Study
The paradox of the plankton
Hutchinson, G. E.
The American Naturalist, 1961
Sets out a contradiction: open water is a relatively unstructured environment offering few limiting resources, yet it supports large numbers of coexisting phytoplankton species — many more than competitive exclusion appears to allow.
- Studied in
- Phytoplankton
- Sample size
- argument from observed plankton diversity
Observed plankton diversity substantially exceeds the number of limiting resources, so the conditions under which competitive exclusion operates are evidently not met in open water.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
The environment does not stay still long enough for exclusion to complete. Continual change means competitive outcomes are repeatedly reset before they can be resolved.
How NatureHQ reads it
This is the record that keeps competitive exclusion honest, and it is unusually good scientific conduct: the author who had done most to formalise the niche published the case that did not fit his own framework. The principle is not refuted by it — the point is that its assumptions are specific, and a lake in summer does not meet them.
- An argument from observed diversity rather than an experiment.
- Several later explanations exist and the relative importance of each remains debated.
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Competitive exclusion
Two species limited by exactly the same thing, in an unchanging environment, cannot coexist indefinitely. Nature rarely offers an unchanging environment — which is why so many similar species do coexist.
Ecology
Disturbed systems sometimes return to something like what they were, sometimes settle into a different arrangement and stay there, and sometimes keep changing. Which one happens is a question, not a property of nature.
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.