Poa fendleriana (Steud.) Vasey, U.S.D.A. Div. Bot. Bull. 13(2): t. 74. 1893.

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 : 23-24

8. Poa fendleriana (Steud.) Vasey, U.S.D.A. Div. Bot. Bull. 13(2): t. 74. 1893. Fig. 8

Eragrostis fendleriana Steud. Syn. Pl. Glumac. 1: 278. 1854. Uralepis poaeoides Buckley, Proc. Acad. Nat. Sci. Philadelphia 14: 94. 1862. Atropis fendleriana (Steud.) Beal, Grass. N. Amer. 2: 576. 1896. Panicularia fendleriana (Steud.) Kuntze, Revis. Gen. Pl. 2: 782. 1891. Puccinellia fendleriana (Steud.) Ponert, Feddes Repert. 84(9-10): 739. 1974. Type: USA, New Mexico (probably in Santa Fe Canyon above Santa Fe), 1847, Fendler 932 (holotype: P-STEUD; isotypes: CAEN, GH!, NY!, US-2891469! specimen with fragm. ex CAEN, fragm. ex NY, and fragm. ex P-STEUD).

Description.

Dioecious (sometimes strictly pistillate). Perennials; tufted, sometimes noticeably sub-rhizomatous to long-rhizomatous, tufts dense to a bit loose, generally of medium girth and height (mostly 10-25 cm tall), pale green to bluish-green; tillers mainly intravaginal (each subtended by a single elongated, 2-keeled, longitudinally split prophyll), usually some extravaginal (basally cataphyllous), with lateral or downward tending, cataphyllous shoots, sterile shoots more numerous than flowering shoots. Culms 15-70 cm tall, erect or bases decumbent, slender or sometimes stout, blades strongly reduced upward, terete or weakly compressed, smooth or slightly scabrous above; nodes terete, 0-1 exerted. Leaves mostly basal; leaf sheaths terete, smooth or scabrous, glabrous or occasionally retrorsely puberulent; bases of butt sheaths thick papery, smooth, glabrous, sub-lustrous; flag leaf sheaths (6-)10-20 or more cm long, margins fused ca. 33% the length, usually more than (5-)9 × long as its blade; collars smooth or scabrous, glabrous or hispidulous; ligules 0.2-18 mm long, decurrent or not, abaxially smooth or scabrous, upper margin ciliolate or glabrous, apices truncate to acuminate; blades of cauline leaves (0.5-)1-3(-4) mm wide, folded, usually involute on the margins, moderately thick and firm, infrequently moderately thin, abaxially smooth or infrequently scabrous, narrowly prow-tipped; cauline blades steeply reduced in length distally along the culm, flag leaf blades usually absent or very reduced, or some up to 1(-3) cm long; sterile shoot blades usually moderately to densely scabrous or hispidulous on and between the veins, or infrequently nearly smooth and glabrous. Panicles 2-12(-30) cm long, erect, contracted (open in anthesis), narrowly lanceoloid to ovoid, congested (except in flowering), with (15-)25-80 (more than 100) spikelets; rachis with 1-2 branches per node; primary branches erect, fairly stout, terete to weakly angled, smooth or scabrous, prickles not confined to angles; lateral pedicels 1/5-1/4 the spikelet in length, sparsely to fairly densely scabrous, prickles fine to fairly coarse; longest branches 1-8 cm, with 3-15(-25) spikelets. Spikelets (3-)4-8(-12) mm long, to 3 × long as wide, sub-lustrous, broadly lanceolate to ovate, laterally compressed, not sexually dimorphic; not bulbiferous; florets 2-7(-13), pistillate or staminate; rachilla internodes terete, usually 0.8-1.3 mm long, smooth, glabrous, sparsely hispidulous, or sparsely softly puberulent to short villous; glumes lanceolate, distinctly keeled, keel smooth or sparingly scabrous, margins fairly broadly scarious, edges smooth or lightly scabrous; apices obtuse to acute; lower glumes distinctly shorter than the lowest lemma, 1-3-veined; upper glumes lanceolate, slightly shorter than lowest lemma, 3-veined; calluses glabrous; lemmas (3-)4.5-6 mm long, lanceolate, pallid green, commonly anthocyanic distinctly keeled, keels and marginal veins short to long villous or softly puberulent, or glabrous, intermediate veins short villous to softly puberulent or glabrous, between veins softly puberulent or glabrous, smooth or sparsely finely scabrous, intermediate veins obscure to moderately prominent, margins narrowly scarious to hyaline, edges smooth or lightly scabrous, apices acute to obtuse, sometimes retusely notched (to 0.25 mm deep); palea keels coarsely scabrous, medially sometimes softly puberulent or long villous, between keels glabrous or infrequently puberulent. Flowers chasmogamous; lodicules of pistillate plants 0.6-0.85 mm long, broadly lanceolate to ovate, with or without a brief lateral lobe from below the middle (lodicules rudimentary in staminate plants); anthers 2-3.2 mm long, or all vestigial and 0.1-0.2 mm long. Caryopses 2-2.5 mm long, elliptical in side-view, subtrigonous in cross-section, honey-brown, sulcus broad and shallow, hilum 0.25 mm long, round, grain adherent to the palea.

Distribution.

The species is widespread in North America and occurs in southwestern and south central Canada, western USA, and northern Mexico in Baja California, Chihuahua, Coahuila, and Sonora.

Ecology.

This dioecious, weakly rhizomatous species occurs in the mountains on open forested slopes derived from calcareous and igneous substrates. It is sometimes strictly pistillate and apomictic. Flowering principally in the spring.

Discussion.

This species provides good springtime forage where it is abundant and all three subspecies occur in Northern Mexico ( Soreng and Van Devender 1989; Soreng et al. 2003a). The sex of specimens is indicated here for purposes of estimating the breeding system (geographical and ecological extent of sexual versus asexual reproduction), along with numbers of individuals of each sex where populations were evaluated. Where only or predominately pistillate plants are found, the species usually reproduces apomicticly by seed. No pollen is required to stimulate seed development in apomictic plants of this species (i.e., they are not pseudogamous). Sexual reproduction predominates where staminate plants are found and relatively numerous. Seed is commonly set in 20% or more of flowers in the apomictic populations and usually less than 10% in pistillate plants in sexual populations. Sex-expression is apparently stable in the species of Poa sect. Madropoa , to which Poa fendleriana belongs. The first author grew samples of the species in a common garden over several years and found that plants did not change sex. Individuals of Poa fendleriana occasionally have a few perfect-flowered spikelets, and a few populations containing these unusual plants have been found in Poa fendleriana subsp. fendleriana in New Mexico and Colorado. Poa fendleriana subsp. albescens is a tetraploid whereas the other two subspecies are principally octoploid ( Soreng 2005).

A specimen from 20 mi N of Durango, Oct 7 1955, B.Emery 334A (TEX), has one flowering culm of Poa fendleriana mixed in with vegetative parts of Trachypogon . The flowers are pistillate and the lemmas are glabrous to sparsely pubescent on the keel; so it appears intermediate between Poa fendleriana subsp. albescens and Poa fendleriana subsp. fendleriana. However, the habitat seems wrong (low spots in grassland of mesquite, Opuntia , and short grasses), making us wonder if the origin of the one culm stems from a collection sorting error.

Key to the subspecies of Poa fendleriana

1	Lemmas glabrous; plants from the Sierra Madre Occidental	8a. Poa fendleriana subsp. albescen s
-	Lemmas pubescent on the keel and marginal nerves	2
2	Ligules of upper culm leaves 0.2-1(-1.5) mm long, truncate to rounded, upper margin minutely ciliate fringed; collar margins usually distinctly scabrous; plants from the range of the species; Baja California, Chihuahua, Sonora, and Coahuila	8b. Poa fendleriana subsp. fendlerian a
-	Ligules of upper culm leaves (1.5-)1.8-11 mm long, obtuse to acuminate, upper margin without a ciliate fringe; collar margins usually smooth or sparingly scabrous; plants from Baja California	8c. Poa fendleriana subsp. longiligul a

Figures

Figure 8. Poa fendleriana (Steud.) Vasey. A, B Poa fendleriana subsp. albescens (Hitchc.) Soreng A ligule B floret C-G subsp. fendleriana C habit D inflorescence E ligule F spikelet G floret H, I subsp. longiligula (Scribn. & T. A. Williams) Soreng H ligule I floret. Drawings from Soreng (2007).