Poa auriculata Soreng & P.M. Peterson, 2016

Peterson, Paul M. & Soreng, Robert J., 2016, A revision of Poa subsection Aphanelytrum (Poaceae, Pooideae, Poaeae, Poinae); and a new species, Poa auriculata, PhytoKeys 63, pp. 107-125 : 116-117

Poa auriculata Soreng & P.M. Peterson sp. nov. Fig. 5

Type.

PERÚ. Departamento Amazonas, Provincia Chachapoyas, summit of Puma-urcu southeast of Chachapoyas, occasional on dry cliff face, 3100-3200 m, 3 Jul 1962, J.J. Wurdack 1145 (holotype: US-2382274!).

Diagnosis.

Poa auriculata differs from Poa scabrivaginata Tovar in having 4-6-flowered spikelets, a glabrous callus, glumes 2-3 mm long, and lemmas 2.5-3.8 mm long.

Description.

Caespitose, annuals or short-lived perennials. Culms 40-72 cm tall, erect, scabrous, shiny, often weak; nodes 3-5. Leaf sheaths 2/3 to 4/5 as long the internodes, membranous, greenish to stramineous, scabrous, upper sheaths open for 1/3 the length, keeled, summit with prominent triangular auricles; ligules 3.3-5 mm long, membranous to hyaline, apex erose, often split down the center; blades 6-15 cm long (flag leaf 3-6 cm long), 3-6 mm wide, flat, thin, lax, linear, scabrous. Panicles 5-11 cm long, 2.5-5 cm wide, ovate, open; branches flexuous, effuse and spreading with numerous spikelets, scabrous, the lower branches capillary. Spikelets 5-7 mm long, 4-6-flowered, glabrous, ovate, greenish-yellow tinged with purple; rachilla 0.4-1.0 mm long; glumes 2-3 mm long, membranous, subequal; lower glumes 2-2.5 mm long, 1-veined, linear lanceolate, apex acuminate; upper glumes 2.4-3 mm long, 3-veined, the veins not conspicuous, lanceolate, apex acute; lemmas 2.5-3.8 mm long, 5-veined, lanceolate, membranous; apex acute, unawned; paleas 2.3-3.7 mm long, membranous, 2-keeled, the keels scabrous, apex minutely bifid; lodicules 0.4-0.5 mm long, ovate, membranous, glabrous; stamens 3; anthers 1.9-2.1 mm long, yellowish; ovaries glabrous with two styles and two stigmas. Caryopses not seen.

Phenology.

Flowering in June and July.

Distribution.

Poa auriculata is known only from the type locality in Cordillera de los Andes of Peru near Chachapoyas between 3100-3200 m growing on a dry cliff face.

Conservation status.

The species is rare, but its conservation status is data deficient ( IUCN 2010).

Etymology.

The specific epithet refers to the triangular auricles that are found on the summit of the sheaths, a feature that is unique among species of Poa .

Comments.

Initially RJS considered Poa auriculata to be related to species in Poa subsect. Aphanelytrum . We do not place the new species in Poa subsect. Aphanelytrum because the spikelets have short rachillas and are 4-6-flowered, the habit is annual to short-lived perennials with erect culms, and the lemmas are unawned without mucros. However, aside from the auricles, Poa auriculata is morphologically consistent with the 300 or so species that reside within Poa subg. Poa supersect. Homalopoa . We hope to include a sample of this species in upcoming molecular analyses.

Poa scabrivaginata differs from Poa auriculata in having 2-flowered spikelets (4-6 in Poa auriculata ), a few cobwebby hairs on the callus (verses glabrous), glumes 3.6-4.3 mm long (verses 2-3 mm), and lemmas 4.2-4.5 mm long (verses 2.5-3.8 mm) [ Tovar 1965]. Poa aequatoriensis Hack., another species possible to confuse with Poa auriculata , differs in having 2- or 3-, rarely 4-flowered spikelets, a few cobwebby hairs on the callus, and lemmas 3.6-4 mm long ( Tovar 1965). Poa aequatoriensis is more wide ranging and has been reported in Colombia, Ecuador, and Peru whereas Poa scabrivaginata is known from the type (Depto. de Huánuco, Tambo de Vaca, J.F. Macbride 4354 at US) and one other possible collection (Depto. de Cajamarca, Celendin, I. Sánchez Vega 2668 at MO) [ Sylvester et al. in press].

Figures

Figure 5. Poa auriculata: A Habit B Sheath, auricles, ligule, and blade C Spikelet D Glumes E Lower glume F Floret G Lemma H Palea, lateral view I Stamens with palea J Pistil enclosed in palea K Lodicules, pistil, and rachilla. (Wurdack 1145, US- 2382274)