Podagrostis trichodes (Kunth) Sylvester & Soreng, PhytoKeys 148: 42. 2020

Sylvester, Steven P., Cuta-Alarcon, Lia E., Bravo-Pedraza, William J. & Soreng, Robert J., 2020, Agrostis and Podagrostis (Agrostidinae, Poaceae) from paramos of Boyaca, Colombia: synoptic taxonomy including a key to Colombian species, PhytoKeys 151, pp. 107-160 : 107

Podagrostis trichodes (Kunth) Sylvester & Soreng, PhytoKeys 148: 42. 2020 Fig. 11

Vilfa trichodes Kunth, Nov. Gen. Sp. [H.B.K.] 1: 139. 1816.

Agrostis trichodes (Kunth) Roem. & Schult., Syst. Veg. (ed. 15 bis) 2: 361. 1817.

Aira trichodes (Kunth) Spreng., Syst. Veg., ed. 16 [Sprengel] 1: 276. 1824.

= Agrostis bogotensis Hack., Repert. Spec. Nov. Regni Veg. 8: 518. 1910. Type: Colombia. S. Cristobal prope Bogota [ près de Bogota], [2500-3000 m alt.], 13 July 1908, F. Apolliniaire s.n. (holotype: W (W19160027256 [image!]); isotypes: BM (BM000938528 [image!]), MPU (MPU027104 [image!]), SI (SI000495 [image!] fragm. ex US), US (US75365 fragm.)).

Type.

Peru. Crescit in crepidinibus Andium Peruvianum justa Montan, Santa Cruz et Guambos, alt. 1350 hexap. [2469 m alt.], floret Augusto, F.W.H.A. Humboldt & A.J.A. Bonpland s.n. (holotype: P; isotypes: HAL (HAL0106929 [image!]), US (US75364! fragm. ex P)).

Description.

Perennial herbs, forming short dense tufts, with the basal mats reaching c. 4-11 cm tall and inflorescences well-exerted from the basal foliage. Tillers intravaginal, without cataphylls. Culms 7-20(-30) cm tall, erect, simple, delicate, with 0(-1) nodes exerted at flowering, smooth. Leaves mostly basal, glabrous, finely to densely scabrous; ligules 0.7-1.7(-2.5) mm long, of basal leaves and tillers 0.7-1.2 mm long, of upper culm leaves generally longer, truncate to obtuse, slightly to usually strongly decurrent with the sheath, abaxial surface smooth or rarely scaberulous; blades 1-4 cm long, 0.3-0.4 mm wide in diameter, involute or convolute, acicular to capillaceous and filiform, usually curved, rigid, apices acute. Panicles 2-5(-6) cm long, 1-2(-3) cm wide, lax and open, ovoid, slightly to usually greatly exerted from the basal foliage, lateral branches with spikelets in the distal 1/3, the lower 2/3 naked, long, ascending to patent, not held close to the central inflorescence axis, central axis and panicle branches usually scaberulous or sometimes smooth; pedicels 1-2 mm long, usually longer than the length of the spikelets, not or slightly dilated at their apex, smooth to usually lightly scabrous. Spikelets 1-1.5 mm long; glumes equal or subequal, the lower often slightly longer than the upper, 1-veined, keels scabrous just in the distal 1/3 to throughout their length, surfaces smooth a scabrous distally, apices obtuse to acute; floret almost equaling the length of the glumes or slightly shorter; calluses glabrous; lemmas 1-1.5 mm long, glabrous, moderately to densely scabrous ( ‘smooth’ possibly mentioned by Tovar 1993!), sometimes granulose, apex obtuse, faintly to strongly 5-veined, awn lacking or to 0.5 mm long, straight, inserted medially or in the upper half of the lemma, not surpassing the glumes; paleas (0.7-)0.9-1.3 mm long, usually reaching from ¾ to subequaling the lemma, less often reaching 2/3 the length of the lemma; rachilla usually prolonged from the base of the floret (sometimes lacking in a small number of spikelets within the inflorescence), 0.2-0.5 mm long, glabrous, smooth to scabrous; anthers 0.4-1 mm long.

Distribution and ecology.

Colombia, Ecuador?, Peru, Venezuela, 2800-4500 m alt. Relatively humid high-Andean puna grasslands of southern and central Peru and páramo grasslands of Ecuador, Colombia and Venezuela. May also occur in Bolivia according to Tovar (1993), although no specimens have been verified. No specimens have been verified from Ecuador, although it is mentioned to occur there ( Hitchcock 1927; Tovar 1993; Jørgensen and Ulloa-Ulloa 1994; Jørgensen and León-Yánez 1999; Luteyn 1999). A common element in moderately grazed areas and path-sides of Boyacán páramo.

Other specimens examined.

See Sylvester et al. (2020).

Notes.

The combination of open panicle, spikelets <1.5 mm long, florets which subequal the apex of the glumes, a palea reaching from (2/3) ¾ to subequaling the lemma, lemmas awnless or with a short (<0.5 mm long) straight awn inserted in the upper ½ of the lemma, and a short glabrous rachilla prolongation emerging from under the palea are diagnostic for this species. The rachilla prolongation (Fig. 11 , indicated by arrows) is sometimes difficult to see if it is tucked between the flanges of the palea, and so spikelet dissection is necessary. All species of Podagrostis from Colombia have involute or convolute leaf blades that can easily separate them from species of Agrostis with well-developed paleas.

Similar species.

Aside from Podagrostis bacillata (Hack.) Sylvester & Soreng and P. exserta (Swallen) Sylvester & Soreng that are found in Central America (see Sylvester et al. 2020), P. trichodes could possibly be mistaken for shorter plants of A. perennans which can have short spikelets as small as 1.8 mm long. Agrostis perennans s.l. has florets which usually do not reach past ¾ the length of the glumes, a minute palea less than ¼ the length of the lemma, and lacks a rachilla prolongation.

Figures

Figure 11. Podagrostis trichodes A spikelet, lateral view with floret detached and raised above the glumes, rachilla prolongation indicated by an arrow B floret, lateral view, rachilla prolongation indicated by an arrow C whole plant. Images: A, B Rodriguez (UPTC 22204), C Cuta-Alarcon 362 (FMB).