Agrostis laxissima Swallen, Contr. U.S. Natl. Herb. 29(9): 402. 1950.

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

10. Agrostis laxissima Swallen, Contr. U.S. Natl. Herb. 29(9): 402. 1950.

Figs 4I , 5I , 21

= Agrostis abietorum Swallen, Contr. U.S. Natl. Herb. 29(9): 403. 1950. Type: Guatemala. San Marcos: dry banks in Cupressus - Abies forest, along road between San Sebastian at km 21 and km 8, 8-18 miles NW of San Marcos, 2700-3800 m alt., 15 Feb 1940, J.A. Steyermark 35652 (holotype: F (F0046562F [image!]); isotype: US [fragm. ex F] (US00156356)).

Type.

Guatemala. San Marcos: dense Abies - Cupressus forest, along road between San Marcos and Serchil, 2700-3150 m alt., 30 Jan 1941, P.C. Standley 85379 (holotype: US ( US 00131078); isotypes: F (V0046566F [image!]), US ( US 00131079)) .

Description.

Plants perennial, caespitose. Tillers extravaginal, with cataphylls. Culms 25-85 cm long, decumbent to erect, nodes 2-6, glabrous, internodes glabrous. Leaves basal and cauline; sheaths 4-15 cm, shorter than the internodes, scaberulous; ligules 2.5-6 mm long, longer than wide, dorsally scaberulous, apices acute, often lacerate; blades 4-15(-25) cm long, 1-4 mm wide, lax, flat, scaberulous on both surfaces. Panicles 7-18 cm long, 2-9 cm wide, open, lax, lanceolate to ovate, sometimes partially included in the upper sheaths; branches ascending to spreading, rebranching about or above mid-length, scaberulous, without spikelets near their base, inferior branches 2-7 cm long; pedicels 1.5-6 mm long, ascending to spreading, scaberulous. Spikelets 1.7-3 mm long, greenish; glumes subequal, lanceolate, apices acute to shortly acuminate, 1-veined, scaberulous on the keel, lower glume 1.7-3 mm long, upper glume 1.5-2.8 mm long; callus pubescent, with two bunches of trichomes; lemmas 1.3-2.2 mm long, elliptic, apices irregularly toothed, 5-nerved, veins inconspicuous, awned from near the base, awn 3-4 mm long, geniculate; paleas absent or up to 0.4 mm long, veinless, glabrous; anthers 3, 0.7-1 mm long. Caryopsis not seen. 2n= unknown.

Anatomy and micromorphology.

Leaf blades flat in transversal section; adaxial furrows medium-sized, wide; adaxial ribs rounded; keel absent; first order bundles circular in outline, sheath interrupted abaxially, abaxial sclerenchyma in girders, narrowing towards the bundle, adaxial sclerenchyma in strands; second order bundles circular in outline, sheath interrupted abaxially, abaxial sclerenchyma in girders, narrowing towards the bundle, adaxial sclerenchyma in strands; intercostal sclerenchyma present, abaxial; leaf margins with well-developed sclerenchyma caps, extending along abaxial side of the leaf; colorless cells absent (Fig. 22A-C ). Lemmas with transversal thickenings irregular to oblong, wider than the unthickened portions of the wall; prickle hairs abundant (Fig. 7I ).

Distribution and habitat.

Endemic. Agrostis laxissima is distributed from Southern Mexico to Guatemala ( Pohl and Davidse 1994). It has also been reported in Honduras ( Soreng and Peterson 2003). This species has been collected from the Mexican state of Chiapas, and the departments of Quezaltenango, Sacatepéquez, San Marcos and Solola in Guatemala (Fig. 18D ). Agrostis laxissima grows in temperate forests, with Abies , Pinus , or Quercus , in cloud forests and grasslands, between 2250-3200 m a.s.l. (Fig. 9M ).

Phenology.

Specimens with spikelets have been collected from June to March, but most of the records are from December and January (Fig. 10M ).

Commentaries.

Agrostis laxissima is often confused with A. ghiesbreghtii (see the note under the description of that species).

Conservation status.

Agrostis laxissima is only known from a few localities of southern Mexico and Guatemala. It is represented by 17 collections, with several populations occurring in six protected areas. The EOO is 2,615 km2 and the AOO is 44 km2. Following the IUCN criteria, the preliminary assessment category is Vulnerable (VU).

Representative specimens examined.

Guatemala. Quezaltenango: Municipio San Juan Ostuncalco, barranco Buena Vista, cuesta El Caracol, Sierra Madre Mountains , about 5 km. northwest of San Juan Ostuncalco , [14.90886385°N, 91.66847343°W], 2800-2900 m alt., 11 Dec 1962, O. Williams et al. 22792 (F, US) . Municipio San Martín Sacatepéquez, cumbre de Tuilacán, SW of San Martín Chile Verde, [14.80612°N, 91.66872°W], 2400 m alt., 8 Mar 1939, P.C. Standley 67819 (F). Sacatepéquez: Municipio Alotenango, Volcan de Acatenango , [14.499453°N, 90.87175°W], 3200 m alt., 11 Sep 1993, I. Arias and M. Véliz 933265a (MEXU [*]), 18 Aug 2000, M. Véliz et al. 10263 (MEXU [*, **]) . Mexico: Chiapas: Municipio Motozintla, NW slope of cerro Mozotlan, below the microwave tower along the road from Huixtla to El Porvenir and Siltepec , [15.42605394°N, 92.34362676°W], 3000 m alt., 30 Dec 1972, D.E. Breedlove 31163 (MEXU [*, **]); 27 km al NO de Motozintla, camino a Coadesmech, torre de microondas, [15.43104735°N, 92.42724341°W], 3030 m alt., 21 Oct 1985, P. Dávila et al. 181 (MEXU [*]). See the Suppl. material 2 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 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 18. Map of known geographic distribution of Agrostis species, based on herbarium specimen data A A. gigantea B A. hyemalis C A. idahoensis D A. laxissima E A. microphylla F A. pallens.

Figure 21. Agrostis laxissima A whole plant B ligular area C spikelet D floret, abaxial view. Based on Breedlove 31163 (MEXU). Scale bars: 3 cm (A); 1 mm (B, C); 0.5 mm (D).

Figure 22. Leaf blade anatomy in transversal section of Agrostis species, in general view, and details of lateral bundles. A - C A. laxissima D - F A. microphylla G - I A. pallens J - L A. perennans. Scale bars: 0.1 mm.