Agrostis bourgaei E. Fourn., Mexic. Pl. 2: 95. 1886.

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

1. Agrostis bourgaei E. Fourn., Mexic. Pl. 2: 95. 1886.

Figs 3 , 4A , 5A

Agrostis bourgaei E. Fourn. ex Hemsl., Biol. Cent.-Amer., Bot. 3: 550. 1885, nom. nud.

= Agrostis thyrsigera Mez, Repert. Spec. Nov. Regni Veg. 17(19): 301. 1921. Type: Mexico. State of México: wet banks, Sierra de las Cruces, 12 Aug 1893, C.G. Pringle 4485 (lectotype, designated by Vigosa-Mercado (2022a: 1): BR (BR0000006863616 [image!]); isolectoypes: BR (BR0000006864217 [image!]), K (K000308369 [image!]), KFTA (KFTA0002213 [image!]), MSC (MSC0129859 [image!]), NDG (NDG07467 [image!]), NY (NY00688876 [image!], NY00688877 [image!]), S (S12-16472 [image!]), W (W18940003052 [image!])).

Type.

Mexico. Mexico City: pedrégal près Tizapan, vallée de Mexico, 2 Aug 1865, E. Bourgeau 682 (holotype: P (P00740531 [image!]); isotype: US [fragm. ex P] ( US 00156379)) .

Description.

Plants perennial, caespitose. Tillers extravaginal, with cataphylls. Culms 0.1-1.2 m long, erect, sometimes shortly decumbent at the base, nodes 2-4, glabrous, internodes glabrous, or sometimes scaberulous below the nodes and panicle. Leaves basal and cauline; sheaths 3-18 cm long, usually shorter than the internodes, glabrous or scaberulous; ligules 1-7 mm long, longer than wide, dorsally scaberulous, apices acute, often lacerate; blades 3-15(-30) cm long, (0.5-)1-6 mm wide, linear, flat, scaberulous on both surfaces. Panicles (2-)9-25(-30) cm long, (0.8-)3-7(-10) cm wide, open, lax, lanceolate, usually long-exserted from the upper sheaths; branches ascending to spreading, rebranching from about or above mid-length, scaberulous, without spikelets near their base, inferior branches (1-)2-10 cm long; pedicels 0.5-3 mm long, ascending to spreading, scaberulous. Spikelets 2-2.7 mm long, usually purplish; glumes subequal to equal, lanceolate, apices shortly acuminate, 1-veined, scaberulous on the keel, lower glume 2-2.7 mm long, upper glume 1.8-2.5 mm long; callus puberulous, with 2 bunches of short trichomes, often inconspicuous; lemmas 1.5-1.8 mm long, elliptic, apices entire, acute or toothed, 5-nerved, veins inconspicuous, unawned; paleas present, (0.4-)0.5-0.7(-1) mm long, veinless, glabrous; anthers 3, (0.3-)0.5-0.7 mm long. Caryopsis 1.2-1.5 mm long, ellipsoid; endosperm soft. 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 adaxially and 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 or t-shaped girders; intercostal sclerenchyma absent; leaf margins with well-developed sclerenchyma caps, rounded; colorless cells absent (Fig. 6A-C ). Lemmas with transversal thickenings polygonal, wider than the unthickened portions of the wall; prickle hairs scarce (Fig. 7A ).

Distribution and habitat.

Endemic. Herbarium specimens of A. bourgaei have been collected in Mexico City and the Mexican states of Hidalgo, México, Michoacán, Morelos, Puebla, and Oaxaca (Fig. 8A ). The species has also been reported for Durango, Guanajuato, Querétaro, Tlaxcala, and Veracruz ( Villaseñor 2016; Dávila et al. 2018; Sánchez-Ken 2019), but no specimens from these states were seen. Agrostis bourgaei is mainly found on edges of streams and moist soils, in open areas of conifer forests of the Trans-Mexican Volcanic Belt, between 1800-3800 m a.s.l., with some outliers in Morelos found lower, at 725 m a.s.l. (Fig. 9D ).

Phenology.

Specimens with spikelets have been collected from June to February, but most of the records are from August (Fig. 10D ).

Commentaries.

Agrostis bourgaei is similar to A. gigantea , and both are often confused. They share very similar leaf anatomy and paleate spikelets, but A. bourgaei is distinguished from the latter in the much more fragile aspect of the plants, caespitose habit, lateral branches of the panicle without spikelets near their base, lemmas with prickle hairs, transversal thickenings, and shorter paleas of up to 0.7(-1) mm long (vs. robust plants, usually rhizomatous habit, often some inferior branches with spikelets near their base, lemmas glabrous, without transversal thickenings, paleas up to 1.2 mm long in A. gigantea ). The specimen García-Mendoza 1116 (MEXU) from Oaxaca lacks vegetative parts that may allow a more acceptable identification, but is included tentatively in this species for its paleate spikelets.

Conservation status.

Agrostis bourgaei is an abundant and widespread species in Central Mexico. It is represented by 61 collections, with several populations occurring in 13 protected areas. The EOO is 45,765 km2 and the AOO is 1,476 km2. Following the IUCN criteria, the preliminary assessment category is Least Concern (LC).

Representative specimens examined.

Mexico. Hidalgo: Municipio Epazoyucan , Peñas Largas, [20.1°N, 98.6°W], 2850 m alt., 22 Dec 1983 J. Rzedowski 38373a (IEB, MEXU, XAL) . México: Municipio Lerma , 5 km al W de La Marquesa, en la desviación a Salazar , [19.304403°N, 99.39047°W], 2800 m alt., 1 Aug 1981, R. Guzmán 3966 (IBUG, MEXU). Municipio Ocuilan, Laguna de Zempoala , [19.05034984°N, 99.31696647°W], 2800 m alt., 1 Aug 1987, J. Castañeda 327 (MEXU [*]). Mexico City: Alcaldía Cuajimalpa, Llano de la Cieneguilla, Puerto de las Cruces, [19.24694444°N, 99.33444444°W], 3500 m alt., 19 Sep 1983, S. Acosta and R. Aguilar 417 (CIIDIR, IEB, MEXU), 418 (CIIDIR, IEB, MEXU [*,**]), 419 (CIIDIR, IBUG, MEXU), 420 (CIIDIR, IBUG, IEB, MEXU); Parque Nacional Desierto de los Leones, 2 km a pie de La Venta por la brecha que va a Santa Rosa, 19.321112°N, 99.306817°W, 2881 m alt., 22 Aug 2021, L. Vigosa and A. Mercado 112 (MEXU [*,**]). Michoacán: Municipio Angangueo, Estación Chincua, Reserva de la Biósfera Mariposa Monarca, [19.65618889°N, 100.2717278°W], 3030 m alt., 5 Aug 2000, M.G. Cornejo et al. 67 (IEB, MEXU [*]). Municipio Maravatío, km 6 carretera Maravatío-Ciudad Hidalgo al S del poblado de Casa Blanca, [19.85705°N, 100.4516389°W], 2000 m alt., J.E. Morales and A. Pastor 56 (IEB, MEXU [**]). Morelos: Municipio Huitzilac, Lagunas de Zempoala , [19.05320158°N, 99.31276612°W, 2800 m alt.], 19 Sep 1938, E. Lyonnet 2518 (FCME [*], MEXU, UAMIZ, US); Municipio Tlaquiltenango, Huaxtla 18.37444444°N, 99.07222222°W, 725 m alt., 23 Feb 2015, G. Rendón et al. s.n. (HUMO). Oaxaca: Municipio San Andrés Lagunas, Laguna Grande, 1 km al N de San Isidro Lagunas, [17.62219847°N, 97.5414394°W], 2200 m alt., 5 Aug 1982, A. García-Mendoza 1116 (MEXU). Puebla: Municipio San Nicolás de los Ranchos, Paso de Cortés, 3 km al S de la carretera a Amecameca, sobre la brecha al Volcán Iztaccíhuatl, 13 km al E de Amecameca, [19.12°N, 98.63°W], 3760 m alt., 1 Nov 1976, S.D. Koch 76237 (CHAPA, US). See Suppl. materials 2, 3 for additional examined specimens .

Figures

Figure 3. Agrostis bourgaei A whole plant B ligular area C spikelet D floret, abaxial view, E floret, lateral view showing the lemma and the palea F palea. Based on Acosta 419 (MEXU). Scale bars: 3 cm (A); 2 mm (B); 0.5 mm (C-E); 0.1 mm (F).

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.