Muhlenbergia coerulea (Griseb.) Mez x M. rigida (Kunth) Kunth.

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 : 147

7. Muhlenbergia coerulea (Griseb.) Mez x M. rigida (Kunth) Kunth. Fig. 5E-K

Podosemum angustatum J. Presl, Reliq. Haenk. 1(4-5):229. 1830. Muhlenbergia angustata (J. Presl) Kunth, Enum. Pl. 1: 202. 1833. Type: Peru, Haenke s.n. (holotype: PR-4657!; isotype: PRC-450958 [image!]).

Muhlenbergia phragmitoides Griseb. var. breviaristata Hack., Annuaire Conserv. Jard. Bot. Genève 17: 291. 1914. Muhlenbergia breviaristata (Hack.) Parodi, Physis (Buenos Aires) 9: 219. 1928. Type: Argentina, Tucumán, Lara, 3200 m s.m., 28 Mar 1912, M. Lillo 11322, Herb. T. Stuckert 22470 (holotype: W-1916-0039607!; isotypes: LIL-40186!, US-3412353 fragm. ex W!).

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.

Panicles (-0.6)1-4 cm wide, spike-like with lower branches slightly prolonged, erect, plumbeous to reddish-purple. Spikelets plumbeous to reddish-purple, scabrous; glumes 2.5-3.5(-4) mm long, ½ to ¾ as long as the floret; lemmas 4-6 mm long, awned, the awns generally 3-8(-10) mm long, straight.

Distribution.

This presumed hybrid is known to occur in Argentina, Chile, Colombia, Ecuador, Peru and Venezuela.

Ecology.

The hybrid occurs on gravelly slopes and near cultivated fields in many different plant communities between 2200-3800 m in association with Alnus , Aristida adscensionis L. Baccharis , Berberis , Calceolaria , Cenchrus clandestinus , Eragrostis pastoensis (Kunth) Trin., Festuca , Jarava , Lantana , Lupinus , Muhlenbergia cenchroides , M. phalaroides , M. rigida , Oxalis , Polygala , Puya , Schinus molle L., Schizochyrium and Solanum .

Comments.

As expected, individuals of M. coerulea × M. rigida have an intermediate morphology, such as: lemma awn length [3-8 (-10) mm], glume length (1/2-3/4 as long as the lemma) and spikelet colouration (plumbeous to reddish-purple). In the Flora of Ecuador, Lægaard and Peterson (2001) recognised two intermediate forms ( “intermediate” and “subangustata”) based on lemma awn length, glume length, colour of the spekelets and surface scabrosity of the glumes and lemmas.

There are no molecular studies investigating the population genetics of the hybrid with both presumed parents but we hope to persue this in the future. In our analysis, two samples of M. coerulea from Peru form a pair with little variation and two samples of M. rigida , one from Mexico and the other from Peru, form a pair with little variation in the analysis of seven DNA sequence markers ( Peterson et al. 2010b). Each of these two clades of M. coerulea and M. rigida were not paired but were placed along a comb-like grade in the M. subg. Trichochloa clade. In our new analysis, there are more samples of M. rigida from Mexico and there is greater genetic variability among individuals of this species (Fig. 1 ). However, overall there appears to be low levels of divergence among species in M. subg. Trichochloa , hence the comb-like appearance suggesting rapid speciation ( Peterson et al. 2010b).

Specimens examined.

Peru. Ancash: 10 km towards Casma, S.A. Renvoize & S. Lægaard 5154 (CPUN); E of Yungay, S.A. Renvoize & S. Lægaard 5058 (CPUN); Prov. Asunción, Chacas, A. Cano 14572, M. La Torre & W. Mendoza (USM); Prov. Bolognesi, above Chiquián, E. Cerrate 1549 (US, USM); Prov. Corongo, Ocshmarca, S. Leiva 51 (USM); Prov. Huaylas, Huascarán National Park, Auquispuquio ruins, D.N. Smith 11960, R. Valencia & M. Buddensiek (CPUN, USM); Huascarán National Park, Pueblo Libre, A. Cano 11619 (USM); Pueblo Libre, Antircán, A. Cano 11714 (USM). Apurimac: Prov. Abancay, 48 km SW of Abamcay on road towards Andahuaylas, 13°42'23.6"S, 72°57'20.3"W, 3280 m, 21 Mar 2002, P.M. Peterson & N. Refulio Rodriguez 16650 (US, USM). Ayacucho: Prov. Huamanga, 23 km S of Ayacucho on hwy 3 towards Abancay, 13°16'21.5"S, 74°13'46.8"W, 3575 m, 15 Mar 2007, P.M. Peterson 20490, 20496, R.J. Soreng, K. Romaschenko & D. Susanibar Cruz (US, USM); 27 km S of Ayacucho on hwy 3 towards Abancay, 13°17'9.8"S, 74°13'41.9"W, 3684 m, 16 Mar 2007, P.M. Peterson 20502, R.J. Soreng, K. Romaschenko & D. Susanibar Cruz (US, USM); Prov. Huanca Sancos, 23 km NW of Putajasa on road towards Huanca Sancos, 13°58'11.1"S, 74°18'9.0W, 3800 m, 25 Feb 2002, P.M. Peterson 16272, A. Cano, M. La Torre, A Ramirez & D. Susanibar (US, USM); Prov. Huanca Sancos, 27 km NW of Putajasa and 3 km S of Sacsamarca, 13°57'51.1"S, 74°18'41.5"W, 3650 m, 25 Feb 2002, P.M. Peterson 16273B, A. Cano, M. La Torre, A Ramirez & D. Susanibar (US, USM); Prov. Lucanas, 13 km E of Puquio at km 172 marker, 14°41'18.5S, 74°4'26.8W, 3730 m, 8 Apr 2004, P.M. Peterson & N. Refulio Rodriguez 18207 (US, USM); Ancamarca, L. Vargas & G. Mora 337 (USM). Cajamarca: Prov. Cajamarca, 12 km N of Cajamarca on road toward Bambamarca, 3020 m, 14 Mar 2000, P.M. Peterson & N. Refulio Rodriguez 14860 (CPUN, US, USM); Cajamarca-Bambamarca, 13-18 km from Cajamarca, D.N. Smith & R. Vasquez M. 3441 (MO, US, USM); Chotén, 4 km de la carretera Pacasmayo, I. Sánchez Vega 2570, V. Torrel & E. Medina (CPUN); Porcón, I. Sánchez Vega 51 (CPUN, US); above La Encañada ruta a Celendín, I. Sánchez Vega & W. Ruiz Vigo 1730 (CPUN); Prov. Celendín, La Tranca, I. Sánchez Vega & W. Ruiz Vigo 1815 (CPUN); Prov. Celendín, 4 air km W of Celendín, 6°54'13.5"S, 78°10'8.4"W, 2687 m, 29 Mar 2008, P.M. Peterson 21921 & 21922, R.J. Soreng & J. Montoya Quino (US, USM); 10 km from Celendín towards Rio Marañon, S.A. Renvoize & S. Lægaard 4883 (CPUN); Celendín to Cajamarca, near Quillimbas, S.A. Renvoize & S. Lægaard 4871 (CPUN); Cerro Conturami 10 km from Celendín, S.A. Renvoize & S. Lægaard 4946 (CPUN); Prov. Contumaza, Tres Cruces, A. Sagástegui & M. Fukushima 5119 (US); Celendín-Balsas road, 3-10 km from Celendín, D.N. Smith & I. Sánchez Vega 4300 (MO, US). Cusco: Prov. Calca, 10 km N of Calca on road towards Lares, 13°16'2.9"S, 71°55'20.1W, 3490 m, 17 Mar 2002, P.M. Peterson & N. Refulio Rodriguez 16597 (US, USM); Prov. Santo Tomas, Chumbivilcas, Apr 1982, M.E. Tapia 208 (USM). Huancavelica: Motcca, cerca a Conaica, 3500 m, 1 Apr, 1967, O. Tovar 5889 (USM); Prov. Huancavelica, Pararpuquio, below Conaica, O. Tovar 169 (MOL, US, USM); Sachahuajta, 7 km to Conaica, O. Tovar 950 (US, USM); near Yauli, O. Tovar 2996 (US, USM); Yacu-huanay, O. Tovar 3695 (USM, US); Prov. Tayacaja, Andaimarca, between Colcabamba and Surcubamba, O. Tovar 1821 (US, USM). Huánuco: Prov. de Huánuco, Mitotambo above Mito, R. Ferreyra 9477 (US, USM); Mito, J.F. Macbride 3320 (F, US). Junín: Prov. Huancayo, Paccba, 20 km S of Huancayo, O. Tovar 3294 (US, USM); Cerro La Libertad, O. Verlarde Nuñez 2637 (MOL). La Libertad: Prov. Bolivar, above Longotea, ruta Bolivar, I. Sánchez Vega 5015 (CPUN); Prov. Otuzco, Agallpampa, A. López M. 1041 (US); Trujillo-Huamachuco road, D.N. Smith & R. Vasquez 3309 (MO, USM). Lambayeque: Prov. Ferreñafe, Inkawasi, S. Llatas Quiroz 4114 (USM). Lima: Prov. Canta, 2 km SE of San Jose Canta, 11°30'2.0"S, 76°40'23.4W, 2232 m, 27 Mar 2004, P.M. Peterson & N. Refulio Rodriguez 17984 (US, USM). Piura: 14 km E of Sondor on road towards Tabaconas, 2540 m, 31 Mar 2000, P.M. Peterson & N. Refulio Rodriguez 15160 (CPUN, 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 5. A-D Muhlenbergia coerulea (Griseb.) Mez A habit B culm and panicle C ligule D spikelet E-K Muhlenbergia coerulea (Griseb.) Mez x Muhlenbergia rigida (Kunth) Kunth E culm and panicle F spikelet G floret H glumes I lemma J paleas, dorsal and ventral view K lodicules, stamens, and pistil. A-D drawn from P. M. Peterson, R. J. Soreng & J. Montoya Quino 21957 (US) E-K drawn from P. M. Peterson & N. Refulio Rodriguez 14860 (US).