Poa matris-occidentalis P.M. Peterson & Soreng, Sida 22(2): 906, 908, f. 1a-c, 2c-l, 3a-c, 4. 2006.

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 : 33-34

11. Poa matris-occidentalis P.M. Peterson & Soreng, Sida 22(2): 906, 908, f. 1a-c, 2c-l, 3a-c, 4. 2006. Figs 10 11

Type:

Mexico, Durango, Sierra Madre Occidental, southwest slope of Cerro Gordo, just below twin rock outcrops, 23°12'32.5" N, 104°56'54.1"W, 3130-3200 m, 26 Sep 2005, P.M.Peterson & F. Sánchez-Alvarado 19145 (holotype: US!; isotypes: CIIDIR!, MEXU!).

Description.

Hermaphroditic. Perennials; tufted, sub-rhizomatous, tufts fairly dense to loose, of moderate girth and height, dark green; tillers mainly extravaginal (basally cataphyllous), with lateral or downward tending, brownish, cataphyllous shoots. Culms 45-80 cm tall, erect or bases slightly decumbent, leafy, terete or weakly compressed, smooth; nodes terete, 2-4, 1-3 exerted. Leaf sheaths compressed, distinctly keeled with a short wing to 0.5 mm deep, smooth, glabrous, or the lower ones sometimes retrorsely scabrous or puberulent; butt sheaths cataphyllous, brownish, smooth, glabrous; flag leaf sheaths 10-15 cm long, margins fused 66-80% the length, 0.4-1.1 × longer than its blade; collars smooth or lightly scabrous, glabrous or ciliate; ligules 3.5-6 mm long, scarious-white to hyaline, abaxially smooth, glabrous, or sometimes puberulent, apex obtuse to acute, entire; blades mostly 10-30 cm long, 2-6 mm wide, flat, to broad-V shaped, thin, lax, abaxial surface and margins lightly scabrous along the veins, adaxially smooth, glabrous throughout, with about 17 veins expressed, apices narrowly prow-tipped; mid-cauline blades 20-30 cm long, ca. 2 × longer than the flag leaf blades, flag leaf blades 12-22 cm long; sterile shoot blades similar to cauline blades. Panicles 12-26 cm long, nodding, open, pyramidal, sparse, with 24-85 spikelets, proximal internode 2.5-5.5 cm long; rachis with (1-)2(-3) branches per node; primary branches ascending to spreading, slender, flexuous, lax, angled, angles sparsely to moderately scabrous; lateral pedicels on average as long as spikelets, moderately scabrous, prickles of moderate coarseness; longest branches 5.5-10 cm, with 3-15 spikelets in the distal 1/3-1/2. Spikelets 4-8 mm long, 1.8-2.7 mm wide, broadly lanceolate, laterally compressed, not bulbiferous, greenish to stramineous; florets 2-3, hermaphroditic; rachilla internodes terete, 1-2 mm long, usually hidden, smooth, glabrous; glumes lanceolate, sub-lustrous, equal to subequal, distinctly keeled, keels scabrous distally, upper surfaces often lightly scabrous, edges smooth or lightly scabrous, apex narrowly acute, lower glumes 3-5 mm long, (1-)3-veined (laterals often short), narrowly lanceolate; upper glumes 3.7-5.6 mm long, distinctly 3-veined, lanceolate to oblanceolate; calluses dorsally webbed, web distinct, hairs 2-3 mm long, woolly; lemmas 4.6-6.3 mm long, lanceolate, 5-veined, green, distinctly keeled, keel and marginal veins glabrous or sometimes proximally sparsely puberulent, distally scabrous, between veins, muriculate to densely scabrous from near the base, intermediate veins distinct, upper margins narrowly scarious-hyaline, edges lightly scabrous, apices acute to narrowly acute, sometimes briefly purple and bronze tinged; paleas 4.4-6 mm long, usually distinctly shorter than the lemma, keels long scabrous for most of the length, between the keels moderately muriculate to short aculeolate. Flowers chasmogamous; lodicules (0.3-)0.6-0.8 mm long, broadly lanceolate to ovate, with a lateral lobe; anthers 2-2.2 mm long, infrequently those of distal flower abortive. Caryopses 2.6-3 mm long, fusiform in side-view, laterally compressed, subtrigonous in cross-section, light brown to olivaceous, sulcus distinct narrow, hilum 0.2-0.25 mm long, oval, grain adherent to the palea. 2 n = unknown.

Discussion.

Originally spelled as Poa " matri-occidentalis ", the epithet is correctly spelled as matris-occidentalis (fide Kanchi Gandhi). The species is endemic to high mountains on the west side of the central Sierra Madre Occidental in southern Chihuahua to southwestern Durango ( Peterson et al. 2006), and is only known from two peaks that are over 300 km apart. Specimens have sometimes passed under the name Poa tracyi Vasey, a species of the mountains of Colorado and New Mexico ( Soreng and Hatch 1983, Soreng 1985, 2007). DNA data (Gillespie and Soreng, unpublished, from the holotype) supports the species placement within Poa subgen. Poa supersect. Homalopoa , rather than in Poa sect. Sylvestres as originally postulated in Peterson et al. (2006) based on tenuous morphological connections.

Key to the subspecies of Poa matris-occidentalis

1	Sheaths of lower leaves smooth, glabrous; collars smooth or with a few hooks, glabrous; lemmas finely muriculate between the veins, keel and marginal veins glabrous below; plants from Durango	11a. Poa matris-occidentalis subsp. matris-occidentali s
-	Sheaths of lower leaves retrorsely scabrous to puberulent; collars ciliate; lemmas densely scabrous between the veins, keels and marginal veins puberulent below; plants from southern Chihuahua	11b. Poa matris-occidentalis subsp. mohinorensis

Figures

Figure 10. Poa matris-occidentalis P. M. Peterson & Soreng. A-C Poa matris-occidentalis subsp. matris-occidentalis A habit B inflorescence C sheath, ligule, and blade D subsp. mohinorensis Soreng & P. M. Peterson D sheath, ligule, and blade. Drawings from Peterson et al. (2006), A-C drawn from holotype collection (Peterson 19145 & Sanchez-Alvarado) D drawn from holotype collection (Nesom 6475 & McDonald).

Figure 11. Poa matris-occidentalis P. M. Peterson & Soreng. A, B Poa matris-occidentalis subsp. mohinorensis Soreng & P. M. Peterson A spikelet B floret; C-L subsp. matris-occidentalis C spikelet D floret E lower glume F upper glume G floret H palea dorsal view I palea ventral view J perfect flower, stamens, ovary, and lodicules, all enclosed in palea K lodicules L young caryopsis. Drawings from Peterson et al. (2006), A, B drawn from holotype collection (Nesom 6475 & McDonald) C-L drawn from holotype collection (Peterson 19145 & Sanchez-Alvarado).