<P> The concept of the keystone species was introduced in 1969 by Robert T. Paine, a professor of zoology at the University of Washington . Paine developed the concept to explain his observations and experiments on the relationship between intertidal invertebrates . In his 1966 paper, Food Web Complexity and Species Diversity, Paine described such a system in Makah Bay in Washington . In his follow - up 1969 paper, Paine proposed the keystone species concept, using Pisaster ochraceus, a species of starfish, and Mytilus californianus, a species of mussel, as a primary example . The concept became popular in conservation, and was deployed in a range of contexts and mobilized to engender support for conservation . Paine's contribution to the ecological theory has been summarized in a HHMI documentary . </P> <P> Given that there are many historical definitions of the keystone species concept, and without a consensus on its exact definition, a list of examples best illustrates the concept of keystone species . </P> <P> A classic keystone species is a small predator that prevents a particular herbivorous species from eliminating dominant plant species . Since the prey numbers are low, the keystone predator numbers can be even lower and still be effective . Yet without the predators, the herbivorous prey would explode in numbers, wipe out the dominant plants, and dramatically alter the character of the ecosystem . The exact scenario changes in each example, but the central idea remains that through a chain of interactions, a non-abundant species has an out - sized impact on ecosystem functions . One example is the herbivorous weevil Euhrychiopsis lecontei and its suggested keystone effects on aquatic plant species diversity by foraging on nuisance Eurasian watermilfoil . </P> <P> Similarly, the wasp species Agelaia vicina has been labeled a keystone species due to its unparalleled nest size, colony size, and high rate of brood production . The diversity of its prey and the quantity necessary to sustain its high rate of growth have a direct impact on local neighboring species . </P>

Can one species be both umbrella and keystone