Piaranthus

Life-forms

Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Eudicots
Cladus: Core eudicots
Cladus: Asterids
Cladus: Lamiids
Ordo: Gentianales

Familia: Apocynaceae
Subfamilia: Asclepiadoideae
Tribus: Ceropegieae
Subtribus: Stapeliinae
Genus: Piaranthus
Species: P. atrosanguineus – P. comptus – P. cornutus – P. decipiens – P. erratus – P. fuscatus – P. geminatus – P. parvulus – P. punctatus
Source(s) of checklist:

Govaerts, R. et al. 2021. Piaranthus in Kew Science Plants of the World Online. The Board of Trustees of the Royal Botanic Gardens, Kew. Published online. Accessed: 2021 Apr. 19. Reference page.

Name

Piaranthus R.Br. (1809)

Type species: Piaranthus punctatus R.Br.

Synonyms

Heterotypic
Obesia Haw., Syn. Pl. Succ.: 42. (1812)
Huerniopsis N.E.Br., J. Linn. Soc., Bot. 17: 171. (1878)

References

Brown, R. (1809) On Asclepiad. 12.
Govaerts, R. et al. 2021. Piaranthus in Kew Science Plants of the World Online. The Board of Trustees of the Royal Botanic Gardens, Kew. Published online. Accessed: 2021 Apr. 19. Reference page.

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-" = fat, "-anthos" = flower).[2][3][4]
Description
Piaranthus parvulus, from the Tankwa Karoo

The plants typically form flat, spreading mats of multiple offsetting stems. The stems are small, compact and four-edged. Tubercles (leaf remnants) appear along the four sides.

The flowers are small, fleshy, and bear five independent petals in a star shape. They appear in clusters, each flower up-turned, on a tiny inflorescence that sprouts from the tip of the stem. Each stem usually only produces a maximum of one inflorescence. The flowers of different species are in a range of colours; most emit unpleasant odours, especially the darker red or brown coloured ones.

The compact, mat-forming stems are very similar to those of the related genus Duvalia, and the two are often confused when not in flower. However the stems of Piaranthus have four sides (in cross-section), while those of Duvalia often have more.
Distribution

The genus Piaranthus is restricted to the western part of Southern Africa. It occurs in arid, sandy areas, in the shade of bushes.
Piaranthus comptus ("comptus" = "adorned") from the Gamka Karoo.

Species

Piaranthus atrosanguineus (N.E.Br.) Bruyns - Botswana
Piaranthus comptus N.E.Br. - South Africa
Piaranthus cornutus N.E.Br. - South Africa
Piaranthus decipiens (N.E.Br.) Bruyns - Western Cape Province
Piaranthus decorus (Masson) N.E. Br. - South Africa
Piaranthus disparilis N.E. Br. - South Africa
Piaranthus fasciculatus (Thunb.) Schult. - Western Cape Province
Piaranthus framesii Pillans - Cape Province
Piaranthus geminatus (Masson) N.E.Br. - South Africa
Piaranthus globosus A.C.White & B.Sloane - South Africa
Piaranthus mennellii C.A.Lückh. - Cape Province
Piaranthus pallidus C.A.Lückh. - Cape Province
Piaranthus parvulus N.E.Br. - Cape Province
Piaranthus pullus (Aiton) Haw.
Piaranthus punctatus (Masson) R. Br. ex Schult. - South Africa
Piaranthus ruschii Nel - Pockenbank in Namibia

formerly included

species transferred to other genera (Caralluma, Hoodia, Huerniopsis, Quaqua)

P. grivanus now Huerniopsis decipiens
P. gussoneanus now Caralluma europaea
P. incarnatus now Quaqua incarnata
P. pilifer now Hoodia pilifera

Taxonomy

Phylogenetic studies have shown the genus to be monophyletic, and to be very closely related to the genera Orbea and Stapelia. More distantly related are the genera Huernia and Tavaresia.[5]
References

Piaranthus R.Br. Plants of the World Online. Retrieved 28 July 2023.
Brown, Robert. 1810. On the Asclepiadeae 12.
Tropicos
Gibbs Russell, G. E., W. G. M. Welman, E. Retief, K. L. Immelman, G. Germishuizen, B. J. Pienaar, M. Van Wyk & A. Nicholas. 1987. List of species of southern African plants. Memoirs of the Botanical Survey of South Africa 2(1–2): 1–152(pt. 1), 1–270(pt. 2).
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.