Allee effects driven by predation
Article first published online: 30 SEP 2004
Journal of Applied Ecology
Volume 41, Issue 5, pages 801–810, October 2004
How to Cite
GASCOIGNE, J. C. and LIPCIUS, R. N. (2004), Allee effects driven by predation. Journal of Applied Ecology, 41: 801–810. doi: 10.1111/j.0021-8901.2004.00944.x
- Issue published online: 30 SEP 2004
- Article first published online: 30 SEP 2004
- Received 8 April 2004; final copy received 1 June 2004
- aggregative response;
- critical thresholds;
- functional response;
- local extinction;
- non-linear dynamics;
- positive density dependence
- 1In a population with Allee effects a positive relationship exists between fitness and population size or density. Allee effects may result in extinction thresholds and are therefore crucial in conservation and management. It has been shown theoretically that Allee effects can be driven by predation; however, there are few empirical data. Previous empirical work on Allee effects has emphasized that taxa with life-history characteristics such as co-operative breeding may be prone to such effects. Because predation is a general ecological mechanism, Allee effects may be more widespread than previously thought.
- 2We used a series of simple heuristic models to develop a theoretical framework for understanding predation-driven Allee effects as a function of predator functional and aggregative responses.
- 3Predators can create an Allee effect if they have a type I (linear) or type II (saturating) functional response without a type III (sigmoid) aggregative response, or vice versa. In addition, predation must be the main driver of prey dynamics, and prey must have little spatial or temporal refuge from predation.
- 4We highlighted several, mainly unrecognized, examples of predation-driven Allee effects from the literature, the majority of which came from systems that had been perturbed by exploitation or introduced predators.
- 5Synthesis and applications. Allee effects can arise from a general ecological process under a variety of different combinations of functional and aggregative responses. Allee effects may thus be present in a broad spectrum of different taxa with different types of life history, not only those taxa, such as broadcast spawners and co-operative breeders, on which empirical work has focused thus far. Conservation biologists and managers working with heavily exploited or threatened populations, or attempting reintroductions, should be aware of the possibility of a threshold population size or density below which extinction is likely. These thresholds can occur regardless of species life history, if predation is a major source of mortality and spatial and temporal predation refuges are limited.