Optimal apostatic selection: how should predators adjust to variation in prey frequencies?

doi:10.1016/j.anbehav.2008.09.032

Animal Behaviour

Volume 77, Issue 1, January 2009, Pages 239-245

https://doi.org/10.1016/j.anbehav.2008.09.032 Get rights and content

Although frequency-dependent predation or apostatic selection has been established as one of the phenomena that may promote prey diversity, little is known about its selection. We studied such selection with a model with two prey types, treating frequency-dependent predator behaviour as an evolving trait determined by two parameters. One parameter controlled change in both prey type detection probabilities as a consequence of detecting a prey individual of a given type, and the other controlled the maximal amount of bias in detection probabilities of the two prey types. We let frequency-dependent behaviour evolve under different conditions of prey frequency variation. We found that frequency-dependent predator behaviour was most beneficial when deviations from equal prey type frequencies were large. Furthermore, different patterns of prey type variation selected for different types of frequency-dependent predator behaviour. We conclude that optimal frequency-dependent predator behaviour is likely to vary with ecological conditions.

Section snippets

Predator Behaviour

Three main features of frequency-dependent predation have been observed across many laboratory studies: (1) repeated detection of a prey type can successively increase a predator's ability to detect that prey type, but (2) such detection has the opposite effect on detection of the other, dissimilar prey type and (3) these effects are reversible (e.g. Pietrewicz and Kamil, 1979, Langley, 1996). We capture these as fundamental features of our model. For simplicity, in our model we assume that the

Comparison Case of Time-invariant Prey Frequencies

Before running the model with varying prey type frequencies, it is instructive to consider the evolutionary response of the predators to unchanging prey type frequencies. We consider two cases: in the first case the prey type frequencies are equal, and in the second case the frequencies are biased, such that type A makes up 60% and type B makes up 40% of the population. In the 50:50 case, we expect that the adjustment (which symmetrically increases the probability of detecting one type and

Discussion

As expected, under a constant and unbiased (50:50) supply of the two prey types, the values of the predators' adjustment parameters p_dev (governing the maximum extent of predator flexibility) and δ (governing the speed of change in a predator's response) were neutral to selection. Under a constant, biased (60:40) supply of prey types, it was advantageous to specialize and attend to the more common prey type only, and this increased the capture probability above 50%.

Compared to these scenarios

Acknowledgments

We are grateful to two anonymous referees and to Edwin van Leeuwen for helpful comments on the manuscript. This study was supported by the Swedish Research Council (S.M.), and NERC grants NE/D010772/1, NE/D010500/1 & NE/E016626/1 (G.D.R.).

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¹: G. D. Ruxton is at the Division of Environmental & Evolutionary Biology, Faculty of Biomedical & Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.

View full text

Optimal apostatic selection: how should predators adjust to variation in prey frequencies?

Section snippets

Predator Behaviour

Comparison Case of Time-invariant Prey Frequencies

Discussion

Acknowledgments

Journal of Theoretical Biology

Biological Journal of the Linnean Society

Behavioural Processes

Frequency-dependent selection by predators

Philosophical Transactions of the Royal Society of London, Series B

Evidence for apostatic selection by wild birds

Nature

Alternative food, switching predators, and the persistence of predator-prey systems

American Naturalist

The evolution of color polymorphism: crypticity, searching images, and apostatic selection

Annual Review of Ecology, Evolution, and Systematics

Balanced polymorphism and the diversity of sympatric species

Limited attention: the constraint underlying search image

Behavioral Ecology

Searching for cryptic prey: the effect of search rate

American Naturalist