Keystone species

Definition

A species that has a disproportionately large impact on its ecosystem relative to its abundance. The removal or reduction of keystone species can have cascading effects throughout the food web.

Etymology

Example

The sea otter is considered a keystone species in kelp forest ecosystems because it preys on sea urchins, which eat kelp. Without sea otters, sea urchin populations would explode, leading to the destruction of kelp forests.

Related Terms

• Trophic cascades
• Food web
• Ecosystem stability

Usage Notes

Keystone species are often apex predators or have a unique role in regulating populations.