Senecio paulsenii Hoffmann

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

27. Senecio paulsenii Hoffmann in Paulsen (1903: 152). TYPE: Pakistan, Chitral , monte arido Pamir, prope lacŭs Jashil Kŭl, [35º49'N 71º59'E], O . V . Paulsen 996 (lectotype, designated by Nordenstam (1989b: 68), C!; isotype, LE!) .

Perennial herb. Rhizome 1.6–12 cm long, 0.5–1.7 cm in diam., ± horizontal, with swelled fastigiate roots. Stem 15–64 cm, erect, leaved, corrugated, solid, not ramificated, glabrescent to weakly arachnoid, base usually with tufts of hairs and remnants of old leaves, sometimes violet coloured. Basal leaves 4.5–16.2 cm long, 1.3–7.2 cm wide, ± persistent, sometimes withering early, oblanceolate to lanceolate (ratio basal leaf width / basal leaf length =

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CALVO ET AL.

0.10–0.80), obtuse, attenuate to cuneate, with a petiole 2–11 cm long, dentate to sinuate (teeth 0.5–8 mm deep, becoming larger towards the lamina base), sometimes subentire, glabrescent to weakly arachnoid (trichomes 0.7–0.8 mm long), concolorous. Cauline leaves 3–9; middle cauline leaves 3.1–17 cm long, 0.3–6.5 cm wide, alternate, oblanceolate to oblong (ratio middle leaf width / middle leaf length = 0.06–0.42), acute to obtuse, sessile to semi-amplexicaul, sometimes attenuated into a petiole up to 12 cm long, dentate towards the lower half (teeth 0.9–10 mm deep), sometimes subentire, glabrescent to weakly arachnoid (trichomes 0.5–1.3 mm long), tertiary venation inconspicuous; upper cauline leaves 0.8–11.5 cm long, 0.1–2.5 cm wide, lanceolate to linear (ratio upper leaf width / upper leaf length = 0.10–0.38), acute, sessile to semi-amplexicaul, entire to slightly dentate (teeth 0.6–2.5 mm deep), glabrescent to weakly arachnoid. Synflorescence 4–26 cm long, corymbose to pseudocorymbose, with linear-oblong bracts. Capitula 1–3(–9), 30.4–48.1 mm in diam.; involucre 13.4–27.5 mm in diam., 11–17 mm long, narrowly cupuliform; involucral bracts (14–)20–21(–24), 9–17.4 mm long, 1.2–2.7 mm wide, with scarious margin 0.3–0.8 mm wide, lanceolate, attenuate, 1–2-keeled, apex usually with a black spot, sometimes violet coloured, glabrescent to weakly arachnoid (trichomes 0.2–1.2 mm long); supplementary bracts (5–)6–9(–14), 2.5–9.2 mm long, 0.6–1.3 mm wide, subulate, without scarious margin, a third to three quarters as long as involucral bracts, glabrescent to weakly arachnoid (trichomes 0.2–1.2 mm long), not imbricated. Ligulate florets 11–16, 16.3–27.7 mm long, yellow; tubular florets 8.9–15.3 mm long, 0.8–2 mm in diam., yellow. Achenes 6.8–10.1 mm long, 0.9–1.7 mm wide, subcylindrical (ratio achene width / achene length = 0.13–0.24), shorter than pappus (ratio achene length / pappus length = 0.49–0.77), with 10–12 ribs, glabrous to hairy (trichomes 0.1–0.2 mm long); pappus 9.8–15.2 mm long, whitish. Chromosome number: unknown.

Etymology: — Senecio paulsenii is named in honor of Ove Vilhelm Paulsen (1874–1947), Danish botanist who collected in the Pamir Mountains during 1898–1899.

Discussion: — Senecio paulsenii is characterized by bearing 1–3(–9) capitula, basal leaves oblanceolate to lanceolate, subentire to sinuate (with teeth becoming larger towards the lamina base), and stem base with tufts of hairs and remnants of old leaves. The length of the achenes (6.8–10.1 mm) is useful to discriminate this Central Asian species from the Anatolian species, in which the achene length rarely reaches 7 mm. Senecio paulsenii is similar to S. franchetii and S. olgae (see comments under the latter). It differs from S. franchetii in its smaller size, a lesser number of capitula [1–3(–9) vs. (1–)4–8(–15)], and the stem base with tufts of hairs and remnants of old leaves. Moreover, S. paulsenii has smaller basal leaves, subentire to irregularly sinuate, while those in S. franchetii usually are larger and regularly dentate. Although these two species are parapatric in Tajikistan, the mentioned characters are useful to distinguish each other.

Senecio paulsenii is a variable species regarding the leaf shape, and the indumentum of involucre and achenes. The latter character is the main one to distinguish between the two subspecies recognized here. In disagreement with Nordenstam (1989b), the shape of the leaves is not a valuable character to distinguish between both subspecies. Although they partially overlap in northeastern Afghanistan, most of the specimens could be easily identified by the character of the achene indumentum.