Muhlenbergia mucronata (Kunth) Trin., Gram. Unifl. Sesquifl. 194, t. 5, f. 23. 1824.

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

17. Muhlenbergia mucronata (Kunth) Trin., Gram. Unifl. Sesquifl. 194, t. 5, f. 23. 1824.

Fig. 13H

Podosemum mucronatum Kunth, Nov. Gen. Sp. 1:129. 1815 (1816). Type: México, Guanajuato, crescit in mountains prope Cerro de Serna, Santa Rosa et Los Ioares, 1270-1360 hexap (2318-2482 m). Sep, F.W.H.A. Humboldt & A.J.A. Bonpland s.n. (holotype: P!; isotypes: BAA-00003945 [image!], BM-000938659 [image!], US-91925! fragm. ex P-Bonpl. y photo). ≡ Agrostis mucronata (Kunth) Spreng., Syst. Veg. 1:262. 1825 ≡ Trichochloa mucronata (Kunth) Roem. & Schult., Syst. Veg. 2:387. 1817. Basionym.

= Muhlenbergia laxiflora Scribn., Zoë 4:389. 1894. Type: México, Baja California Sur, La Chuparrosa, 17 Oct 1893, T.S. Brandegee 74 (lectotype designated by A.S. Hitchcock, Contr. U.S. Natl. Herb. 17: 298. 1913: UC-122474!; isolectotypes: NY-00381444 [image!], US! fragm.ex UC).

Description.

Densely caespitose perennials. Culms 75-100(-120) cm tall, erect, scabrous or strigulous below the nodes, rounded near base. Leaf sheaths shorter than internodes, glabrous or scaberulous, purplish in part, rounded below; ligules (2-)5-8 mm long; blades 20-40 cm long, 2-3 mm wide, flat or loosely involute, scabrous abaxially, scabrous on ribs adaxially, attenuate into a long apex. Panicles (5-)10-15(-20) cm long, 1-3(-6) cm wide, oblong-cylindrical, spreading, purple, rarely purplish-green; primary branches 4-8(-10) cm long, ascending or appressed; pedicels 1-3 mm long, usually shorter than the spikelets, slender, scabrous below spikelets. Spikelets (4-)4.5-5 mm long; glumes 1.5-2 mm long, acute, subequal, scabrous near the apex; lemmas (4-)4.5-5 mm long, scaberulous between veins, mucronate or shortly awned from 2 minute teeth, the mucro or awn 0.5-1(-2) mm long; callus hairy, the hairs 0.5-0.7 mm long; paleas about as long as the lemma, scabrous between the veins, apex acute or acuminate; anthers 2-2.2 mm long, purplish. Caryopses 2-2.5 mm long, about 0.5 mm wide, ellipsoid, reddish-brown.

Distribution.

This Mexican endemic is known from: Baja California and Chihuahua in the north throughout central México to Oaxaca, Veracruz, and Chiapas in the south (Herrera Arrieta and Peterson 2018).

Ecology.

Muhlenbergia mucronata grows in oak-pine forests at elevations of 1350-2650 m.

Comments.

Muhlenbergia mucronata is morphologically similar to M. rigida , differing from the latter in having mucronate to short-awned lemmas, narrower panicles, and usually shorter pedicels.

Muhlenbergia mucronata is a member of M. subg. Trichochloa and pairs with M. subaristata Swallen in a recent biogeographical analysis based on plastid and nuclear DNA sequences (Fig. 1 ; Peterson et al. 2021).

Specimens examined.

Mexico. Chiapas: San Cristóbal de las Casas: 7 km E of San Cristobal las Casas in road to Zontehuitz, D.E. Breedlove 11153 (US-3113121, US-3113122). Tenejapa: along river Chik Ha, barrio of Yashanal, D.E. Breedlove 11125 (US-3113120). Zinacantán: along hwy 190 at Granadilla, D.E. Breedlove 10607 (US-3113119), D.E. Breedlove 52324 (CAS) citado en Flora Mesoamercana.

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 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).