Agrostis exarata Trin., Gram. Unifl. Sesquifl. 207. 1824.

Vigosa-Mercado, J. Luis, Delgado-Salinas, Alfonso, Alvarado Cardenas, Leonardo O. & Eguiarte, Luis E., 2023, Revision of the genus Agrostis (Poaceae, Pooideae, Poeae) in Megamexico, PhytoKeys 230, pp. 157-256 : 157

5. Agrostis exarata Trin., Gram. Unifl. Sesquifl. 207. 1824.

Figs 4E , 5E , 14

= Polypogon monspeliensis (L.) Desf. var. monolepis Torr., Pacif. Railr. Rep. 5(2): 366. 1858. Agrostis exarata Trin. var. monolepis (Torr.) Hitchc., Amer. J. Bot. 21(3): 136. 1934. Agrostis ampla Hitchc. fo. monolepis (Torr.) Beetle, Bull. Torrey Bot. Club 72: 544. 1945. Type. USA. California: Pose Creek, Walkers Pass, Aug 1853, Blake s.n. (holotype: NY (NY431434 [image!]); isotype: US [fragm. ex NY] (US04019109 [image!]).

= Agrostis durangensis Mez, Repert. Spec. Nov. Regni Veg. 17(19-30): 301. 1921. Type: MEXICO. Durango: collected at the city of Durango and vicinity, 1896, E. Palmer 190 (lectotype, designated by Vigosa-Mercado (2022a: 1): MO (MO-128909 [image!]; isolectotypes F (F0046563F [image!]), FCME! [fragm. ex US], GH (GH00022993 [image!]), NY (NY00327644 [image!]), US (US00151844 [image!], US00151845 [image!], US00151846 [image!], US00156413 [image!], US00486604 [image!])).*

Type.

USA. Alaska: Unalaska, 1829, J.F. Eschscholtz s.n. (holotype: LE (LE00009316 [image!]); isotype: LE) .

Description.

Plants perennial, caespitose, rarely shortly rhizomatous. Tillers extravaginal, with cataphylls. Culms 10-90 cm long, erect or decumbent at the base, nodes 2-4, glabrous, internodes glabrous. Leaves basal and cauline; sheaths 3-10 cm long, usually shorter than the internodes, glabrous; ligules 2.5-5 mm long, longer than wide, dorsally scaberulous, apices acute, often lacerate; blades 3-15 cm long, 1.5-4(-8) mm wide, linear, flat, scaberulous on both surfaces. Panicles (2-)4-20(-30) cm long, 0.4-2(-3) cm wide, contracted, usually dense and spiciform, lanceolate to oblong, sometimes interrupted at the base, sometimes partially included in the upper sheaths; branches appressed to ascending, rebranching about or below mid-length, scaberulous, usually with spikelets almost to the base, inferior branches 1-5 cm long; pedicels 0.5-3 mm long, appressed, scaberulous. Spikelets 2-2.5 mm long, greenish to stramineous; glumes subequal to unequal, lanceolate, apices acute to shortly acuminate, 1-veined, scaberulous on the keel, sometimes also on the body, sometimes awned, awn ca. 1 mm long, lower glume 2-2.5 mm long, upper glume 1.5-2.3 mm long; callus glabrous or with 2 bunches of few, short trichomes, often inconspicuous; lemmas 1.2-2 mm long, elliptic, apices acute or shortly toothed, 5-nerved, veins prominent distally or inconspicuous throughout, usually unawned, sometimes awned about mid-length, awn up to 3 mm long, geniculate or straight; paleas absent or 0.3-0.8 mm long, veinless, glabrous; anthers 3, 0.3-0.7 mm long. Caryopsis 1-1.5 mm long, elliptic; endosperm soft or solid. 2n= 28, 42, 56 ( Harvey 2007).

Anatomy and micromorphology.

Leaf blades flat in transversal section; adaxial furrows deep, narrow; adaxial ribs rounded; keel sometimes present, with three vascular bundles; first order bundles circular in outline, sheath interrupted abaxially, abaxial and adaxial sclerenchyma in girders, narrowing towards the bundle; second order bundles circular in outline, sheath interrupted abaxially, abaxial sclerenchyma in girders, narrowing towards the bundle, adaxial sclerenchyma in strands; intercostal sclerenchyma absent; leaf margins with well-developed sclerenchyma caps, rounded; colorless cells present, associated with first and second order vascular bundles (Fig. 15A-C ). Lemmas with transversal thickenings polygonal, wider than the unthickened portions of the wall; prickle hairs absent or scarce (Fig. 7E ).

Distribution and habitat.

Agrostis exarata is distributed from Alaska to central Mexico, and is also found in Kamchatka and the Kuril Islands ( Harvey 2007). In the study zone, this species has been collected in the USA states of Arizona, California, New Mexico and Texas, and in the Mexican states of Baja California, Baja California Sur, Chihuahua, Coahuila, Durango, Guanajuato, Hidalgo and Sonora (Fig. 8E ). It has also been reported from Mexico City and the Mexican states of México and Puebla ( Villaseñor 2016; Sánchez-Ken 2019), but no specimens from these states were seen. It grows in moist soils of stream edges and lake margins, in open areas of temperate forests with Pinus or Quercus , and shrublands, between 350-2900 m a.s.l. (Fig. 9H ). The USA and Baja California populations of this species grow in lower elevations than the southern ones.

Phenology.

Specimens with spikelets have been collected from April to November (Fig. 10H ).

Commentaries.

For other regions it has been reported that the panicles can reach 4 cm wide, and paleas up to 0.5 mm long ( Harvey 2007).

Agrostis exarata is a variable species. Several specific names or infraspecific taxa have been proposed, but none of them are recognized in this work. Mexican populations of this species have been called A. durangensis , and are characterized by the unawned lemmas, and the presence of a short, veinless palea, but these characters overlap with populations of other regions. Agrostis exarata is often confused with several Polypogon species, which are often sympatric, but differs from them in the spikelets disarticulating above the glumes (vs. disarticulation below the glumes, with a pedicel fragment). Mexican populations of A. exarata are sometimes confused with some individuals of A. tolucensis with wide leaf blades, but differ from it in the spikelets often with a palea, and lemma usually unawned (vs. spikelets without a palea, lemma awned in A. tolucensis ). This species is also confused with A. blasdalei and A. densiflora (see the notes in excluded species).

Conservation status.

Agrostis exarata is a widespread species in the study zone. It is represented by 61 collections, with several populations occurring in 13 protected areas. The EOO is 1,402,821 km2 and the AOO is 188 km2. Following the IUCN criteria, the preliminary assessment category is Least Concern (LC).

Representative specimens examined.

Mexico. Baja California. Municipio Ensenada, Sierra San Pedro Mártir, head of arroyo Copal , steep canyon on E sidelong crest of range, 1.5 km N of cerro Observatorio , [31.04418346°N, 115.463326°W, 2800 m alt.], 16 Jul 1988, S. Boyd and T. Ross 2544 (F, MEXU [*], NY) . Baja California Sur: Municipio Comondú, along small dry streambed, on open rolling ridge tops, La Chuparosa , [26.22975°N, 111.97158°W, 350 m alt.], 12 Apr 1955, A. Carter and R.S. Ferris s.n. (SD) . Chihuahua: Municipio Ocampo, Parque Nacional de la Cascada de Basaseachi , [28.16666667°N, 108.2083333°W], 1600 m alt., 26 Apr 1985, R. Spellenberg et al. (MEXU), 9056 (MEXU) . Without municipality, by springs, Sierra Madre , 2900 m alt., 3 Oct 1887, C.G. Pringle 1421 (F, MEXU) . Coahuila: Municipio Zaragoza, Sierra del Carmen, Canyon de Sentenela [Centinela] on Hacienda Piedra Blanca , [29.11021676°N, 101.7054129°W, 860 m alt.], 6 Jul 1936, F.L. Wynf and C.H. Muller 547 (MSC) . Durango: Municipio San Dimas: Vencedores , camino a las cabañas, 24.44944444°N, 105.7758333°W, 2355 m alt., 25 Aug 2013, S. Heynes 587 (MEXU [*,**]) ; Guanajuato: Municipio San Felipe, Vergel de la Sierra , [21.38504722°N, 101.6354389°W], 2440 m alt., 3 Sep 1981, R. Guzmán 4543 (MEXU [*,**]), R. Santillán 154-R (MEXU) . Hidalgo: Municipio Acaxochitlán, San Francisco , [20.1897756°N, 98.14532383°W], 2000 m alt., 30 May 1985, A. Villa 186 (MEXU) . Sonora: Sonora , 24 Jun 1855, A. Schott s.n. (F) . USA. Arizona: Cochise County, Rucker Canyon , [31.757451°N, 109.360505°W], 2495 m alt., 28 May 1952, E.R. Blakley 1301 (DES) . California: San Diego County, Cuyamaca Rancho State Park, 0.4 mile NE of intersection of state highway 79 and Stonewall Mine road, ca. 100 m NE of Los Caballos equestrian campground and 20 m south of Stonewall Mine road in north-treading drainage, 32.9728°N, 116.5714°W, 1440 alt., 26 Jun 2005, L. Hendrickson 1093 (BSCA, SD [*,**]) . New Mexico: Grant County, Mimbres River , [32.858382°N, 107.977694°W], 1676 m alt., 1 Jul 1904, O.B. Metcalfe 1073 (F, NY) . Texas: Brewster County, Lower Oak Creek, Chisos Mountains , [29.266025°N, 103.301199°W, 1700 m alt.], 6 Jul 1937, B.H. Warnock 20153 (TEX). See Suppl. materials 2, 3 for additional examined specimens .

Figures

Figure 4. Florets of Agrostis species observed with SEM A A. bourgaei B A. calderoniae C A. capillaris D A. elliottiana E A. exarata F A. ghiesbreghtii G A. gigantea H A. hyemalis I A. laxissima J A. microphylla K A. pallens L A. perennans M A. scabra N A. stolonifera O A. subpatens P A. subrepens Q A. tolucensis R A. turrialbae S A. variabilis. Scale bars: 0.3 mm.

Figure 5. Calluses of Agrostis species observed with SEM A A. bourgaei B A. calderoniae C A. capillaris D A. elliottiana E A. exarata F A. ghiesbreghtii G A. gigantea H A. hyemalis I A. laxissima J A. microphylla K A. pallens L A. perennans. Scale bars: 50 μm.

Figure 7. Lemma surface of Agrostis observed with SEM A A. bourgaei B A. calderoniae C A. capillaris D A. elliottiana E A. exarata F A. ghiesbreghtii G A. gigantea H A. hyemalis I A. laxissima J A. microphylla K A. pallens L A. perennans. Scale bars: 15 μm.

Figure 8. Map of known geographic distribution of Agrostis species, based on herbarium specimen data A A. bourgaei B A. calderoniae C A. capillaris D A. elliottiana E A. exarata F A. ghiesbreghtii.

Figure 9. Elevation histograms of Agrostis species A all records B native species C introduced species D A. bourgaei E A. calderoniae F A. capillaris G A. elliottiana H A. exarata I A. ghiesbreghtii J A. gigantea K A. hyemalis L A. idahoensis M A. laxissima N A. microphylla O A. pallens.

Figure 10. Phenology histograms of Agrostis species A all records B native species C introduced species D A. bourgaei E A. calderoniae F A. capillaris G A. elliottiana H A. exarata I A. ghiesbreghtii J A. gigantea K A. hyemalis L A. idahoensis M A. laxissima N A. microphylla O A. pallens.

Figure 14. Agrostis exarata A whole plant B ligular area C spikelet D floret, abaxial view, E floret, adaxial view F palea. Based on Spellenberg et al. 9056 (MEXU). Scale bars: 3 cm (A); 1 mm (B); 0.5 mm (C); 0.3 mm (D, E); 0.2 mm (F).

Figure 15. Leaf blade anatomy in transversal section of Agrostis species, in general view, and details of lateral bundles A - C A. exarata D - E A. ghiesbreghtii F - H A. gigantea I - K A. hyemalis. Scale bars: 0.1 mm.