Poa orizabensis Hitchc. Contr. U.S. Natl. Herb. 17(3): 374 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 : 39-41

14. Poa orizabensis Hitchc. Contr. U.S. Natl. Herb. 17(3): 374 1913. Figs 13 M-O 14

Type:

Mexico, Puebla, Mt. Orizaba, bald hill, 13,000 ft [3940 m], spreading, infrequent, 17-18 Aug 1910, A.S.Hitchcock 6254 (holotype: US-691227!; isotype: ISC-66032!).

Description.

Hermaphroditic. Perennials; tufted, tufts usually dense, generally medium small girth and height ([5-]10-20 cm tall), green to bluish-grey-green; tillers all or mainly extravaginal (basally cataphyllous), without lateral or downward tending, cataphyllous shoots, or with very short thin ones, sterile shoots more numerous than flowering shoots. Culms 25-60 cm tall, erect or loosely ascending, leafy, terete or weakly compressed, smooth; nodes 2-3, 1-2 exerted. Leaf sheaths strongly compressed, smooth, glabrous; butt sheaths becoming papery to somewhat fibrous, bases of butt sheaths glabrous; flag leaf sheaths 12-18 cm long, margins fused ca. 35% their length, ca.4 × longer than its blade; throats and collars smooth or slightly scabrous, glabrous; ligules 1.6-2 mm long, not decurrent, scarious, white, abaxially moderately to densely scabrous, upper margin erose to denticulate, asperous, apex truncate to obtuse to acute, sterile shoot ligules to 0.5 mm long, mostly shorter than those of the upper culm; blades 1-15 cm long, 2-4 mm wide, folded, somewhat thick and firm, margins involute, abaxially smooth or distally lightly scabrous, margins densely scabrous, adaxially nearly smooth or distinctly scabrous above costae, apex distinctly prow-tipped; flag leaf blades 1-3.5 cm long; sterile shoot blades like those of the culm. Panicles 7-13 cm long, erect or nodding, open, spreading or drooping, with 50-100 spikelets, peduncle scabrous, axis scabrous, proximal internode 1.5-3.8 cm long;; rachis with 1-2(-3) branches per node; primary branches spreading, slender, flexuous, slightly angled, proximally sparsely to moderately scabrous, distally densely scabrous on the angles lightly between them; lateral pedicels usually 1/4-1/2 the spikelet in length, sparsely to moderately scabrous angled, prickles coarse to moderately coarse, sometimes with papillae about the juncture with the glumes; longest branches 2-7 cm, with 10-25 spikelets crowded in distal 1/2. Spike lets 2.5-4.5 mm long, 2-3 × as long as wide, ovate, strongly laterally compressed, not bulbiferous, strongly anthocyanic; florets (1-)2(-4), hermaphroditic; rachilla internodes terete, mostly 0.4-0.8 mm long, smooth or muriculate, glabrous; glumes lanceolate, broadly lanceolate, or ovate, strongly anthocyanic, subequal, distinctly keeled, proximally smooth to scabrous most of the length, distally scabrous on the keel and lateral veins, margins narrowly scarious-hyaline, edges smooth or sparsely asperous, apex acute; lower glumes 2.5-3.2 mm long, (1-)3-veined, 2/3-4/5 the lower lemma in length, lanceolate to broadly lanceolate; upper glumes 2.5-4.2 mm long, slightly shorter to slightly longer than the lowest lemma, 3-veined; calluses dorsally webbed, web scant, hairs 0.5-1 mm long, woolly; lemmas 2.7-3.4(-3.8) mm long, 5-veined (lowest sometimes 7-veined), ovate to broadly lanceolate, 2.6-4.2 × longer than wide, body firmly chartaceous, green below, apically anthocyanic, strongly keeled, keel and lateral veins and sparsely to densely scabrous, surfaces distally sparsely to moderately scaberulous, keel usually, and marginal veins sometimes, near the base sparsely puberulent, main lateral veins distinct, margins and apex narrowly white scarious to hyaline, apex entire, obtuse to acute; paleas glabrous, keels scabrous for most of the length. Flowers weakly chasmogamous; lodicules 0.35-0.4 mm long, broadly lanceolate, apex obtuse, blunt, with a broad lateral lobe; anthers 0.8-1.1(-1.25) mm long. Caryopses 1.5 mm long, elliptical in side-view, laterally compressed, light olivaceous-brown, sulcus distinct, hilum 0.2 mm long, oval, grain adherent to the palea. 2 n = unknown.

Distribution.

The species occurs in Mexico in the states of Mexico, Puebla, and Veracruz; and Guatemala.

Ecology.

This species occurs in subalpine to low alpine meadows and slopes of volcanoes, between (2700-)3000-4300(-4570) m. Flowering July through September.

Conservation status.

The species is endemic on the slopes of two volcanoes in Mexico where it is locally common. The disposition of some specimens from the Departamento of Huehuetenango, Guatemala, requires further study.

Specimens examined.

Mexico. Mexico: Popocatepetl, 12000 ft [3660 m], 5-6 Aug 1910, A.S.Hitchcock 5988 (US). 9000-10000 ft [2725-3050 m], 5-6 Aug 1910, A.S.Hitchcock 6004 (US). Paso de Cortes, 3680 m, 17 Sep 1958, J.H.Beaman 2564 (MEXU). P.N. Izta-Popo, 8 Jul 1980, A.A.Beetle M-5190 (MEXU). Municipio de Tlalmanalco, region de la cabeza del Ixtaccihuatl, La Cienega, 3600 m, 18 Jul 1982, J.Rzedowski 37857 (MEXU). 17 km by road east of Amecameca highway 115 jct., W of Paso del Cortez, 19.097°N, 98.683°W, 3325 m, 2 Oct 1987, R.J.Soreng 3307 & N.Soreng (US). SW flank of Ixtaccihuatl 1 km N of La Joya Trail Head, 19.1507°N, 98.6525°W, 3965 m, 2 Oct 1987 R.J.Soreng 3312 & N.Soreng (US). Paso del Cortez between Popo and Ixtaccihuatl, 19.0858°N, 98.6471°W, 3660 m, 3 Oct 1987, R.J.Soreng 3314 & N.Soreng (DNA barcode voucher, unpublished, and Soreng 1990 cpDNA voucher). Municipio Ixtaccihuatl, Estacion Experimental de Investigation y Ensenanza de Zoquiapan, 8 km south de Rio Frio, Llano Colecto, 3350 m, 12 Sep 1975, S.D.Koch 75519 (TEX). Puebla: Pico de Orizaba, southwest side of mountain in Cañada, 3770 m, 10 Sep 1958, J.H.Beaman 2511 (MEXU, toward Poa ruprechtii ). Sierra Negra, SE of Pico de Orizaba, east side of mountain, sandy gravelly soil in grassy meadow on moderately steep slope above timberline, ca. 4200 m., 10 Sep 1958, J.H.Beaman 2517 (TEX, US, WIS, toward Poa ruprechtii ). 23 road km above Tlatlachichua, ca. 6 km NNW of Pico de Orizaba, near head of Rio Quatzalapa, ca. 2 km SW of Cerro Mihas, 19.086°N, 97.288°W, 3660 m, 4 Oct 1987, R.J.Soreng 3325 & N.Soreng (US). Municipio Cholula, 30 km E de Cholula, 3000 m, 30 Jun 1989, P. Dávila 391, P.Tenorio & J.Sanches-Ken (MEXU). Ixtaccihuatl, south side of mountain, ca. 6 km N of Paso de Cortes, ca. 3900 m, 18 Jul 1959, J.H.Beaman 2874 (US). Puebla or Veracruz: Mt. Orizaba, 14-15000 ft [4265-4570 m], 25-26 Feb 1892, J.G.Smith 571 (NY). Rio Frio (Camino de Puebla), Jul 1927, E.Lyonnet 68 (US). Veracruz: prope La Joya, 1836, Schiede s.n. (BAA, HAL, LE, US; basis of Poa schiediana Trin ex Steud., nom. nud.); Cordillera, Orizaba, Jun-Oct 1840, H.Galeotti 5767 bis (LE; basis of Poa glycerioides Rupr., nom. nud.).

Discussion.

We have seen a few specimens from Guatemala that are tentatively placed here but verge on the limits accorded to Poa ruprechtii : Huehuetenango, San Juan Ixcoy, ca. del cruce para Chanchocal, 3200 m, J. Rios 6229, N. Hernandez & M. Veliz (MEXU), Sierra de los Cuchumatanes, at km 311 on Ruta National 9N (between Paquix and Chemal, ca. 3360 m, 2 Aug 1959, J.H.Beaman 3011 (MO, US, US "P. atala" ined.). Also reported from Huehuetenango are J.H.Beaman 3799b (US), and J.Rios s.n., N.Hernandez & M.Veliz (MEXU). Poa orizabensis and Poa ruprechtii are difficult to separate when lemma pubescence is scantly developed in the latter, but as interpreted here the former has broader glumes and more compact spikelets, and the sides of the lemmas are glabrous. Further study is needed.

Figures

Figure 13. A-D Poa mulleri Swallen A spikelet B floret C palea D pistil E-H Poa seleri Pilg. E spikelet F floret G palea H pistil I-L Poa scaberula Hook. f. I spikelet J floret K palea L pistil M-O Poa orizabensis Hitchc. M spikelet N floret O palea P-R Poa ruprechtii Peyr. P spikelet Q floret R palea. A-D drawn from Beaman 4470 E-H drawn from deKoninck 134 from Guatemala I-L drawn from Peterson 11087 et al M-O drawn from Soreng 3314 & Soreng P-R drawn from Davidse 9771.

Figure 14. Poa orizabensis Hitchc. Photo of holotype collection (Hitchcock 6254).