, J. C. Soto 13361 con D. Sutton, R. Hampshire, R. Lira y A. Reyes (MEXU); km 11.5 de la carr. Tuxtla Gutierrez-Cañon del Sumidero, en el lugar denominado El Zacabastal, E. Rodríguez s/n (MEXU); 16 km N of Tuxtla Gutiérrez on road to El Sumidero, D.E. Breedlove & B.M. Bartholomew 55491 (CAS, MO). Venustiano Carranza: 3 miles S of Aguacatenango along the road to Pinola Las Rosas, D.E. Breedlove & P.H. Raven 13433 (DS). Villa Corzo: above Colonia Vincente Guerrero on the road to Finca Cuxtepec, D.E. Breedlove & G. Davidse 54600 (CAS, MO); near Revolucion Mexicana, D.E. Breedlove & G. Davidse 54520 (CAS, MO). Zinacantán: near Paraje Sequentic [Zequentic], D.E. Breedlove & G. Davidse 53909 (CAS, MO); Along Mexican Highway 190, 10 miles southeast of the road to Simojovel. Paraje of Granadia, D. E. Breedlove 7274 (DS); at Kampana Ch’en along Mexican Highway 190, 3 miles west of paraje Navenchauk, R.M. Laughlin 2279 (DS); along road from Zinacantán center to Ixtapa near Paraje Vo Bits, D.E. Breedlove 40725 (MO). Nicaragua. Managua: Sierra de Managua, H.A. Garnier 1953 (GH, 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 20. A-E Muhlenbergia robusta (E. Fourn.) Hitchc. A habit B ligule C glumes D floret E stamens, pistil, and lodicules F, G Muhlenbergia uniseta (Lag.) Columbus F habit G primary inflorescence branch with three spikelets. A-E drawn from P. M. Peterson & C. R. Annable 6131 (US) F, G drawn from F. W. Gould 10391 (US- 3000113).