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The Role of Size-Specific Predation in the Evolution and Diversification of Prey Life Histories Author(s): Troy Day, Peter A. Abrams, Jonathan M. Chase Source: Evolution, Vol. 56, No. 5 (May, 2002), pp. 877-887 Published by: Society for the Study of Evolution Stable URL: http://www.jstor.org/stable/3061628 Accessed: 13/09/2009 12:57
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Evolution, 56(5), 2002, pp. 877-887

THE ROLE OF SIZE-SPECIFIC PREDATIONIN THE EVOLUTIONAND OF DIVERSIFICATION PREY LIFE HISTORIES
TROY DAY,1,2 PETER A. ABRAMS,1 AND JONATHAN M. CHASE3 'Department of Zoology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada 2E-mail: dayt@zoo. utoronto.ca 3Department of Biological Sciences, University of Pittsburgh,Pittsburgh, Pennsylvania 15260 Abstract.-Some of the best empirical examples of life-history evolution involve responses to predation. Nevertheless, most life-history theory dealing with responses to predation has not been formulated within an explicit dynamic foodweb context. In particular, most previous theory does not explicitly consider the coupled population dynamics of the focal speciesand its predators and resources. Here we present a model of life-history evolution that explores the evolutionary consequences of size-specific predation on small individuals when there is a trade-off between growth and reproduction. The model explicitly describes the population dynamics of a predator, the prey of interest, and its resource. The selective forces that cause life-history evolution inthe prey species emerge from the ecological interactions embodied by this model and can involve importantelements of frequency dependence. Our results demonstrate that the strength of the coupling between predatorand prey in the community determines many aspects of life-history evolution. If the coupling is weak (as is implicitly assumed in many previous models), differences in resourceproductivity have no effect on the natureof life-history evolution. A single life-history strategy is favored that minimizes the equilibrium resource density (if possible). If the coupling is strong, then higher resource productivities select for faster growth into the predation size refuge. Moreover, under strong coupling it is also possible for natural selection to favor an evolutionary diversificationof life histories, possibly resulting in two coexisting species with divergent life-history strategies. Key words.-Food web, life-history theory, predator, reproductive effort, resource gradient. Received July 12, 2001. Environmental sources of mortality represent one of the most important selective factors governing life-history evolution, and mortality is often size specific (Stearns 1992;...