Poa wendtii Soreng & P.M. Peterson, 2012

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 : 67-69

23. Poa wendtii Soreng & P.M. Peterson sp. nov. Figs 22 23

Type:

Mexico, Coahuila, [Sierra de Santa Rosa], Rincón de María, on Hacienda La Babia, ca. 70 road mi NW from Múzquiz, 28°27'30"N, 102°05'W, 1750 m, Steep NE facing talus and stabilized areas below high cliffs in southwest part of rincón, southwest of "Slump Spring", woods of Abies coahuilensis , Yucca cf. thompsoniana Trel., Quercus gravesii Sudw., Quercus sp., Tilea , Cercis , Juglans , Agave sp., 27 Apr 1975, T.L.Wendt 883 & D.Riskind (holotype: LL-TEX-75341!).

Diagnosis.

Poa wendtii differs from other open-panicled, broad-leaved, long-anthered species of Poa from around the region (e.g. Poa matris-occidentalis , Poa palmeri , and Poa tracyi ) by having abruptly reduced upper culm leaf blades and more compact, ovate (non lanceolate) spikelets in lateral view.

Description.

Hermaphroditic (apparently). Perennials; tufted, sub-rhizomatous, tufts loose, moderate girth and height, bluish-grey-green; tillers extravaginal (basally cataphyllous), with lateral or downward tending, cataphyllous shoots, cataphylls smooth, sub-lustrous, brownish or anthocyanic. Culms 50-70 cm tall, erect, blades reduced upward, terete, smooth; nodes 3-4, 0 or uppermost node exposed. Leaf sheaths slightly compressed, proximal culm ones smooth, glabrous, middle ones densely finely scabrous, upper ones moderately to lightly scabrous; butt sheaths cataphyllous, smooth, glabrous; flag leaf sheaths 13-16 cm long, margins fused for 30-42% their length, 14-16 cm long, 10-20 × longer than its blade; collar margins of lower and mid culm leaves slightly asperous to coarsely short ciliate; ligules 1.2-1.8 (top leaf), 2.7-3.3(2nd leaf down), to 3 mm on the longest leaves, whitish, abaxially sparsely to moderately scabrous, margins smooth, apices obtuse to acute, slightly irregular; blades to 22 cm long, mostly 3-5 mm wide, blades folded or flat when fresh, distinctly keeled, moderately thick, retaining form on drying, glaucous (all surfaces waxy coated), margins abruptly slightly inrolled, abaxially densely short scabrous, with short broad-based closely appressed hooklets, ribs slightly expressed, margins somewhat thickened, and finely scabrous, adaxially smooth to sparsely short scabrous, with very shallow ridges and furrows, broader leaves with ca. 15 ribs, prominently prow-tipped; lower mid-cauline blades the longest, each succeeding that, shorter than the one below by ca. 1/2, that of the flag leaf blades reduced, 0.7-1.3 cm long; sterile shoot blades similar to cauline blades in form. Panicles 13-14 cm long, erect to slightly nodding, open, broadly pyramidal, slightly secund, fairly sparse, well exerted, with 50-70 spikelets, peduncles smooth, proximal internode 2.5-4 cm long, smooth or lightly scabrous; rachis with 2-3 branches per node; primary branches widely spreading to reflexed, slender, slightly flexuous, proximally terete or slightly angled, distally moderately angled, proximally smooth, distally moderately scabrous mostly on the angles; lateral pedicels about half as, to as long as, their spikelets, m oderately scabrous; longest branches 5-7 cm, longest with 8-11 spikelets in the distal 1/2. Spikelets 4-6 mm long, 2.5-3 × as long as wide, broadly lanceolate, laterally compressed, not bulbiferous, purplish throughout at maturity; florets (2-)3(-4), hermaphroditic; rachilla internodes terete, 0.5-1 mm long, mostly hidden, terete, muriculate, glabrous; glumes lanceolate, sub-lustrous, slightly unequal, both shorter than or the 2nd equaling the first lemma, distinctly keeled, keels sparely to moderately short scabrous distally, surfaces with smooth, with scarce short cells, or with some hooks near the apex, edges smooth, apices acute, lower glumes 2.5-3.2 mm long, 1-3-veined; upper glumes 3.3-3.7 mm long, 3-veined; calluses dorsally webbed, web distinct, hairs to ca. 1-2 mm long, woolly; lemmas 3.5-4 mm long, 5-veined, elliptical in side view, anthocyanic at maturity, distinctly keeled, keel and marginal and intermediate veins villous for 2/3, 1/3, and sometimes 1/4 their length, respectively, between veins sparsely to moderately lanate in proximal half, intermediate veins distinct, upper margins narrowly to broadly bronzy-scarious to hyaline, edges smooth or sparingly scabrous, apices obtuse to broadly acute, palea keels scabrous in the distal half, sometimes with a several soft hairs medially, intercostal region sulcate, densely muriculate, usually sparsely puberulent in the proximal third. Flowers chasmogamous; anthers 1.6-2.1 mm long. Caryopses 1.7-2.0 mm long, elliptical in side-view, compressed, laterally compressed, brown, distinctly shallow sulcate, hilum 0.25 mm long, oval, grain adherent to the palea. 2n = unknown.

Distribution.

The new species is known only from the type collection from the Sierra de Santa Rosa, Coahuila.

Ecology.

The species occurs on sheltered talus and cliff bases, in forests of Abies coahuilensis I.M. Johnst. at 1750 m. The only specimen known has perfect flowers. Flowering in Apr to May.

Etymology.

It is our pleasure to name this new species in honor of Thomas Leighton Wendt (born 1950) who collected this and many other plants (including Poa ) in the Chihuahuan Desert region.

Conservation status.

The species is rare.

Discussion.

The type collection is presumed to be a unicate (T.L.Wendt, pers. comm. 2011). The species which appears to be endemic to the Sierra de Santa Rosa, should be considered extremely rare and possibly endangered.

Figures

Figure 22. Poa wendtii Soreng & P. M. Peterson A habit B culm C inflorescence D blade apex E ligule F spikelet G lower glume H upper glume I floret. Drawn from the holotype collection (Wendt 883 & Riskind).

Figure 23. Poa wendtii Soreng & P. M. Peterson A lemma B lemma abaxial view C palea dorsal view D palea ventral view E perfect flower enclosed in palea with lodicules, pistil, and stamen filaments F perfect flower with pistil / partly developed caryopsis G lodicules and rachilla internode H caryopsis ventral view, with sulcus and hilum I caryopsis dorsal view. Drawn from the holotype collection (Wendt 883 & Riskind).