Podagrostis trichodes (Kunth) Sylvester & Soreng, 2020

Sylvester, Steven P., Peterson, Paul M., Romaschenko, Konstantin, Bravo-Pedraza, William J., Cuta-Alarcon, Lia E. & Soreng, Robert J., 2020, New combinations and updated descriptions in Podagrostis (Agrostidinae, Poaceae) from the Neotropics and Mexico, PhytoKeys 148, pp. 21-50 : 21

Podagrostis trichodes (Kunth) Sylvester & Soreng comb. nov. Fig. 5

Aira trichodes (Kunth) Spreng., Syst. Veg. [Sprengel]) 1: 276. 1825[1824]. Agrostis trichodes (Kunth) Roem. & Schult., Systema Vegetabilium 2: 361. 1817. Vilfa trichodes Kunth, Nova Genera et Species Plantarum (quarto ed.) 1: 139. 1815[1816].

= Agrostis bogotensis Hack., Repert. Nov. Sp. Fedde 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. [not seen])).

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 [not seen]; isotypes: HAL (HAL0106929 [image!]), US (US75364! fragm. ex P)).

Description.

Tufted perennial forming short dense tufts, with the basal mats reaching c. 4-11 cm tall and inflorescences well-exserted from the basal foliage. Tillers intravaginal. Culms 7-20(-30) cm tall, erect, simple, delicate; nodes and internodes terete, smooth, nodes usually hidden in the sheaths with 0(-1) nodes exposed at flowering, uppermost internode usually <1 cm long, usually not longer than the sheath. Leaves generally basal; sheaths terete, glabrous, finely to densely scabrous; flag sheath 2-5.6 cm long; basal sheaths 0.7-1.5 cm long, striate, becoming fibrous; ligules 0.7-1.7(-2.5) mm long, membranaceous, slightly to usually strongly decurrent with the sheath; flag ligules acute with a obtuse to truncate apex, usually slightly erose towards the apex; ligules of tillers 0.7-1.2 mm long, truncate; blades 1-4 cm long, 0.3-0.4 mm wide in diameter, involute or convolute, acicular to capillaceous and filiform, usually curved, abaxial surface glabrous, finely to densely scabrous, adaxial surface glabrous, lightly to usually densely scabrous with prickle hairs usually short, less often long and robust. Panicles 2-5(-6) × 1-2(-3) cm, open, ovoid; panicle branches ascendant to patent, branched above the middle, filiform, with spikelets not present near the base, smooth to usually scaberulous, longest branches 0.8-3 cm long; pedicels 1-2 mm long, usually longer than the length of the spikelets, divaricate, smooth to usually lightly scabrous. Spikelets 1-1.5 mm long; glumes remaining on the inflorescence at maturity or one or both readily caducous at maturity and falling before the floret, equal or subequal, the lower often slightly longer than the upper or less often vice versa, almost equaling the length of the floret or slightly longer, oblong-lanceolate, slightly to distinctly keeled, apex obtuse to acute, glabrous, keels scabrous just in the distal 1/3 to throughout their length, surfaces smooth a scabrous distally; lower glume 1-veined; upper glume 1- or 3-veined; lemmas 1-1.5 mm long, glabrous, moderately to densely scabrous ( ‘smooth’ possibly mentioned by Tovar 1993!), sometimes granulose, faintly to strongly 5-veined, apex obtuse, awn lacking or to 0.5 mm long, straight, inserted medially or in the upper half of the lemma; 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, keels obscure to fairly prominent, smooth, apex bifid and erose; rachilla absent or 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. Calluses 0.05-0.1 mm long, slightly elongated or not, glabrous. Flowers; lodicules c. 0.4 mm long, lanceolate with acute apices, not lobed; anthers 3 in number, 0.4-1 mm long. Caryopses c. 1 mm long, subterete, sulcus distinct, dark brown with apex dark; hilum 0.25 mm long, narrowly ovoid; endosperm solid. 2n = unknown.

Distribution and ecology.

Bolivia?, 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. Tovar (1993) mentions that the species may also occur in Bolivia, presumably in high-elevation cool and humid sites such as the Bolivian Yungas which have been referred to as páramo ( García and Beck 2006), although no specimens have been verified by the authors. No specimens at the US herbarium were found from Ecuador after careful searching by the first author, although it is mentioned to occur there ( Hitchcock 1927; Tovar 1993; Jørgensen and Ulloa-Ulloa 1994; Jørgensen and León-Yánez 1999; Luteyn 1999). In Colombia, the taxon is known from multiple collections from páramos of the Cordillera Oriental of the Colombian Andes, belonging to Departamentos Cundinamarca, Boyacá, Santander, Santander Norte and Cesar. We present new regional records of the species for Departamentos Santander Norte and Cesar which are not mentioned in the recent checklist ( Giraldo-Cañas et al. 2016). Giraldo-Cañas et al. (2016) also cite Agrostis trichodes for Departamento Meta, in the southernmost part of the Cordillera Oriental, and Departamento Magdalena, which contains páramos of the Sierra Nevada de Santa Marta, although no specimens have been verified. In Venezuela, the species is found in páramos of the Cordillera de Merida.

Usually found in frequently grazed areas where its short basal tufts of leaves are difficult for grazers to reach. Specimens from Peru appear to be found in humid habitats, with the specimens studied by Tovar (1993) collected from the Abra Malaga of the Cusco region which is relatively humid and receives updrafts of moisture-laden air from the Amazon ( Sylvester et al. 2014, 2017). While P. trichodes is relatively common in páramos of Colombia and Venezuela, it may be that this species is much rarer further south and, in Peru, belongs to a thin band of humid páramo-like vegetation that extends from the Peruvian Jalca down through southern Peru and into the Bolivian Yungas (Antoine Cleef, pers. communication).

Other specimens examined.

Colombia. Boyacá: Munic. Chiscas, Vereda Rechiniga, Páramo de la Mesa, área húmeda semiperturbada de Páramo, con Espeletia, Puya, Ageratina e Hypericum, 6.59515N, 72.44359W, 3741 m alt., 3 Mar. 2018, S.P. Sylvester 3091 (K, US, FMB); Munic. Chiscas, Páramo de Chacaritas, límites entre páramo y superpáramo, 6.62865N, 72.39440W, 4064 m alt., 4 Mar. 2018, S.P. Sylvester 3103 (K., US); Munic. Chiscas, Páramo el Peñon, borde de bosque de Polylepis , 6.60119N, 72.43715W, 3917 m alt., 5 Mar. 2018, S.P. Sylvester 3157 (K, US, FMB, COL, UPTC, SI); Munic. Duitama, Páramo de la Rusia, en la carretera que conduce a la Peña Negra, páramo con rocas expuestas, 5,58389N, 73,053263W, 3970 m alt., 21 Nov. 2017, M. Vorontsova 2218 (K, US, FMB, SI). Munic. Duitama, Páramo de la Rusia, vía que conduce a la Vereda Avendaños, 5.93247N, 73.0798W, 3726 m alt., 4 Oct. 2017, S.P. Sylvester 3038 (K, US, FMB, UPTC); Munic. Duitama, Páramo de Agueros, en la vía que conduce a la vereda Avendaños, Se observa evidencia de fuego y pastoreo, 5.91464N, 73.07114W, 3445W m alt., 28 Oct. 2017, S.P. Sylvester 3067ª (K, US, FMB); Munic. Mongua, Páramo de Oceta, Valle de Laguna Negra, vegetación de pajonal frailejonal con presencia de pastoreo de vacunos, 5.69525N, 72.79133W, 3694 m alt., 29 Nov. 2017, L.E. Cuta-Alarcón 354 (K, US, FMB). Santander: Paramo de la Angostura, Vereda El Mortino, 06°57'30"N, 72°43'30"W, 3605 m alt., 17 Nov. 2007, M.C. Gomez 1 (US-3534984). Santander Norte & Cesar: Limites entre Santander Norte y Cesar jurisdicciones, Cerro de Oroque, 3700-3900 m alt., 22-27 July 1974, H. Garcia-Barriga 20588 (US29665591; US2966621).

Venezuela. Mérida: Sierra Nevada, 9000 ft, 1847, Funck & Schlim 1630 (US); Sierra Nevada de Santo Domingo, between partaderos and Timotes, Paramo de Mucuchies, Pico Aguila, 4118 m alt., 21-26 Nov. 1959, H.G. Barclay 9685 (US3044346); Sierra Nevada de Santo Domingo, Paramo de Mucubaji, alrededores de la Laguna Grande, 3560-3600 m alt., 19 Nov. 1959, H.G. Barclay 9546 (US3096576); Sierra Nevada de Santo Domingo, Paramo Laguna de Mucubaji, carretera Barinas-Merida, 4200 m alt., 15 Nov. 1958, B. Trujillo 4072 (US3652663). Trujillo: Munic. Bocono, Laguna Eco to Pico Guarigay (summit), Monumento Natural Teta de Niquitao-Guirigay, summit of Pico Guarigay, 3600-3870 m alt., 16 Sep. 2003, B. Stergios 20450 (US00772686); Munic. Bocono, Laguna Larga, via Laguna Las Parias to Laguna Eco, Paramo de Motumbo, Monumento Natural Teta de Niquitao-Guirigay, 3400-3600 m alt., 15 Sep. 2003, B. Stergios 20420 (US00772685); Along the border with Merida state, 3400 m alt., 14 Sep. 2003, B. Stergios 20315 (US00772683); B. Stergios 20358 (US00772684); Monumento Natural Teta de Niquitao-Guirigay, sector Las Veguitas, 3060-3080 m alt., 20-21 Aug. 2002, L.J. Dorr 9157 (US00728039); Monumento Natural Teta de Niquitao-Guirigay, Paramo Guirigay, 3400-3600 m alt., 2-3 Aug. 2002, B. Stergios 19851 (US00728050).

Notes.

Briceño (2010) noted the possible relationship of Agrostis trichodes to Podagrostis based on the rachilla prolongation. While studying specimens of A. trichodes from páramos of Colombia and Venezuela, SPS noted certain characteristics differed from the type collected in Peru, the protologue, and the description in the treatment of grasses of Peru ( Tovar 1993). These characteristics, including presence of a rachilla prolongation emerging from the base of the florets, and lemmas sometimes with a short dorsally inserted awn, are also shared by A. bacillata and A. exserta , and highlight the connection of this species to Podagrostis .

The character of awn presence was not noted for this species by Hitchcock (1927) nor Tovar (1993), although Briceño (2010) mentions this for Venezuelan material. While Hitchcock (1927) highlights the rachilla prolongation as a crucial character for distinguishing this species from other Agrostis , Tovar (1993) did not mention it. This information is also lacking from the protologues of both Vilfa trichodes and Agrostis bogotensis . The Vilfa trichodes isotype at HAL bears spikelets which lack a rachilla extension, and lemmas that lack awns (Marcus Lehnert and Natalia Tkach, pers. communication). It appears that Oscar Tovar, when preparing his treatment of the grasses of Peru ( Tovar 1993), had only seen the US isotype fragment, which lacks florets. His mention that the glumes are ‘glabrous’ (by which Tovar meant glabrous and smooth) raises ambiguity, although most other characters found in the description and illustration match. The flag leaf ligule of the US isotype fragment reached 1.5 mm long, while Tovar (1993) mentions the ligule to measure 2-2.5 mm long, with most material studied from Colombia and Venezuela having flag leaf ligules to 1.7 mm long, with those of the tillers c. 0.5 mm long. Tovar’s (1993) description seems to have been based largely on Tovar and Rivas-Martínez 8076, 8080 from Abra Malaga of the Cusco region of southern Peru, which were not seen by us. The first author visited the Abra Malaga site to conduct extensive field surveys and botanical collecting during different seasons from 2010-2013 ( Sylvester et al. 2014, 2017) but no specimens were encountered. Aside from the type, no specimens from Peru have been located despite careful searching through the US herbarium.

Podagrostis trichodes closely resembles P. exserta and P. bacillata , considered endemic to alpine grasslands of Guatemala or páramos of Costa Rica and Panama, respectively ( Pohl and Davidse 1994). Key similarities include: a) an overall similar habit (i.e. short tufted herbs with exserted open panicles); b) involute or convolute, acicular or filiform leaf blades; c) presence of a short glabrous rachilla extension emerging from the base of the floret; and d) a short awn often found inserted medially on the lemma dorsal surface. Both P. bacillata and P. exserta have smooth panicle branches, pedicels, glume surfaces (with only the keels being lightly scaberulous), and lemma surfaces while these are usually lightly to densely scabrous in P. trichodes , although specimens have been encountered with almost smooth panicle branches and pedicels [e.g., M.C. Gomez 1 (US3534984), H.G. Barclay 9685 (US3044346), 9546 (US3096576)]. The overall habit of P. exserta more closely resembles that of P. trichodes than P. bacillata , in lacking a visible elongated culm internode and having a shorter panicle (<5 cm long vs. 4-11 cm long in P. bacillata ). However, P. exserta can be differentiated from P. trichodes in having smooth leaf blade abaxial surfaces, lemma surfaces, panicle branches, and pedicels (vs. usually scaberulous to densely scabrous, panicle branches and pedicels infrequently smooth in P. trichodes ), its glume keels and surfaces being mostly smooth with only few prickle hairs found on the keel distally (vs. glume keels often densely scabrous for most their length with surfaces often scabrous distally in P. trichodes ), and larger spikelets (usually 1.5-2 mm long vs. 1-1.5 mm long in P. trichodes ).

Podagrostis bacillata can be differentiated from P. trichodes in having culms with at least one visible elongated internode and an exserted node (vs. usually without a visible elongated internode and exserted node in P. trichodes ), panicles usually larger, 4-11 cm long (vs. 2.5-6 cm long in P. trichodes ), panicle branches and pedicels generally smooth (vs. usually lightly to densely scabrous, infrequently smooth in P. trichodes ), longer spikelets, 1.7-2 mm long (vs. 1-1.5 mm long in P. trichodes ), glumes smooth apart from the lightly scaberulous keel (vs. glume keels often densely scabrous for most their length, with surfaces often scabrous distally in P. trichodes ), lemmas smooth (vs. lightly to densely scabrous in P. trichodes ), and rachilla prolongation 3-1.4 mm long (vs. 0.2-0.5 mm long in P. trichodes ).

Specimens from páramos of Departamento Boyacá, Colombia, were noted to have the unusual character of glumes being readily caducous at maturity and falling before the floret, with mature inflorescences lacking glumes and only the florets remaining on the pedicels. It is not clear whether this may be a reaction to a pathogen or whether it is taxonomically informative since other specimens sometimes lack this character.

Certain specimens of Freire Apolliniaire are annotated as isotypes of Agrostis bogotensis at P (P00740431 [image!]) and NY (NY00327650 [image!], NY00688633 [image!]) that differ in collection dates, collection numbers, and/or localities from the holotype, with NY00688633 also obviously not the same species. These should be disregarded as type material and reexamined. Apolliniaire s.n. K000308373 may be an isotype but the full collection date is missing to help clarify this.

Figures

Figure 5. Podagrostis trichodes. A Whole plant B spikelets, with the floret detached and raised above the glumes so that the rachilla prolongation (indicated with a red arrow) can be seen C section of inflorescence D leaf blade, showing abaxial surface. A, B images of specimen L. E. Cuta-Alarcon 362 (FMB) C, D images of specimen M. C. Gomez 1 (US 3534984).