Poa urubambensis S.P. Sylvester & Soreng, 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 : 79-81

Poa urubambensis S.P. Sylvester & Soreng sp. nov. Fig. 4

Type.

PERU. Región CUSCO. Prov. Calca: Distr. Calca, top of the prominent tower known by locals as “Kontorqayku”, 5 km NE of Huarán, 4401 m, S13°16'05.9", W72°01'17.2", 27 May 2011, S.P. Sylvester 1317 (holotype: USM!; isotypes: CUZ!, K-000501720!, US!, Z-000099199!)

Plants gynomonoecious. Perennials or (rarely) annuals; Rhizomatous with well developed, slender, lateral tending, rhizomes, solitary and erect, or rarely tufted, often rooting from nodes. Tillers extravaginal. Culms (3-)15-30(-42) cm tall, decumbent to ascending, sometimes erect, fairly slender, not branching above the base, leafy; Culm nodes 1-2(-3), terete or slightly compressed, smooth, usually 1 node exposed at flowering; Culm internodes 3-15(-20) cm long, terete, smooth. Leaves mostly basal; Sheaths slightly compressed to keeled, smooth or scabrous along the veins; Butt sheaths papery, smooth, glabrous; Uppermost culm sheaths (3.5-) 8-16 cm long, margins fused 25-60% the length, 1.8-2.7 × longer than their blades; Collars and throats smooth or scabrous, glabrous, collar margins of sterile shoot leaves sometimes flared; Ligules 1-4 mm long, not decurrent, scarious to hyaline, adaxially glabrous to scabrous, upper margins entire or irregularly dentate, apices acute and entire to irregularly dentate above, sterile shoot ligules generally shorter and more scabrous than those of the culm leaves; Cauline blades 2-15(-22) cm long, (1.5-) 2-3 mm wide, flat or folded, margins often becoming involute, thin to moderately thin, soft or (rarely) curved, surfaces abaxially and adaxially lightly to moderately scabrous or rarely smooth, margins scabrous, narrowly to abruptly prow-tipped; Mid-cauline blades the longest, 10-22 cm long, shorter upward, flag leaf blade 3.5-7.7 cm long; Sterile shoot blades similar to cauline blades, sometimes more involute. Panicles (4-) 8-13 cm long, erect, loosely contracted to open, ovoid to narrowly pyramidal, sparsely to moderately congested, with 13-40(-80) spikelets, proximal internode 1.4-3 cm long, smooth or scaberulous, usually scabrous towards its apex; Rachis with (1-)2-3(-5) branches per node; Primary branches ascending, fairly flexuous, weakly angled, moderately scabrous; Lateral pedicels mostly 3/4 to equaling the spikelets, moderately to densely scabrous, prickles moderately coarse; Longest branches 3-5 cm long, with 5-15 spikelets in distal 1/2, loosely arranged. Spikelets 3.7-6.5 mm long, to 3.7 × long as wide, lanceolate, laterally compressed, not bulbiferous, two toned; Florets 2-3(-4), proximal 1 or 2 florets hermaphroditic and distal 1 or 2 pistillate or sterile; Rachilla internodes terete, distal internodes 0.6-1 mm long, terete, smooth, glabrous; Glumes equal to subequal, narrow lanceolate, herbaceous and pale green below, scarious bronzy and sometimes anthocyanic in margins and apex, veins distinct, distinctly keeled, usually scabrous purely on the veins and sometimes between veins, margins scarious-hyaline, edges entire or dentate, smooth, apices acute, entire; Lower glumes 3.1-3.5 mm long, 2/3-4/5 as long as adjacent lemmas, 1-veined, narrow; Upper glumes 3.4-3.9 mm long, c. 2 × wider than the lower, 3-veined; Calluses glabrous; Lemmas (the lowest) 3.2-3.9 mm long, 5-veined, lanceolate in side-view, the proximal one c. 4-8 × longer than wide at maturity, proximally light green and distally bronzy-anthocyanic at maturity, moderately laterally compressed, thin, keeled, keels to 1/3-5/6 and marginal veins to 3/5-4/5, proximally smooth, keel and sides distally sparsely to moderately scaberulous, intermediate veins obscure to moderately prominent, not extending to near the margin, margins broadly scarious-hyaline, edges scabrous, apices acute; Paleas to 1.6 mm shorter than the lemma, glabrous, keels distally sparsely to moderately scabrous, between keels narrow (0.3-0.4 mm). Flowers chasmogamous; Lodicules c. 0.25 mm long, obscurely to shallowly lobed; Anthers 0.7-1.1(-1.3) mm long, infrequently vestigial in upper florets of spikelets. Caryopses c. 1.9 mm long, elliptical in side-view, sulcus broad and shallow, brown, hilum 0.2 mm long, oval, grain free from the palea. 2 n = unknown.

Distribution.

Restricted to undisturbed areas of Polylepis woodland in hard to access areas throughout the Cordillera Urubamba, Cusco, Peru, at 4390-4802 m. Known from three localities; 1) Cliff ledges of the prominent SW facing cliff face 1.5 km S (170°) of Cancha Cancha village, Huarán. 2) Ledges of the prominent tower known by locals as “Kontorqayku”, 5 km NE of Huarán. 3) Ridgeline to the W of Laguna Manalloqsa, Área de Conservación Privada (ACP) Mantanay, 10 km up the valley from Yanahuara in the small valley 3 km E of Laguna Ipsaycocha.

Habitat.

Relatively dry and exposed sites in montane Polylepis forest and forest edges.

Etymology.

The name ' urubambensis ' refers to the Cordillera Urubamba.

Conservation status.

This narrow endemic is locally common.

Additional specimens examined.

PERU. Región CUSCO. Prov. Calca: Distr. Calca, large ledge situated on the prominent SW facing cliff face 1.5 km S (170°) of Cancha Cancha village, Huarán, 4524 m, S13°14'35.1", W72°01'14.1", 21 March 2011, S.P. Sylvester 812 (CUZ!, MO!, US!, Z!); Distr. Calca, large ledge situated on the prominent SW facing cliff face 1.5 km S (170°) of Cancha Cancha village , Huarán, 4517 m, S13°14'35.0", W72°01'13.7", 24 March 2011, S.P. Sylvester 869 (CUZ!, US!, Z!); Distr. Calca, within the SW facing forest at the top of the prominent tower known by locals as “Kontorqayku”, 5 km NE of Huarán, 4390 m, S13°16'07.7", W72°01'16.8", 11 June 2012, S.P. Sylvester 1636 (US!) ; Distr. Calca, within the SW facing forest at the top of the prominent tower known by locals as “Kontorqayku”, 5 km NE of Huarán, 4390 m, S13°16'07.7", W72°01'16.8", 11 June 2012, S.P. Sylvester 1637 (CUZ!, SI!, US!, Z!); Distr. Calca, top of the prominent tower known by locals as “Kontorqayku”, 5 km NE of Huarán, 4401 m, S13°16'05.9", W72°01'17.2", 11 June 2012, S.P. Sylvester 1695 (CUZ!, US!, Z!); Prov. Urubamba: Distr. Urubamba, ACP Mantanay, 10 km up the valley from Yanahuara in the small valley 3 km E of Laguna Ipsaycocha, ledges on cliff side 250° W of Laguna Manalloqsa, 4676 m, S13°12'01.3", W72°08'47.4", 28 January 2011, S.P. Sylvester 403 (CUZ!, US!) ; Distr. Urubamba, ACP Mantanay, 10 km up the valley from Yanahuara in the small valley 3 km E of Laguna Ipsaycocha, topmost of the ridge to the W of Laguna Manalloqsa, 4802 m, S13°12'08.9", W72°08'43.9", 25 June 2012, S.P. Sylvester 1727 (CUZ!, MO!, US!, Z!) .

Discussion.

This new species is similar to other members of Poa sect. Homalopoa s.l. from Peru, Bolivia and Argentina, all of which have open panicles and spikelets with 2-5(-8) florets, the lowermost florets hermaphroditic while the upper florets are pistillate. Poa urubambensis is easily recognised in the field by the combination of an open-panicled inflorescence, glabrous lemmas and calluses, and exceptionally small anthers for members of Poa supersect. Homalopoa. Poa urubambensis also bears resemblance to Poa oscariana , but is distinguished by a less robust habit, the leaf blades being mainly basal and the anthers being smaller.

This species was found during a large scale ecological study attempting to reconstruct the potential natural vegetation (PNV) and soils of the high-elevation Puna grasslands (see Heitkamp et al. 2014 and Sylvester et al. 2014 for pilot studies). In this research, pristine zonal vegetation, only accessible with mountaineering equipment, was compared with surrounding slopes which have been grazed and burnt consistently over millennia ( Thompson et al. 1988; Chepstow-Lusty et al. 1996, 2009; Kuentz et al. 2011). Poa urubambensis was a common element in undisturbed Puna vegetation in the Cordillera Urubamba, being found associated with Polylepis Ruiz & Pav. forests from three different sites and also found growing alongside other species new to science, e.g. Bartsia lydiae S.P. Sylvester (2014: 41). Following indicator species analyses, Poa urubambensis has been found as an indicator species for the PNV, due to its frequency and abundance within relict patches of near natural vegetation (Sylvester et al., unpubl. data). This species has not been found in accessible, disturbed or secondary, vegetation at similar or lower elevations in the Andes of the Cuzco region, despite a more thorough botanical exploration. This may relate to its susceptibility to disturbance from grazing and burning (Sylvester, pers. observation).

Figures

Figure 4. Poa urubambensis. A Habit B Basal portion of plant showing extravaginal shoots C Inflorescence D Ligular zone E Segment of inflorescence F Spikelet G Lower glume dorsal view H Upper glume dorsal view I Proximal floret J Lemma, lateral view K Palea, ventral view L Pistil, stamens and lodicules from perfect floret. Drawn from type material (S. P. Sylvester 1317, US).