Senecio inghamii Montesinos, 2018

Montesinos-Tubée, Daniel B., Pino, Guillermo & Zárate-Gómez, Ricardo, 2018, Three new species of Senecio (Compositae: Senecioneae) from the Alto Marañón, Huánuco region, Central Peru, Phytotaxa 347 (3), pp. 213-223 : 217

2. Senecio inghamii Montesinos , sp. nov. ( Fig. 4A–F , 5A–D )

Type:— PERU. Huánuco: Huacaybamba, Huacaybamba, Copuma Bridge, arid scrublands with cacti, 09°04’25” S, 76°56’26” W, 2156 m, 13 May 2017, D. Montesinos 5578 (Holotype HSP, isotypes HUSA, CUZ, HUT, F, B, K, MO).

Diagnosis. Differs from similar Andean Senecio species by its short-sized, oblanceolate-ovate to rhombic-quadrate leaves with a unique serrate-quadrate dentation, the upper surface being lustrous and glossy and lower surface densely covered with whitish lanuginose pubescence, capitules bear trilobulated ray florets and achenes copiously covered by fimbriate hairs.

Description. Habit: Shrubby annual plant, ramified from the base, rarely prostrate, 25–35 cm tall. Stems erect, partly covered with plicate arachnoid pubescence, consistent on leaf nodes, about 5–8 mm wide in the lower section and 2 mm wide in the upper stems, bark smooth, dark red to pale brown with age, bearing 14–16 pale brown ribs. Trichomes lanuginose, arachnoid, ca. 0.1–0.2 mm thick. Leaves: basal leaves absent. Cauline leaves alternate, 0.6–2.5 cm long, 0.5–1.6 cm wide, subcoriaceous, oblanceolate-ovate to rhombic-quadrate with maturity; upper surface lustrous, glossy, yellowish dark green to brown and rugose with maturity, glabrous except in the midrib, cuticle composed of translucid glands; lower surface pale green turning pale brown with age, densely covered with a thin indumentum of whitish lanuginose hairs (layer of 0.4 mm thick) turning greyish white with age; margin glabrous, serrate-quadrate, with 2–4 acute mucronate lobes (0.4–2.2 mm long); apex acuminate, mucronate; base attenuate to oblique; central nerve 0.1–0.5 mm width, somewhat inconspicuous on the upper surface, covered by a thin narrow layer of white pubescence (less thick to gradually absent in secondary veins) of about 0.1–0.6 mm thick, midrib prominent at the base on the lower surface with gradually fewer cover of pubescence towards the apex; petioles 2–15 mm long, conspicuously winged. Synflorescence solitary, with short calycular bracts, linear, 4–9 mm long, pubescent on the lower surface and the apex. Pedicels 4–6 cm long, about 1 mm thick, scarcely covered with whitish pubescence. Capitules radiate, 2.2–2.6 cm in diam., 1.5–2 cm long; involucre cylindrical, 5–7.5 mm in diam., 6–10 mm long. Receptacles ca. 3.4–4.5 mm wide, 1 mm high, convex, glandular, glossy brown. Phyllaries 10–12, 6–10 mm long, 1–2.1 mm wide, fimbriate, oblong, acuminate, upper surface scarcely pubescent, hairs 0.5–1 mm long, glabrous or pubescent along margins, apex acute-acuminate (1–1.3 mm long) bearing a tuft of dense white multicellular hairs, 0.3–0.6 mm long. Ray florets female, 9–11, 15–18 mm long, 2.5–3.2 mm wide, oblong, trilobulated, glabrous, bright yellow, usually curved towards the apex, lamina disposing 4–5 parallel nerves, pale yellow, 0.1–0.2 mm width; floret 4–5 mm long, style trifurcated, curved, 6–8 mm long, and covered by minute glands at the tip. Disc florets hermaphrodite, ca. 30–40, 6–10 mm long, corolla dark yellow, lobes 5, acute, ca. 1 mm long; tube 3–5 mm long. Anthers crowned by an oblong, membranous appendage. Style 6–10 mm long, slender, bifurcated, thickened at the base; style branches papillose at the tip. Achenes heteromorphic, linear, rarely oblong, copiously covered by fimbriate hairs. Achenes: Ray achenes 4–5 mm long, 0.5– 0.9 mm wide, pale brown, with 4–5 longitudinal brown ribs, densely papillose; disc achenes 4.5–5.5 mm long, 0.5–1 mm wide, with four longitudinal ribs, compactly papillose. Papillae of the achenes ranging from 0.1–0.2 mm long. Pappus scabrous, setulose; ray floret pappus 5–10 mm long and disc floret pappus 6–12 mm long.

Figures

FIGURE 4. A. Senecio inghamii Montesinos. A. Variation of leaf morphology (upper side and under side), B. Capitules, C. Calycular bract, D. Achene with floret and pappus, E. Leaf lateral view showing the pubescence, F.Achene cross-section showing the trichomes.

FIGURE 5. Photographs of Senecio inghamii Montesinos. A. Habit (Copuma Bridge, Huacaybamba, Huánuco, 2156 m), B. Stem with leaves and immature buds, C. Detail of the capitule and pappus, D. Single capitule with curled ligules.