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The evidence for Allee effects

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Kramer, Andrew M.; Dennis, Brian; Liebhold, Andrew M.; Drake, John M.

Year Published



Population Ecology. 51: 341-354.


Allee effects are an important dynamic phenomenon believed to be manifested in several population processes, notably extinction and invasion. Though widely cited in these contexts, the evidence for their strength and prevalence has not been critically evaluated. We review results from 91 studies on Allee effects in natural animal populations. We focus on empirical signatures that are used or might be used to detect Allee effects, the types of data in which Allee effects are evident, the empirical support for the occurrence of critical densities in natural populations, and differences among taxa both in the presence of Allee effects and primary causal mechanisms. We find that conclusive examples are known from Mollusca, Arthropoda, and Chordata, including three classes of vertebrates, and are most commonly documented to result from mate limitation in invertebrates and from predator?prey interactions in vertebrates.


critical density; depensation; inverse density dependence; mate limitation; predator satiation; positive density dependence


Kramer, Andrew M.; Dennis, Brian; Liebhold, Andrew M.; Drake, John M. 2009. The evidence for Allee effects. Population Ecology. 51: 341-354.

Last updated on: June 5, 2009