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Family: Aizoaceae (vygie, mesem family)

[= Mesembryanthemaceae]

Life > eukaryotes > Archaeoplastida > Chloroplastida > Charophyta > Streptophytina > Plantae (land plants) > Tracheophyta (vascular plants) > Euphyllophyta > Lignophyta (woody plants) > Spermatophyta (seed plants) > Angiospermae (flowering plants) > Eudicotyledons > Core Eudicots > Order: Caryophyllales

Worldwide there are about 1854 species in 135 genera in the family Aizoaceae, and most of these species are native to southern Africa (1735 species in 134 genera in southern Africa). The vast majority of species are succulents, falling in the previously recognised family Mesembryanthemaceae and loosely termed mesems. The arid regions of southern Africa have been the centre of speciation for mesems and have given rise to a huge array of forms, including flat disk-like species that look like stones. 

There has been controversy over a long period about whether the Mesembryanthemaceae should be included in the Aizoaceae or kept as a separate family. The Aizoaceae is interpreted here in the broad sense to include the mesems and follows the conclusions of the Angiosperm Phylogeny Group. The reasoning behind combining the mesems in the Aizoaceae is that evidence suggests that they are derived from this family and to keep them in a separate family would make the Aizoaceae paraphyletic. 

 In the classification below, the old Mesembryanthemaceae family is relegated to 2 subfamilies under the Aizoaceae: the Mesembryanthemoideae and the Ruschioideae. The remaining subfamilies (Aizooideae, Sesuvioideae and Tetragonioideae) fall under Aizoaceae in its strict sense.  

Genera native to southern Africa

Subfamily: Aizooideae

Acrosanthes

Five species, endemic to the Western Cape.

Aizoanthemum

Four species, endemic to Namibia.

Aizoon

About 25 species worldwide (mainly in the Mediterranean region), with 11 species native to southern Africa.

Galenia

Twenty-nine species, all endemic to southern Africa.

Plinthus

Five species, all endemic to southern Africa.

Subfamily: Sesuvioideae

Sesuvium

About 12 species, native to the tropics and subtropics, mainly African with five species native to southern Africa. Occurs on saline dunes and beaches, and in riverbeds and marshes.

Trianthema

About 17 species, found in the tropics and subtropics worldwide, with five species native to southern Africa.

Zaleya

Six species, native to Africa, Asia and Australia, with one species, Zaleya pentandra, native to southern Africa. See Flora of Zimbabwe.

Subfamily: Tetragonioideae (sometimes put at family level as the Tetragoniaceae)

Tetragonia

The 50-60 species are native to Asia, Africa, Australia, New Zealand and temperate South America. Thirty-five species are native to southern Africa.

Tribulocarpus

One species: Tribulocarpus dimorphanthus, endemic to Namibia.

The 'Mesems'

Publications

  • Angiosperm Phylogeny Group 1998. An ordinal classification for the families of flowering plants. Annals of the Missouri Botanical Garden 85: 531-553.

  • Klak, C., Reeves, G. and Hedderson, T. 2004. Unmatched tempo of evolution in southern African semi-desert ice plants. Nature 427, 63–65.

  • Ellis A.G. and Weis A.E. 2006. Coexistence and differentiation of ‘flowering stones’: the role of local adaptation to soil microenvironment. J. Ecol. 94, 322–335.

 

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