Paspalum sect. Pectinata Chase ex Rodríguez (1992: 22)

Delfini, Carolina, Souza, Vinicius Castro & Zuloaga, Fernando Omar, 2017, Taxonomic revision and nomenclatural update of Paspalum sect. Pectinata (Poaceae, Panicoideae, Paspaleae), Phytotaxa 323 (1), pp. 1-26 : 4

Paspalum sect. Pectinata Chase ex Rodríguez (1992: 22) .

Type: Paspalum pectinatum Nees von Esenbeck ex Trinius (1828: 117) .

Perennial, occasionally annual, caespitose or rhizomatous. Culms compressed, erect or decumbent, simple to branched, frequently glabrous, nodes pilose, occasionally geniculate. Sheaths laterally compressed, conduplicate, glabrous or vestite. Ligules membranous, narrowly ovate, triangular or occasionally spatulate, pseudoligule absent. Blades linear to lanceolate, flat or conduplicate, sometimes with involute margins, subrigid to rigid, glabrous or vestite. Inflorescences terminal, sometimes axillary inflorescences present, (1–)2–numerous spiciform racemes, unilateral, subdigitate or conjugate (when two). Rachis triangular, flat, linear to slightly sinuous, winged, wings membranous and brown at maturity, glabrous, scabrous, sparsely pilose to papillose-pilose, ciliate, ending in a naked point and terminal spikelets absent. Spikelets ovate, lanceolate or oval-lanceolate, dorsiventrally compressed, occasionally awned, shortly pedicellate, solitary, arranged in two series in the rachis, sometimes paired with the secondary spikelet rudimentary; lower glume absent; upper glume inserted above the articulation spikelet–pedicel; upper glume and lower lemma membranous subequal or slightly larger than the upper anthecium, the apex acute to obtuse, surface opaque or shiny, glabrous or vestite, ciliate, 3–7-nerved, the nerves conspicuous, midnerve present; upper anthecium sessile; lower palea absent; upper lemma and upper palea indurate, subequal, upper palea not enclosed by the margins of the upper lemma, surface minutely papillose, opaque or shiny, pale yellow, glabrous or with a tuft of trichomes at the apex of the upper lemma; lodicules 2; stamens 3; styles 2, free; stigmas plumose. Caryopsis obovate or oblong, embryo ⅓ to ½ of caryopsis length, hilum elliptic, obovate or punctiform. Chromosome numbers 2 n = 20 in P. cordatum ( Peñaloza et al. 2008) , 2 n = 40 in P. lanciflorum ( Peñaloza et al. 2008) and 2 n =20, 30, 40 in P. pectinatum ( Gould & Soderstrom 1967, Davidse & Pohl 1972). Anatomic structure C 4 –Kranz, MS subtype ( Brown 1977).

The spikelets strongly dorsiventrally flattened, imbricate, and lanceolate in shape, and the upper glume usually winged and cordate are remarkable characteristics of this section that separate it from all other Paspalum species and sections. Section Pectinata shares morphological similarities with the Dissecta group, both having the rachis of the racemes foliaceous and winged, but the latter is distinguished by having glabrous spikelets and upper glume not winged. Despite the morphological similarities between these taxa, the phylogeny ( Scataglini et al. 2014) does not indicate a close relationship between section Pectinata and the Dissecta group, nor with the other species of subgenus Ceresia . On the contrary, the two Dissecta species sampled by Scataglini et al. (2014) were segregated into two different poorly supported clades, whereas species of Paspalum sect. Pectinata were strongly related to P. rufum Nees ex Steudel (1853: 26) and P. durifolium Mez (1917:67) , an ungrouped complex ( Scataglini et al. 2014). Both P. durifolium and P. rufum are robust caespitose perennials, up to 2 m tall, with sheaths and blades keeled; they differ from species of sect. Pectinata by having a narrow, not winged, rachis, branches of the inflorescence ending in a developed spikelet, and spikelets ellipsoid to long ellipsoid, with the upper glume not winged.