Some species of hummingbirds are keystone species in the Sonoran Desert. Hummingbirds pollinate many varieties of native cactus and other plants. In areas of the Sonoran Desert with few hummingbirds, invasive species such as buffelgrass have taken over the ecosystem
Prairie dogs are a keystone species, a species whose contribute to soil and water quality in their plains ecosystem. Their foraging retains water in the soul and forces fresh new grasses to continually grow. Young grasses have more nutrients for species such as vision and elk.
Keystones species are often predators, like mountain lion in Glacier National Park, Wyoming. The deer, rabbits, and bird species in the ecosystem are at least partly controlled by the presence of the mountain lion. Their feeding behavior, or where they choose to make their nests and burrows, is largely a reaction to the mountain lion's activity.
Elephants are keystone species on African grasslands, known as savannas. Without the presence of elephants, grasslands would probably develop into forests. Elephants graze on trees such as acaclas, above, preventing them from growing to maturity.
Sea otters are one of the most important keystone species in the kelp forest habitat. Kelp, a giant species of seaweed, us home to hundreds of species, from sea stars to sharks. Sea otters eat kelp, sea urchins, preventing an overpopulation of urchins from destroying the ecosystem.
Sea stars are an important keystone species in tide pools. They eat sea urchins, mussels, and other shellfish that have no other natural predators.