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Adaptations for water conservation

All cacti have some adaptations to promote efficient water use. Most cacti— opuntias and cactoids —specialize in surviving in hot and dry environments (i.e. are xerophytes), but the first ancestors of modern cacti were already adapted to periods of intermittent drought. A small number of cactus species in the tribes Hylocereeae and Rhipsalideae have become adapted to life as climbers or epiphytes, often in tropical forests, where water conservation is less important.