Poa tayacajaensis Soreng & S.P. Sylvester, 2016

Sylvester, Steven P., Soreng, Robert J., Peterson, Paul M. & Sylvester, Mitsy D. P. V., 2016, An updated checklist and key to the open-panicled species of Poa L. (Poaceae) in Peru including three new species, Poa ramoniana, Poa tayacajaensis, and Poa urubambensis, PhytoKeys 65, pp. 57-90 : 75-79

publication ID


persistent identifier


treatment provided by

PhytoKeys by Pensoft

scientific name

Poa tayacajaensis Soreng & S.P. Sylvester

sp. nov.

Poa tayacajaensis Soreng & S.P. Sylvester sp. nov. Figs 2 View Figure 2 , 3 View Figure 3


PERU: Región HUANCAVELICA. Prov. Tayacaja: Distr. Colcabamba, Chuspi-Hda., Tocas , entre Colcabamba y Paucarbamba, monte bajo, 2900 m, [vic. S12.5°, W74.6°], 22 Apr 1954, Ó. Tovar. S. 2038 (holotype: US-2181284!; isotype: USM p.p.) GoogleMaps

Plants gynomonoecious. Perennials; tufted, without lateral or downward tending shoots. Tillers intravaginal. Culms 55-65 cm tall, erect or decumbent (when decumbent sometimes extravaginally branching at the lower culm nodes, i.e. Peterson et al. 20369); Culm nodes 3-4, terete, smooth, 2-3 nodes exposed at flowering; Culm internodes terete, smooth. Leaves; Sheaths slightly laterally compressed, keeled, lower culm and lateral ones densely scaberulous distally; Butt sheaths thin papery, somewhat loosely investing the shoots; Uppermost culm sheaths 10-13 cm long, margins fused 60-75 % their length, slightly shorter than their blades; Collars and throats smooth, glabrous; Ligules 2.0- 3.5 mm long, not decurrent, abaxially sparsely to moderately densely scabrous, apices obtuse to subacute, margins densely scabrous, ligules of sterile shoots and lower culm leaves 0.5-1 mm long; Cauline blades 6-15 cm long, 3-5 mm wide, well developed, longer than their sheaths, generally flat, keeled, thin, lax, abaxially, marginally, and adaxially scabrous mainly along the veins, folded near the apex, apex gradually tapered to a slender point; Blades gradually increasing in length up the culm, flag leaf blade 10-15 cm long; Sterile shoot blades like those of the culm, but somewhat shorter and smoother. Panicles 18-20 cm long, loose, open, exerted, slightly lax, to 5 cm wide, with more than 100 spikelets, proximal internodes 3.5-4 cm long, smooth; Rachis with (3) 5-6 branches at lower nodes; Primary branches slender, mostly laxly ascending, sometimes spreading, one sometimes reflexed, angled, proximally smooth to moderately scabrous mainly on the angles; Lateral pedicels mostly <1 mm long, scabrous; Longest branches 6-8 cm long, with 14-22 spikelets in the distal half, slightly overlapping. Spikelets 4.5-6 mm long, c. 2 × longer than wide, lanceolate, laterally compressed, not bulbiferous, greyish-green to somewhat anthocyanic at maturity; Florets (3-)4(-5), proximal florets hermaphroditic and distal one pistillate; Rachilla internodes terete, distal internodes 0.7-1 mm long, terete, smooth, glabrous; Glumes unequal, narrow lanceolate to lanceolate, herbaceous and pale green below, sometimes anthocyanic in margins and apex, veins distinct, distinctly keeled, keels sparsely short scabrous distally, surfaces smooth, margins scarious-hyaline, edges entire smooth, apices sharply acute, entire; Lower glumes 1.7-2.5 mm, 2/3-4/5 as long as adjacent lemmas, 1-veined, very narrow, slightly sickle shaped; Upper glume 2.4-3 mm, c. 2 × wider than the lower, 3-veined; Calluses webbed, with a dense, long dorsal tuft of wooly hairs; Lemmas (the lowest) 2.8-3.7 mm long, 5-veined, lanceolate in side view, the proximal one c. 5 × longer than wide at maturity, greyish-green, to strongly anthocyanic at maturity, strongly laterally compressed, distinctly keeled, thin, keel to 3/4 the length and marginal veins and sometimes the intermediate veins to 1/2 the length, loosely sericious to villous, between veins sparsely to moderately densely appressed pubescent or occasionally glabrous on the proximal lemma, keel distally weekly scabrous, intermediate veins distinct, not extending to near the margin, margins inrolling below at maturity, very narrowly hyaline above, edges smooth or with a few hooks, apices acute, briefly hyaline; Paleas shorter than the lemmas by c. 0.5 mm, keels scabrous distally, sometimes weakly so, sparsely puberulent medially or nearly so, glabrous. Flowers chasmogamous; Lodicules c. 0.25 mm long, obscurely lobed; Anthers 1.2-1.4 mm long, vestigial in the upper floret. Caryopsis 1.8-2 mm long, strongly laterally compressed, sulcate, honey brown, firm, adherent to the lemma and palea, hilum 0.2 mm long, elliptical. 2 n = unknown.


Endemic to the central Andes of Peru. Known from Huancavelica and Huánuco, although the Huánuco specimen is only tentatively placed.


Shrublands on Andean slopes at mid elevations.

Conservation status.

Data insufficient.

Additional specimens examined.

One other specimen appears to represent this species but is too immature to be certain. The specimen in question has extravaginal shoots branching from lower culm nodes; PERU: Región HUÁNUCO. Prov. Pachitea: Distr. Chaggla, canyon of the Rio Grande , c. 20 km above confluence with Rio Huallaga, E of Huánuco c. 44 air km, 1.7 air km SSW of Estación Huacachay (Huacachi), 2650 m, S9.86836 W75.83306, 8 Mar 2007, Peterson, Soreng & Romaschenko 20369 ( US!) GoogleMaps .


These plants bear similarities to Poa aequatoriensis but differ by having lemmas which are generally shorter (2.8-3.7 mm long), pubescent between the veins, and by more densely scabrous sheaths, with more-or-less smooth glabrous throats, ligules generally shorter. Tovar (1993) placed his voucher of this form (2038) in Poa aequatoriensis . However, among the 20 sheets and the US isotype reviewed of Poa aequatoriensis , all have lemmas that are smooth and glabrous between the veins (consistent with the description of Ecuadorian material by Hjorth, 1991), and the keel and marginal veins can be glabrous or sparsely puberulent. The species also bears some slight similarity to Poa myriantha Hack. and Poa hieronymi Hack. from the Yungas cloud-forests, Argentina, that differ by size of the anthers and ligule being much smaller (anthers <1 mm long, ligules <1 mm long) and overall habit being larger (culms 60-350 cm long with 10-15 internodes, and panicles 20-36 cm long) and glumes having both antrorse and retrorse scabrocities.