The Succulent Karoo in southwestern Namibia and South Africa possesses the highest plant diversity of any desert biome in the world, with more than 6000 species in an area of approximately 103,000 km2. There are approximately 1700 species of leaf succulents, and this dominance is unique among the world's deserts. The rich biodiversity of the Succulent Karoo is due in large part to an extensive and complex array of subtle biotic and abiotic changes, the latter derived from topographic, edaphic, and climatic diversity in the region's landscape. Speciation can be seen most notably in the Mesembryanthema of the Aizoaceae, with 108 genera and 1132 species in the biome. Keywords: Biodiversity hotspot, Desert, Little Karoo, Mesembryanthemaceae, Namaqualand, Plant endemism, South Africa, Succulent plant, Tankwa Karoo, Winter rainfall.