Podagrostis bacillata (Hack.) 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 bacillata (Hack.) Sylvester & Soreng comb. nov. Fig. 1

Agrostis bacillata Hack., Oesterr. Bot. Z. 52(2): 59. 1902.

Type.

Costa Rica. Cerro de la Muerte, Jan. 1897, H. Pittier 10477 (holotype: W (W19160027240 [image!]); isotypes: BAB (BAB00000206 [image!]), BR (BR0000006595845 [image!]), G (G00192030 [image!]), US (US00131726 [not seen], US00131725 [not seen], US00131136 fragm. [not seen]).

Description.

Tufted perennial forming dense tufts, with the basal mats reaching c. 6-17 cm tall and inflorescences usually well-exserted from the basal foliage. Tillers intravaginal. Culms 10-30(-50) cm tall, erect, simple, delicate; nodes and internodes terete, smooth, usually with at least 1 or 2 elongated internodes visible, with (0-)1-3 nodes exposed at flowering, uppermost internode c. 4-13 cm long, longer than the sheath. Leaves generally basal; sheaths terete, glabrous, smooth to lightly scabrous with very short scabers; flag sheath 4-13 cm long; basal sheaths 1-4 cm long, striate, becoming fibrous; ligules 1.7-4.3 mm long, membranous, slightly to usually strongly decurrent with the sheath; upper culm ligules acute to acuminate with a obtuse to acuminate apex, sometimes slightly erose towards the apex; ligules of tillers similar to those of the culm, sometimes slightly shorter; blades 2-15 cm long, 0.2-0.3(-0.4) mm wide in diameter, involute or convolute, acicular to capillaceous and filiform, straight to slightly curved, abaxial surfaces glabrous, lightly to usually densely scabrous, adaxial surfaces glabrous, lightly to usually densely scabrous on the veins with scabers varying in size from short to long and robust. Panicles (3.5-)4-11.5 × (1-)3-5 cm, open to slightly congested when young, usually ovoid; panicle branches ascendant to patent, branched above the middle, filiform, with spikelets not present near the base, glabrous, smooth, longest branches 1-4.5 cm long; pedicels (1-)2-6 mm long, usually longer than the length of the spikelets, divaricate, glabrous, smooth. Spikelets 1.7-2 mm long; glumes remaining on the inflorescence at maturity, equal or subequal, the lower usually slightly longer than the upper, almost equaling the length of the floret to 0.5 mm longer, oblong-lanceolate, slightly keeled, apex broadly acute, glabrous, keels lightly scaberulous just in the distal 1/3, surfaces smooth; lower glume 1- (or 3-)veined, lateral veins usually vestigial; upper glume 1- (or 2- or 3-)veined, lateral veins usually vestigial; lemmas 1.4-1.6 mm long, glabrous, smooth, faintly 5-veined, apex obtuse, awn lacking or to 0.6 mm long, straight, inserted medially or in the upper 1/3; paleas well-developed, 0.8-1.5 mm long, usually reaching from ¾ to subequaling the lemma, keels slightly obscure, smooth, apex bifid and sometimes erose; rachilla 0.3-1.4 mm long, prolonged from the base of the floret, glabrous, rarely smooth, usually scabrous, sometimes with scabers extending into very short hairs <0.2 mm long. Calluses 0.1-0.2 mm long, slightly elongated, glabrous, smooth. Flowers; lodicules c. 0.3-0.5 mm long, lanceolate with acute apices, not lobed; anthers 3 in number, 0.8-1 mm long. Caryopses not seen. 2 n = 28.

Distribution and ecology.

Costa Rica and Panamá, páramo grasslands, 2200-3900 m alt. Pohl (1980) mentions that this species apparently flowers throughout the year.

Additional specimens examined.

Costa Rica. Cartago: Canyon of Rio Tiribi, 3 km NW of Llano Grande, 2200 m, 7 Feb. 1969, R.W. Pohl 11705A (US3096988). Limon: Cordillera de Talamanca, Atlantic slope, Kamuk Massif, páramo north-east of the main Kamuk peak, 9°1'-9°17'N, 83°00'-83°0'W, 3000-3300 m alt., 17-18 Sep. 1984, G. Davidse 29277 (US3041608). San Jose: Cerro Chirripo, treeless páramo SW of and around summit, 11000-12000 ft [3353-3658 m alt.], 24-26 Aug. 1967, A.M. Evans 145 (US2589766A); Cerro de la Vueltas, páramo, 2700-3000 m alt., 29 Dec. 1925-1 Jan. 1926, P.C. Standley 43625 (US1307153); P.C. Standley 43678 (US1307155); Cordillera de Talamanca, Cerro de la Muerte, Asuncion, 3250 m alt., 13 July 1968, R.W. Pohl 10693 (US3096655).

Notes.

The possible affinity of Agrostis bacillata to Podagrostis was mentioned previously ( Pohl and Davidse 1994; Briceño 2010), with Pohl and Davidse (1994) recommending transfer of A. bacillata to Podagrostis . The species is similar to P. trichodes and P. exserta (see notes under these taxa on how to differentiate them). The character of adaxial leaf blade surface with conical trichomes intermixed with scabers across a scaberulous surface, mentioned by Pohl and Davidse (1994) to be a key character for differentiating P. bacillata from P. exserta , was not found in any of the Costa Rican specimens studied at US, including specimen Pohl 10693 that was cited by Pohl and Davidse (1994). All specimens studied of this species were generally densely scabrous on the veins of the adaxial blade surface, with short to long and robust scabers of similar consistency to the abaxial surface. This could be attributed to a difference in interpretation by the authors, although similar long scabers, in a similar density, were found on the adaxial leaf blade surface of specimens of P. exserta , meaning this character is not considered useful for species delimitation of these taxa. Instead, we found that a key character for differentiating the two species was the presence or absence of scabrocities on the abaxial leaf blade surface, with P. bacillata usually being densely scabrous with short hooks while P. exserta is smooth.

Although we have not studied characters of foliar anatomy, Pohl and Davidse (1994) mention these to be important in separation of P. exserta and P. bacillata . Pohl and Davidse (1994) also mention that spikelets are amply open at maturity in P. exserta , while those of P. bacillata are more closed, although this distinction is not always clear. Caryopsis shape is also mentioned to be distinct ( Pohl and Davidse 1994), although no fruiting specimens were found among specimens at US.

Pohl (1980) mentions the glumes of P. bacillata to be 3-veined, although this is not mentioned by Pohl and Davidse (1994) or Morales-Quirós (2003). Most of the spikelets that we examined had 1-veined glumes, with vestigial lateral veins sometimes present.

Figures

Figure 1. Podagrostis bacillata. A Whole plant B spikelets, the center spikelet at anthesis with the palea opened out and the rachilla prolongation visible (indicated with a red arrow) C leaf blades showing the densely scabrous abaxial surface and the central blade opened out to reveal the scabrous adaxial surface. A, B Images of specimen A. M. Evans 145 (US 2589766 A) courtesy of United States National Herbarium (US) C image of specimen R. W. Pohl 11705 A (US 3096988).