Senecio alatopetiolatus J. Calvo, E. Freire & Sklenář, 2016

Calvo, Joel, Freire, Efraín & Sklenář, Petr, 2016, A new species of Senecio (Compositae, Senecioneae) from Ecuador, Phytotaxa 243 (2), pp. 175-179 : 177-178

Senecio alatopetiolatus J. Calvo, E. Freire & Sklenář , sp. nov. ( Fig. 1 )

Type:— ECUADOR. Tungurahua: near laguna at the western side of Cerro Hermoso, 1°13ʹ51ʺ S, 78°18ʹ04ʺ W, 3870 m, 3 Dec 2010, P. Sklenář 13100 (holotype: PRC-405860, isotypes: MO, QCA-215788).

Senecio alatopetiolatus differs from other scandent discoid Senecio species from the montane forests and páramos in its conspicuously winged petioles of the middle cauline leaves and its indumentum composed of glandular-hirsute and sericeous trichomes.

Scandent subshrub. Stem up to 2 m long, erect, leaved (the lower leaves withering early), corrugated, solid, branched at the synflorescence, with two types of trichomes: glandular-hirsute(multicellular) and sericeous (unicellular). Basal leaves absent. Middle cauline leaves 2.7–6 cm long, 0.8–1.2 cm wide, alternate, lanceolate to trullate, acute, truncate to cuneate, petiolated, subentire to sinuate at the lower half, revolute, with glandular-hirsute trichomes mixed with sericeous trichomes on both faces (denser on the adaxial face); petiole 1.8–4 cm long, conspicuously winged and semiamplexicaul at the base. Upper cauline leaves becoming sessile, narrowly panduriform to lanceolate. Synflorescence cymose-corymbose, with bracts subtending the synflorescence branches similar to the upper cauline leaves. Capitula 8–20, discoid, nodding; involucre 16–22 mm in diam., 9–12 mm long, bell-shaped; involucral bracts 18–22, 8.5–10 mm long, 1.5–2.2 mm wide, with scarious margin 0.2–0.8 mm wide, lanceolate, abruptly attenuate, smooth, with multicellular hirsute trichomes and some sericeous trichomes; supplementary bracts 12–16, 5.8–7 mm long, 0.6–0.8 mm wide, subulate, without scarious margin, a half to three quarters as long as involucral bracts, with multicellular hirsute trichomes and some sericeous trichomes. Disc florets ca. 70–75, 6.7–8.8 mm long, 1.2–1.8 mm in diam., pale yellow; style branches penicillate. Immature achenes glabrous; pappus whitish. Chromosome number: unknown.

Distribution and habitat: —Only known from the type locality at Cerro Hermoso (Tungurahua, Ecuador) ( Fig. 2 ). It was collected over thickets around a creek in a humid shrubby páramo with Neurolepis aristata , at 3870 m.

Etymology: —The specific epithet refers to the winged petioles that this species displays; a unique character among the species of the Lasiocephalus group.

Discussion: — Senecio alatopetiolatus is easily recognized by the combination of the following characters: scandent habit, discoid nodding capitula, middle cauline leaves with winged petioles, and indumentum composed of glandular-hirsute and sericeous trichomes.

The petioles of the middle cauline leaves, which are clearly winged, particularly characterize the species as this character has not been noticed in other species of the Lasiocephalus group. A similar species is S. pindilicensis Hieronymus (1894: 65) (= Lasiocephalus heterophyllus ( Turczaninow 1851: 85) Cuatrecasas (1978: 310)) , which displays some of the upper cauline leaves sublyrate or with large auricles at the base, hirsute indumentum on the stem and leaves, and glandular-hirsute indumentum on the involucre. However, they can be easily differentiated by the number of involucral bracts (18–22 in S. alatopetiolatus vs. 12–14 in S. pindilicensis ), and by the narrower cauline leaves of S. alatopetiolatus (0.8–1.2 cm wide vs. 2.6–4.2 cm in S. pindilicensis ). Moreover, this latter species has the middle cauline leaves broadly lanceolate to ovate, with the lamina base subcordate to cordate, whereas those of S. alatopetiolatus are lanceolate to trullate, with the lamina base truncate to cuneate. Their distribution ranges do not overlap.

The indumentum of S. alatopetiolatus closely resembles that of S. eliseae Calvo (2015: 70) , another species recently described from the southern Ecuadorian Andes. Since the latter species displays sessile cauline leaves and erect habit, any confusion is very unlikely.

Further field work is needed to properly draw the distribution area of this putative endemic species, and more collections would help to better know its morphological variability.

Figures

FIGURE 1. Holotype of Senecio alatopetiolatus (PRC-405860).

FIGURE 2. Distribution map of Senecio alatopetiolatus (Ì).