Poa mulleri Swallen, J. Wash. Acad. Sci. 30(5): 211. 1940.

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 : 35-37

12. Poa mulleri Swallen, J. Wash. Acad. Sci. 30(5): 211. 1940. Figs 12 13 A-D

Type:

Mexico, Nuevo León, Municipio de Galeana, collected in pine woods on the Peak of Cerro Potosí, 21 Jul 1935, C.H. Meuller 2251 (holotype: US-1645320!; isotypes: GH!, US-1646008!).

Description.

Hermaphroditic. Perennials; tufted, tufts dense, fairly small and low (mostly 6-10 cm tall), pale green, to slightly bluish-grey-green; tillers intravaginal (each subtended by a single elongated, 2-keeled, longitudinally split prophyll), and extravaginal (basally cataphyllous), without lateral or downward tending, cataphyllous shoots, sterile shoots more numerous than flowering shoots. Culms 9-28(-42) cm tall, erect to loosely ascending, sometimes decumbent or geniculate, terete, smooth; nodes 2-3, upper 0-1(-2) exerted, uppermost at mid-culm. Leaves mostly basal; leaf sheaths slightly keeled, smooth, glabrous; butt sheaths papery or becoming slightly fibrous in age, smooth glabrous; flag leaf sheaths 4-8(-11) cm long, margins fused 13-25% their length, sheath ca. 2-6 × longer than its blade; collars smooth, glabrous; ligules 0.25-0.8 mm long, abaxially minutely scabrous, upper margin irregular, minutely scabrous; apex truncate, sterile shoot ligules like those of the culm leaves; blades to 8(-12) cm long, 1-2 mm wide, involute, margins inrolling, soft, moderately thick, abaxially smooth, papilliate, veins slightly expressed, margins scabrous, adaxially papilliate, slightly scabrous over the costae, apex prow-tipped; culm blades more or less equal in length or the middle ones longest, flag leaf blades 0.9-3.5 cm long; sterile shoot blades like those of the culm blades. Panicles 3.4-8 cm long, erect, open, pyramidal, exerted, fairly sparse, with 20-60 spikelet, peduncles and axis smooth or sparsely scabrous, proximal internode 0.7-2 cm long; rachis with branches (1-)2 per node; primary branches widely spreading to reflexed, slightly flexuous, weakly to distinctly angled, moderately to densely scabrous, hooks mostly on the angles, minutely papilliate; lateral pedicels mostly 1/5-1/2 the spikelet in length, sparsely to moderately coarse scabrous, densely papilliate; longest branches 1.4-3.8 cm, with 3-8 spikelets somewhat clustered, in the distal 1/2 to quarter. Spikelets 4-5 mm long, broadly lanceolate to lanceolate, laterally compressed, not bulbiferous, pale green, slightly anthocyanic; florets (1-)2, hermaphroditic; rachilla internodes to 1 mm long (extension to 1.5 mm), smooth, glabrous; glumes broadly lanceolate to lanceolate, usually somewhat anthocyanic, subequal to equal, slightly shorter than adjacent lemmas, distinctly veined, distinctly keeled, slightly thinner than lemmas, smooth or keel apically slightly scabrous, surfaces obscurely papilliate, apex acute; lower glumes 2.5-3.2 mm long, 3-veined; upper glumes 3-3.5 mm long, 2 × to equal lower glumes in width, (3-)5(-7)-veined; calluses glabrous; lemmas 3-4 mm long, broadly lanceolate, lower one 5-7-veined, upper 5-veined, green with or without anthocyanic flush, distinctly keeled, keel smooth or distally sparsely scabrous, keel and marginal veins glabrous or thinly and loosely puberulent, between veins glabrous or loosely puberulent in lower 1/3, intermediate veins prominent, margins and apex narrowly scarious hyaline, edges smooth, apices acute, incurved; palea keels smooth or sparsely to moderately scabrous, glabrous, between keels glabrous or sparsely puberulent. Flowers chasmogamous; lodicules 0.75 mm long, broadly lanceolate, apex sharp, with a well developed lateral lobe; anthers 1.6-2 mm long, sometimes poorly formed. Caryopses 1.8 mm long, elliptical in side-view, round on back, almost cylindrical in cross-section, pale brown, sulcus very shallow, hilum 0.25 mm long, round to oval to elliptical, grain free from the palea. 2 n = unknown.

Distribution.

The species is known only from the Cerro Potosí, Nuevo León.

Ecology.

The species occurs on open or sparsely wooded slopes derived from calcareous rocks on the upper slopes of Cerro Potosí, and is associated with Pinus culminicola Andresen & Beaman, Trisetum spicatum (L.) K. Richt., Senecio sp., and Festuca hephaestophila Nees ex Steud., and Festuca hintoniana E.B. Alexeev; between 3650-3800 m. Flowering July to August.

Conservation status.

This narrow endemic is locally uncommon.

Specimens examined.

Mexico. Nuevo León: Cerro Potosí, ca. 20 mi NE of Galeana, ascent of Sierra Potosi by the north hogback, 26 Jul 1934, C.H.Mueller 1248 & M.T.Mueller (GH, MEXU, TEX); ditto, summit, ca. 3650 m, 1 Jul 1959, J.H.Beaman 2643 (GH, MSC, TEX, US). at NE summit of mountain, ca. 3650 m, 13 Sep 1960, J.H.Beaman 4470 (GH, MSC, TEX, US); ditto, 25 Mar 1962, A.A.Beetle M-475 & P.Rojas-M. (WYAC); ditto, 20°52'23"N, 100°13'48"W, 3650 m, 15 Aug 1998, Ing.M.Castillo-B. 345 & Ing.J.Garza-C. (MEXU & MEXU p.p. "b", p.p. "a" is Poa pratensis subsp. alpigena fide RJS on both sheets); ditto, near summit, 3674 m, 21 Oct 2007, P.M.Peterson 21459, J.M.Saarela, & D. Stančik (US; DNA voucher, unpublished); ditto, just below summit, 26 Jul 1985, S.Ginzbarg 217, A.Whittemore & A.McDonald (TEX). Municipio Galeana, 3800 m, 21 Aug 1969, G.B.Hinton 17253 et al. (TEX); ditto, Cima del Cerro Potosí, 3670 m, 3 Aug 1988, A.Garcia 70 (MEXU). 3660 m, 15 Aug 1989, A.Garcia 163, S.Gonzales & M.Gonzalez (MEXU).

Discussion.

Poa mulleri is an odd species perhaps related to Poa orizabensis , but the characters are quite unusual, and it deserves a subsection of its own. Papillae on long cells of the leaf blade in Poa are known from some species of Poa sect. Secundae subsect. Halophyllae Soreng, and from Poa arida Vasey and a few other species. No other species of the genus are known to have multiple small papillae per cell, a character state that to our knowledge is novel in the tribe Poeae, and possibly in Pooideae but is common in Bambusoideae and Ehrhartoideae ( Metcalfe 1960). Upper glumes in Poa are almost invariably 3-viened, and when 3 to 5 veins occur, the 5-veined state is infrequent within a species (e.g., Poa macrantha Vasey). In Poa mulleri , the upper glumes are 5-7-veined and the lower lemmas of each spikelet are 5-7-veined. Preliminary DNA data place it in the large supersect. Homalopoa clade (L. Gillespie and N. Amiri pers. com. 2012), for which the sectional and infrasectional taxonomy remains poorly resolved ( Gillespie et al. 2009; Soreng et al. 2009).

Figures

Figure 12. Poa mulleri Swallen. Photo of holotype collection (Mueller 2251).

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.