Podagrostis (Griseb.) Scribn. & Merr. Contr. U.S. Natl. Herb. 13(3): 58. 1910.

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 (Griseb.) Scribn. & Merr. Contr. U.S. Natl. Herb. 13(3): 58. 1910.

Agrostis sect. Podagrostis Griseb. Fl. Ross. 4(13): 436. 1852.

Type.

Agrostis canina var. aequivalvis Trin. (lectotype designated by: Hitchcock 1920: 127).

Description.

Perennials, loosely to densely tufted, sometimes forming small tussocks, sometimes subrhizomatous (North American, including Mexico, and Austral South American taxa). Culms 5-90 cm tall, slender. Tillers either extra- or intravaginal. Leaves; ligules 0.2-5.5 mm long, hyaline, glabrous, smooth or lightly scabrous, apices truncate, obtuse, acute or acuminate, entire to lacerate; blades involute, folded, or flat. Inflorescence 1-12 cm long, a panicle, lax and open to loosely to moderately densely contracted; panicle branches and pedicels glabrous, often smooth or infrequently scaberulous. Spikelets 1-4.2 mm long, 1-flowered, disarticulating above the glumes, weakly laterally compressed; glumes equal or subequal, the lower often longer than the upper, equaling or subequaling the length of the floret or slightly longer, persisting on the plant after the florets have fallen or sometimes readily caducous, glabrous, keel smooth or usually scabrous at least distally, lateral veins smooth or slightly scabrous distally, surfaces usually smooth, less often scabrous; lower glume 1- or 3-veined; upper glume 1- (2-) or 3-veined; floret 1 in number, sessile, subequaling to equaling the apex of the glumes; lemmas membranaceous, often slightly thicker than the glumes, dorsally rounded, 3- or 5-veined, lateral veins not evident to distinct, glabrous, smooth or scabrous, apex muticous or with a short straight awn 0.2-0.6 mm long, inserted medially or in the upper 1/3 of the lemma, not surpassing the glumes, (awn well-developed, 1.6-2 mm long, inserted in lower 1/3 of lemma, straight or geniculate and usually not surpassing glumes in P. rosei ); paleas well-developed, reaching from (2/3) ¾ to subequaling the lemma, keels obscure to distinct, glabrous, smooth; calluses rounded, blunt, usually glabrous, or with two short lateral tufts of hairs to 0.5 mm long in some species, abaxially smooth; rachilla prolongation present, slender, varying from rudimentary to 2/3 the floret in length (obscure or absent in many P. rosei spikelets), glabrous or sometimes with short strict hairs to 0.3 mm long emerging only distally, smooth or scaberulous. Flowers perfect; lodicules 2 in number; anthers 3 in number, 0.3-1.6 mm long (-2.2 mm long in P. colombiana ); ovaries glabrous. Caryopses slightly shorter to equaling the lemmas, concealed at maturity, subterete to fusiform, hardened, sulcus distinct; hilum punctiform to narrowly ovoid; embryo c. ¼ -1/3 length of the caryopsis; endosperm solid (information on caryopses taken from Harvey 2007, Rúgolo de Agrasar 2012 and P. trichodes specimens). 2 n = 14 (in P. aequivalvis , P. humilis , P. thurberiana , P. rosei ) or 28 ( P. bacillata ).

Distribution and ecology.

New World i.e. North, Central, and South America. Found in cold and wet, often high-elevation environments.

Notes.

The taxonomic disposition of Podogrostis as part of Agrostis or a separate genus has long been an obstacle to transfer of the species to the genus. Now that molecular evidence has confirmed the independence of these two genera ( Saarela et al. 2017; Konstantin Romaschenko unpublished data) for the type species as well as other species from North America, we feel confident that the genus can be expanded based on shared morphological characteristics. The genus is here considered to contain at least ten distinct species ( Podagrostis aequivalvis , P. bacillata , P. colombiana , P. exserta , P. humilis , P. liebmannii , P. rosei , P. sesquiflora , P. thurberiana , P. trichodes ). Aside from the characters mentioned in the key above, species of Podagrostis from Guatemala to NW South America can be easily distinguished from Agrostis species with well-developed paleas by the leaf blades being involute or convolute, while being generally flat in the Agrostis species with well-developed paleas ( A. capillaris generally has basal blades involute and culm blades flat). Further distinction of P. exserta and P. trichodes from other species of Agrostis with well-developed paleas in Guatemala and NW South America can be made by the very short panicles, usually <5 cm long, versus panicles> 5 cm long in the latter.

In high-elevation Guatemala and páramos of Central and NW South America, species are known to only have a densely tufted or tussock-forming habit with intravaginal innovations. A loosely tufted habit and extravaginal innovations, that often leads to a rhizomatous or subrhizomatous habit, is only found in species from Mexico ( P. liebmannii , P. rosei ), the USA and Canada ( P. aequivalvis , P. thurberiana ) and from Chile and Argentina ( P. sesquiflora ).

Calamagrostis meridensis (Luces) Briceño, a species from Venezuelan páramos that is stated to have a rhizomatous habit ( Briceño 2010) and which Sylvester et al. (2019b) mentioned may possibly bear affinity to Podagrostis , does share certain characteristics with P. sesquiflora , such as the flat leaf blades and callus and rachilla apex with short hairs. However, stipitate florets and certain spikelets with a second, albeit reduced, floret at the end of the rachilla prolongation ( Briceño 2010; Sylvester pers. observation) suggests this species more likely belongs in Deschampsia P. Beauv. The generic placement of C. meridensis needs to be confirmed with molecular data.