Glottiphyllum and Pleiospilos have their centers of species richness and endemism in the Little Karoo.    From Wordnik.com.  [Succulent Karoo] Reference

Lithops spp. (all Mesembryanthemaceae) in the Sperrgebiet and Richtersveld, and species in the following genera in the Tanqua Karoo: Augea, Cephalophyllum, Crassula, Pleiospilos, Psilocaulon, Hereroa, Rhinephyllum, Ruschia, and Sphalmanthus.    From Wordnik.com.  [Succulent Karoo] Reference