Poa fendleriana albescens (Hitchc.) Soreng, Great Basin Naturalist 45(3): 407 1985.

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 : 25-26

8 a. Poa fendleriana albescens (Hitchc.) Soreng, Great Basin Naturalist 45(3): 407 1985. Fig. 8 A, B

Poa albescens Hitchc. Contr. U.S. Natl. Herb. 17(3): 375 1913. Type: Mexico, Chihuahua, at Miñaca, 1 Apr 1908, J.N.Rose 11648 (holotype: US-454361!♀).

Poa griffithsii Hitchc. Contr. U.S. Natl. Herb. 17(3): 375 1913. Type: Mexico, Sonora, Cananea, 7-8 Jul 1903, D.Griffiths 4865 (holotype: US-691228!♀; isotype: US-3063989!♀).

Description.

Leaf collars often scabrous or hispidulous near the throat; ligules of middle cauline leaves 0.2-1.5 mm long, not decurrent, abaxially smooth or scabrous, upper margin scabrous or ciliolate or glabrous, apices truncate; sterile shoot blades frequently glabrous adaxially. Spikelet rachilla internodes smooth, glabrous; lemma keels and marginal veins smooth or sparingly scabrous, glabrous or sparsely short villous to softly puberulent; palea keels glabrous, between keels glabrous. Lodicules 0.6-0.7 mm long, broadly lanceolate to ovate, with or without a brief lateral lobe from below the middle. 2 n = 28, 28+II.

Distribution.

The subspecies is endemic to southeastern Arizona, southwestern New Mexico, USA, and the northern Sierra Madre Occidental of Mexico (Chihuahua, Sonora).

Ecology.

The subspecies is found in canyons and rocky slopes in forests and is associated with: Cupressus , Juniperus , Pinus arizonica Engelm., Poa discolor D.K. Bailey & Hawksw., Poa engelmannii Carrière, Poa leiophylla Schiede ex Schltdl. & Cham., Poa strobiformis Engelm., Populus tremuloides , Quercus hypoleucoides A. Camus, Quercus rugosa Née, Quercus sideroxyla Bonpl., Abies , Pseudotsuga , and Picea chihuahuana Martínez. The subspecies ranges in elevation from 1380-2850 m, and is primarily restricted to regions with summer monsoons and occasional winter snows. Flowering in spring.

Specimens examined.

Mexico. Chihuahua: Arroyo del Gato, 1 mi W of Talayotes, 27°55'N, 107°49' W, 17 mi SW of San Juanito, 7626 ft [2325 m], 29 Apr 1985, R.J.Soreng 2615, R.W.Spellenberg & R.Corrales (US, population sample: 4♀ & 3♂). Basasiachic, in deep barranca below ca. 240 m waterfall, ca. 6500 ft [1890 m], 28°1'N, 108°15'W, 27 Apr 1985, R.J.Soreng 2606, R.W.Spellenberg & R.Corrales (US, population sample: 14♀ & 4♂). 10 mi SE of Basasiachic on road to San Juanito, 8 mi SE of junction with Yecora-Tomochic road, ca. 8900 ft [2715 m], 28 Apr 1985, R.J.Soreng 2609a, R.W.Spellenberg & R.Corrales (US, population sample: 25♀, 19♂). Municipio Bocoyana, S of San Ignacio Arareco, S of Creel air strip, [27.7°N, 107.7°W], on steep north facing rocky cliffs, ca. 7400 ft [2255 m], 20 Jul 1972, R.Bye Jr. 2404 (TAES♂); ditto, along Rio Oteros, west of Creel, R.A. Bye 3673 (MEXU, TEX ♀). Miñaca, vic. of, [107.35°N, 28.45°W], 1 Apr 1908, J.N.Rose 11648 (US-454361♀). Creel air strip 3 mi due S of Creel, 27°43'N, 107°45'W, 7800 ft [2380 m], 15 Apr 1984, R.J.Soreng 2309 & Spellenberg (NMC, US, sexual population: ♂ & ♀; 2 n = 28; Soreng 1990, cpD NA voucher). 5 km SSW of San Juanito, El Rialito, [107.6°N, 27.9°W], 2400 m, 13 May 1974, W.G.Spaulding s.n., P.S.Martin & P.M.Wiseman (ARIZ ♂ & ♀). Rancho Blanco, 28.2°N, 107.6°W, 19 mi N of San Juanito toward La Junta, ca. 6900 ft [2105 m], 29 Apr 1985, R.J.Soreng 2620, R.W.Spellenberg & R.Corrales (US, population sample: 5♀ with high seed, 0♂). 4 mi N of Rancho Blanco, 24 mi N of San Juanito, ca. 6800 ft [2075 m], 29 Apr 1985, R.J.Soreng 2623, R.W.Spellenberg & R.Corrales (US, population sample: 9♀ with much seed, 0♂). Sierra Las Manzanas, 2 km SW of Tosanachic on road to Agua Caliente, ca. 53 km due W of Ciudad Guerrero, 28.30'N, 108°05W, 6396 ft [1950 m], 13 Apr 1984, R.J.Soreng 2305 & R.W.Spellenberg (NMC, US, population sample: 44♀, 34♂; Soreng 1990, cpDNA voucher). Rio Oteros origin above Arroyo El Ranchito, 27°57.5'N, 107°45'W, 11 road mi SW of San Juanito, 7954 ft [2425 m], 29 Apr 1985, R.J.Soreng 2618, R.W.Spellenberg & R.Corrales (US, population sample: 26♀, 9♂). Tomachic, 6.7 mi E and 5 mi W of Cieneguita, on road to Cuauhtemoc, 30 km SW of Ciudad Guerrero, 28°20'N, 107°43'W, 7400 ft [2255 m], 14 Apr 1984, R.J.Soreng 2307 & R.W.Spellenberg (NMC ♀, US ♀, population all pistillate, apomictic, lemmas all glabrous, 2 n = 28). crest of pass between Yepomera and Babicora, [29.2°N, 107.9°W], 8 May 1959, D.S.Correll & I.M.Johnston 21635-a (LL♀, very sparsely pubescent to glabrous, intermediate, US♀). between Yepomera and Babicora, [29.2°N, 107.9°W], 8 May 1959, D.S.Correll & I.M.Johnston 21626 (LL, ♀ sparsely pubescent to glabrous, intermediate, US). 9 mi SE of Yoquivo on Basasiachic-San Juanito road, 28.0311°N, 107.9234°W, ca. 7900 ft [2410 m], 28 Apr 1985, R.J.Soreng 2610, R.W.Spellenberg & R.Corrales (US, population sample: 9♀, 10♂). Tal des Rios Tecorichic [garbled] Tarahumare, 4 Apr 1906, Endlich 1209 (US ex B). Sonora: Cananea, 7-8 Jul 1903, D.Griffiths 4865 (US-691228♀; US-306389♀). ca. 3 mi NW of Cananea, road to microwave station N of Mexico Highway 2, ca. 7000ft [2135 m], 31.036°N, 110.375°W, 19 Mar 1982, R.J.Soreng 1780 & R.W.Spellenberg (NMC, US, population sample: 5♂, 2 n = 28; Soreng 1990, cpDNA voucher). Santa Cruz, Parry s.n., [Mexican Boundary Survey] (GH, ♂ very sparse pubescent, ♀ pubescent to sparse pubescent, intermediates; another label on same GH sheet says Munro 165, G.Thurber Herb.). Sierra del Pinito, [30.5°N, 109.5°W], 2500 m, 9 Apr 1977, J.L.Fernandez 3 (ARIZ♀). Sierra Guacomea, Pozo del Santo Nino, Rancho La Alameda, 31°03'22"N, 110°58'06"W, 1472 m, 5 Apr 2005, A.L.Reina-G. 2005-562, T.R.VanDevender & J.Ruiz-C. (ARIZ, US♂); ditto, Rancho La Arboleda, Arroyo El Volteadero, 31°03'10"N, 110°57'04"W, 1385 m, 2 Apr 2005, T.R.VanDevender 2005-493, A.L.Reina-G. & J.Ruiz-C. (ARIZ, US♀).

Discussion.

This subspecies has glabrous lemmas and short ligules, and is the most common subspecies of Poa fendleriana in Mexico. It is often sexually reproducing with dioecious populations and staminate plants are common, but sometimes apomictic individuals with pistillate spikelets are found. Intermediates have sparsely pubescent lemmas and are almost always pistillate. Distribution maps of the subspecies, distribution of staminate and pistillate plants, and a discussion of the breeding system and fossil record is given in Soreng and Van Devender (1989). Hitchcock (1913) suggested this taxon ( Poa albescens ) is allied to Poa chilensis Trin. (= Poa holciformis J. Presl) from Argentina and Chile, a member of Poa sect. Dioicopoa E. Desv., but DNA data have shown that is not the case ( Gillespie et al. 2009).

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).