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| Senecio namibensis Swanepoel & A.E.van Wyk, in Swanepoel, Becker, De Cauwer & van Wyk, 2022. Photographs by W. Swanepoel. |
Abstract
Senecio namibensis is described as a new species known only from the northern part of the Namib Desert in northwestern Namibia. It is a range-restricted species near-endemic to the Kaokoveld Centre of Endemism. These dwarf shrubs grow on rocky outcrops under harsh desert conditions. Diagnostic characters for Senecio namibensis include the annual or perennial habit, succulent leaves, and radiate capitula with 3–6 yellow ray florets. A comparison of some of the more prominent morphological features to differentiate between S. namibensis and its possible nearest relatives, S. englerianus and S. flavus, is provided. All three species have superficially similar looking succulent leaves, but an obvious difference is that the capitula in S. englerianus are discoid and in S. flavus disciform or obscurely radiate. Based on IUCN Red List categories and criteria, a conservation assessment of Least Concern (LC) is recommended for the new species.
Keywords: endemism, flora, Kaokoveld Centre of Endemism, Namib Desert, Senecio englerianus, Senecio flavus, succulent,
taxonomy
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| Senecio namibensis, morphology of capitula. A. Capitulum viewed from above, showing female ray florets and fertile hermaphrodite disc florets. B. Capitulum viewed from the side, showing calyculate and involucral bracts. C. Capitulum viewed obliquely from below, showing calyculate and involucral bracts. Scale bar = 2 mm. Photographs by W. Swanepoel. |
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| Senecio namibensis, plants in flower, showing habit and variation in leaf morphology (at type locality). A. Leaves succulent; blade with base strongly cordate, margin conspicuously dentate; capitula radiate. B. Leaves succulent; blade with base weakly cordate, margin weekly dentate. Photographs by W. Swanepoel. |
Senecio namibensis Swanepoel & A.E.van Wyk, sp. nov.
Diagnosis: — Dwarf shrub up to 0.4 m high, morphologically most similar to Senecio englerianus and S. flavus: from S. englerianus it differs in having the leaf blade cordate to suborbicular or reniform (vs. cordate, suborbicular, reniform, ovate or oblate); blade base cordate to deeply cordate (vs. cordate-reniform or truncate); capitula radiate (vs. discoid); involucre usually shorter and narrower: 5.3–7.4 mm long, 3.5–4.0 mm diam. (vs. 6.3–8.0 mm long, 4.4–5.6 mm diam.); from S. flavus it differs in having the capitula distinctly radiate (vs. disciform or obscurely radiate; ray florets scarcely longer than involucre); involucre usually shorter and wider: 5.3–7.4 mm long, 3.5–4.0 mm diam. (vs. 7.0– 9.5 mm long, 2.7–2.9 mm diam.); pappus bristles free, non-fluked and lacking hooklike apical appendages [vs. ca. 33%—according to Coleman et al. (2003) and Milton et al. (2022) —of pappus bristles connate and fluked—see “Materials and methods” for definition of “fluked” bristles—with grappling hook-like apical appendages].
Etymology: —The specific epithet refers to the Namib Desert, which, in its broadest definition, stretches along the Atlantic Ocean from Saõ Nicolau (Bentiaba) in Angola through Namibia to the Olifants River in South Africa ( Seely 2004, Goudie & Viles 2015).
Wessel Swanepoel, Rolf Becker, Vera De Cauwer and Abraham E. van Wyk. 2022. Senecio namibensis (Asteraceae: Senecioneae), A New Species from Namibia. Phytotaxa. 571(2); 103-111. DOI: 10.11646/phytotaxa.571.2.1