Muhlenbergia plumbea (Trin.) Hitchc., Contr. U.S. Natl. Herb. 17(3): 296. 1913.

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

24. Muhlenbergia plumbea (Trin.) Hitchc., Contr. U.S. Natl. Herb. 17(3): 296. 1913.

Fig. 18A-E

Vilfa plumbea Trin., Mém. Acad. Imp. Sci. Saint-Pétersbourg, Sér. 6, Sci. Math., Seconde Pt. Sci. Nat. 6,4(1-2): 98. 1840. Type: México, Mineral del Monte, Schlechtendal s.n. (holotype: TRIN-1724.01!; isotype US-557435! fragm. ex LE). ≡ Sporobolus plumbeus (Trin.) Hemsl.. Biol. Cent.-Amer., Bot. 3(19): 546-547. 1885. Basionym.

= Sporobolus pooides Hack., Repert. Spec. Nov. Regni Veg. 10(243-247): 167. 1912[1911]. Type: México, Puebla, Rancho Posada, 2194m, Aug 1910, F.G. Nicolas 5423 (holotype: W1916-0032028 [image!]; isotype: US-87219! fragm. ex W).

Description.

Perennials with slender, scaly rhizomes; rhizome scales 7.5-16 mm long, acute often deteriorating with age. Culms 10-40(-50) cm tall, erect, decumbent near base, little or much branched below, glabrous; internodes 0.4-6 cm long, glabrous, smooth to nodulose-roughened, the nodes green or purple, constricted. Leaf sheaths 1-5 cm long, mostly longer than the internodes, glabrous, margins hyaline; ligules 0.3-0.5(-0.7) mm long, membranous, truncate, decurrent; blades 2-10(-12) cm long, 1-2.4(-3.0) mm wide, flat or folded, glabrous. Panicles 4-9(-14) cm long, 0.5-4(-8) cm wide, open, usually well exerted with 6-12 branches; primary branches mostly 2-8 cm long, ascending and spreading up to 50° from the culm axis, with 3-30 spikelets, widely spaced, naked below, one per node, scabrid; pedicels 0.5-2 mm long, shorter than the spikelets, scaberulous. Spikelets 2.5-3.2(-3.5) mm long, plumbeous; glumes 1-1.6 (-1.8) mm long, shorter than the florets, equal or subequal, the upper often slightly longer than the lower, 1-veined, apex acute; lemmas 2.2-3(-3.3) mm long, lanceolate to ovate, glabrous or occasionally scabrous, faintly 3-veined, dark green, apex acute; paleas 2-2.8(-3.1) mm long, about as long as the lemma, glabrous, faintly 2-veined, apex acuminate; anthers 1.4-2 mm long, dark green or purplish turning yellow with age. Caryopses 1.4-1.6 mm long, ellipsoid, greenish-brown. 2 n = 40 ( Reeder 1967).

Distribution.

In Central America M. plumbea is known only from a single specimen collected in Guatemala. The species is wide ranging in México having been reported in Baja California, Chihuahua, Ciudad de México, Coahuila, Durango, Guanajuato, Hidalgo, México, Michoacán, Puebla, San Luis Potosí, Sonora, Tlaxcala, and Zacatecas. ( Dávila et al. 2018; Sanchez-Ken 2018).

Ecology.

This species occurs in wet depressions and alkaline meadows associated with pine and fir forests but is often collected near cultivated fields; 1800-3050m.

Comments.

Muhlenbergia plumbea is morphologically similar to M. utilis , in Central America known only from Chiapas, the former having longer panicles [4-9(-14) cm versus 1-5 cm] that are usually well exserted (partially included in the upper sheath in M. utilis ) with longer primary branches (2-8 cm versus 0.2-1.2 cm], longer spikelets [2.5-3.2(-3.5) mm versus 1.4-2.4 mm], and longer anthers [1.4-1.6 mm versus 0.7-1.4 mm].

This species has not been included in a molecular DNA sequence study to date but based on morphology it appears allied with the M. filiformis - M. ligularis - M. vaginata clade in M. subg. Bealia or the M. repens (J. Presl) Hitchc.- M. utilis - M. villifora Hitchc. clade in M. subg. Pseudosporobolus (Fig. 1 ; Peterson et al. 2021).

Specimens examined.

Guatemala. Tan abundante como el “Zacachiquin”, 19 Jun 1954, M. de Koninck 31 (US-2151621) .

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 18. A-E Muhlenbergia plumbea (Trin.) Hitchc. A habit B ligule C glumes D floret E stamens and lodicules F-L Muhlenbergia utilis (Torr.) Hitchc. F habit G rhizome H ligule I glumes J floret K stamens, pistil, and lodicules. A-E drawn from C. G. Pringle 9581 (US- 396634) F-L drawn from A, S. Hitchcock 5652 (US).