The species having greater influence on community characters in spite of being low numbers and biomass are called keystone species.
The keystone species concept was put forward Robert T Paine to explain the relationship between Pisaster ochraceus (Starfish) and Mytilus californianus (Mussel).
Fig trees in a tropical rain forest support moneys, bats and birds. Any removal of these tress will adversely affect the animal population.
Sea Otters are a keystone species of the kelp forest ecosystem. Kelp is home to hundreds of species like crabs, snails, sea urchins and geese etc that depend on kelp for food.
Beavers, the mammalian architect construct dams and transforming streams into ponds, create new habitats for many plants and animal species.
The flying fox is a key stone specie on tropical islands.It pollinates many of the plants, and is a key disperser of seeds.
The prairie dog is a keystone species of the prairie ecosystem. They contribute to the lives of the other mammals by providing habitat and food.
African elephants are the keystone species that maintain the entire savannah ecosystem. Elephants eat acacia and even if an acacia tree grows to a height of several feet, elephants are able to knock over the tree and uproot it.
Some species of hummingbird are keystone species in the Sonoran Desert of North America. Hummingbirds pollinate many varieties of native cactus and other plants.