Muhlenbergia spiciformis Trin., Mem . Acad. Imp. Sci. Saint-Petersbourg . Ser . 6, Sci. Math., Seconde Pt. Sci. Nat. 6,4(3-4): 288. 1841. (Fig. 14, E-I).

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

31. Muhlenbergia spiciformis Trin., Mem. Acad. Imp. Sci. Saint-Petersbourg. Ser. 6, Sci. Math., Seconde Pt. Sci. Nat. 6,4(3-4): 288. 1841. (Fig. 14, E-I).

Fig. 21A-E

= Muhlenbergia acutijolia E. Fourn., Mexic. PI. 2:86. 1886. Type: México, Veracruz, Orizaba, 8 Nov 1866,M. Bourgeau 3327 (holotype: P!; isotypes: MO-2974301!, US-87235! fragm! US-2561240!).

= Muhlenbergia parviglumis Vasey, Contr. U.S. Natl. Herb. 3(1):71. 1892. Type: U.S.A., Texas, 1887, G.C. Nealley s.n. (holotype: US-81638!; isotype: US-994967!).

Type.

México, "Southern México,” Karwinsky s.n. (lectotype: W-0002567! designated by Peterson et al. 2007b in J. Bot. Res. Inst. Texas 1(2): 989; isolectotype: LE fragm!) .

Description.

Caespitose perennials, often short-lived and appearing as annuals. Culms 25-80 cm tall, erect, slender and wiry, freely branching at the base, strigose to glabrous below the nodes; internodes mostly glabrous, usually 4-8 nodes per culm. Leaf sheaths 3.5-12 cm long, shorter than the internodes, scaberulous; ligules 1-3 mm long, deeply lacerate, margins hyaline, apex acuminate; blades 2-12 cm long, 1-3 mm wide, flat to involute, hirsutulous to scabrous above and scaberulous below. Panicles 4-18(-20) cm long, (0.6-)l-2.8 cm wide, narrow, contracted, sometimes interrupted below, loosely flowered; primary branches 0.6-5 cm long, ascending and appressed occasionally spreading up to 30° from the rachises; pedicels 0.1-3.0 mm long. Spikelets 2.8-4 mm long, erect; glumes 0.3-1.0 mm long, less than 1/2 as long as the lemma, 1-veined, unequal, apex obtuse to acute, sometimes erose; lower glumes shorter than the upper glumes; lemmas 2.8-4 mm long, narrowly lanceolate, awned, purplish, scabrous roughened, sparsely appressed-pubescent on the calluses and lower 1/4 of the midveins and margins, the hairs less than 0.3 mm long, apex acuminate, the awn (10-)20-40 mm long, straight to flexuous; paleas 2.6-3.9 mm long, narrowly lanceolate, sparsely pubescent between the veins on the basal 1/3, apex acuminate, scabrous; anthers 0.9-1.6 mm long, purplish. Caryopses 2-2.6 mm long, fusiform, brownish. 2 n = 40.

Distribution.

This species ranges from the southwestern United States south to México (Chiapas, Chihuahua, Coahuila, Hidalgo, Nuevo León, Oaxaca, Puebla, Queretaro, San Luis Potosí, Tamaulipas, Tlaxcala, Veracruz) [ Peterson et al. 2007b; Sanchez-Ken 2018)].

Ecology.

Muhlenbergia spiciformis grows on rocky slopes, cliffs, and calcareous rock.

outcrops, often in thorn-scrub and open woodland communities associated with Quercus ssp., Pinus ssp., P. cembroides , Juniperus deppeana , Pseudotsuga menziesii , Abies , Cupressus , Agave , Ceanothus , Acacia , Salvia , Arbutus , Opuntia and Fraxinus ; 450-2800 m.

Comments.

In addition to being morphologically similar to M. setarioides (see earlier comments under M. setarioides ), M. spiciformis can be confused with M. microsperma but differs in not having cleistogamous spikelets in the axils of the lower culm branches, panicles narrow, contracted, 0.6-2.8 cm wide (1-6.5 cm wide in M. microsperma ) primary branches spreading up to 30° from the rachises (primary branches spreading up to 80° from the rachises in M. microsperma ), and ligules acuminate (truncate to obtuse in M. microsperma ) [ Peterson et al. 2007b].

Muhlenbergia spiciformis is a member of M. subg. Muhlenbergia and is sister to the M. romaschenkoi - M. Muhlenbergia tenuifolia pair in a recent biogeographical study based on DNA sequence analysis ( Peterson et al. 2021).

Specimens examined.

Mexico. Chiapas: Comitán de Domínguez: Laguna Chamula microwave station, 4 km SW of Highway 190 between Comitán and Amatenango del Valle, D.E. Breedlove & G. Davidse 54857 (CAS, MO). Jilotol: 10 km N of Jitotol near Rio Hondo, D.E. Breedlove & G. Davidse 55151 (CAS, MO). La Trinitaria: along Mexican Highway 190, 3 miles south of La Trinitaria, D.E. Breedlove & P.H. Raven 13235 (DS, US). San Cristobal de las Casas: NE edge of San Cristobal de las Casas, D.E. Breedlove & G. Davidse 54748 (NY, CAS, MO); Northeast edge of San Cristóbal Las Casas, D.E. Breedlove & G. Davidse 54722 (CAS, MO); W edge of San Cristobal Las Casas, D.E. Breedlove & G. Davidse 53980 (CAS, MO, US); About 2 miles SE of San Cristóbal, J.R. Reeder & C.G. Reeder 6066 (MO); Grassy slope of Cerro San Cristóbal, R.M. Laughlin 1761 (DS).

Figures

Figure 21. A-E Muhlenbergia spiciformis Trin. A habit B ligule C glumes D floret E stamens, pistil, and lodicules F-J Muhlenbergia setarioides E. Fourn. F habit G ligule H glumes I floret J stamens, pistil, and lodicules. A-E drawn from P. M. Peterson & C. R. Annable 8361 (US) F-J drawn from D. E. Breedlove 9350 (US).