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Mesembryanthemaceae (ca. 2000 species, 116 genera) is the dominating family in the succulent flora of the Succulent Karoo Region (southern Africa), to which the vast majority of species of this family are restricted. The success of this family is due to an extremely broad spectrum of highly specialized life forms and life strategies. The family must have developed a tempo of evolution that is probably unrivaled within angiosperms, since the mega-niche Succulent Karoo opened up only 5 million years BCE at most.

The remarkable biodiversity of this family is the result of a complex interaction between the availability of numerous diverse niches, often very small in extent, a climate characterized by steep gradients, and a strong genetic drift caused by a very low rate of gene exchange among populations and frequent breakdown of populations. It is suggested that a special genetic potentiality plays a crucial role in the evolutionary processes of this family. This potentiality allows fast and easy rearrangement of high-ranking regulatory ’’homeotic’’ genes. This process is strongly canalized by the shortage of resources, i.e. changes in one place in the life cycle usually force changes in other places. Perhaps by repeated changes in homeotic genes, this family has succeeded in evolving numerous novel and diverse complex life forms and life cycles in spite of a very limited set of subordinate ontogenetic programs.