The cactus family (Cactaceae; ‘cacti’) is an interesting case study. Cacti are a conspicuous component of the arid regions of the New World and represent one of the world's most spectacular desert radiations (Edwards et al. 2005). The family is distributed from southern Patagonia in Argentina and Chile to Alberta and British Columbia in Canada (Edwards et al. 2005), with the only exception being Rhipsalis baccifera (mistletoe cactus), which is thought to have originated in tropical Americas, but was apparently dispersed across the Atlantic Ocean by birds, reaching southern Africa, Madagascar and Sri Lanka