A species that exerts a large, stabilizing influence throughout an ecological community, despite its relatively small numerical abundance
Species that interacts with a large number of other species in a community Because of the interactions, the removal of this species can cause widespread changes to community structure Compare with immigrant species, indicator species, and native species
A species whose niche (occupation) in its ecosystem is vital to the survival of many other species The disappearance of keystone species thus leads to a series of extinctions in an ecosystem
A plant or animal that plays a more significant role in the habitat than other species; they provide essential services that are unique Without the work of these key species, the habitat will change significantly
These are species whose activities are critical to the structure of the community in which they live
A species of animal on which associated animals depend for support (For example, starfish are keystone species off the coast of British Columbia They feed on clams which would otherwise eat all other sea animals in the region If starfish are removed, the clams flourish, and the marine animal population plunges )