Many of the eleven or so families of the Caryophyllales have been particularly successful at living in xeric environments. Four families have shown the greatest amount of adaptive changes: (1) the ice-plants (Aizoaceae), (2) the cacti (Cactaceae), (3) the Old World cacti (Didiereaceae), and the portulacs (Portulacaceae). The ice-plants adapted to the harsh conditions of the deserts of southern Africa; many evolved leaf succulence to an extreme degree, some went underground, others lost the ability to make normal wood, and all had to adapt their reproductive strategies in pollination or seed dispersal. The cacti adapted to deserts of South, Central, and North America by losing their leaves over time and evolving two types of succulent stems: columnar (ex. saguaros) and rotund (ex. peyote). Cacti adapted by greatly reducing the presence of vessels in their wood, evolving a novel tracheid type termed wide-band tracheids, and evolving CAM and C4 metabolisms. Plants of the Didiereaceae adapted to the harsh Madagascaran environment by evolving both stem and leaf succulence, and evolving the columnar stem form, but these plants maintained their normal woody growth. Members of the Portulacaceae evolved in many different xeric areas of southern Africa, but all evolved leaf succulence rather than stem succulence, much the same as was found in the Aizoaceae. Each family evolved varying strategies for living in water stressed environments. Common themes among these distantly related plants are leaf and/or stem succulence, anatomical and physiological adaptations, and varying reproductive strategies.

Key words: Aizoaceae, Cactaceae, desert, Didiereaceae, Portulacacese, succulent