Study
Food web complexity and species diversity
Paine, Robert T.
The American Naturalist, 1966
A predatory sea star was removed by hand from a marked section of rocky shore and kept out for several years, with an adjacent comparable section left untouched as a control. Species present and the area each occupied were recorded on both through time.
- Studied in
- Pisaster ochraceus, Mytilus californianus
- Sample size
- a removal plot and an adjacent control, maintained for years
On the removal plot, mussels expanded and progressively monopolised the rock. Species number fell from around fifteen to roughly eight. The control plot retained its species composition.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Predation on a competitively dominant prey species maintained the diversity of the community, so removing the predator reduced it.
How NatureHQ reads it
The experiment that changed what ecologists thought a predator does. The mussel is the best competitor for rock space and would take all of it; the sea star eats mussels faster than they can monopolise, and everything else lives in the gaps that leaves. The design is what makes this stick — one plot cleared by hand for years, one untouched beside it — and it is the model for the removal experiments the rest of this subject depends on.
- One shore, one predator and one prey species, with a single removal plot and a single control.
- Rock space is an unusually simple limiting resource, and the result should not be assumed to transfer to systems where it is not.
Taking the sea stars off the rock, and keeping them off
What does a predator do to the community it hunts in — beyond reducing the numbers of what it eats?
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Sea stars
Take one sea star off a patch of rocky shore and keep it off, and mussels take over the rock. Species number fell from about fifteen to about eight — while the untouched plot beside it did not change.
Trophic cascades
Removing a predator sometimes changes vegetation two links down the chain. It is demonstrated in small manipulable systems and much harder to establish in large ones — where it is asserted most often.
Published by: University press journalsPublished in a university press journal.
Checked against Crossref on 2026-09-28, and they agree on the title, the authors and the year.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-09-04.