Agrostis calderoniae Acosta, Phytologia 62(6): 449, Fig. 1. 1987.

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

2. Agrostis calderoniae Acosta, Phytologia 62(6): 449, Fig. 1. 1987.

Figs 4B , 5B , 11

Type.

Mexico. State of México: Municipio Tlalmanalco , La Ciénega, región de Peñas Cuatas, ladera NW del Iztaccíhuatl, 3600 m alt., 19 Aug 1984, S. Acosta 687 (holotype: ENCB! (ENCB003243 [image!]); isotypes: MEXU! (MEXU00436130 [image!]), CHAPA! (CHAPA0000037 [image!]), IEB, TEX) .

Description.

Plants perennial, caespitose. Tillers extravaginal, with cataphylls. Culms 10-40 cm long, erect, nodes 1-2, glabrous, internodes glabrous. Leaves mostly basal; sheaths 3-10 cm long, usually longer than the internodes, glabrous; ligules 1.5-4 mm long, longer than wide, glabrous, apices acute, often lacerate; blades (1-)2-10 cm long, up to 2 mm wide, linear, conduplicate to convolute, scaberulous on both surfaces. Panicles 5-13 cm long, 2-10 cm wide, open, lax, lanceolate to ovate, long-exserted from 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 1-3 mm long, ascending to spreading, scaberulous. Spikelets 2.5-3.5 mm long, purplish; glumes subequal to equal, lanceolate, apices shortly acuminate, 1-veined, scaberulous on the keel, lower glume 2.5-3.5 mm long, upper glume 2.2-3.5 mm long; callus glabrous; lemmas 2-2.5 mm long, elliptic, apices irregularly toothed, 5-nerved, veins inconspicuous, unawned; paleas present, 0.5-1 mm long, veinless, glabrous; anthers 3, 0.7-1 mm long. Caryopsis not seen. 2n= unknown.

Anatomy and micromorphology.

Leaf blades convolute or v-shaped in transversal section; adaxial furrows deep, narrow; adaxial ribs rounded to triangular; keel absent; first order bundles circular in outline, sheath interrupted abaxially, abaxial sclerenchyma in strands or girders in the central bundle, narrowing towards the bundle, adaxial sclerenchyma in strands; second order bundles circular in outline, sheath not interrupted, abaxial and adaxial sclerenchyma; intercostal sclerenchyma present, abaxial; leaf margins with well-developed sclerenchyma caps, rounded; colorless cells absent (Fig. 6D, E ). Lemmas with transversal thickenings irregular, wider than the unthickened portions of the wall; prickle hairs abundant (Fig. 7B ).

Distribution and habitat.

Endemic. Agrostis calderoniae has only been collected in the western slope of the Iztaccíhuatl volcano, in the state of México (Fig. 8B ). This species grows in moist soils near the edge of streams, in open areas of temperate forests with Pinus , between 3500-3800 m a.s.l. (Fig. 9E ).

Phenology.

Specimens with spikelets have been collected in January, July, and August (Fig. 10E ).

Commentaries.

This species is similar to A. bourgaei , in the caespitose habit and paleate spikelets, but it is distinguished in the mostly basal leaves, leaf blades conduplicate or convolute, with deep adaxial furrows, abaxial intercostal sclerenchyma, longer spikelets of 2.5-3.5 mm long, and lemmas with transversal thickenings of irregular shape (vs. basal and cauline leaves, leaf blades flat, with medium-sized adaxial furrows, without intercostal sclerenchyma, spikelets of 2-2.7 mm long, lemmas with polygonal transversal thickenings in A. bourgaei ).

Conservation status.

Agrostis calderoniae only has been collected in two localities of the Iztaccíhuatl-Popocatéptl National Park, where it is reported as scarce in the labels of the herbarium specimens. The EOO and AOO cannot be calculated, but by the scarcity and size of the populations of this species, the category of Endangered (EN) is suggested.

Specimens examined.

Mexico. México: Municipio Amecameca , vertiente SW del Iztaccíhuatl, 4 km al N de la estación retransmisora de TV, [19.14308652°N, 98.64774789°W], 3800 alt., 15 Jul 1965, J. Rzedowski 20161 (ENCB). Municipio Tlalmanalco , vertiente NW del Iztaccíhuatl, en la región de Peñas Cuatas, La Ciénega, [19.225278°N, 98.680833°W], 3650 m alt., 6 Jan 1966, J. Rzedowski 21798 (ENCB); La Ciénega, región de la cabeza del Iztacccíhuatl, [19.225278°N, 98.680833°W], 19 Aug 1984, S. Acosta 692 (IEB [*,**]); 3600 m alt., 18 Jul 1982, J. Rzedowski 37855 (ENCB) .

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 6. Leaf blade anatomy in transversal section of Agrostis species, in general view, and details of lateral bundles. A - C A. bourgaei D - E A. calderoniae F - G A. capillaris H - I A. elliottiana. Scale bars: 0.1 mm.

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 11. Agrostis calderoniae A whole plant B ligular area C spikelet D floret, abaxial view E floret, adaxial view F palea. A based on Acosta 687 (isotype, MEXU), B-F based on Acosta 692 (IEB). Scale bars: 3 cm (A); 1 mm (B); 0.5 mm (C-E); 0.2 mm (F).