Robert Paine studied sea stars in the intertidal zone along the northern Pacific coast. When he removed sea stars from a study area, their prey, two mussel species, increased exponentially. This crowded out other species, and the overall biodiversity of the community was greatly reduced. What role in the community did the sea star play?

Sea star  

Explanation:

In the given example sea star played the role of keystone species

Robert Paine actually coined the term keystone species to describe the effect that the sea stars had on biodiversity in this communityKeystone species are those species which are least abundant but play a governing role to decide the structure and function of community Loss of keystone species in a community can lead to disturbance in structure and function of a community and it cannot be recovered by other species