text: The majority of plants possessing CAM are either epiphytes (e.g., orchids, bromeliads) or succulent xerophytes (e.g., cacti, cactoid Euphorbias), but CAM is also found in hemiepiphytes (e.g., Clusia); lithophytes (e.g., Sedum, Sempervivum); terrestrial bromeliads; wetland plants (e.g., Isoetes, Crassula (Tillaea), Lobelia); and in one halophyte, Mesembryanthemum crystallinum; one non-succulent terrestrial plant, (Dodonaea viscosa) and one mangrove associate (Sesuvium portulacastrum).
  The only trees that can do CAM are in the genus Clusia; species of which are found across Central America, South America and the Caribbean. In Clusia, CAM is found in species that inhabit hotter, drier ecological niches, whereas species living in cooler montane forests tend to be . In addition, some species of Clusia can temporarily switch their photosynthetic physiology from  to CAM, a process known as facultative CAM. This allows these trees to benefit from the elevated growth rates of  photosynthesis, when water is plentiful, and the drought tolerant nature of CAM, when the dry season occurs. 
  Plants which are able to switch between different methods of carbon fixation include Portulacaria afra, better known as Dwarf Jade Plant, which normally uses C fixation but can use CAM if it is drought-stressed, and Portulaca oleracea, better known as Purslane, which normally uses  fixation but is also able to switch to CAM when drought-stressed.
  CAM has evolved convergently many times. It occurs in 16,000 species (about 7% of plants), belonging to over 300 genera and around 40 families, but this is thought to be a considerable underestimate. The great majority of plants using CAM are angiosperms (flowering plants) but it is found in ferns, Gnetopsida and in quillworts (relatives of club mosses). Interpretation of the first quillwort genome in 2021 (I. taiwanensis) suggested that its use of CAM was another example of convergent evolution. 
  The following list summarizes the taxonomic distribution of plants with CAM: