Muhlenbergia microsperma (DC.) Kunth, Revis . Gramin. 1:64. 1829.

Peterson, Paul M., Vega, Isidoro Sanchez, Romaschenko, Konstantin, Giraldo-Canas, Diego & Rodriguez, Nancy F. Refulio, 2018, Revision of Muhlenbergia (Poaceae, Chloridoideae, Cynodonteae, Muhlenbergiinae) in Peru: classification, phylogeny, and a new species, M. romaschenkoi, PhytoKeys 114, pp. 123-206 : 161

13. Muhlenbergia microsperma (DC.) Kunth, Revis. Gramin. 1:64. 1829. Fig. 7E-H

Trichochloa microsperma DC., Cat. Pl. Horti Monsp. 151. 1813. Muhlenbergia microsperma (DC.) Trin., Gram. Unifl. Sesquifl. 193. 1824, nom. inval. Type: Mexico, cultivated at the botanical gardern at Montpellier from seeds collected in Mexico and distributed by the Botanical Garden of Madrid, M. Sésse & J.M. Mociño s.n. (holotype: MPU; isotypes: G-00099434 [image!], P!, US fragm. ex P!).

Agrostis microsperma Lag., Gen. Sp. Pl. 2. 1816. Type: Mexico, plants grown at H.R. Matritensis (= Herbario del Real Jardín Botánico de Madrid, see Sutherland 1997) from seeds collected by M. Sessé & J.M. Mociño in Nueva Espania, Oct, 1806, M. Sessé & J.M. Mociño s.n. (lectotype, here designated: SEL-H10620 [image!]).

Podosemum debile Kunth, Nov. Gen. Sp. (quarto ed.) 1: 128. 1816. Trichochloa debilis (Kunth) Roem. & Schult., Syst. Veg. 2:385. 1817. Muhlenbergia debilis (Kunth) Trin., Gram. Unifl. Sesquifl. 193, t. 5, f. 18. 1824. Type: Ecuador, Prov. Pichincha, Quito, F.W.H.A. Humboldt & A.J.A. Bonpland s.n. (holotype: P-Bonpl!; isotypes: B-W, P!, US-91924 fragm. ex P-Bonpl!).

Podosemum setosum Kunth, Nov. Gen. Sp. (quarto ed.) 1:129. 1816. Trichochloa setosa (Kunth) Roem. & Schult., Syst. Veg. 2:386. 1817. Agrostis setosa (Kunth) Spreng., Syst. Veg. 1:262. 1825. Muhlenbergia setosa (Kunth) Trin., Gram. Unifl. Sesquifl. 193, t. 5, f. 22. 1824. Muhlenbergia setosa (Kunth) Kunth, Révis. Gramin. 1:63. 1829, isonym. Type: Mexico, between Gueguetoque and Tula, Aug, F.W.H.A. Humboldt & A.J.A. Bonpland 4174 (holotype: P-Bonpl!; isotypes: B-W, US-91917 fragm. ex P-Bonpl!).

Muhlenbergia purpurea Nutt., J. Acad. Nat. Sci. Philadelphia, ser. 2, 1:186. 1848. Type: U.S.A., California, Santa Barbara Co., Santa Barbara and Santa Catalina Island, Gambel s.n. (holotype: K!).

Muhlenbergia ramosissima Vasey, Bull. Torrey Bot. Club 13(12):231. 1886. Type: Mexico, Chihuahua, SW Chihuahua, Aug–Nov 1885, E. Palmer 158 (lectotype: NY-00381467! designated by Hitchcock, N. Amer. Fl. 27:441. 1935, but without indicating the specific specimen; Peterson and Annable, Syst. Bot. Monogr. 31:61. 1991, indicated the specific specimen; isolectotypes: LE!, GH-00024043 [image!], MO-2974152!, NY-00381468 [image!], P-00644106!, PH-00018772 [image!], US-995580!, W-19160027660 [image!]).

Description.

Caespitose annuals, sometimes appearing as short-lived perennials. Culms 10-80 cm tall, often geniculate at the base, slender, often striate, much branched near the base, scaberulous below the nodes; internodes 1.8-8.6 mm long, mostly scaberulous or smooth. Leaf sheaths 2.2-6.6 mm long, commonly shorter than the internodes, glabrous, smooth or scaberulous; ligules 1-2 mm long, membranous to hyaline, decurrent, margins often extended, apex truncate to obtuse; blades 3 –8.5(– 10) cm long, 1-2.5 mm wide, flat or loosely involute, scabrous below, strigulose above, often deciduous with age. Panicles 6.5-13.5 cm long, 1-6.5 cm wide, open and not densely flowered, often purplish; primary branches 1.6-4 cm long, ascending or diverging up to 80° from the rachises, spikelet-bearing to the base; pedicels 2-6 mm long, appressed to divaricate, antrorsely scabrous. Cleistogamous panicles with 1-3 spikelets present in the axils of the lower sheaths. Spikelets 2.5-5.5 mm long; glumes 0.4-1.3 mm long, exceeded by the florets, 1-nerved, obtuse, often minutely erose; lower glumes 0.4-1 mm long; upper glumes 0.6-1.3 mm long; lemmas 2.5 –3.8(– 5.3) mm long, narrowly lanceolate, mostly smooth, scaberulous distally, lower 1/2 of the margins and midveins, the hairs 0.2-0.5 mm long, the callus hairy, apices acuminate, often bidentate, awned, awns 10-30 mm long, straight to flexuous; paleas 2.2-4.8 mm long, narrowly lanceolate, acuminate; anthers 0.3-1.2 mm long, purplish. Caryopses 1.7-2.5 mm long, fusiform, reddish-brown. 2 n = 20, 40, 60.

Distribution.

Muhlenbergia microsperma occurs in Hawaii, south-western U.S.A., Mexico, Guatemala, Colombia, Venezuela, Ecuador (including the Galapagos Islands), Peru and Bolivia ( Peterson and Annable 1991).

Ecology.

Rocky slopes, rock outcrops, sandy drainages, cliffs and disturbed roadsides usually in desert scrub vegetation with Acacia , Aristida adcensionis L., Baccharis , Bothriochloa , Bombacaceae , Cactaceae , Dodonaea viscosa , Eragrostis nigricans , E. lugens Nees, Fucraea , Heliotropium , Heteropogon contortus (L.) P. Beauv. ex Roem. & Schult., Lantana , Muhlenbergia rigida , Pitcairnia , Prosopis , Puya , Salvia , Schinus molle and Schizachyrium ; 1150-3500 m.

Comments.

Muhlenbergia microsperma can sometimes be confused with M. romaschenkoi and differs from it by having cleistogamous panicles in the axils of the lower sheaths and shorter, obtuse glumes, 0.4-1.3 mm long (glumes acute to acuminate, 2-2.8 mm long in M. romaschenkoi ).

In a molecular DNA sequence study, M. microsperma forms a strongly supported clade with two other annuals, M. appressa C.O. Godding and M. brandegei C.G. Reeder, all members of M. subg. Muhlenbergia (Fig. 1B ; Peterson et al. 2010b). These three species produce cleistogamous spikelets in the axils of the lower culm branches, enclosed by a sheath ( Peterson and Annable 1991). Cleistogamous spikelets appear to have evolved twice within Muhlenbergia , once in M. subg. Muhlenbergia within the M. appressa - M. brandegei - M. microsperma clade and once in M. sect. Pseudosporobolus in M. cuspidata (Torr. ex Hook.) Rydb. ( Morden and Hatch 1984; Peterson et al. 2010b).

Specimens examined.

Peru. Ancash: at the Rio Yanamayo crossing, 57 km N of San Luis on road towards Pomabamba, 2540 m, 24 Mar 1997, P.M. Peterson & N. Refulio Rodriguez 13896 (US, USM); 68 km from Casma towards Huaraz, 1700 m, 4 Apr 1988, S.A. Renvoize & S. Lægaard 5047 (CPUN, K); Pallasca, divide between Rio Conchucos and Rio Plata, low end of road up to Pampas from Rio Conchucos, above Mollapata crossing of Rio Tablachaca, 8°12'9.1"S, 77°56'20.6"W, 2233 m, 21 Mar 2008, P.M. Peterson & R.J. Soreng 21833 (MO, US, USM). Apurimac: Aymaraes, 16 km NW of Chalhuanca, 14°10'16.4"S, 73°19'26.1"W, 2670 m, 14 Mar 2002, P.M. Peterson & N. Refulio Rodriguez 16511 (US, USM); Chincheros, canyon of Rio Pampas, between Ayacucho and Abancay on hwy 7, 7 km S of bridge over Rio Pampas, 13°28'42.1"S, 73°49'32"W, 2049 m, 17 Mar 2007, P.M. Peterson, R.J. Soreng, K. Romaschenko & D. Susanibar Cruz 20535 (MO, US, USM). Ayacucho: alrededores de Huanta, 2400 m, 30 Apr 1964, O. Tovar 4829 (US, USM). Cajamarca: Cajabamba, WSW of Cajabamba, 14 air km E of Araqueda, 7°39'9.1"S, 78°9'58.9"W, 2242 m, 23 Mar 2008, P.M. Peterson & R.J. Soreng 21855 (US, USM); Cajamarca, Cerro Huacaris, valle de Cajamarca, 1 Jun 1971, I. Sánchez Vega 726, W. Ruiz Vigo & J. Tejada (CPUN); Cajamarca, abajo de San Juan, siguiendo la carretera Cajamarca–Pacasmayo, 1900 m, 18 May 1986, I. Sánchez Vega 4072 (CPUN); Cajamarca, entre San Juan y Magdalena, 1800 m, 15 May 1971, I. Sánchez Vega 657 & W. Ruiz Vigo (CPUN); entre Chancay y Valle de Condebamba, 2600 m, 6 May 1972, I. Sánchez Vega 944, W. Ruiz Vigo & M. Malpica R. (CPUN); Dist. Ichocán, en el Arboretum Ichocán II de CICAFOR, entre la localidad de Chacay y Valle Condebamba, 2450 m, 29 Mar 1981, I. Sánchez Vega 2409, V. Torrel & E. Medina (CPUN); Celendin, Marañón River Valley, Chachapoyas-Cajamarca road, 1900 m, 28 May 1984, D.N. Smith & J. Cabanillas 7254 (MO, US); Chota, Dist. Cochabamba, a 1km sobre la carretera Cochabamba–Cutervo, 1720 m, 15 Jun 1980, I. Sánchez Vega 2288 (CPUN). Cusco: Anta, Sisal, Limatambo, 2300 m, 15 Mar 1963, C. Vargas C. 14327 (US, USM); Anta, Sisal-Cunyaee, 2100 m, 14 May 1965, C. Vargas C. 16316 (US, USM). Huancavelica: Salcabamba-Colcabamba, camino a Pampas, 2000 m, 22 Apr 1962, O. Tovar 3834 (US, USM); Tayacaja, alrededores de Mayoc, 2400 m, 9 Apr 1966, O. Tovar 5589 (US, USM). Huánuco: Huánuco, W side of canyon of Rio Huallaga, S of Ambo, 7 km on hwy 3 towards Cerro de Pasco, 10°11'49"S, 76°9'54"W, 2345 m, 6 Mar 2007, P.M. Peterson, R.J. Soreng & K. Romaschenko 20326 (US, USM); Huánuco, 2125 M, 25 Apr 1923, J.F. Macbride 3514 (F, US); 5 Apr 1923, J.F. Macbride 3217 (F, US). La Libertad: Bolivar, 4.6 air km NW of Longotea, SE of San Vicente on road from Balsas to Longotea, 7°0'38"S, 77°54'15.2"W, 2058 m, 31 Mar 2008, P.M. Peterson, R.J. Soreng & J. Montoya Quino 21970 (MO, US, USM); Otuzco, Quirrpe-Membrillar, 1150 m, 7 Dec 1952, A. López Miranda 927 (US); Santiago de Chuco, 22 km E of Huamachuco on road towards Sarin above Rio Chusgon, 2500 m, 29 Mar 1997, P.M. Peterson & N. Refulio Rodriguez 13973 (US, USM). Lima: Canta, 2 km SE of San Jose Canta, 11°30'2"S, 76°40'23.4"W, 2232 m, 27 Mar 2004, P.M. Peterson & N. Refulio Rodriguez 17985 (MO, US, USM); Huarochiri, Matucana, 2430 m, 12 Apr 1922, J.F. Macbride & Featherstone 392 (F, US); Huarochiri, km 70 carretera Lima-Oroya, 1800 m, 15 May 1963, R. Ferreyra 14892 (US, USM); km 68, cerca Surco, entre Chosica y Matucana, 1400 m, 27 Mar 1955, R. Ferreyra 10498 (US, USM); km 72 de la carretera Lima-Oroya, cerca de Surro, 1800 m, 14 May 1948, R. Ferreyra 3485 (MOL, US, USM); Prov. Lima, above Paya, E. Asplund 10825 (NY). Piura: Huancabamba, 10 km N of Sondor and 3 km S of Huancabamba, 1860 m, 1 Apr 2000, P.M. Peterson & N. Refulio Rodriguez 15167 (CPUN, MO, US, USM). Tacna: Zarata, Sitiqui, 3500 m, 7 Apr 1959, C. Vargas C. 12588 (US, USM).

Figures

Figure 1. A, B Maximum-likelihood 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 red occur in South America; scale bar = 2 %.

Figure 7. A-D Muhlenbergia diversiglumis Trin A habit B ligule C glumes D floret E-H Muhlenbergia microsperma (DC.) Kunth E habit F ligule G glumes H lemma. Drawings from Peterson and Annable (1991) A-D drawn from P. M. Peterson & C. R. Annable 4158 (WS) F-H drawn from P. M. Peterson & C. R. Annable 4185 (WS).