[Dave]

Cacti are almost exclusively New World plants. This means that they are native only in North America and South America. There is however one exception, Rhipsalis baccifera; this species has a pantropical distribution, occurring in the Old World in tropical Africa, Madagascar and Sri Lanka as well as in tropical America.

This plant is thought to be a relatively recent colonist in the Old World (within the last few thousand years), probably carried as seeds in the digestive tracts of migratory birds. Many other cacti have become naturalized to similar environments in other parts of the world after being introduced by people.