Senecio ticsanicus Montesinos

Montesinos-Tubée, Daniel B., Trinidad, Huber & Chicalla-Rios, Kent J., 2017, A new species of Senecio (Asteraceae, Senecioneae) endemic to the pumices of the Ticsani Volcano in Moquegua, South Peru, Phytotaxa 309 (3), pp. 271-277 : 272-274

Senecio ticsanicus Montesinos & Trinidad, sp. nov. ( Figs 1 , 2 )

Type: — PERU. Moquegua: Mariscal Nieto, Torata, pumice stony soils on the slopes of the eastern side of the Ticsani Volcano, 16°45’44” S, 70°28’12” W, 4641 m, 11 June 2015, H. Trinidad 3719 (holotype USM, isotypes HSP).

The new species is morphologically similar to S. moqueguensis Montesinos (2015: 3) but differs in its longer indumentum, leaf shape (elliptic-spathulate, lobulate, revolute vs. oblong-spathulate, subpinnatifid), leaf length (shorter in S. moqueguensis ), wider involucres, greater number of phyllaries per capitula, narrower calycular bracts, and shorter pappus.

Perennial herb, low-growing, with dense fibrous roots, forming mats 3–5 cm tall and 10–14 cm in diam. Indumentum lanate, glandular, dense and irregularly distributed, composed of multicellular trichomes 0.4–1.2 mm long with 8–12 subrotund cells (each 30–50 μm long) and a rotund apical cell. Stems 2–4 cm long, often two or three times branched, covered with thin trichomes (less than 0.2 mm long). Basal leaves absent. Cauline leaves elliptic-spatulate; lamina 10– 16 mm long, 3–5 mm wide, densely covered by thin trichomes, apex acute, base truncate, margins revolute, irregularly lobed, with 4–5 subacute lobes on each side; petiole 4–11 mm long, 1–2 mm wide, with midrib and two parallel nerves on each side, densely covered with trichomes, which are irregularly distributed but less dense towards the base. Synflorescence reduced to a solitary capitulum, sessile or subsessile, homogamous, discoid. Involucre campanulate, ca. 8–11 mm long, 9–10 mm wide; phyllaries 15–20, 7–9 mm long, 1–1.4 mm wide, oblong, pale green on the surface and margins, covered with sparse thin trichomes on the abaxial surface and glabrous along the margins, apex dark brown with short maroon multicellular trichomes; calycular bracts 15–20, 7–9 mm long, 0.8–1 mm wide, linear to rarely lanceolate, densely covered by trichomes on the whole surface, apex dark brown, covered with short trichomes. Florets 25–32, tubular, abruptly constricted near the base, 5-lobed, each lobe 0.5 mm long, with a tube 4–5 mm long, 0.8–1 mm wide, pale yellow; anthers linear-lanceolate, 1.5–2.5 mm long, 0.2–0.4 mm wide, ecalcarate, terminal appendages lanceolate, obtuse, margin yellowish-transparent and becoming yellow towards the center; style purple-red, truncate, with papillae covering the whole surface of the apex. Achenes cylindrical, covered with trichomes 2.5–3 mm long, 0.8–1 mm wide, light brown; carpopodium symmetrical in a small ring; pappus of smooth bristles, 4.5–5.5 mm long, white, finely barbellate.

Ecology and distribution: — Senecio ticsanicus grows on pumice stony soils on the slopes of the Ticsani Volcano at elevations between 4600 to 4800 m. Other species recorded in the same habitat are Festuca orthophylla and Senecio trifurcifolius . Flowers and fruits were observed between March and June.

Etymology: —The specific epithet refers to the Ticsani Volcano, where the only locality of the new species was found.

Discussion: —The new species is morphologically similar to S. moqueguensis but can be easily distinguished from the latter by its longer indumentum (0.4–1.2 mm long vs. 0.1–0.3 mm in S. moqueguensis ), leaf shape (elliptic-spatulate, dentate vs. oblong-spatulate, subpinnatifid), leaf length (10–16 mm vs. 8–12 mm), wider involucres (9–10 mm vs. 6–8.5 mm), narrower calycular bracts (0.8–1 mm vs. 1–2.5 mm), a greater number of phyllaries per capitulum (15–20 vs. 9–12), and shorter pappus (4.5–5.5 mm vs. 5–6 mm). From S. digitatus the new species differs in its denser indumentum (plants glabrous in S. digitatus ), narrower phyllaries (1–1.4 mm vs. 1.5–2.0 mm), glabrous margins of the phyllaries (vs. lanate), and the color of the florets (yellow in S. ticsanicus vs. white in S. digitatus ).

Furthermore, the new species differs from S. tassaensis Montesinos-Tubée (2014: 11–14) by longer leaves (10–16 mm vs. 6–9 mm), a larger size of the involucres (8–11 × 9–10 mm vs. 6–8 × 5–7 mm), longer calycular bracts (7–9 mm vs. 4–6 mm), and the indumentum of the phyllary margins (glabrous vs. densely lanate); besides, S. tassaensis occurs on clayey soils in the north of the Moquegua and Arequipa regions ( Montesinos-Tubée 2014). The differences of the new species with S. laucanus Ricardi & Marticorena (1964: 17) are the leaf length (10–16 mm vs. 6–9 mm in S. laucanus ), petiole indumentum (lanate vs. glabrous), width of calycular bracts (0.8–1 mm vs. 1.5–1.7 mm), floret color (yellow vs. white), pappus length (4.5–5.5 mm vs. 4.3–4.5 mm); S. laucanus is distributed in northern Chile. Further comparisons with other related species are: in Senecio pucapampaensis Beltrán (2009: 212) the involucres narrower (9–10 mm vs. 8–9 mm), calycular bracts longer (7–9 mm vs. 6–7 mm) and phyllaries longer (7–9 mm vs. 6–7 mm), the number of phyllaries lesser (12–14 vs. 15–20), corolla color different (yellow vs. white), and achenes glabrous; S. pucapampaensis inhabits the highlands of Junín, in Central Peru; S. aquilaris Cabrera (1950: 74) has a longer size of the involucre (11–14 mm vs. 8–11 mm), and margins of the phyllaries glabrous (vs. covered with sparse thin trichomes). The new species further differs against S. trifurcifolius and S. puchii Philippi (1891: 45) by the absence of hairs on leaves, petioles, bracts, and phyllaries. Senecio aquilaris is distributed in NW Argentina, N of Chile and W of Bolivia ( Zuloaga et al. 2008, Jørgensen et al. 2014) and has recently been reported from Peru by Gonzáles et al. (2016).

Conservation status: —Following the criteria and categories of IUCN (2001), a preliminary status of Critically Endangered (CR) is assigned. The new species deserves protection because: its total area covers less than 100 km ² (ca. 50 km ²) (B1); only one population is known (B1b); habitat inferred to be constantly declining (B1b(i-iii)); population estimated to comprise fewer than 300 individuals (D). The suitable habitats for S. ticsanicus on the pumice slopes near the Ticsani Volcano are regarded as endangered because of volcanic activity, road constructions, and exploitation of natural resources.

Figures

FIGURE 1. Senecio ticsanicus Montesinos & Trinidad. A. Capitula, B. Phyllaries, C. Calycular bract, D. Achene without pappus, E. Stamen, F. Stamen arrangement in a floret, G. Pappus bristle, H. Floret, I. Leaf (abaxial surface), J. Leaf (adaxial surface), K. Leaf trichomes, L. Young leaf (abaxial surface), M. Young leaf (adaxial surface), N. Style, O. Papillose stigma.

FIGURE 2. Senecio ticsanicus on the pumice soils of the Ticsani Volcano slopes (4642 m).