Study
Challenges in the quest for keystones
Power, Mary E.; Tilman, David; Estes, James A.; Menge, Bruce A.; Bond, William J.; Mills, L. Scott
BioScience, 1996
Reviews how the keystone label had been applied since 1969 and proposes that it be reserved for species whose community impact is both large and disproportionate to their abundance, with impact measured against a stated baseline.
- Studied in
- Animalia, Plantae
- Sample size
- review of keystone designations and how they were established
The term had been applied to species of every abundance and to effects of every size, including cases where the species was simply dominant. Making it meaningful requires measuring effect per unit abundance, which few designations had done.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Keystone status is a quantitative claim about impact relative to abundance and should be demonstrated rather than asserted.
How NatureHQ reads it
The correction from inside the field, and a good example of a concept being rescued rather than abandoned. The useful test it supplies is simple to state: if the species were as influential as its abundance predicts, it is not a keystone — it is just common and important, which is a different and much less interesting claim.
- Proposes a standard rather than applying it; most existing designations were never re-examined against it.
- Measuring impact per unit abundance requires removal experiments that are impractical for large or protected species.
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Keystone species
A keystone species has an effect out of proportion to how much of it there is. That "out of proportion" is the whole content — an abundant, obviously important species is not a keystone, just dominant.
Foundation species
A foundation species shapes a system by being abundant and structural — a dominant tree, a kelp bed, a reef. That is close to the opposite of a keystone, which matters more than its abundance predicts.
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.