It has been defined operationally by Davic in 2003 as "a strongly interacting species whose top-down effect on species diversity and competition is large relative to its biomass dominance within a functional group." Ī classic keystone species is a predator that prevents a particular herbivorous species from eliminating dominant plant species. Definitions Ī keystone species was defined by Paine as a species that has a disproportionately large effect on its environment relative to its abundance. The concept became popular in conservation, and was deployed in a range of contexts and mobilized to engender support for conservation, especially where human activities had damaged ecosystems, such as by removing keystone predators. When Paine removed the ochre starfish the mussels quickly outgrew the other species crowding them out. The ochre starfish keeps the population numbers of the mussels in check along with the other preys allowing the other seaweeds, sponges, and anemones to co-exist that ochre starfish do not consume. The favourite food for these starfish is the mussel which is a dominant competitor for the space on the rocks. The ochre starfish is a generalist predator and feeds on chitons, limpets, snails, barnacles, echinoids, and even decapod crustacea. In his 1969 paper, Paine proposed the keystone species concept, using Pisaster ochraceus, a species of starfish generally known as ochre starfish, and Mytilus californianus, a species of mussel, as a primary example. In his 1966 paper, Food Web Complexity and Species Diversity, Paine had described such a system in Makah Bay in Washington. He removed the starfish from an area, and documented the effects on the ecosystem. Paine developed the concept to explain his observations and experiments on the relationships between marine invertebrates of the intertidal zone (between the high and low tide lines), including starfish and mussels. The concept of the keystone species was introduced in 1969 by zoologist Robert T. Although the concept is valued as a descriptor for particularly strong inter-species interactions, and has allowed easier communication between ecologists and conservation policy-makers, it has been criticized for oversimplifying complex ecological systems.Ĭalifornia mussels ( Mytilus californianus), the seastar's prey It became a popular concept in conservation biology, alongside flagship and umbrella species. Similarly, an ecosystem may experience a dramatic shift if a keystone species is removed, even though that species was a small part of the ecosystem by measures of biomass or productivity. While the keystone is under the least pressure of any of the stones in an arch, the arch still collapses without it. The role that a keystone species plays in its ecosystem is analogous to the role of a keystone in an arch. Some keystone species, such as the wolf, are also apex predators. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. Keystone species play 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. The jaguar: a keystone, flagship, and umbrella species, and an apex predator The beaver: a keystone species, and habitat creator, responsible for the creation of lakes, canals and wetlands irrigating large forests and creating ecosystemsĪ keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance, a concept introduced in 1969 by the zoologist Robert T. Not to be confused with foundation species.
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