''Duvalia'' is a succulent plant genus in the subfamily

Asclepiadoideae The Asclepiadoideae are a subfamily of plants in the family Apocynaceae. Formerly, they were treated as a separate family under the name Asclepiadaceae, e.g. by APG II, and known as the milkweed family. They form a group of perennial herbs, twin ...

, in the family

Apocynaceae Apocynaceae (from ''Apocynum'', Greek for "dog-away") is a family of flowering plants that includes trees, shrubs, herbs, stem succulents, and vines, commonly known as the dogbane family, because some taxa were used as dog poison Members of the ...

(dogbane). The genus was first described in 1812, named after the French physician and botanist Henri-Auguste Duval (1777-1814).

Description

Duvalia caesp elegans - flowers 2 - Copy

Duvalia caespitosa vestita - Malgas-Infanta - Copy

Vegetative

The ''Duvalia'' species are succulent, perennial plants with low, planar growth. The stems are clavate, cylindrical to spherical, in cross-section four-, five-or six-edged, and to about 10 inches long. They can range from green, gray to mottled reddish in color. The stems of some species, such as the rounded '' Duvalia parviflora'', are distinctive, and these species can be identified even when not in flower. However the stems are very variable, and most ''Duvalia'' species can only be distinguished from each other when the flower is seen. The stems are superficially very similar to those of the related genus ''

Piaranthus ''Piaranthus'' is a succulent plant genus in the subfamily Asclepiadoideae, in the family Apocynaceae. It was first described in 1810. Its name comes from Greek and is descriptive of the fleshy, succulent flowers typical of the genus (''"piar-" ...

'', and the two are often confused when not in flower. In cross-section, ''Duvalia'' stems are sometimes five or six sided (''

'' stems are always four-sided in cross-section). To accurately distinguish them however, it is necessary to examine the flowers.

Floral

The distinctive flowers are on long, bare stalks, which grow from the base of the stems. Each flower has five thin, elongated petal-like lobes, radiating in a star-shape, from a central raised disk or

annulus Annulus (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to: Human anatomy * ''Anulus fibrosus disci intervertebralis'', spinal structure * Annulus of Zinn, a.k.a. annular tendon or ''anulus tendineus com ...

. The colour of most species flowers is shades of reddish brown, except for those of the rare '' Duvalia parviflora'' which are cream-coloured. The hermaphroditic flowers measure 1–5 cm in diameter, and have five parts. The crown is yellow ocher, brown, red to dark purple. The five corolla lobes are flat or folded along the middle nerve.

Distribution

It occurs in

southern Africa Southern Africa is the southernmost subregion of the African continent, south of the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to a number of ...

. The majority of the species are restricted to the western part of

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

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 ...

, with the greatest number of species occurring in the

Great Karoo The Karoo ( ; from the Afrikaans borrowing of the South Khoekhoe !Orakobab or Khoemana word ''ǃ’Aukarob'' "Hardveld") is a semi- desert natural region of South Africa. No exact definition of what constitutes the Karoo is available, so its ex ...

region, on the edge of the winter rainfall area. Only one species, '' Duvalia polita'' extends further east, and as far north into tropical Africa as

Malawi Malawi (; or aláwi Tumbuka: ''Malaŵi''), officially the Republic of Malawi, is a landlocked country in Southeastern Africa that was formerly known as Nyasaland. It is bordered by Zambia to the west, Tanzania to the north and northeast ...

and

Zambia Zambia (), officially the Republic of Zambia, is a landlocked country at the crossroads of Central Africa, Central, Southern Africa, Southern and East Africa, although it is typically referred to as being in Southern Africa at its most cent ...

. Four species, occurring on the other side of the continent on the verges of the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; T ...

, were formerly included in the genus ''Duvalia''. However phylogenetic studies have shown them to be relatively unrelated to the rest of the genus, and more closely related to genus '' Ballyanthus'' Bruyns.P. Bruyns, C. Klak, P. Hanacek: ''Evolution of the stapeliads (Apocynaceae-Asclepiadoideae) - repeated major radiation across Africa in an Old World group. Molecular Phylogenetics and Evolution.'' 2014. v. 77, no. 1, p. 251--263. ISSN 1055-7903. ;SpeciesThe Plant List, ''Duvalia''
/ref> ;formerly included transferred to '' Mannia'' *''Duvalia rupestris'' now '' Mannia rupestris''

References

''Portions of this page were translated from the equivalent page on the German wikipedia accessed July 3, 2012'' {{Taxonbar, from=Q291868 Apocynaceae genera