''Didelta spinosa '' (L.f.) Aiton, belonging to the family of

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

, is a Southern African woody shrub or small tree endemic to the

West Coast West Coast or west coast may refer to: Geography Australia * Western Australia *Regions of South Australia#Weather forecasting, West Coast of South Australia * West Coast, Tasmania **West Coast Range, mountain range in the region Canada * Britis ...

and found from

Saldanha Bay Saldanha Bay ( af, Saldanhabaai) is a natural harbour on the south-western coast of South Africa. The town that developed on the northern shore of the bay, also called Saldanha, was incorporated with five other towns into the Saldanha Bay Local Mu ...

in the south across the

Gariep The Orange River (from Afrikaans/Dutch: ''Oranjerivier'') is a river in Southern Africa. It is the longest river in South Africa. With a total length of , the Orange River Basin extends from Lesotho into South Africa and Namibia to the nort ...

into the south-west corner of

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

. 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'' (L.f.) Aiton. Recent phylogeny studies have placed the genus ''Didelta'' and ''Berkheya spinosissima'' on the same

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

. The beetle '' Julodis viridipes'' Laporte has been recorded feeding on the foliage of ''D. spinosa'', whereas the

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

s '' 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 Carl Linnaeus the Younger, Carolus Linnaeus the Younger, Carl von Linné den yngre (Swedish; abbreviated Carl von Linné d. y.), or ''Linnaeus filius'' (Latin for ''Linnaeus the son''; abbreviated L.fil. (outdated) or L.f. (modern) as a botanic ...

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 Joseph Gaertner (12 March 1732 – 14 July 1791) was a German botanist, best known for his work on seeds, ''De Fructibus et Seminibus Plantarum'' (1788-1792). Biography He was born in Calw, and studied in Göttingen under Albrecht von Haller. ...

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

External links

iSpot habitat image
{{Taxonbar, from=Q15576433 Arctotideae