| Didelta spinosa | |
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| Habit of plant in Goegap Nature Reserve | |
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| Flowerheads, Nardouwsberg, Clanwilliam | |
Scientific classification 
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| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Asterids |
| Order: | Asterales |
| Family: | Asteraceae |
| Genus: | Didelta |
| Species: | D. spinosa |
| Binomial name | |
| Didelta spinosa (L.f.) Aiton | |
| Synonyms | |
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Didelta spinosa, belonging to the family of Asteraceae, is a Southern African woody shrub or small tree endemic to the West Coast and found from Saldanha Bay in the south across the Gariep into the south-west corner of Namibia. Growing 2–3 m tall and drought-resistant, its preferred habitat is on dry, rocky slopes. This species was introduced to Europe by Thunberg and Masson.
Leaves are opposite, shiny, oval to elliptic with margins rolled under (revolute) with irregular spine-tipped teeth - young leaves and twigs somewhat felted; flowers with an outer row of unusually large and leaf-like bracts with mucronate apices, and which become membranous with age; fruits in spine-fringed cells. Flowering takes place from midwinter to early spring. There are only 2 species in this genus, the other being Didelta carnosa. Recent phylogeny studies have placed the genus Didelta and Berkheya spinosissima in the same clade.
The beetle Julodis viridipes has been recorded feeding on the foliage of D. spinosa, whereas the nematodes Scutellonema brachyurus, Paratrichodorus meyeri and Xiphinema loteni have a close association with the tree.
History
The two currently recognised species of Didelta were first described in 1781 by Carl Linnaeus the Younger and placed in the genus Polymnia, an American genus to which they were ill-suited. In 1785 a detailed colour plate by Buc'hoz was published in Grand Jardin de l'Univers of a plant that had been cultivated at Trianon and named Breteuillia trianensis by him - the plant clearly being Linnaeus' Polymnia carnosa. The genus Didelta was based on this same plant and published in L'Heritier's Stirpes novae in 1786 as Didelta tetragoniifolia. The genus Breteuillia thus predates Didelta but Burtt recommended that the name Didelta should be conserved because of its wide usage. Didelta tetragoniifolia was later shown to be Linnaeus the Younger's Polymnia carnosa, and this species, together with its sibling Polymnia spinosa, was transferred to Didelta. Joseph Gaertner in his monumental work "De frvctibvs et seminibvs plantarvm" of 1788-1792 published the species as Favonium spinosum (see illustration). Thunberg in his 1800 work Prodromus Plantarum Capensium v2 p163 placed both species in a new genus Choristea.
References
- Kirkel, Judd. "Photos of South African Plants - Category: Shrubs - Image: Didelta spinosa".
- 'Encyclopaedia Londinensis', Volume 5
- "Tree Atlas of Namibia - Official Web Page - Didelta spinosa". Archived from the original on 2015-03-09. Retrieved 2015-03-06.
- Wortley, Alexandra H.; Funk, V. A.; Skvarla, John J. (2008). "Pollen and the Evolution of Arctotideae (Compositae)". The Botanical Review. 74 (3): 438–466. doi:10.1007/s12229-008-9014-8. S2CID 24494447.
- Bellamy, C. L.; Westcott, R. L.; Verity, D. S. (1 January 1988). "New Synonymy, Distributional and Adult and Larval Host Records for Some Southern African Buprestidae (Coleoptera)". The Coleopterists Bulletin. 42 (1): 73–83. JSTOR 4008567.
- Swart, A.; Marais, M. (August 2002). "Plant nematodes in South Africa. 4. Modimolle area, Limpopo Province" (PDF). African Plant Protection. 8 (1–2): 25–32.
- Burtt, B. L. (1 January 1948). "Didelta and Cuspidia". Kew Bulletin. 3 (1): 69–73. doi:10.2307/4118925. JSTOR 4118925.
- Prodromus plantarum Capensium ?quas in promontorio Bona Spei Africes, annis 1772?1775 /Collegit Carol. Pet. Thunberg. Upsalia : J. Edman. 1794.
External links
| Taxon identifiers | |
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| Didelta spinosa | |