5 MUHLENBERGIA PILOSA (POACEAE: ERAGROSTIDEAE), A NEW SPECIES FROM MEXICO Paul M. Peterson Department ofBotany, National Museum ofNatural History, DC Smithsonian Institution, Washington, 20560 J. K. Wipff and Stanley D. Jones S. M. Tracy Herbarium, Department ofRangeland Ecology and Management, Texas A&M University, College Station, TX 77843 Abstract Muhlenbergia pilosa from Mexico isdescribedand illustrated. Thenewspeciesis distinguished by its densely pilose florets; hirsute internodes; hairy sheath summits; mm membranous,deeplylaceratetoshortciliateligules,0.5-2.5(5.0) long;andawned, pilose,secondglumes.AtabularcomparisonwithM. lucidaSwallenandM. versicolor Swallen is given. Resumen MuhlenbergiapilosadeMexico,sedescribeeilustra. Lanuevaespeciesedistingue por sus flosculos densamente pilosos; entrenudos hirsutos; apice de las vainas pu- bescentes; Hgulas membranaceas, profundamente laceradas a cortamente ciliadas, mm 0.5-2.5(5.0) delongitud;ysegundaglumaaristada,pilosa. Sepresentaunatabla comparativa con M. lucida Swallen y M. versicolorSwallen. The genus Muhlenbergia is represented in Mexico by about 11 species, of which 47% are endemic (Beetle 1987). Morphological characters that delimit the genus are spikelets with single perfect florets and lemmas with three, usually prominent, nerves. There has been considerable floristic work in the state ofMexico (Reiche 1926; Sanchez 1969) and more recently, 22 additions have been reported to the grass flora from the valley ofMexico, including the following four species ofMuhlenbergia: M. hintonii Swallen, M. orophila Swallen, M. polycaulis Scribn., and M. seatonii Scribn. (Herrera 1988). While making routine determinations at TAES the junior authors noted the unusual morphological features ofa new species and sent it to the senior author for clarification. The new species is presented prior to completion ofthe revision ofthe entire genus in Mexico (Peterson in preparation) so others working in that country may become aware ofits existence and perhaps search for additional locations. The specific epithet ofthe new species refers to the dense covering ofepidermal hairs on the dorsal surface ofthe lemma and the palea. Madrono, Vol. 39, No. 2, 150-154, 1992 1 1992] PETERSON, WIPFF&JONES: MUHLENBERGIA PILOSA 15 & MuhlenbergiapilosaP. Peterson, Wipff, S. D. Jones, sp. nov. (Fig. 1).—Type: MEXICO, Mexico, Municipio Tejupilco, 17 km NE ofTejupilco on road to Temascaltepec, 18°59'N, 10°04'W, 30 Oct 1982, S. D. Koch andP. A. Fryxell82256 (holotype, CHA- PA; isotypes, CHAPA, IEB, MEXU, MICH, TAES!, US, XAL). A Muhlenbergia lucida culmis (50)90-130 cm altis, internodiis hirsutis,vaginispilisadapicem,ligulismembranislaciniisadapicem mm mm 0.5-2.5(5.0) longis, antheris 1.3-1.9 longis recedit. Caespitose perennial without rhizomes. Culms (50-)90-130 cm tall, erect, rounded and purplish near base, hirsute just below and above the mostly basal nodes, the hairs appressed; internodes gla- brous to antrorsely scaberulous. Sheaths (5-)20-50(-70) cm long, many times longer than the mostly basal internodes, antrorsely sca- berulous, in age becoming somewhat fibrillate and shredded below, often brown; sheath margins with a few, hyaline hairs, the hairs up mm to 2.5 long and more numerous near the summit. Ligules 0.5- mm 2.5(-5.0) long, delicate, hyaline, deeplylaceratetheentirelength or reduced to a short ciliate membrane in age; apex obtuse to trun- mm cate. Blades 15-35 cm long, 1-3.1 wide, flat to tightly involute, antrorselyscaberulousbelowto scabrousandsparselyhirsuteabove; margins with intermittent hairs. Panicles 20-45 cm long, 3-8 cm wide, somewhat loosely flowered, the ascending branches 0.8-4.7 cm long, purplish, spreading 20-60° from the culm axis with a tuft mm ofhairs in the axils; pedicels 1-7 long, delicate, purplish, short mm hispidulous to glabrous. Spikelets 2.4-3.7 long, erect, 1-flow- mm ered. Glumes (1.8)2.1-3.2 long, shorter to longer than the lem- ma, usuallyequalin length, 1-nerved, pilose on theback, sometimes sparingly near the apex; first glume narrowly lanceolate, unawned, the second more broadly lanceolate, awned; apex acuminate, the awn up to 0.6 mm long, delicate, hyaline. Lemma 2.1-3.7 mm long, lanceolate to oblong-elliptic, 3-nerved, awned, densely pilose on the mm dorsal surface, the hairs up to 1.6 long, whitish; apex acute to acuminate, sometimes minutely bifid with acute teeth, the teeth up mm mm to 0.2 long; lemma awn 18-31 long, flexuous, delicate, mm often purplish. Palea 2.0-3.5 long, oblong-elliptic, 2-nerved, mm densely pilose on the dorsal surface, the whitish hairs up to 1.5 mm long; apex acute to acuminate. Stamens three; anthers 1.3-1.9 mm long, purplish yellow. Caryopsis 1.1-1.4 long, fusiform, light brownish. Chromosome number unknown. Paratypes: MEXICO, Mexico, 5 km NE of Tejupilco on Mex 134 to Temascaltepec, 18°57'N, 100°8'W, 6 Oct 1991, Peterson and Annable 11061 (ANSM, CHAPA, ENCB, IEB, K, MEXU, MO, RSA, TAES, UC, US, UTC, WIS); 26 km NE ofTejupilco on Mex 134 and 2.4 km S ofTemascaltepec, 19°01'N, 100°3'W, 6 Oct 1991, MADRONO 152 [Vol. 39 Fig. 1. Muhlenbergiapilosa, Mexico, Mexico {Koch andFryxell82256). A. Habit. B.Ligule.C.Inflorescence. D. Inflorescencebranch.E.Spikelet.F.Glumes.G.Lower glume, ventral view. H. Upper glume, ventral view. I. Floret. J. Lemma, ventral view. K. Palea, dorsal view. L. Paleaenclosingthe stamens, pistil, andlodicules. M. Caryopsis. 1992] PETERSON, WIPFF&JONES: MUHLENBERGIA PILOSA 153 Table 1. SalientCharactersDistinguishingMuhlenbergiapilosa, M. lucida, ANDM. VERSICOLOR. A4 nilnsn Af. lucidcL A/f vpy^icoloy Culm height (m) (0.5-)0.9-1.3 0.25-0.6 (0.8-)l-1.5(-2) Internode hirsute glabrous to pu- glabrous to puber- berulent ulent Sheath auricles absent absent well-developed Sheath summit hairy puberulent puberulent Blade flat to involute involute folded Ligule delicate below, firm below, en- firm below, entire lacerateabove tire above above Ligule length 0.5-2.5(-5.0) 3-6 (5-)10-22 (mm) Inflorescence spreading 20-60° spreading 20-80° ascendingand ap- branches from culm axis from culm axis pressed Secondglume awned, pilose unawned, pilose awned, scaberu- lous Antherlength 1.3-1.9 2.1-2.4 1.6-2.0 (mm) PetersonandAnnable11072(ANSM,CHAPA, ENCB, IEB, MEXU, MO, US). Distribution, Habitat, and Relationships MuhlenbergiapilosaisknownonlyfromthestateofMexiconorth- eastofTejupilco alongthe road to Temascaltepec. It occurs in open, oak and pine-grass savannahs on steep rocky slopes and roadcuts in clayish soils between 1530 and 1810 m. It is found associated with species ofStevia Cav., Bouteloua Lagasez, Heteropogon Pers., Stipa L., Trachypogon Nees, Pennisetum Rich, in Pers., and Aegopogon tenellus (DC.) Trin., Rhynchelytrum repens (Willd.) C. E. Hubb., Pereilema crinitum Presl, and Muhlenbergia ciliata (Kunth) Kunth. The morphological characters that can consistently be used to dis- tinguish among M. pilosa, M. lucida Swallen, and M. versicolor Swallen are listed in Table 1. Muhlenbergia pilosa differs from the lattertwospeciesbypossessinghirsuteinternodes,hairysheathsum- mits, and membranous, deeply lacerate to short-ciliate ligules, 0.5- mm 2.5(5) long. Muhlenbergia pilosa superficially resembles M. lucida, a species knownonlyfromtheSierraMadreOccidentalofwesternChihuahua (Swallen 1936). Muhlenbergia lucida occurs in a very different hab- itat from M. pilosa. The formeris found on gray to reddish orwhite volcanic pumice, lapilli tuff, and altered rhyolite lava flows in dry rocky sites among boulders at elevations between 2000 and 2600 m (Peterson et al. in review). Characteristics shared by both species are flat to involute leaf blades; whitish, densely pilose florets that are borne on delicate pedicels; and pilose glumes. MADRONO 154 [Vol. 39 The new species seems most closely related to M. versicolor, a member ofsection Epicampes, which ranges in Mexico from Gua- najuato, Michoacan, Morelos, Guerrero, Mexico, Distrito Federal, Veracruz, Oaxaca, and Chiapas to Guatemala and Honduras (Swal- len 1950; Soderstrom 1967; Breedlove 1986). Muhlenbergia versi- color occurs sympatrically with M. pilosa and is found in slightly more mesic sites, in pine-needle or oak-leaflitter. Besides the gross morphological differences observed between the leaf blades, i.e., foldedinM. versicolorversesflattoinvoluteinM.pilosa, theadaxial ribs are angled with a pointed apex in the former and flat-topped with a flattened apex in the latter. Acknowledgments We thank Alice Tangerini for providing the illustration, Socorro Gonzalez E. for preparingtheSpanishabstract, and DanNicolson forcorrectingthe Latindiagnosis. Literature Cited Beetle, A. A. 1987. Noteworthy grasses from Mexico XIII. Phytologia 63:209- 297. Breedlove,D.E. 1986. ListadosfloristicosdeMexicoIV.FloradeChiapas.Institu- to de Biologia (UNAM), Mexico. Herrera, Y. A. 1988. Nuevos registros y nuevascombinacionesdegramineasdel Valle de Mexico. Boletin de la Sociedad Botanica de Mexico 48:19-22. Peterson, P. M., M. R. Duvall, andA. H. Christensen. Allozymedifferentiation among Bealia mexicana, Muhlenbergia lucida, and M. argentea (Poaceae: Era- grostideae). American Journal ofBotany (in review). Reiche, C. 1926. Floraexcursoriaen el ValleCentraldeMexico. TalleresGraficos de la Nacion, Mexico, D.F. Sanchez,O. S. 1969. LafloradelValledeMexico. EditorialHerrero, Mexico,D.F. Soderstrom, T. R. 1967. Taxonomic study ofsubgenus Podosemum and section EpicampesofMuhlenbergia(Gramineae). ContributionsfromtheUnitedStates National Herbarium 34:75-189. Swallen, J. R. 1936. Three new grasses from Mexico and Chile. Journal ofthe Washington Academy ofSciences 26:207-209. . 1950. New Grasses from Mexico, Central America, and Surinam. Contri- butions from the United States National Herbarium 29:395-428. (Received 2 Sept 1991; revision accepted 14 Nov 1991.)