Muhlenbergia rigida (Kunth) Kunth, Revis . Gramin. 1: 63. 1829.

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

28. Muhlenbergia rigida (Kunth) Kunth, Revis. Gramin. 1: 63. 1829.

Fig. 13A-G

Podosemum rigidum Kunth, Nov. Gen. Sp. (quarto ed.) 1: 129. 1816. Type: México, Guanajuato, near Guanajuato, Sep, F.W.H.A. Humboldt & A.J.A. Bonpland s.n. (holotype: P!; isotypes: BAA!, US-91920 fragm. ex P!). ≡ Trichochloa rigida (Kunth) Roem. & Schult., Syst. Veg. 2: 386. 1817. ≡ Agrostis rigida (Kunth) Spreng., Syst. Veg. 1: 262. 1825. Basionym.

= Podosemum elegans Kunth, Nov. Gen. Sp. (quarto ed.) 1: 130. 1816. Type: Ecuador, Chimborazo, Paramo de las Puntas & Pomallacta, Jun, F.W.H.A. Humboldt & A.J.A. Bonpland s.n. (holotype: P!; isotype: BAA!). ≡ Trichochloa elegans (Kunth) Roem. & Schult., Syst. Veg. 2: 387. 1817. ≡ Agrostis quitensis Spreng., Syst. Veg. 1: 262. 1825.

= Podosemum glabratum Kunth, Nov. Gen. Sp. (quarto ed.) 1: 130. 1816. Type: México, Santa Rosa de la Sierra and Cañada de Acabuca, Sep, F.W.H.A. Humboldt & A.J.A. Bonpland s.n. (holotype: P-Bonpl!; isotype: US-91921 fragm. ex P-Bonpl!). ≡ Trichochloa glabrata (Kunth) Roem. & Schult., Syst. Veg. 2: 387. 1817. ≡ Agrostis glabrata (Kunth) Spreng., Syst. Veg. 1: 262. 1825.

= Muhlenbergia berlandieri Trin., Mém. Acad. Imp. Sci. Saint-Pétersbourg, Sér. 6, Sci. Math., Seconde Pt. Sci. Nat. 6,4(3-4): 299. 1841. Type: México, Distrito Federal, Mountains near México, Aug 1827, J.L. Berlandier 676, 684 (lectotype: LE-TRIN-1487.01! designated by Peterson et al. in PhytoKeys 114: 195. 2018; isolectotypes [all Berlandier 676]: COL-000006382 [image!]; P-00644117 [image!], P-00644119 [image!], US-2557457!, US-87241 fragm!, W-239604!, W-0029177 [image!]).

= Muhlenbergia affinis Trin., Mém. Acad. Imp. Sci. Saint-Pétersbourg, Sér. 6, Sci. Math., Seconde Pt. Sci. Nat. 6,4(3-4): 301. 1841. Type: México, México, Toluca, J.L. Berlandier 1083 (lectotype: P-00644141 [image!] designated by Peterson et al. in PhytoKeys 114: 195. 2018; isolectotypes: G-00099411 [image!], G-00099410 [image!], G-00099409 [image!], LE-TRIN-1485.01 fragm.!, P-00644142 [image!], US-87237 fragm.!). ≡ Podosemum affine (Trin.) Bush, Amer. Midl. Naturalist 7(2):40. 1921.

= Muhlenbergia phragmitoides Griseb., Abh. Königl. Ges. Wiss. Göttingen 19: 255. 1874. Type: Argentina, Tucumán: Cuesta de Anfama, Sierra de Tucumán, 23 Mar 1872, P.G. Lorentz 79 (lectotype: GOET-006649 [image!] designated by Peterson et al. in PhytoKeys 114: 195. 2018; isolectotypes: BAA-00002225 [image!], CORD-00004622 [image!], GOET-006648 [image!], SI-002780 [image!], US-91911 fragm. ex GOET!).

= Muhlenbergia elegans var. atroviolacea Kuntze, Revis. Gen. Pl. 3(3): 357. 1898. Type: Bolivia, Cochabamba, 3000 m, 26 Mar 1892, O. Kuntze s.n. lectotype: NY-00381485 [image!] designated by Peterson et al. in PhytoKeys 114: 195. 2018.

= Muhlenbergia elegans var. subviridis Kuntze, Revis. Gen. Pl. 3(3): 357. 1898. Type: Bolivia, Tunari Mts, 1600 m, O. Kuntze (lectotype: NY-00381486 [image!] designated by Peterson et al. in PhytoKeys 114: 195. 2018).

= Muhlenbergia metcalfei M.E. Jones, Contr. W. Bot. 14: 12. 1912. Type: USA, New Mexico: Grant Co., Santa Rita Mountains, in and around S end of the Black Range, 7000 ft, 9 Oct 1904, O.B. Metcalf 1485 (holotype: POM-116640!; isotypes: GH-00023980 [image!], MO!, US!).

= Muhlenbergia holwayorum Hitchc., Contr. U.S. Natl. Herb. 24(8): 389. 1927. Type: Bolivia, Sorata, 16 Apr 1920, E.W.D. Holway & M.M. Holway 530 (holotype: US-1108445!).

Description.

Densely caespitose perennials. Culms 40-100 cm tall, stiffly erect, glabrous to scaberulous below the basal, terete nodes, usually 1 node per culm; internodes mostly glabrous. Leaf sheaths 2-30 cm long, longer than the internodes, glabrous to scaberulous, rounded near base; ligules (1-)3-6(-8) mm long, often lacerate, firmer below, strongly decurrent, apex obtuse to acute; blades 12-35 cm long, 1-3 mm wide, flat or involute, glabrous to scaberulous below and scaberulous to hirsutulous above. Panicles (4-)10-35 cm long, (2-)3-5(-12) cm wide, loosely contracted to open and lax, sometimes diffuse, reddish-purple; primary branches 0.4-10 cm long, sometimes capillary, ascending and spreading up to 80° from the rachises; pedicels 1-10 mm long, mostly longer than the spikelets. Spikelets 3.5-5 mm long, reddish-purple; glumes 1-1.7(-2) mm long, much shorter than the floret, about equal, 1-veined, unawned, apex obtuse to subacute, sometimes hirsutulous, rarely mucronate; lemmas 3.5-5 mm long, narrow lanceolate, scaberulous to scabrous, purple, awned, callus with hairs up to 0.5 mm long, apex acuminate, the awns (8-)10-22 mm long, flexuous; paleas 3.5-5 mm long, narrow lanceolate, purple, scaberulous, apex acuminate; anthers 1.7-2.3 mm long, reddish-purple. Caryopses 2-3.5 mm long, fusiform, brownish. 2 n = 40, 44.

Distribution.

Muhlenbergia rigida ranges from Arizona, New Mexico, and southwestern Texas, throughout México, Guatemala, and Honduras to South America where it occurs along the Andes from Columbia, Venezuela, Ecuador, Bolivia, Peru, and Argentina ( Peterson et al. 2001).

Ecology.

This species occurs on rocky slopes, ravines, and sandy, gravelly slopes derived from granitic and calcareous substrates associated with Acacia , Agave , Aristida , A. adscensionis , Baccharis , Berberis , Bidens , Bouteloua curtipendula (Michx.) Torr., Caesalpinia , Colletia spinosissima , Cortaderia bifida , C. jubata , Desmodium , Dodonaea viscosa , Ephedra , Eragrostis , Eucalyptis , Eupatorium , Festuca , Fucaria , Hypericum , Jarava , Krameria , Lepechinia , Lupinus , Lycium , Melinus minutiflora , Mirabilis , Opuntia , Paspalum , Cenchrus clandestinus , Peperomia , Puya , Salvia , Schinus molle L., Schizachyrium , Sporobolus , Tillandsia , and Trichocereus ; 2000-3650 m.

Comments.

This species is highly variable and is one of the most common upland bunchgrasses forming almost pure stands in northern México, less common in Peru and South America where it is usually found in smaller populations.

Molecular DNA sequence analysis indicates M. rigida lies within Muhlenbergia subg. Trichochloa and genetically is highly variable ( Peterson et al. 2010b; Peterson et al. 2021).

Specimens examined.

Guatemala. Huehuetenango: upper and off canyon near Huehuetenango, A.A. Beetle 6 (MEXU). Honduras. Francisco Morazán: along road 13 km W of Mateo, R.W. Pohl 12737 (CR). Mexico. Chiapas: Ococingo: a 4 km al S de Ejido Benemérito de las Américas camino a Flor de Cacao, E. Martínez 10785 (ENCB); Arroyo del Rancho Pellizzi, al E de San Cristóbal, A. Méndez 9158 (CIIDIR, MEXU). San Cristóbal de las Casas: 7 km E of San Cristóbal de las Casas, along the road to Zontehuitz, D.E. Breedlove 11155 (ENCB); NE edge of San Cristobal de las Casas, D.E. Breedlove 53858 (NY); Northeast edge of San Cristóbal Las Casas, D.E. Breedlove & G. Davidse 54745 (CAS, MO); East side of San Cristóbal Las Casas, D.E. Breedlove & G. Davidse 52327 (CAS, MO). San Fernando: Sobre cerro ubicado al E de la subestación de CFE, entrada por la zona de extración de arena, carretera Tuxtla-San Fernando, A. López C. 1359 (HEM, MO). Tenejapa: barrio of Yashanal, paraje of Mastab, steep slope along the river of Chik Ha’, D.E. Breedlove 11125 (ENCB). Teopisca: about 15 mi SE of Teopsca on a heavily grazed slope, J.R. Reeder & C.G. Reeder 2029 (ENCB); S edge of Teopisca, D.E. Breedlove & P.H. Raven 13097 (ENCB). Zinacantan: near paraje Nachij, D.E. Breedlove 54703 (NY).

Figures

Figure 13. A-G Muhlenbergia rigida (Kunth) Kunth A habit B inflorescence (narrow) C inflorescence (open) D ligule E glumes F floret G stamens and pistil H Muhlenbergia mucronata (Kunth) Trin. H floret. A, B drawn from P. M. Peterson 9659 (US) C-I drawn from P. M. Peterson, C. R. Annable & J. Valdes-Reyna 10876 (ANSM, US) H drawn from P. M. Peterson & C. R. Annable 10778 (US).