Agrostis variabilis Rydb., Mem. New York Bot. Gard. 1: 32. 1900.

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

20. Agrostis variabilis Rydb., Mem. New York Bot. Gard. 1: 32. 1900.

Fig. 4S , 30G , 40

Agrostis varians Trin., Mém. Acad. Imp. Sci. Saint-Pétersbourg, Sér. 6, Sci. Math., Seconde Pt. Sci. Nat. 6,4(3-4): 314. 1841, nom. illeg. hom., non Thuillier 1799. Type: America borealis [Rocky Mountains?], J.D. Hooker T-217 (holotype: LE-TRIN; isotypes: MO (MO-992441 [image!], NY (NY327643 [image!], US (US00156511 [image!])).

Type.

Based on Agrostis varians Trin.

Description.

Plants perennial, slender, usually caespitose, rarely rhizomatous. Tillers extravaginal, with cataphylls. Rhizomes if present, up to 2 cm long. Culms 10-45 cm long, erect, nodes 1-2, glabrous, internodes glabrous. Leaves mostly basal; sheaths 0.8-6(-10) cm long, the lower ones longer than the internodes, the upper ones shorter, scaberulous; ligules 1-2.2 mm long, longer than wide, dorsally scaberulous, apices acute, erose to lacerate; blades 1-7 cm long, 0.5-1 mm wide, filiform, conduplicate to convolute, scaberulous on both surfaces. Panicles 1.5-13 cm long, 0.2-0.7 cm wide, contracted, dense, spiciform, linear, sometimes interrupted at the base, sometimes partially included in the upper sheaths; branches appressed, rebranching from below mid-length, scaberulous, with spikelets near their base, inferior branches up to 1 cm long; pedicels 0.3-2.2 mm long, appressed, scaberulous. Spikelets 1.4-2 mm long, greenish to stramineous, often tinged with purpure; glumes subequal, lanceolate, apices acute, 1-veined, scaberulous on the keel, lower glume 1.4-2 mm long, upper glume 1.3-1.9 mm long; callus glabrous; lemmas 1-1.4 mm long, elliptic, apices entire, acute, 5-veined, veins prominent distally, usually unawned, rarely awned above mid-length, awn up to 1 mm long, straight, not reaching the lemma apices; paleas absent; anthers 3, 0.3-0.6 mm long. Caryopsis 0.9-1.2 mm long, elliptic; endosperm solid. 2n= 28 ( Harvey 2007).

Anatomy. Leaf blades convolute to v-shaped in transversal section; adaxial furrows medium-sized to deep, narrow; adaxial ribs rounded to triangular: keel absent; first order bundles circular in outline, sheath interrupted abaxially, abaxial sclerenchyma in strands or girders, narrowing towards the bundle, adaxial sclerenchyma in strands; second order bundles circular in outline, sheath interrupted abaxially, abaxial and adaxial sclerenchyma in strands; intercostal sclerenchyma absent; leaf margins with well-developed sclerenchyma caps, rounded; colorless cells absent (Fig. 37E, F ). Lemmas with transversal thickenings irregular to oblong, wider than the unthickened portion of the wall; prickle hairs present, scarce (32G).

Distribution and habitat.

Agrostis variabilis is distributed from Alaska to the northern peninsula of Baja California, Mexico. In the study zone, it has been collected in the USA state of California, and the Mexican state of Baja California (Fig. 39B ). This species has also been reported from Chihuahua ( Sánchez-Ken 2019), but no specimens from this state were seen. Agrostis variabilis grows in open areas of temperate forests with Pinus , between 2400-2639 m a.s.l. (Fig. 27H ).

Phenology.

Specimens with spikelets have been collected from July to September (Fig. 28H ).

Commentaries.

It has been reported for other regions that the spikelets can reach 2.5 mm long ( Harvey 2007). This species is often confused with the smaller forms of A. exarata , but differs from them in the mostly basal leaves, with filiform and convolute to involute leaf blades, 0.5-1 mm wide (vs. basal and cauline leaves, leaf blades linear, flat, 1.5-4(-8) mm wide in A. exarata ).

Conservation status.

Agrostis variabilis is apparently a rare species in the study zone. It is represented by six collections, with its populations occurring in two protected areas. The EOO is 1,621 km2 and the AOO is 16 km2. Following the IUCN criteria, the preliminary assessment category is Endangered (EN).

Specimens examined.

Mexico. Baja California: Municipio Ensenada, Sierra San Pedro Mártir, fairly common in dry meadow W of Vallecitos, 31.01089°N, 115.49504°W, 2450 m alt., 23 Aug 1968, R. Moran 15395 (SD [*,**], UC); common on gravelly arroyo bank, Tasajera, ca. 3 km NW of Los Llanitos, 30.98333°N, 115.44167°W, 2500 m alt., 3 Sep 1979, R. Moran 28010 (SD); Sierra San Pedro Mártir, fairly common in arroyo, Jeffrey Pine forest , Yerba Buena, 31.01292°N, 115.48002°W, 2475 m alt., 16 Aug 1967, R. Moran and R.F. Thorne 14157 (SD). Sierra San Pedro Mártir, 25 Sep 1982, A. Preciado 299 (MEXU [*,**]); Sierra San Pedro Mártir, campground and main gate area, 31N, 115.557W, 2461 m alt., 14 Jul 2013, S. Ratay et al. 235 (SD) . USA. California: Riverside County, Mt. San Jacinto State Park, N side of Hidden Lake , 33.80022°N, 116.64119°W, 2639 m alt., 12 Jul 1999, L. Hendrickson 10430 (BSCA) .

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 27. Elevation histograms of Agrostis species A A. perennans B A. scabra C A. stolonifera D A. subpatens E A. subrepens F A. tolucensis G A. turrialbae H A. variabilis.

Figure 28. Phenology histograms of Agrostis species A A. perennans B A. scabra C A. stolonifera D A. subpatens E A. subrepens F A. tolucensis G A. turrialbae H A. variabilis.

Figure 30. Calluses of Agrostis species observed with SEM A A. scabra B A. stolonifera C A. subpatens D A. subrepens E A. tolucensis F A. turrialbae G A. variabilis. Scale bars: 50 μm.

Figure 37. Leaf blade anatomy in transversal section of Agrostis species, in general view, and details of lateral bundles. A, B A. tolucensis C, D A. turrialbae E, F A. variabilis. Scale bars: 0.1 mm.

Figure 39. Map of known geographic distribution of Agrostis species, based on herbarium specimen data A A. turrialbae B A. variabilis.

Figure 40. Agrostis variabilis A whole plant B ligular area C spikelet E floret, abaxial view F floret, adaxial view. Based on Moran 15395 (SD). Scale bars: 3 cm (A); 1 mm (B); 0.3 mm (C); 0.2 mm (D, E).