Senecio piedrahitae J. Calvo & F. Ávila, 2016

Calvo, Joel & Ávila, Fabio, 2016, Senecio piedrahitae (Compositae, Senecioneae), a new species from the Colombian Andes, Phytotaxa 283 (1), pp. 91-95 : 92-94

Senecio piedrahitae J. Calvo & F. Ávila , sp. nov. ( Fig. 1 )

Type:— COLOMBIA. Tolima: municipio de Santa Isabel, Cordillera Central, camino del paso de la quebrada del África, [4°45’N 75°22’W], 4100–4300 m, 7 Feb 1980 (fl., fr.), S. Díaz-Piedrahita & R. Jaramillo 1914 (holotype COL-000084428).

Senecio piedrahitae differs from other scandent discoid Senecio species from the montane forests and páramos in its lanceolate leaves, petiolated the middle cauline ones, asymmetrical at the lamina base, floccose above and lanate beneath, its synflorescence branches densely lanate, and its involucre glabrescent or slightly arachnoid.

Scandent subshrub. Stem approximately up to 0.8 m long, flexuous, leaved (the lower leaves withering early), corrugated, solid, branched, with lanate-floccose indumentum that persists on the upper part as it grows older. Basal leaves absent. Middle cauline leaves 5–9 cm long, 1–1.5 cm wide, alternate, lanceolate to narrowly lanceolate, acute at the apex, truncate to cuneate and usually clearly asymmetrical at the base, petiolated, denticulate, plane or undulate, with indumentum floccose above and lanate beneath; petiole 1.2–1.5 cm long, auriculate at the base. Upper cauline leaves becoming sessile, usually amplexicaul, lanceolate to narrowly ovate. Synflorescence cymose-corymbose, with bracts subtending the synflorescence branches similar to the upper cauline leaves. Capitula 2–4 per synflorescence branchlet, discoid, nodding; involucre 14–16 mm in diam., 11–12 mm long, widely bell-shaped; receptacle scrobiculate; involucral bracts 21, 7.5–9 mm long, 1.1–2.3 mm wide, with fimbriate scarious margin 0.4–0.6 mm wide, lanceolate, abruptly attenuate, smooth, glabrescent to slightly arachnoid; supplementary bracts 14–15, 5–6 mm long, 1.1–1.2 mm wide, lanceolate, without scarious margin, a quarter to a third as long as involucral bracts, glabrescent to slightly arachnoid. Disc florets 85–95, 9–11 mm long, 0.2–0.4 mm and 1.5–1.7 mm in diam. (throat and apex respectively), pale yellow; style branches penicillate. Achenes 1.5–1.6 mm long, glabrous; pappus whitish of ca. 80–90 barbellate bristles. Chromosome number: unknown.

Distribution and habitat: —Known from the volcanic complex Nevado de Tolima, Nevado de Santa Isabel, and Nevado del Ruiz. The studied specimens were collected in the departments of Tolima and Caldas, although the species is also expected to be found in the adjacent páramos belonging to Risaralda and Quindío departments. According to the label information this species grows in the páramo and Polylepis forest between 4100 and 4300 m.

Etymology: —This species honors Santiago Díaz-Piedrahita (1944–2014), a collector of the holotype and a renowned Colombian synantherologist.

Additional specimens examined (paratypes): — COLOMBIA. Tolima: pic Tolima, cueva del Tigre, [4°38’N 75°21’W], July 1844, J. Goudot s.n. (P-03734857 digital image!). Caldas: alrededores del Nevado del Ruiz y de Sta. Isabel, [4°50’N 75°21’W], 4140–4300 m, 9 Oct 1978, O. Rangel, H. Sturm & O. Vargas 1799 (COL-000084476!).

Discussion: — Senecio piedrahitae can be recognized by its lanceolate leaves, asymmetrical at the lamina base, floccose above and lanate beneath; the middle cauline leaves being distinctly petiolated and auriculate at the insertion point on the stem, and the upper cauline ones being amplexicaul. The lanate indumentum of the synflorescence branches and the glabrescent involucre (or slightly arachnoid) are also useful characters. The synflorescences are usually lax, with 2–4 capitula per synflorescence branchlet. The morphologically closest species are S. otophorus var. christophori , S. longepenicillatus , and S. senecioides .

Senecio piedrahitae differs from S. otophorus var. christophori in the leaf shape, length of involucral bracts, number of disc florets, and indumentum of the upper leaf surface, involucre, and stem. The cauline leaves of S. piedrahitae are longer (narrowly lanceolate), usually clearly asymmetrical at the lamina base, and the floccose indumentum of the upper surface tends to be persistent. In contrast, S. otophorus var. christophori has triangular-lanceolate leaves (the middle ones usually with a constriction at the lower half of the lamina), often not asymmetrical at the base, and thicker. The indumentum of the upper leaf surface is arachnoid when young but it disappears with time. Senecio piedrahitae also has shorter involucral bracts (7.5–9 vs. 9–11 mm) and a lesser number of disc florets (85–95 vs. 100–120). Another useful character is the indumentum of the involucre, which is floccose in S. otophorus var. christophori (at least on the supplementary bracts) and glabrescent or slightly arachnoid in S. piedrahitae . Regarding the stem indumentum, S. otophorus var. christophori differs because it is usually composed of long sericeous trichomes as S. otophorus Weddell (1856: 98) var. otophorus displays. Senecio piedrahitae is sympatric with the typical subspecies of S. otophorus , but we did not find records of S. otophorus var. christophori growing in the volcanic complex Tolima-Santa Isabel-Ruiz.

Another similar species is S.longepenicillatus from Venezuela and northeastern Colombia.They can be distinguished by the leaf shape and the morphology of the supplementary bracts. The cauline leaves of S. longepenicillatus are clearly attenuate into the petiole, usually acuminate at the apex, and not auriculate at the petiole base. The upper cauline leaves are sessile instead of amplexicaul. This species also displays a lesser number of supplementary bracts (11–12 vs. 14–15 in S. piedrahitae ). Their distribution areas do not overlap.

Senecio senecioides (= S. antisanae Bentham (1845: 210) , see Calvo 2016) is an endemic of Ecuador that also has the upper leaf surface floccose. However, the indumentum of the lower leaf surface easily allow to separate both species (glabrescent in S. senecioides vs. lanate in S. piedrahitae ). In addition, the capitula of S. senecioides are smaller and usually more numerous.

Although the conservation status of this species has not been assessed under the IUCN categories, it grows in a protected natural area, Los Nevados National Natural Park, which was established in 1973. Nevertheless, cattle farming and cultivation in the northern Andes make a permanent pressure on the conservation of the páramos as evidenced by Vásquez et al. (2015); but the number and size of the populations is far from being well known. Further fieldwork is required to gain knowledge of this new species, as well as to improve the understanding of plant diversity in the páramos and the diversity of the Compositae in the northern Andes.

Figures

FIGURE 1. Holotype of Senecio piedrahitae (COL-000084428).