Poa gymnantha Pilg., Bot. Jahrb. Syst. 56 (Beibl. 123): 28. 1920.

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 : 29-32

9. Poa gymnantha Pilg., Bot. Jahrb. Syst. 56 (Beibl. 123): 28. 1920. Figs 6 A-E 9

Type:

Peru, 15°50' to 16°00'S, südlich von Sumbay, Eisenbahn Arequipa-Puno, Tola-Heide, 4000 m, Apr 1914, A. Weberbauer 6905 (lectotype: S! designated by Anton and Negritto 1997: 236; isolectotypes: BAA-2555!, MOL!, US-1498091!, US-2947085! specimen & fragm. ex B, USM!).

Poa ovata Tovar, Mem. Mus. Hist. Nat. "Javier Prado" 15: 17, t.3A. 1965. Type: Peru, Cuzco, Prov. Quispicanchis, en el Paso de Hualla-hualla, 4700 m, 29 Jan 1943, C.Vargas 3187 (holotype: US1865932!).

Poa pseudoaequigluma Tovar, Bol. Soc. Peruana Bot. 7: 8. 1874.Type: Peru, Ayacucho, Prov. Lucanas, Pampa Galeras, Reserva Nacional de Vicunas, entre Nazca y Puquio, Valle de Cupitay, 4000 m, 4 Apr 1970, O.Tovar & Franklin 6631 (holotype: USM!; isotypes: CORD!, MO-3812380!, US-2942178!, US-3029235!).

Description.

Pistillate. Perennials; tufted, tufts dense, usually narrow, low (4-6 cm tall), pale green; tillers intravaginal (each subtended by a single elongated, 2-keeled, longitudinally split prophyll), without cataphyllous shoots, sterile shoots more numerous than flowering shoots. Culms 4-6 (45) cm tall, erect or arching, leaves mostly basal, terete or weakly compressed, smooth; nodes terete, 0-1, not exerted, deeply buried in basal tuft. Leaves mostly basal; leaf sheaths laterally slightly compressed, indistinctly keeled, basal ones with cross-veins, smooth, glabrous; butt sheaths becoming papery to somewhat fibrous, smooth, glabrous; flag leaf sheaths 2-3.5(-10) cm long, margins fused 30-40% their length, ca. 2.5 × longer than its blade; throats and collars smooth or slightly scabrous, glabrous; ligules to 1-0.5(-7) mm long, decurrent, scari ous, colorless, abaxially moderately densely scabrous to hirtellous, apex truncate to obtuse, upper margin erose to denticulate, sterile shoot ligules equaling or shorter than those of the upper culm leaves; blades 1.5-3(-12) cm long, 0.6-1.5(-3) mm wide (expanded), folded to involute, slightly thick, slightly firm, margins involute, abaxially smooth, veins not expressed, margins long scabrous for most of the length, adaxially densely scaberulous, with 2 rows of buliform cells, apex slightly prow-tipped; flag leaf blades like the others; sterile shoot blades like those of the culm. Panicles 1.5-1.7(-8) cm long, 2-2.5(-1.2) mm wide, erect, tightly contracted, linear, slightly secund, included in the leaves or slightly exerted, congested, with 7-10 (many) spikelets, peduncle smooth, proximal internode 0.4-0.7 cm long; rachis with 1-2(-3) branches per node; primary branches erect, appressed, stout, slightly angled, smooth or distally slightly to moderately scabrous to hirtellous on the angles; lateral pedicels less than 1/2 their spikelet in length, moderately scabrous, prickles fine; longest branches 0.3-0.8 cm (?), with 1 to 2 spikelets (?), flowered from near the base. Spikelets 3 mm 6.5 long, 1-1.3(-2.5) mm wide; 2-3 × as long as wide, lanceolate to ovate, laterally compressed, not bulbiferous, slightly lustrous, two toned; florets 1-2(-3), pistillate; rachilla internodes terete, mostly 0.2-0.4 (?) mm long, smooth or scabrous, glabrous; glumes broadly lanceolate, herbaceous and pale green below, scarious bronzy and sometimes anthocyanic in margins and apex, veins distinct, equal to subequal, distinctly keeled, sometimes a bit asymmetrical, subequal to the spikelet, smooth (or scabrous), margins broadly scarious-hyaline, edges entire or dentate, smooth, apices entire; lower glumes 2.5-3(-3.4) mm long, (1-)3-veined; upper glumes 2.7-3(-4.8) mm long, 3-veined; calluses glabrous; lemmas 2.5-3(-5) mm long, 5-veined, (ovate) elliptical (lanceolate), chartaceous green below keeled, surfaces glabrous, proximally smooth, keel and sides distally moderately to densely scabrous (prickle hairs sometimes a bit flexuous) to scaberulous, intermediate veins indistinct, upper margins broadly bronzy-anthocyanic, apex entire, obtuse to acute, paleas glabrous, keels distally scabrous. Flowers; lodicules broadly lanceolate, apex acute, with or without a lateral lobe; anthers vestigial, 0.1-0.2(-0.8) mm long. Caryopses 1.7-1.8 mm long, elliptical in side-view, subcylindrical in cross-section, light honey-brown, sulcus indistinct, hilum 0.25 mm long, round, grain free from the palea. 2 n = 70.

Distribution.

In South America the species occurs Argentina, Bolivia, Chile, and Peru; and is known only from the state of Mexico.

Ecology.

This species is typically found on well drained slopes, in loam, sandy loam, scree, or rocky crevices, on alpine volcanic slopes between 4000-4200 m. Flowering in August.

Specimens examined.

Mexico. Mexico: Monte Tlaloc, near summit of mountain, 4100-4140 m, 22 Aug 1958, J.H.Beaman 2342 (US-2381582, TEX, WIS).

Discussion.

This is the first report of this species for Mexico. Poa gymnantha is known from the high Andes (ca. 8-16°S lat.; Negritto et al. 2008) in Argentina (Jujuy and Salta), Chile (Region 1 and Parinacota), Bolivia (La Paz, Oruro, and Potosí), Peru (Ancash, Apurimac, Arequipa, Ayacucho, Cuzco, Huancavelica, Junín, Moquegua, Puno, and Tacna). Negritto et al. (2008) discusses the taxonomy and reproductive biology of this high polyploid, pistillate, apomictic species. Although low growing forms, often treated as Poa ovata and Poa pseudoaequigluma (see synonyms above)are excluded from Poa gymnantha sensu Negritto et al. (2008), we have made over 84 collections of this species from across its Andean range, and examined many other collections at LPB, US, USM. We cannot find a single morphological feature that can be used to separate these taxa, and instead only see a range or continuum of these features across the entire range. Negritto in Giussani et al. (2012) now accepts Poa ovata and Poa pseudoaequigluma as synonyms with expressed need for further study. The description provided here is based on one small Mexican collection, with extreme ranges from South American material noted in parentheses [given as "(?)" where the full character state range was not documented for South America samples]. In South America small and large plants ( Poa gymnantha s.s.) are often mixed within populations, and the stature appears to depend on elevation and microhabitat variations in moisture and light intensity, and exposure to herbivory. Although the type and few other specimens of Poa ovata have well developed stamens, hundreds of other specimens examined have only staminodes and regularly produce seed, a situation that indicates apomixis ( Soreng and Van Devender 1989; Negritto et al. 2008). John Beaman (notes in US herbarium) intended to describe his no. 2342 as a new species, with the epithet "acrophila". The features that join the Mexican collection with Poa gymnantha s.l. are the small stature (5 to 6 cm tall); very narrow, contracted panicles (most like the type of Poa pseudoaequigluma ); basal sheaths that become a bit fibrous in age; leaf-blades involute, abaxially smooth, with scabrous margins and densely scaberulous adaxial surfaces; ligules abaxially scabrous; lemmas that are glabrous, the apical 1/3-1/4 portion brown, scareous, and scaberulous; and florets pistillate. In contrast to Poa chamaeclinos , the tufts of Poa gymnantha are erect, not mat forming, leaf blades are erect to ascending, involute and adaxially densely scaberulous, the lemmas are distally scabrous with indistinct lateral veins. Although both species generally occur between 4000-5000 m, from our experience in the Andes, Poa gymnantha grows on dry slopes and plains, instead of perennially wet or "waterlogged" habitats. We provide a photo of the Beaman collection from Mexico ( Fig. 9 ) but chose to illustrate a Peruvian specimen with 2-flowered spikelets ( Fig. 6 A-E ) because the Beaman specimens are quite depauperate and immature. In South America depauperate specimens of the species with one-flowered spikelets are fairly common.

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 9. Poa gymnantha Pilg. Photo of Beaman 2342.