Pisaster ochraceus is an efficient predator of the common mussel, Mytilus californicus .
It reduces abundance of M. californicus , allowing other macroinvertebrates to persist.
If Pisaster present = diverse intertidal community.
Based on the research of Dr. Robert T. Paine
Dr. Robert T. Paine’s Work (a) The sea star Pisaster ochraceous feeds preferentially on mussels but will consume other invertebrates. With Pisaster (control) Without Pisaster (experimental) Number of species present 0 5 10 15 20 1963 ´64 ´65 ´66 ´67 ´68 ´69 ´70 ´71 ´72 ´73 (b) 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.
Removing three species of kangaroo rats changed a desert plain into an arid grassland. In areas without kangaroo rats, grasses filled in between the shrubs, stems and other plant litter accumulated, large-seeded plants replaced those with smaller seeds, snow melted more slowly and the numbers of the other rodents increased significantly.