Carnegiea gigantea Keystone Species A huge species of cactus able to produce fruit and a nectar flower. Its waxy skin helps hold its main source of water being a benefit as a water source to other organisms. That and the fact that its flesh, fruit and nectar provide food it is the keystone of the ecosystem. If the largest biomass producer in this ecosystem was removed the a major source of energy would be eliminated and many first level consumers would quickly move to the other species of cacti or die off. For more information visit http://plants.usda.gov/core/profile?symbol=CAGI10.
jumping cholla
Opuntia bigelovii A small 3-7 ft cactus with a single trunk and several branches called segments with spines completely covering them. A unique adaptation developed is that the segments are extremely sensitive and will "jump" off the plant if a organism or strong enough wind is blown against the cactus. The cactus actually depends on the fallen segments to take root and reproduce.
Organ Pipe Cactus
Stenocereus thurberi A huge plant that a single vertical stem can from 15-25 feet high. Made with a single base this cactus has large amount of vertical stems that rarely branch resulting to the shape of an old fashioned organ. It produces a sweet edible fruit.