Keystone Species
A species that has a disproportionately large effect on its environment relative to its abundance. Such species are described as playing a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community.
Origin
American zoologist Robert T. Paine (1933–2016) coined the term in his 1969 paper, following his 1966 description of a rocky intertidal ecosystem in Makah Bay, Washington. Beginning in 1963, Paine studied how the starfish Pisaster ochraceus controlled mussel populations. He named crucial creatures whose influence far exceeds their abundance "keystone species," after the central stone preventing an arch from crumbling. The 1969 paper was a watershed, cited in over ninety publications within twenty years, transforming ecology.