Succulent growth forms in arid environments

Distinctions among plants with succulent above-ground organs are discussed. Water storage is not the only possible utility of fleshy organs; dilution of salt and malate may also be important functions. Regions with high levels of succulent plant diversity and dominance are enumerated together with their climates. Emphasizing potentially limiting conditions, the authors discuss general features of succulent CAM plant ecology. These attributes are used to derive a set of climatic characteristics favoring cactoids. Two regions possess appropriate climates: coastal deserts cooled by polar currents and semiarid subtropical montane areas. These 2 types of environments have probably been centered of succulent CAM evolution. Within these regions rocky slopes provide the most favorable habitats for CAM succulents. The absence of native cactoids from Australia may be due to the prevalence of unfavorable climates and habitats during much of the Quaternary, but historical accidents are an equally likely explanation. -from Authors