In an
ecosystem, a
keystone predator is a predator which, amazingly, maintains high levels of
species diversity through its feeding on the dominant secondary or primary
consumers. To understand this, consider the following situation:
Species A and B are of roughly equal
survival capability. As such, they are in constant
rivalry for
resources. Should at any time one gain an advantage over the other due to
circumstantial factors, their
population will experience a boost, providing them the advantage necessary to eventually consume such a disproportionate number of the
ecological resources so as to eventually gain control over the entire
niche.
Species C preys on either A or B, with no real
preference for either. Due to the lack of real preference, it is driven largely to feed upon whichever is most numerous. This will create a tendency toward
populational
equilibrium between species A and B.
A popular example is the
starfish Pisaster, which feeds primarily upon
mussels and other creatures in certain
intertidal communities. When the starfish is experimentally removed from this community, the mussels are known to "take over", and completely imbalance the local ecosystem.
An
interesting, if tangential, analogy results from the comparison of keystone predation to regular
government intervention in
capitalist societies. Limits placed upon dominant
corporations provide for the success of smaller corporations, increasing the overall richness of the
economic community.