What are the characteristics of a keystone species?
A keystone species is a non-abundant species that can, through a series of chain reactions, have a damaging impact on various ecosystem functions. This species generally has a relatively tiny physical impression but is vital to the health of its ecosystem.
The extinction of a keystone species would ultimately lead to the extinction of numerous other species. A keystone species sustains the ecosystem that it is a part of. Their presence decides the types and numbers of species within an environment.
If a keystone species were to be removed, an ecosystem would experience a massive change. The diversity and character of the environment would be dramatically altered.
There are two types of keystone species: predators and engineers.
Predators prey on different species, keeping their populations in check. Their prey generally has no other natural predators.
Engineers alter their environments. Their actions physically change the ecosystem.
Documentation of Sources
1) Wikimedia Foundation
2) Prairie Dogs.org