Senecio crassiandinus Montesinos & Pino, 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 : 214

1. Senecio crassiandinus Montesinos & Pino , sp. nov. ( Fig. 2A–E , 3A–D )

Type:— PERU. Huánuco: Huamalies, Llata, Cerro Jagraraj, steep rock formations with dense scrublands, 09°37’38” S, 76°44’41” W, 3990 m, 24 Jul 2016, D. Montesinos 4812 (Holotype HSP, isotypes HUT, USM, HOXA, F, B).

Diagnosis. Senecio crassiandinus differs from all other South American Senecio species in its succulent leaves with cuticle composed of translucid white glands, bright yellow disc florets with blotches of pale reddish-brown in the corolla throat and linear-oblong achenes covered with trichomes.

Description. Habit: perennial shrub, prostrate or pendulous, 40–60 cm tall, woody in old tissues, ramified from the base. Stems erect when young, then decumbent, branching alternately every 1–2 cm, scarcely covered with lanuginose pubescence, consistent on leaf nodes and scarcer among internodes, stem 3–5 mm diam. at base slowly tapering to 1–2 mm diam. at tips, bark smooth, light brown, striate. Trichomes lanuginose in the internodes and stems (1–2 mm long), villous in the calycule (0.1–0.3 mm long). Both lanuginose and villous trichomes mixed in the upper stems near the calycules. Leaves: Basal leaves persistent, succulent, usually covering old stems every 3–5 mm. Cauline leaves alternate, spaced every 5–7 mm or more towards tips, 6–14 mm long, 1–2.4 mm wide, 1–1.4 mm thick, succulent, oblong-elliptic, slightly recurvate; upper surface lustrous, glossy, dark green to brown and rugose with maturity, scarcely pilose or glabrous, cuticle composed of translucid white glands (0.1–0.2 mm width); lower surface dark green turning pale brown with age, pilose or glabrous; margin pilose or glabrous, entire, rarely dentate (1–2 pairs of teeth per margin, 0.6–0.8 mm long each); apex acute or rarely obtuse; base attenuate; central nerve 0.1–0.3 mm width, inconspicuous, usually lighter than the leaf lamina; petioles 2–4 mm long, conspicuously winged. Synflorescence solitary or in corymbs, pendulous, with short calycular bracts, 2–4 mm long, linear-ovate, villous, margin nearly glabrous, apex disposing a tuft of white multicellular hairs, 0.3–0.4 mm long. Pedicels curved, 5–30 mm long, 1 mm diam., covered with pubescence. Capitules discoid, 7–9 mm diam., 7–14 mm long; involucre cylindrical-campanulate, 5–10 mm diam., 5–7.5 mm long. Receptacles scaly, ca. 1.8–2.2 mm diam., 0.8–1 mm high, convex. Phyllaries pale green, 8–14, 5–7 mm long, 1–2 mm wide, glabrous, linear-lanceolate, acute, upper surface densely villous, margins glabrous, apex bearing a tuft of dense white multicellular hairs, 0.2–0.6 mm long. Disc florets hermaphrodite, ca. 24– 27, 6–7.5 mm long, corolla tubular, bright yellow except by the few blotches of pale reddish-brown in the of the corolla throat (infrequent), lobes 5, acute, 0.7–0.9 mm long, margin yellow; tube 1–2 mm long, base conical. Anthers crowned by an oblong, whitish-yellow, membranous appendage. Style 4.5–11 mm long, slender, bright yellow, bifurcated, thickened at the base; style branches papillose at the tip. Achenes heteromorphic, linear-oblong, striate, 1.4–2 mm long, 0.4–0.8 mm wide, with 10–14 longitudinal ribs, covered with trichomes ca. 0.1 mm long. Pappus white, scabrous, setulose, 5–7 mm long.

Figures

FIGURE 2. A. Senecio crassiandinus Montesinos & Pino.A. Leaf, B. Capitules, C. Calycular bract, D.Achene with floret, E.Achene with pappus, F. Achene lateral view showing the trichomes.

FIGURE 3. Photographs of Senecio crassiandinus Montesinos & Pino.A. Habit (Cerro Jagraraj, Huánuco, 3990 m), B. Stem with leaves and immature buds, C. Detail of the capitule.