Muhlenbergia tenella (Kunth) Trin., Gram. Unifl. Sesquifl. p. 192. 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

32. Muhlenbergia tenella (Kunth) Trin., Gram. Unifl. Sesquifl. p. 192. 1824.

Fig. 17C-F

Podosemum tenellum Kunth, Nov. Gen. Sp. (quarto ed.) 1: 128. 1816. 1817. Type: México,Veracruz, inter Río Frío et Barranca Honda, F.W.H.A. Humboldt & A.J.A. Bonpland s.n. (holotype: P-Bonpl!; isotypes P!, US-91922! fragm. ex P). ≡ Trichochloa tenella (Kunth) Roem.& Schult., Syst. Veg. 2: 385. 1817. ≡ Polypogon tenellus (Kunth) Spreng., Syst. 1: 243. 1825. ≡ Polypogon gracilis (Kunth) Spreng., Syst. 5: 558 (index).1828. Basionym:

= Muhlenbergia sprengelii Trin., Gram. Unifl. Sesquilfl. 189. 1824. Type: México, F.W.H.A. Humboldt & A.J.A. Bonpland s.n. (holotype: B-W!). ≡ Arundo tenella Spreng., Pl. Min. Cogn. Pug. 2: 6. 1815, nom. Illeg. hom.

= Muhlenbergia exilis E. Fourn., Mexic. Pl. 2: 84. 1886. Type: México, Barranca près Cuernavaca, Iturbide, 14 Nov 1865, E. Bourgeau 1298 (lectotype, designated here: P-00644178 [image!]; isolectotypes: G-00099415 [image!], MPU-026954 [image!], P-00644177 [image!], US-87216!).

Description.

Slender, delicate annuals, sometimes in small tufts. Culms 10-30 cm tall, erect or sprawling, glabrous, branching from the lower and middle nodes; 0.3-0.4 mm diameter just below the inflorescence; internodes 17-36 mm long. Leaf sheaths 12-37 mm long, mostly shorter than the internodes, glabrous or sparsely pilose especially near the apex and along the margins; ligules 0.3-0.9 mm long, a ciliate membrane; apex truncate; margin with a tuft of hairs up to 1 mm long; blades 2-5 cm long, 0.5-2.0 mm wide, flat, often secund or lying to one side of the culm, sparsely appressed pilose pubescent on both surfaces to almost glabrous. Panicles 3.0-12.6 cm long, 0.5-2.5 cm wide, slender, usually included in the upper sheath, terminal, with 7-12 nodes; primary branches 2-4.8 mm long, 1 per node, ascending and appressed to the culm axis, bearing spikelets to their base; pedicels 1-3 mm long, glabrous, to minutely scaberulous, appressed. Spikelets 1.7-2.7 mm long, overlapping, erect; glumes 0.5-1.8 mm long, unequal, mostly glabrous, 1-veined, the single greenish vein antrorsely scabrous; apex acute to acuminate, sometimes minutely pubescent, usually mucronate, the mucro up to 1 mm long; lower glume 0.5-1.3 mm long; upper glume 0.7-1.8 mm long, narrower; lemmas 1.7-2.7 mm long, slender, narrow lanceolate, awned, whitish, strongly 3-veined, veins greenish, the appearance of intermediate “veins” actually rows of short barbs on top of folded epidermal ridges, occasionally ciliate on the lateral veins on upper part but mostly glabrous, the awns 12-26 mm long, flexuous; callus minutely short pubescent; paleas 1.8-2.8 mm long, a little longer than the lemma, narrow lanceolate, glabrous to minutely antrorsely scabrous; anthers 0.4-0.5 mm long, yellowish. Caryopses 1.4-1.6 mm long, narrowly fusiform, light brownish. Cleistogamous spikelets absent. 2 n = 20.

Distribution.

Muhlenbergia tenella occurs throughout México ranging to Central America (Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama) and extending into Columbia ( Peterson and Annable 1991; Peterson et al. 2001).

Ecology.

Individuals of M. tenella are usually restricted to perennial wet rocky cliffs, rock walls, and sandy or rocky places along water courses in tropical and subtropical forests and moist pine-oak woodlands; 250-2400 m.

Comments.

Muhlenbergia tenella can be separated from M. ciliata in having long-awned [12-26 mm long versus (1-)5-11(-18) mm long in the latter), mostly eciliate lemmas, appressed panicle branches, secund leaf blade insertion, and its affinity for perennially wet rocky cliffs and rock walls associated with small drainages ( Peterson and Annable 1991).

Based on DNA sequence analyses Muhlenbergia tenella forms a clade with M. ciliata and M. pectinata in M. subg. Muhlenbergia (Fig. 1 ; Peterson et al. 2010b, 2021).

Specimens examined.

Belize. Cayo: Raspaculo River to Macal River near the junction of both rivers, mixed tropical hardwood forest dominated by secondary species along the side of the river, T. Hawkins 1292 (MO). Costa Rica. Alajuela : Carrillos de Poas , cerca del Rio Poas , A.M. Brenes 17414 (CR); Carrillos de Poas , Old road to Poás, A.M. Brenes 17390 (CR); San Pedro de San Ramon (orillas del Rio Barranca ), A.M. Brenes 21894 (CR); Naranjo, San Juan, R. Ocampo 764 (CR); Atenas, alrededores de las Oficinas Administrativas, Escuela Centroamericana de Ganaderia , J. Gómez 6102 (CR); La Garita, dam on the Rio Grande de Tarcoles , W of Alajuela, R.W. Pohl & G. Davidse 11353 (US, CR); Aguacate, A.S. Oersted 14145 (US), A.S. Oersted 14147 (US), A.S. Oersted 14050 (US); Grecia, E. Anderson 1324 (US). Cartago: Turrialba, Terrenos del Instituto Interamericano de Ciencias Agricolas , J. León 412 (MO); Growing on rocks along the Rio Pacuare , between San Rafael and Moravia, R.W. Pohl & G. Davidse 11476 (CR); Turrialba, Terrenos del IICA, J. León 1485 (CR), 412 (MO); Navarro, 1 km N of Puente Negro, R.W. Pohl & G. Davidse 11184 (US, CR); Tres Rios, H. Pittier 3029 (US, CR). Guanacaste: Cañas, Finca La Pacifica , R. Daubenmire 345 (USJ); Carrillo, J. A. Echeverría 289 (CR); Nicoya, R. Ocampo 757 (CR); Santa Rosa National Park, 30 km NW of Liberia, D. H. Janzen 12267 (MO); Parque Nacional Guanacaste Sector Agua Buena, margen occidental del Rio Animas , A. Chacón et al. 667 (MO, INB, CR); Santa Rosa National Park. Nature trail, forest, R. Liesner 4313 (MO, CR); La Cruz, Quebrada Costa Rica, Santa Rosa National Park, E.J. Judziewicz 4286 (MO, CR); Bagaces, 7 km by road N of Bagaces. Quercus -Curtella savanna on volcanic tuff, R.W. Pohl & M. Lucas 13077 (MO, CR); Deciduous broad-leaf forest with tress to 20 m tall. Between Liberia and Bagaces near the Rio Potrero along the Interamerican hwy, W. Burger & W. Ramirez 4120 (US, CR). Heredia: 5 km al Oeste de San Joaquin de Flores , en un paredón, M. Montiel s.n. (CR); vicinity of horseback-riding facility at Tajo de Cariari , ca. 1 km SE of Ciudad Cariari, along Rio Virilla , M. Grayum 4294 (MO, CR); San Vicente, Bosques residuales en las vegas del Rio Bermudez , J.A. González 2485 (CR). Limón: Salamanca, Telire, R. Ocampo 3893 (CR). Puntarenas: Montes de Oro , low cliffs along the Rio Ciruelas at the Interamerican Hwy, 8 km N of the Puntarenas intersection, R.W. Pohl & G. Davidse 11288 (CR); Cordillera de Tilaran , Monteverde, cliff edge and descending ridge below Hotel de Montana , W. Haber & W. Zuchowski 10893 (CR, MO, INB); Monteverde, 6 km SW Santa Elena on road to Inter American highway. Dry ridge above Rio Lagarto , W. Haber & W. Zuchowski 10155 (INB, MO, CR); Montes de Oro , Quebrada Seca, Cerro Zapotal, Miramar, L. D. Gómez et al. 23988 (MO); Barranca, 1.5 km S of the Puntarenas intersections on the Carretera Interamericana, R. W. Pohl & G. Davidse 11346 (CR). San Jose : Cul-de-sac at N. end of Calle 9, Khan et al. 142 (MO, CR); On walls, Museo Nacional, R.W. Pohl 14168 (MO); Sur un rocher au bord du rio Virilla , sous le pont du F. T. R., près San Juan, A. Tonduz 17557 (CR); Techados y paredones de San Jose , O. Jiménez 50 (CR); San Pedro, near Pulperia La Luz , along Avenida Central, R.W. Pohl & G. Davidse 11248 (US, CR); Acosta, R. Ocampo 1137 (CR); Sur les mur a San Jose , H. Pittier 544 (CR); Sur un rocher au bord d’un ruisseau a La Verbena, pres Alajuelita, A. Tonduz 9086 (US, CR); Toits des maisons a San Jose , H. Pittier (Tonduz, A.) 3015 (US, CR); vicinity of La Verbena, P. C. Standley 32288 (US); Between San Pedro de Montes de Oca and Curridabat, P. C. Standley 32816 (US); San Jose , P.C. Standley 41243 (US); Toiss des maisons a San Jose , A. Tonduz 775 (US); Hills SW of San Jose, E.W.D. Holway 304 (US), 408 (US); San Jose , A.S. Hitchcock 8460 (US), 8501 (US), 8509 (US); San Jose , H. Pittier 33 (US, CR); Acosta, San Ignacio, R.A. Ocampo 792 (CR); Acosta. Bajo Jupa, camino a Bajo Palma, J.F. Morales 7438 (CR. INB); Cuenca del Pirris-Damas . Valle del Rio Candelaria , Quebrada Guápiles, antes del Soslayo, J.F. Morales 11629 (INB, MO). El Salvador. Ahuachapán: San Benito, al E de la vuelta del rio Aguachapio , E. Sandoval & Chinchilla 793 (MO); El Impossible, by Las Positas river , evergreen tropical moist forest, canopy height ca 30 m., A. Monro et al. 1912 (MO); El Impossible, bosque el Pacayito, quebrada La Cascada, W.G. Berendsohn et al. 1332 (LAGU, MO); San Fco. Menéndez, Hda. San Benito, Rio Guayapa , E. Sandoval & Chinchilla 102 (MO); Ahuachapán, S.A. Padilla 133 (US). Chalatenango: La Palma, Recreo Obrero El Refugio, P. Bernhardt & E.A. Montalvo 41 (MO, ITIC). La Libertad: Finca La Giralda , 5 km before Gomasagua, cafetal de sombra orgánica, hasta 12-20 m de alto, dominado por Inga, A. Monro et al. 3080 (MO). Morazán: Arambala, A. P. Sapo, cantón Cumaro, camino a piedra x, R. A. Carballo & J. Monterrosa 935 (MO); L. Lara 240 (MHES); J.F. Morales 14135 (LAGU, MHES); Jocoaitique, rio Araute , sector Las Raices, D. Rodríguez et al. DR-00537 (B, BM, LAGU, MO). San Miguel: Finca El Pacayal, Volcán Chinameca, coffee farm, shade (60%) with low diversity of shade trees, canopy to ca. 12-14 m, A. Monro et al. 2940 (MO). San Salvador : vicinity of San Salvador, P.C. Standley 22410 (MO), 21783 (MO); 19256 (MO); San Salvador, S. Calderón 497 (MO); San Salvador, N.L.H. Krauss 1002 (US). San Vicente : vicinity of San Vicente, P.C. Standley 21208 (US). Sonsonate : vicinity of Sonsonate, P.C. Standley 21783 (MO); Coastal plain, rocks along river, A.S. Hitchcock 8974 (US). Usulután: Laguna de Alegria , cerca de la entrada, D. Williams & R.W. Herrera 361 (MO), 341 (MO), D. Williams s.n. (MO); J. Menjívar et al. 639 (MHES); Laguna de Alegria , D. Williams s.n. (MO). Guatemala. Chiquimula: Quebrada Shusho , above Chiquimula, P. C. Standley 74318 (US). Escuintla: along Rio Guacalate , P.C. Standley 58243 (US). Guatemala: San Raimundo , along National Hwy. 5, between Salamá and Guatemala City (via El Chol ), 2 km past turnoff to San Raimundo (leaving paved road), dry oak forest, T.B. Croat & D.P. Hannon 63517 (MO); Damp wooded barranca 10 km south of San Raimundo , damp shaded bank, P.C. Standley 62868 (US); Fiscal , near Guatemala, W.A. Kellerman 6244 (MO). Santa Rosa: Santa Rosa, Heyde & Lux 3913 (MO). Jutiapa: Hills between Jutiapa and Plan de Urrutia , north of Jutiapa, P. C. Standley 75531 (US). Santa Rosa: Santa Rosa, J. Donnell Smith 3913 (US, MO). Suchitepéquez: Mazatenango , Bernoulli 35 (US). Honduras. Comayagua: Ojo de Agua , orilla Rio Humuya , 30 km N de ciudad Comayagua , bosque de vega tropical rodeado de pinares, C. Nelson et al. 6830 (MO), 7000 (MO); Chichipates , orilla del Rio Yure , bosque tropical de vega; 30 km E Lago Yojoa, pinares y robledales, C. Nelson et al. 6716 (MO); Rio Yure , unión del rio Yure con el Rio Humuya , 100 km NO de Ciudad de Comayagua, bosque tropical de vega húmedo, pinares y robledales, C. Nelson et al. 6113 (MO); Agua Caliente , vaguada de Ríos Chamo y Humuya , 35 km E Lago Yojoa, pinares y robledales, bosque de vega tropical, C. Nelson et al. 6391 (MO); In stream course of Quebrada Cana , 3 km S and W of Las Flores, C.L. Johannessen 59 (US). Copán: Santa Rosa, bosque de pinos, M.E. Villena 22 (MO); Santa Rosa, damp shady places, also rock walls, W.A. Archer 3855 (US); Santa Rosa de Copán, M.E. Villeda 22 (MO). Cortés: Orilla del Rio Humuya , 40 km N Santa Cruz de Yojoa, bosque de vega tropical, C. Nelson et al. 5840 (MO). El Paraiso : 9 km S of Yuscaran, R.W. Pohl & M. Gabel 13441 (MO, CR). Francisco Morazan : San Antonio de Oriente , Campus of Escuela Agricola at El Zamorano , R.W. Pohl 12482 (MO, CR); San Antonio de Oriente , Las Mesas , ca. 5 km E of El Zamorano, near Riachuelo Las Mesas, R.W. Pohl 12520 (MO, CR); Distrito Central , Parque del Cerro El Picacho , pinares, bosque premontano húmedo, V.L. Ochoa 83 (MO); Distrito Central , Cerro el Hatillo, 15 km al NE de Tegucigalpa; bosque premontano húmedo, L.M. Ordóñez 58 (MO): Road toward San Antonio de Oriente , region El Jicarito , above El Zamorano , P.C. Standley 27477 (MO); San Antonio de Oriente , Zamorano , bosque seco subtropical, D. Aguilar S. 38 (MO); San Antonio de Oriente , near Las Mesas L.O. Williams & A. Molina R. 10830 (MO); vicinity of El Zamorano , rocky river banks, Galeras, J. R. Swallen 10775 (US); bosque mixto entre Cuesta de los Muertos y Monte Obscuro , La Montañita, L. O. Williams & A. Molina R. 11161 (US); Drainage of the Rio Yaguare , Rivera del Rio Yaguare cerca de Finca San Francisco, Zamoran, A. Molina 1581 (US); San Antonio del Oriente , moist shady bank, J.R. Swallen 10917 (US); vicinity of Suyapa. Moist bank along road near Suyapa, J.R. Swallen 11294 (US); Foothills of Mt. Uyuca , beyond Las Floras , moist open banks, J.R. Swallen 11297 (US); Carretera a Valle Angeles , 15 km NO de Tega, L. Trochez 219 (US). La Paz : Montana de Opatoro , 36 km SE de Marcala, bosque húmedo subtropical, R. Martínez 284 (MO); Olancho : Juticalpa , Rio Guayapa , between Jutiapa and Concordia, R.W. Pohl & M. Gabel 13762 (MO, CR). Santa Barbara : Alrededores de Santa Barbara , area de Pino-roble de Rio Ulua , A. Molina 3789 (US). Yoro : Victoria , orilla del Rio Sulaco , bosque de vega tropical, C. Nelson et al. 7217 (MO). Mexico. Chiapas. Ocozocuautla, Cañada "El Aguacero". Selva baja. En las laderas del cañón "La Venta", J.J. Ortíz Díaz 1010 (MO). Acala : Wooded slope along the Rio Grijalva , 10 kilometers south of Mexican Highway 190 along the road to Acala at Nandaburri, R.M. Laughlin 2813 (DS). Angel Albino Corzo : slopes of Rio Cuxtepec below Finca Cuxtepec, D.E. Breedlove & G. Davidse 54700 (CAS, MO); slopes of Rio Cuxtepec below Finca Cuxtepec, D.E. Breedlove & G. Davidse 54675 (CAS, MO). Arriaga : 13 km N of Arriaga along Mex. Hwy. 195, D. E. Breedlove 28273 (NY). Chiapa de Corzo : El Chorreadero 5.6 miles east of Chiapa de Corzo along Mexican Highway 190, R.M. Laughlin 2608 (DS). Frontera Comalapa : S of Frontera Comalapa on Mex hwy 211 and 18 mi SW of Jtn 190 and 211, small rocky water course which feeds Rio Grijalva , P.M. Peterson & C.R. Annable 4704 (ARIZ, ENCB, GH, MEXU, MICH, MO, NMC, NY, RSA, TAES, UC, UNLV, US, UTC, WIS, WS); 13 km N of Arriaga along Mex. Hwy. 195, D.E. Breedlove & G. Davidse 54150 (CAS, MO). Ixtapa : 1 km W of Ixtapa, F.W. Gould 12715 (US, MO); along Mex 190 in the Zinacantán paraje of Muctajoc, D.E. Breedlove 13820 (US, DS); near Ixtapa , D.E. Breedlove & G. Davidse 54265 (CAS, MO); at Escopetazo, D.E. Breedlove & G. Davidse 54944 (CAS, MO); at Esc opetazo, D.E. Breedlove & G. Davidse 53944 (CAS, MO). Ocosingo : near El Real , E of Ocosingo, D.E. Breedlove & G. Davidse 56381 (CAS, MO). Ocozocoautla de Espinoza : El Aguacero , canyon of the Rio La Venta , G. Davidse et al. 30071 (MO); El Aguacero en el rio La Venta , E. Martínez 22006 (MEXU). Tonalá: Cerro Vernal [Cerro Bernal], 21 km S of Tonalá, G. Davidse et al. 38123 (MO). Tuxtla Gutierrez : El Zapotal , Ruiz 017 (MEXU); 16 mi W of Pan American Hwy, Carlson 2066 (MICH). Villa Corzo : 65 km S of Mexican Highway 190 on road from Tuxtla Gutierrez to Nueva Concordia, D.E. Breedlove & G. Davidse 54464 (CAS, MO); Above Colonia Vincente Guerrero on road to Finca Cuxtepec, D.E. Breedlove & G. Davidse 54595 (CAS, MO); near Colonia Vicente Guerrero, D.E. Breedlove 48607 (CAS, MO); 58 km S of Mexican Highway 190 on road to Nueva Concordia, D.E. Breedlove 37645 (MO). Nicaragua. Chontales: Hacienda Veracruz , including Cerro La Batea , pasture on rocky slopes and deciduous forest on basaltic mesas, W. D. Stevens 23359 (MO), 23309 (MO); Hacienda San Martin , near confluence of Rio El Jordan and Rio La Pradera ; remnant tall evergreen forest, W.D. Stevens 22862 (MO, CR); Rio El Bizcocho , along road from Juigalpa NE toward La Libertad , ca. 17.4 km NE of Río Mayales, at ford of Rio El Bizcocho ; pastures, gallery forest and steep cliffs S of river, W.D. Stevens 4033 (MO). Granada : shore of Lago de Nicaragua , very dry soil except at water’s edge [Seymour series], J.T. Atwood 1078 (MO). Jinotega : Salto Kayaska , Rio Bocay , among rocks along river to top of hills SW of falls, tall evergreen forest on hill, limestone, W.D. Stevens et al. 16602 (MO). Managua : Tipitapa , 22 km N of Managua [Seymour series], H. Zelaya M. 40A (MO). Matagalpa : Finca La Salvadora , Vuelta del Coyolito , bordeando el Rio Yasica ; zona boscosa, D. Castro C. 2217 (MO). Nueva Segovia : Ocotal , 3 km W of city; mostly in deep ravine along dry river bed [Seymour series], J. T. Atwood 758 (MO), C.E. Nichols 819 (MO). Rivas : Southwest of La Virgen and northeast of San Juan del Sur , route 16 where road crossed brook, km 136 [Seymour series], J.T. Atwood 1174 (MO). Panama. Chiriqui: vicinity of Boquete , from Boquete to 3 mi N., second growth, cultivared areas, and roadside, W.H. Lewis et al. 332 (MO); On rocks along Rio Cuvibora ca. 5 miles N of Tolé on road past Alto Caballero, B. Hammel 6256 (MO); Rio Caldera , NW of Boquete, just S of Horqueta, near a small waterfall, volcanic cliff, P.M. Peterson & C.R. Annable 7375 (MO, US); Cerro Vaca , eastern Chiriqui , in savannas, H. Pittier 5308 (US); Foothills , vicinity of El Boquete , on bare rock, hilltop, A.S. Hitchcock 8316 (US). Cocle : Valley of the upper Rio Mata Ahogado , P.H. Allen 137 (MO), 141 (MO); Hills south of El Valle de Antón, P.H. Allen 2806 (MO) .

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 17. A, B Muhlenbergia phalaroides (Kunth) P. M. Peterson A culm with inflorescence B spikelet C-F Muhlenbergia tenella (Kunth) Trin. C habit D ligule E glumes F floret. A, B drawn from S. Laegaard 71419 (AAU) C-F drawn from P. M. Peterson & C. R. Annable 4755 (US, WS).