Competitive exclusion principle

1: A smaller (yellow) species of bird forages across the whole tree.
2: A larger (red) species competes for resources.
3: Red dominates in the middle for the more abundant resources. Yellow adapts to a new niche restricted to the top and bottom and avoiding competition.

In ecology, the competitive exclusion principle,^[1] sometimes referred to as Gause's law,^[2] is a proposition that two species which compete for the same limited resource cannot coexist at constant population values. When one species has even the slightest advantage over another, the one with the advantage will dominate in the long term. This leads either to the extinction of the weaker competitor or to an evolutionary or behavioral shift toward a different ecological niche. The principle has been paraphrased in the maxim "complete competitors cannot coexist".^[1]

^ ^a ^b Garrett Hardin (1960). "The competitive exclusion principle" (PDF). Science. 131 (3409): 1292–1297. Bibcode:1960Sci...131.1292H. doi:10.1126/science.131.3409.1292. PMID 14399717. Archived from the original (PDF) on 2017-11-17. Retrieved 2016-11-24.
^ Pocheville, Arnaud (2015). "The Ecological Niche: History and Recent Controversies". In Heams, Thomas; Huneman, Philippe; Lecointre, Guillaume; et al. (eds.). Handbook of Evolutionary Thinking in the Sciences. Dordrecht: Springer. pp. 547–586. ISBN 978-94-017-9014-7.

[hardin60-1] Garrett Hardin (1960). "The competitive exclusion principle" (PDF). Science. 131 (3409): 1292–1297. Bibcode:1960Sci...131.1292H. doi:10.1126/science.131.3409.1292. PMID 14399717. Archived from the original (PDF) on 2017-11-17. Retrieved 2016-11-24.

[Pocheville2015-2] Pocheville, Arnaud (2015). "The Ecological Niche: History and Recent Controversies". In Heams, Thomas; Huneman, Philippe; Lecointre, Guillaume; et al. (eds.). Handbook of Evolutionary Thinking in the Sciences. Dordrecht: Springer. pp. 547–586. ISBN 978-94-017-9014-7.

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