Testing a keystone predator hypothesis.
- The sea star Pisaster ochraceous
feeds preferentially on mussels but will consume other invertebrates.
- When Pisaster was removed from an intertidal zone,
mussels eventually took over the rock face and eliminated most other invertebrates and algae.
In a control area from which Pisaster was not removed, there was little change in species diversity.
In the absence of the sea star as a keystone predator, mussels become a dominant species in
intertidal communities.
Another example of keystone species is the sea otter
in kelp forest communities.