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| Zahora ait-atta Lemmel & M.Koch |
Abstract
Zahora ait-atta Lemmel & M.Koch, a new species from the Moroccan Sahara, is described and documented here and constitutes a monotypic new genus. The new taxon belongs to the tribe Brassiceae (Brassicaceae), and cytogenetic and phylogenetic analyses reveal that this diploid species has a remote status of Miocene origin in the northwestern Sahara Desert. We examined the morphological differences between morphologically related genera and provide photographs of the new species. The new genus may play a key role in future Brassica-Raphanus crop research since it is placed phylogenetically at the base of a generically highly diverse clade including Raphanus sativus, and it shows affinities to various Brassica species.
Keywords: Brassiceae, Brassicaceae, flora of the Sahara, Morocco, new genus, Zahora ait-atta
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| Figure 1. Zahora ait-atta in its natural environment. Border region with Algeria. Near Errachidia. Oued Bou-Ibourine – type locality a sandy habitat b flowering plant c rosette during winter d lyrate leaf from lower part of the plant e rosette starts building the inflorescence f ripening heteroarthrocarpic fruits g flowers and detailed view on sepals h siliques releasing seeds from dehiscent distal part of fruit.
Images taken by C. Lemmel and Z. Attioui.
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Type: Morocco. Meknés-Tafilalet/Drâa-Tafilalet: Border region with Algeria. Near Errachidia. Oued Bou-Ibourine, « Zizaou n´oudad », gps 31.4114, -3.7220, 900 m a.s.l., 11th March 2019, C. Lemmel s.n. (Holotype, HEID 505689; Isotype, G00394714, Conservatoire et jardin botanique de Genève; Paratype, HEID 505749, 505750, ex. cult. Botanical Garden Heidelberg 2019).
Description: Herbs, woody at base, monocarpic, simple trichomes; rhizome fleshy, 2–3 cm in diam. Stems 80–140(-180) cm tall, robust, up to 1.4 cm in diam, erect, simple at base, often alternately branched in lower part. Basal leaves rosulate, fleshy; leaves lyrate, distal lobecordate, (10-)15–25(-40) cm, margin entire to distantly dentate, numerous simple trichomes on lower surface mostly along veins, upper side loosely covered with simple trichomes; cauline leaves similar but apex obtuse to weakly subacute, 10–15 × 5–7 cm. Raceme ebracteate, elongating in fruit, 40–100 cm; often branched. Sepals erect, saccate ca. 8 mm long, with few simple trichomes; petals pale-yellow,1.5–1.7 cm long, 6–7 mm wide, petal claw 8 mm long, obtuse at apex, glabrous. Filaments tetradynamous, ca. 9 mm long; nectar glands 4, rounded, elateral pair larger. Stigma entire. Infructescence with up to 100(-200) siliques, (30-)40–45(-48) mm, petiolate (9–11 mm). Fruits heteroarthrocarpic with a distal indehiscent balloon-like structure with two viable seeds (3.5–5 × 6–8 mm); proximal part dehiscent, terete (30–45 mm); 20–40 ovules; septum complete. Seeds biseriate, mucilaginous, 1.3–1.4 × 1.4–1.5 mm.
Etymology: Zahora means “flower” in Arabic, indicating the attractive and peculiar appearance of the plant. “Aït-atta” are a Berber tribal confederation of south eastern Morocco who locally know the plant under the name «Zizaou n’oudad» (Barbary-sheep’s cabbage).
Habitat: All places are in sandy beds of oueds flowing from the base of the kreb (cliff) of the Hamada du Guir or the Bin el Korbine.
Ecology: Greenhouse and pollination experiments showed that the species is largely self-compatible. At its natural stands the plant is annual and monocarpic. However, in cultivation the plant species can be kept growing when cutting frutescence. There are two different options of seed release, either directly into a local soil seed bank from the dehiscent part of fruit or via the distal indehiscent part carrying two seeds, which may allow distributing effectively with water in the wadi systems at rare and occasional events.
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| Figure 2. Distribution of known localities (red dots) of Zahora ait-atta documented from 2015 to 2019 (satellite map was taken from image metadata Copernicus/Landsat). |
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| Figure 3. BEAST analysis of tribe Brassiceae based on ITS DNA sequence data (Suppl. material 2). The new genus Zahora is highlighted, and its respective stem group node is indicated (red dot). Divergence times are given as Mya (million years ago). Agronomically important species, Brassica oleracea and Raphanus sativus, are indicated and shown with their respective clades. Brassica nigra and B. carinata are also indicated with an asterisk (orange). |
Conclusion:
Zahora ait-atta is described as a new species of a new monotypic genus. Zahora shows a peculiar fruit feature, namely heteroarthrocarpic fruits, and the species might mediate evolutionary between Core Oleracea clade (e.g. Brassica oleracea, Brassica napus) and Raphanus sativus and related genera. Both represent important crop plant groups with seeds playing an enormous agronomical role. The diploid new species might, therefore, serve as important germplasm reservoir to study traits and characters in a number of Brassiceae crop plants.
