Senecio roseoandinus Montesinos & R. Zárate, 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 : 219-221

3. Senecio roseoandinus Montesinos & R. Zárate , sp. nov. ( Fig. 6 , 7 )

Type:— PERU. Huánuco: Huacaybamba, Pinra, Tinyash Archaeological Site, Puna grasslands, 08°56’44” S, 77°00’01” W, 4170 m, 14 May 2017, D. Montesinos 5581 (Holotype HSP, isotypes CUZ, HUT, HUSA, AMAZ, F, MO, B).

Diagnosis. Senecio roseoandinus Montesinos & R. Zárate differs from other Senecio species by its lanuginose and arachnoid trichomes almost covering all surfaces of the plant (except at the leaf lamina which can be densely arachnose to glabrous); the discoid capitules have a corolla pale yellow turning fuchsia-pink with maturity; moreover, the achenes are oblong, striate, and glabrous.

Description. Habit: Perennial herb, solitary or forming clumps, rhizomatous, rosettiform, erect, 20–70 cm tall. Stems covered with a tuft of arachnoid pubescence, consistent, 4–7 mm width in the lower section and 2–5 mm width in the upper stems, bark smooth, bearing black pustules of about 0.1 mm width, with 13–15 pale purple ribs, dark green to pale yellow age. Trichomes lanuginose, arachnoid, bright white, ca. 0.2–0.4 mm thick. Leaves: Basal leaves alternate, elliptic-lanceolate, 7–25 cm long, 1.5–4 cm wide, thick, coriaceous; upper surface densely arachnoid to glabrous (lustrous, glossy, dark green) with maturity except at the margins and midrib; lower surface pale green, densely covered with a thick indumentum of whitish lanuginose hairs (layer of 0.4–0.5 mm thick) turning greyish white with age; margin pubescent, entire to crenate; apex acute; base cuneate; central nerve 2–4 mm width, covered by a thick layer of white pubescence; petioles 2.5–10 cm long, conspicuously winged. Cauline leaves purple, alternate, sessile, covered with pubescence, 1–6.5 cm long, 0.4–1.5 cm wide, base rounded-truncate, apex acute-acuminate. Synflorescence in racemes, with short calycular bracts, 4–14 mm long, linear-lanceolate, pubescent or glabrous, curved, scarious margin. Pedicels purple, 5–30 cm long, 1–2 mm wide, covered with pubescence. Capitules discoid, 5–14 per individual, 1.4–1.9 cm in diam., 1–1.5 cm long; involucre globular-campanulate, 0.8–1.5 cm in diam., 8– 1.2 cm long. Receptacles ca. 3.6–4.4 mm wide, 2–2.2 mm high, convex, epalpeate. Phyllaries dark purple, 20–24, 9–11 mm long, 1–2 mm wide, glabrous, linear-oblong, acute, upper surface and margins scarcely pubescent or glabrous, apex bearing a tuft of dense white multicellular hairs, 0.3–0.6 mm long. Disc florets hermaphrodite, ca. 120–130, 5–8 mm long, base narrow, corolla pale yellow turning fuchsia-pink with maturity, corolla throat tubular to globular with age; lobes 5, acute, ca. 0.5 mm long, margin yellow orange to dark pink with age; tube 3–4 mm long.Anthers crowned by an oblong, yellow-orange, membranous appendage. Style 6–9 mm long, slender, dark pink, bifurcated, thickened at the base; style branches papillose at the tip. Achenes heteromorphic, oblong, striate, 1–1.8 mm long, 0.3–0.6 mm wide, with 10–12 longitudinal ribs, glabrous. Pappus white, scabrous, setulose, 5–7 mm long.

Habitat and distribution. Senecio roseoandinus has been observed until now only in the north of the Huánuco region, Central Andes of Peru, on Puna grasslands with scattered stones at around 4100–4200 m. Flowers and fruits between May and June.

Etymology. Roseo - Pink capitules, andinus - referring to the distribution in the Central Andes.

Discussion. Senecio roseoandinus appears to be closely related to S. mitonis Cuatrecasas (1951: 40) which grows in S Huánuco but approaches the known range of S. roseoandinus within an approximate distance of one hundred kilometres. The new species can be easily distinguished from S. mitonis by the larger petiole and leaf size (25–100 mm, 70–250 mm vs. 15–30 mm, 25–45 mm), leaf margin (entire to crenate vs. dentate-crenate), leaf midrib (not visible either on young or mature leaves vs. visible), pedicel size (50–300 mm vs. 20–40 mm), synflorescences (racemes vs. single), number of capitules per stem (5–14 vs. 2–3), involucre length and diameter (8–12 mm, 8–15 mm vs. 15 mm, 20 mm), shape of the phyllaries (linear-oblong vs. lanceolate), number of florets per capitule (120–130 vs. 60), floret colour (pink vs. yellow), achene size (1–1.8 mm vs. 2–2.4 mm). Although Cuatrecasas (1951) described the achenes of S. mitonis as glabrous, a stereoscopic analysis of the type specimen stored at F displayed thin trichomes between the ribs of the achenes (more than 10 achenes examined, both in mature and immature state).

The new species is further differentiated from S. hypsiandinus Cuatrecasas (1960: 189) by the leaf shape and margin (elliptic-lanceolate, entire to crenate vs. subspathulate-oblong, dentate), leaf size (shorter in S. hypsiandinus ), upper surface of the leaves (arachnose to glabrous vs. lanose-tomentose), capitules (racemes vs. solitary), fewer number of phyllaries and shorter in size (20–24, 9–11 mm vs. 37, 15 mm), less number of flowers per capitule (120–130 vs. 250) and floret colour (yellow in S. hypsiandinus ). Senecio hypsiandinus is distributed in the Ancash and Pasco regions in Central Peru at 4350–4650 m according to herbarium material analysed at USM ( Cano et al. #9773, Smith & Buddensiek #11118). Further differences found with S. rauranus Cuatrecasas (1960: 190) are leaf shape and margin (subspathulate-oblong, dentate in S. rauranus ), congested pubescence in the leaves; larger pedicel size, involucre size and fewer number of phyllaries (15–20 mm, 12–14 mm, 30 in S. rauranus ), larger number of florets per capitule and colour (200, yellow in S. rauranus ). Moreover, S. rauranus is distributed at 4900 m in steep rocky slopes of the Central Andes.

Figures

FIGURE 6. A. Senecio roseoandinus Montesinos & R. Zárate.A. Leaf (under side), B. Leaf (upper side), C. Capitule, D. Calycular bract, E. Achene with floret, F.Achene with pappus, G. Leaf lateral view showing the lanuginose, arachnoid trichomes.

FIGURE 7. Photographs of Senecio roseoandinus Montesinos & R. Zárate.A. Habit (Tinyash Archaeological Site, Pinra, Huacaybamba, Huánuco, 4170 m), B. Habit with open capitules, C. Detail of the capitules.