Poa strictiramea Hitchc. Contr. U.S. Natl. Herb. 17(3): 375. 1913.

Soreng, Robert J. & Peterson, Paul M., 2012, Revision of Poa L. (Poaceae, Pooideae, Poeae, Poinae) in Mexico: new records, re-evaluation of P. ruprechtii, and two new species, P. palmeri and P. wendtii, PhytoKeys 15, pp. 1-104 : 62-65

21. Poa strictiramea Hitchc. Contr. U.S. Natl. Herb. 17(3): 375. 1913. Figs 6 K-M 20 H-L

Type:

Mexico, Chihuahua,cool ledges of La Bufa Mountain above Cusihuiriachic, 2 Sep 1887, C.G.Pringle 1437 (holotype: US-820909!; isotypes: GH!, MA, MSC, NY-431381!, NY-431383!). Poa involuta Hitchc., Proc. Biol. Soc. Wash. 41: 159. 1928. Type: USA, Texas, Brewster Co., on the upper slopes of hills, Chisos Mountains, first ridge southwest of Juniper Canyon, 2200 m, 15-18 Jul 1921, R.S.Ferris & C.D.Duncan 2811 (holotype: US-1125239!; isotypes: CAS!, US-1865159!). Poa filiculmis Swallen, Contr. U.S. Natl. Herb. 29(9): 400. 1950 (non. Roshev. 1949), Poa coahuilensis Beetle, Phytologia 52(1): 17 1982. Type: Mexico, Coahuila,15 km west of Concepcion del Oro, just within the Coahuila, 24°54'N, 101°45'W, valley floor sparsely covered by Yuccas and Larrea , 2300 m, 19 Jul 1941, L.R.Stanford, K.L.Retherford & R.D.Northcraft 477 (holotype: US-1815803!; isotypes: ARIZ-10805!, GH!, MO-1221136!, NY-431379!, NY-431380!).

Description.

Hermaphroditic (often functionally pistillate). Perennials; tufted, tufts dense, usually medium to medium large girth and height (11-30 cm tall), pale green or bluish-grey-green; tillers intravaginal (each subtended by a single elongated, 2-keeled, longitudinally split prophyll), and sometimes extravaginal (basally cataphyllous), all erect, sterile shoots more numerous than flowering shoots. Culms 30-90 cm tall, erect, or bases slightly decumbent, slender, not branching above the base, leafy terete, smooth or lightly scabrous above; nodes (2-)3, terete, upper (0-)1-2 exerted, uppermost at mid-height. Leaves mostly basal; leaf sheaths terete, moderately to densely scabrous, glabrous; butt sheaths papery, smooth, glabrous; flag leaf sheaths 8.5-22 cm long, margins fused 18-48(-75)% the length, fused by an invaginated hyaline margin for much of that length (0.5-)1-3.5 × longer than its blade; collars not flared, smooth or scabrous, glabrous or coarse ciliate; ligules 1.25-4(-6) mm long, adaxially moderately to densely scabrous, apices obtuse, entire or slightly dentate/lacerate, sterile shoot ligules like those of the culm leaves; blades of cauline leaves to 22 cm long, 1-2(-4) mm wide (expanded), involute or initially flat, moderately thick and moderately firm to firm, margins strongly involute, abaxially sparsely to densely antrorsely scabrous all over, adaxially scabrous over the veins and usually between them, sometimes densely so, narrowly prow-tipped; flag leaf blades 28-93(-190)% longer than their sheath, flag leaf blade 4-23 cm long; sterile shoot blades (3-)15-30 cm long, usually involute. Panicles (3-)7-30 cm long, erect to slightly nodding, contracted to eventually open, pyramidal, moderately congested, to spikelets (11-)70 to well over 100, proximal internode 1-5 cm long; rachis with (1-)2-5 branches per node; primary branches spreading initially or tardily, straight or slightly flexuous, angled, mostly densely scabrous mostly on the angles to all around; lateral pedicels averaging ca. 1/2 the spikelet in length, densely scabrous, prickles fairly coarse; longest branches (1-)2-10(-15) cm, with (2-)8-40 spikelets in distal ½. Spikelets 4-7(-7.5) mm long, lanceolate, laterally compressed, not bulbiferous, pale greenish to bluish; florets 2-5, pistillate or hermaphroditic; rachilla internodes terete, 0.8-1(-1.5) mm long, sparsely to densely scabrous, sometimes densely hirtellous; glumes narrowly lanceolate to lanceolate, slightly unequal, distinctly keeled, keels sparsely to densely scabrous for most of the length, lateral veins smooth to moderately scabrous, apical surfaces smooth or lightly scabrous, edges smooth or lightly scabrous, apex sharply acute; lower glumes 2-3.3 mm long, 1-3-veined; upper glumes 2.7-4.3 mm long, mostly 2 × as wide as the lower one, 3-veined; calluses glabrous (rarely dorsally webbed, web scant, with a few short hairs); lemmas 2.7-4(-4.6) mm long, short to long lanceolate, distinctly keeled, smooth or sparsely to densely scabrous, keels and marginal veins glabrous or softly puberulent to short villous, between veins glabrous or infrequently sparsely softly appressed puberulent near the base, intermediate veins moderately prominent to prominent, edges narrowly scarious-hyaline, smooth or with a few short hooks, apices obtuse to acuminate; paleas scabrous over the keels, prickles sub-erect, between keels asperous. Flowers chasmogamous; lodicules 0.4 mm long, ovate; anthers 2.2-2.5 mm long, often aborted late in development and 1-2 mm long (functionally pistillate). Caryopses 1.8-1.9 mm long, fusiform in side-view, slightly laterally compressed, light brown, sulcus narrow, very shallow, hilum 0.2 mm long, round to oval, grain adherent to the palea. 2 n = 28-29, 29+II.

Distribution.

The species occurs in the USA: Texas (Chisos Mountains) and Mexico: Chihuahua, Coahuila, Durango, Zacatecas.

Ecology.

The species is found on steep protected slopes and bases of cliffs derived from igneous and calcareous substrates in the mountains, and the Chihuahuan Desert vegetation from upper creosote bush flats to middle elevations in pine-oak zones, between 1700-2800(-3195) m. The species is probably apomictic, in part, because many of the specimens have sterile, late-aborted anthers. Flowering March to July.

Specimens examined.

Mexico. Chihuahua: 2-3 mi SW of Babicora, on south side of and above road to Madera, 29.2469°N, 107.7659°W, ca. 7000 ft [2135 m], 12 Apr 1984, R.J.Soreng 2304 & R.W.Spellenberg (NMC, US; 2 n = 28+I, 2304a, 2 n = 28-29+I, 2304b, Soreng 2005; Soreng 1990, cpDNA voucher). ca. 20 km SE of Chuatemoch, north side of La Bufa Mountain, Silver mine, 28.2443°N, 106.8039°W, 2050 m, 13 Apr 1984, R.J.Soreng 2308 & R.W.Spellenberg (NMC, US). Coahuila: Cañon de la Hacienda, Sierra de la Madera, northwest of Cuatro Cienega, conifer-oak forest above log-cutters camp, 8000-9000 ft [2440-2745 m], D.Pinkava P1364, McGill, Reeves, & Nash (ASU pistillate). Sierra de Parras, Apr 1905, C.A.Purpus 1146 (NY, GH, NY); ditto, Mar 1905, C.A.Purpus 1112 (GH, NY♂, NY). 9 km south of Parras on Sierras Negras, scrubby woodland association of pine, juniper, oaks, heavily grazed by goats, 2400 m., 3 Jul 1941, L.R.Stanford 167, K.L.Retherford & R.D.Northcraft (DS♀, ARIZ♀, GH♀, MEXU, MO, US). Mina el Aguirreno, north side of Sierra de la Paila, 1700-2200 m, chaparral, very steep slopes of limestone, calcareous gravel, 5 Jul 1973, M.C.Johnston 11706, T.L.Wendt & F.Chiang (MEXU, MO, LL-TEX♀). valley floor, 15 km west of Concepcion del Oro, just within Coahuila, 24°54'N, 101°45'W, 2300 m, 19 Jul 1941, L.R.Stanford 477, R.L.Retherford & R.D.Northcraft (ARIZ, GH, MO, NY, US, Marshall Johnston thinks this may be in Zacatecas, pers. comm. ca. 1986, the habitat is odd for this species or Poa in general, and we suspect it was collected on protected slopes near this vicinity). Durango: Sierra del Rosario, steep limestone sierra with some zones of igneous mineralization, 1800-2655 m, 25 Jun 1973, M.C.Johnston 11463, F.Chiang-C. & T.L.Wendt (CAS, MO, LL-TEX♀); ditto, 11464 (CAS, MEXU, MO, LL-TEX♀). Zacatecas: Sierra del Astillero, SE from Tanque el Alto, 2500-3195 m, limestone, 2 Jul 1973, M.C.Johnston 11566I, T.L.Wendt & F.Chiang-C. (LL-TEX♀); ditto, 11566J (MEXU, LL-TEX♀); ditto, 11566K (LL-TEX♀); ditto, 11566L (LL - TEX♀). Sierra El Astillero, ca. 1.8 mi SW of Santa Rosa and 5.4 mi SW of San Pedro at trail head above water pump, 24°38'5.8"N, 101°6'47.5"W, 2550 m, 21 Oct 2007, P.M.Peterson 21451, J.M.Saarela, & D. Stančik (US).

Discussion.

This species is endemic to the mountains in and around the Chihuahuan Desert. It ranges from the Chisos Mts. of Texas, throughout the drier mountains of Coahuila, to the front ranges of the Sierra Madre Occidental, from northern Chihuahua south to northern Durango and Zacatecas. It is highly variable in stature, leaf form, ligule and spikelet length, but we have found no correlation among the morphological characteristics, geography, and/or substrate type. Ligule length is variable from 0.5 mm in some specimens to 2.5-7.5 mm in others. Spikelet length varies independently of ligule length and blade traits. Soreng (1991b, 524-525) placed Poa involuta and Poa filiculmis in synonymy of Poa strictiramea and discussed the variations. The majority of the collections are functionally pistillate (♀) with anthers aborted late in development, and only one was determined as staminate. The species is presumably apomictic in large part. It differs from Poa palmeri in having scabrous leaf blades that are more often involute, a web absent or of a few short hairs, and lemmas that are glabrous or have sparse or short lemma pubescence. Citations for Nuevo León ( Soreng 1991b, Espejo Serna et al. 2000, Dávila Aranda et al. 2006) are presumably from misidentifications of Poa palmeri (R.L.McGregor 385 et al. at US). One specimen (Gentry 2716 at MO) identified by P.C. Standley in Gentry (1942) as Poa involuta from Memelichi, Chihuahua, initially determined as Poa tracyi , is actually a Trisetum filifolium Scribn. ex Beal. with a very short dorsal awn. Herrera-Arrieta (Grasses of Chihuahua, in prep.) report the following additional specimens from Chihuahua: R.Bye 8242 & W.A.Weber (MEXU); Sierra Mojinora, D. Stančik 6187 & S.Gonzalez (MEXU), G.Nesom s.n. & A.McDonald s.n. (ARIZ), the latter two may prove to be Poa matris-occidentalis .

Figures

Figure 6. A-E Poa gymnantha Pilg. A spikelet B lemma and palea C palea D staminode and lodicules (pistillate-flower) E pistil (pistillate-flower) F-I Poa chamaeclinos Pilg. F spikelet G floret H palea I pistil (pistillate-flower) J Poa palmeri Soreng & P. M. Peterson J spikelet K-M Poa strictiramea Hitchc. K spikelet L floret M palea N-P Poa calycina var. mathewsii (Ball) Refulio N spikelet O floret P palea. A-E drawn from Peterson 12863 et al. from Peru F-I drawn from Soreng 3315 & Soreng; J drawn from Peterson 18790 & Valdes-Reyna K-M drawn from Soreng 3204 & Spellenberg N-P drawn from Beaman 1732.

Figure 20. A-G Poa secunda J. Presl. subsp. secunda A habit B sheath, ligule, blade C inflorescence D spikelet E floret F palea G anthers H-L Poa strictiramea Hitchc. H basal tuft I sheath, ligule, blade, ventral view J inflorescence K spikelet L floret. Drawings A-L from Soreng (2007) H, J, L originally drawn from Swallen 1110 as Poa involuta in Hitchcock (1935).