Ecological Extinction - Keystone Species

Keystone Species

Robert Paine (1969) first came up with the concept of a keystone species while studying the effects of the sea star predator, Pisaster ochraceus, on the abundance of the herbivorous gastropod, Tegula funebralis. This study took place in the rocky intertidal habitat off the coast of Washington; Paine removed all Pisaster in 8m x 10m plots weekly while noting the response of Tegula for two years. He found that removing the top predator, in this case being Pisaster, reduced species number in the treatment plots. Paine defined the concept of a keystone species as a species that has a disproportionate effect on the community structure of an environment in relation to its total biomass. This keystone species effect forms the basis for the concept of ecological extinction.