Podagrostis rosei (Scribn. & Merr.) 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 rosei (Scribn. & Merr.) Sylvester & Soreng comb. nov. Fig. 4

Agrostis rosei Scribn. & Merr., Bull. Div. Agrostol., U.S.D.A. 24: 21, f. 5. 1901.

Type.

Mexico. Zacatecas: Sierra Madre mountains, [between Huasemote, Durango, and San Juan Capistrano], 18 Aug. 1897, J.N. Rose 2373 (holotype: US-301286 [not seen]; isotype: NY (NY00327649 [image!])).

Description.

Tufted perennial forming lax tufts, with the basal foliage reaching c. 4-9 cm tall and inflorescences well-exserted from the basal foliage. Tillers extravaginal. Culms 34-65 cm tall, erect or geniculate at the base, simple, delicate; nodes and internodes terete, nodes smooth, internodes and segment below the panicle smooth throughout, usually with at least 2 elongated internodes visible, with 1-3 nodes exposed at flowering, uppermost internode c. 5.6-9 cm long, longer than the sheath. Leaves basal and cauline, somewhat dimorphic with basal leaf blades filiform, flat or folded, while culm blades are wider and flat; sheaths terete, glabrous, lower sheaths smooth, upper sheaths smooth to very lightly scaberulous with short hooks; flag sheath 9-11.5 cm long; basal sheaths c. 1-2 cm long, striate, becoming fibrous, smooth; ligules c. 1-3 mm long, membranaceous to scarious, strongly decurrent with the sheath, sometimes lacerated, abaxially smooth or very lightly scaberulous; upper culm ligules 1.5-3 mm long, obtuse, sometimes deeply lacerated or erose towards the apex; ligules of tillers shorter to those of the culm, c. 1-1.3 mm long, truncate to obtuse; blades 1.5-9 cm long, 0.2-2.6 mm wide when opened out, basal blades 1.5-7 cm long, 0.2-0.6(-1) mm wide when opened out, usually narrower than the culm blades, filiform, flat or folded, flaccid to slightly firm, culm blades (2.8-)3.5-9 cm long, 1-2.6 mm wide, flat or sometimes slightly convolute towards the apices, flaccid to moderately firm, abaxial and adaxial surfaces glabrous, smooth or usually lightly to moderately scabrous on the veins with short hooks, edges scaberulous to scabrous. Panicles 8-14 × (1-)2.5-9 cm, open to slightly congested when immature, usually ovoid; panicle branches ascendant to patent, branched above the middle, filiform, with spikelets not present near the base, smooth, longest branches 2.5-7 cm long; pedicels 1-2.5 mm long, shorter or longer than the length of the spikelets, divaricate, smooth or lightly scaberulous. Spikelets 1.9-2.3 mm long; glumes remaining on the inflorescence at maturity, equal or subequal, the lower usually slightly longer than the upper by up to 0.2 mm, subequaling the length of the floret or to 0.2 mm longer, lanceolate, slightly keeled, apices acute, glabrous, keels completely smooth or scaberulous just in distal 1/3, surfaces smooth; lower glume 1- (or 3-)veined, lateral veins, if present, vestigial; upper glume 1- (or 3-)veined, lateral veins, if present, vestigial; lemmas 1.6-1.8 mm long, glabrous, smooth, strongly 5-veined with slightly excurrent prominent veins distally, apex broadly acute with 4 deltoid teeth, awn present, 1.6-2 mm long, straight, flexuous or geniculate, inserted in the lower 1/3 of the lemma, sometimes inserted basally c. 0.3 mm from the base, reaching the apex of the lemma, the glumes or sometimes briefly surpassing the glumes, glabrous, smooth proximally, scabrous distally; paleas well-developed, 1.3-1.7 mm long, usually reaching at least ¾ the length of the lemma to subequaling the lemma apex, keels obscure, smooth, apex bifid and sometimes erose; rachilla rudimentary or prolonged from the base of the floret, to 0.3 mm long, glabrous, smooth. Calluses not or slightly elongated, 0.05-0.1 mm long, glabrous, smooth. Flowers; lodicules c. 0.4-0.5 mm long, lanceolate with acute apices, not lobed; anthers 3 in number, 0.8-1 mm long. Caryopses not seen. 2 n = 14 (based on Reeder 4662).

Distribution and ecology.

Mexico, endemic. Ranges from Durango state in the north to Zacatecas in the south. Found in open forests at high elevations, 2600-2750 m alt. The authors have only verified specimens from Durango and Zacatecas states, with Beetle (1983), Villaseñor Ríos (2016), Dávila et al. (2018) and Sánchez-Ken (2019) variously mentioning the species to also occur in the states of Distrito Federal, Hidalgo, Jalisco, Mexico, Querétaro, and San Luis Potosí.

Other specimens examined.

Mexico. Durango: Pine forest with scattered oaks and occasional junipers, about 2 miles E of Puerto Buenos Aires, 9000 ft [2743 m alt.], 11 Oct. 1966, J.R. Reeder 4662 (US00486613); Sierra Madre Occidental, 0.5 miles SE of Los Charcos near small arroyo with Pinus cooperi , Juniperus and Panicum bulbosum , 23°0'57.5"N, 104°17'23.0"W, 2690 m alt., 21 Sep. 2005, P.M. Peterson 19053 (US00895358); Sierra Madre Occidental, 2.3 miles E of Los Mimbres along ridgetop with Pinus , Muhlenbergia and Quercus , 23°28'31.4"N, 104°55'3.6"W, 2630 m alt., 25 Sep. 2005, P.M. Peterson 19124 (US00900682).

Notes.

This species is distinct from all other species of Podagrostis currently circumscribed by the presence of a well-developed awn inserted in the lower dorsal surface of the lemma. Molecular data supports its inclusion in Podagrostis (Konstantin Romaschenko, pers. communication) with morphological attributes also corroborating this such as the florets subequalling the apices of the glumes, a well-developed palea> ¾ the length of the lemma, and completely glabrous spikelets. The lax and open, large panicles, and completely glabrous and mostly smooth spikelets, pedicels and panicle branches places it very close to P. liebmannii .

Figures

Figure 4. Podagrostis rosei. A Whole plant B ligular area of upper culm leaf C section of inflorescence showing spikelets. D Floret, lateral view, with the rachilla prolongation indicated with a red arrow. A Digitized image of specimen P. M. Peterson 19503 (US 00895358) courtesy of United States National Herbarium (US) B, C image of specimen P. M. Peterson 19124 (US 00900682) D image of specimen J. R. Reeder 4662 (US 00486613).