Senecio doronicum (Linnaeus) Linnaeus (1759: 1215)

Calvo, Joel, Álvarez, Inés & Aedo, Carlos, 2015, Systematics of Senecio section Crociseris (Compositae, Senecioneae), Phytotaxa 211 (1), pp. 448-450 : 448-450

2. Senecio doronicum (Linnaeus) Linnaeus (1759: 1215) . Solidago doronicum Linnaeus (1753: 880) , nom. cons. Crociseris doronicum (Linnaeus) Fourreau (1868: 404) . Senecio tomentosus Cariot & Saint-Lager (1888 –1889: 470), nom. illeg. ( McNeill et al. 2012, ICN Art. 53.1), non Michaux (1803: 119). Senecio doronicum var. typicus Fiori (1903: 218) , nom. inval. ( McNeill et al. 2012, ICN Art. 24.3). Senecio doronicum subsp. eu-doronicum Briquet & Cavillier (1916: 31), nom. inval. ( McNeill et al. 2012, ICN Art. 26.2). TYPE: France, Haute-Savoie, Bonneville, Brezon, près de la Glacière, [46°02′N 6°25′E], July 1848, E. Bourgeau 129 (typ. cons., proposed by Calvo et al. (2011b: 1215) and Calvo (2012: 1133), P-3777644 image!; isolectotypes, BM-810151 image!, G-308097 image!, K!, LE!, MPU-19494 image!, P-3777665 image!, P-3777666 image!, P-3777667 image!).

Perennial herb. Rhizome 2.3–6.9 cm long, 0.3–0.5 cm in diam., ± horizontal, with swelled fastigiate roots. Stem 11–71 cm, erect, leaved, corrugated, solid, not ramificated, glabrescent to arachnoid, base usually without remnants of old leaves or tufts of hairs. Basal leaves 4.2–14 cm long, 1.4–5.4 cm wide, persistent, occasionally withering early, lanceolate to oblanceolate (ratio basal leaf width / basal leaf length = 0.15–0.64), obtuse to acute, attenuate to cuneate, with a petiole 1.1–14 cm long, dentate to slightly dentate, sometimes subentire (teeth 0.2–2.5 mm deep), glabrescent to covered with scattered arachnoid trichomes above (trichomes 0.2–1.1 mm long), glabrescent to arachnoid beneath, concolorous. Cauline leaves 3–11; middle cauline leaves 2.8–18 cm long, 0.4–5.1 cm wide, alternate, lanceolate to oblanceolate (ratio middle leaf width / middle leaf length = 0.08–0.31), acute, rarely obtuse, sessile to semi-amplexicaul auriculate, rarely attenuated into a petiole up to 8 cm long, dentate to slightly dentate, rarely subentire (teeth 0.2–3.6 mm deep), glabrescent to covered with scattered arachnoid trichomes above (trichomes 0.1–1.9 mm long), glabrescent to arachnoid beneath, tertiary venation inconspicuous; upper cauline leaves 0.8–8.5 cm long, 0.1–2.7 cm wide, lanceolate to oblong (ratio upper leaf width / upper leaf length = 0.04–0.50), acute, sessile to semi-amplexicaul auriculate, entire to dentate (teeth 0.4–2.2 mm deep), glabrescent to arachnoid. Synflorescence reduced to a solitary capitulum or corymbose, 3.5–35 cm long, with linear-oblong bracts. Capitula 1–4(–9), 28.7–60.4 mm in diam.; involucre 12.5–26 mm in diam., 12–19 mm long, cupuliform; involucral bracts (18–)24–31(–34), 6.8–13.4 mm long, 0.8–2.2 mm wide, with scarious margin 0.2–0.5 mm wide, lanceolate to ensiform, acute, 0–2-keeled, apex usually with a black spot, glabrescent to arachnoid, usually covered with scattered arachnoid trichomes (trichomes 0.1–0.9 mm long); supplementary bracts (7–)13–18(–26), 6.4–17 mm long, 0.5–1.5 mm wide, subulate, without scarious margin, two thirds to as long as involucral bracts, sometimes longer, glabrescent to arachnoid, usually covered with scattered arachnoid trichomes (trichomes 0.1–1.1 mm long), not imbricated. Ligulate florets 13–23, 14.4–29.6 mm long, yellow to orange; tubular florets 5.6–10.5 mm long, 0.6–1.9 mm in diam., yellow to light orange. Achenes 3.9–5.8 mm long, 0.8–1.5 mm wide, subcylindrical (ratio achene width / achene length = 0.16–0.38), shorter than pappus (ratio achene length / pappus length = 0.58–0.76), with 11–14 ribs, glabrous, sometimes with scattered trichomes near the top ca. 0.1 mm long; pappus 6.4–9.8 mm long, whitish.

Etymology: —The epithet doronicum probably refers to the similarity of its flowers with the genus Doronicum Linnaeus (1753: 885) .

Discussion: — Senecio doronicum is characterized by bearing solitary or several capitula, which are relatively large, usually showing supplementary bracts as long as the involucral ones. This taxon displays a wide distribution through the southern European mountain ranges, from Cantabrian Mountains to northern Dinaric Alps. As in other species with wide distributions, its intraspecific morphological variability is expectedly high, mainly in number of capitula, number of supplementary bracts, indumentum of involucre, and also in shape and indumentum of leaves. The similar species are S. provincialis , S. lagascanus , and S. scopolii , with which it shares part of its distribution area. Senecio doronicum differs from S. provincialis in its linear-oblong supplementary bracts, which usually are two thirds to as long as involucral bracts or sometimes longer, and its lanceolate to oblanceolate, attenuate, ± concolorous basal leaves. In contrast, S. provincialis has supplementary bracts widened at the base, usually a quarter to three quarters as long as involucral bracts, and basal leaves ovate to lanceolate, rounded to cuneate

14 • Phytotaxa 211 (1) © 2015 Magnolia Press

CALVO ET AL.

(rarely attenuate), ± discolorous. It differs from S. lagascanus in its longer supplementary bracts, slightly numerous, usually larger capitula, and in the absence of patent long multicellular trichomes on the lower part of the stem. Senecio doronicum has sparsely multicellular trichomes or arachnoid trichomes, although not obviously patent on the lower part of the stem. Senecio doronicum can also be mistaken for S. scopolii but they differ in the supplementary bracts (usually in higher number, ± imbricated, and without the black spot at the summit in S. scopolii ), the colour of ligulate florets (pale yellow in S. scopolii vs. yellow to orange in S. doronicum ), and the leaves thickness (soft and thin in S. scopolii subsp. scopolii vs. thick in S. doronicum ). In the populations from Marche and Abruzzo (Apennine Mountains), where S. doronicum co-occurs with S. scopolii , these mentioned characters lose consistency and many specimens show characters of both species or intermediate characters, making identifications uncertain.

Fiori (1903: 218) described S. doronicum var. pseudoarachnoideus as an intermediate form between S. doronicum and S. scopolii , embracing specimens weakly floccose and almost glabrous, which may grow mixed with S. scopolii or even separately. The unclear distribution of these populations and the inconsistency of the distinctive characters lead us to think that hybridization might have an important role in the evolutionary history of these populations. Likewise, some populations from Maritime Alps region, included here within S. doronicum , display a combination of morphological character states that are considered diagnostic for S. doronicum or S. provincialis . In this case, the involucre with many supplementary bracts as long as the involucral ones (or even longer), ± imbricated, without a black spot at the summit, and a dense indumentum, is quite remarkable. Difficulties with characterizing these populations as either S. provincialis or S. doronicum were already noted by Reichenbach (1853), Rouy (1903), and Briquet & Cavillier (1916). See Calvo et al. (2013) for more details and phylogenetic relationships.

This variability follows geographical patterns, and in most cases these populations can be easily distinguished morphologically. For this reason, the following subspecies are recognized in the present taxonomic treatment.