Evol Ecol Res 7: 993-1012 (2005)     Full PDF if your library subscribes.

Intraspecific competition affects the strength of individual specialization: an optimal diet theory method

Richard Svanbäck1,2* and Daniel I. Bolnick3,4

1Department of Ecology and Environmental Science, Umeå University, SE-901 87 Umeå, Sweden,  2Department of Limnology, Evolutionary Biology Centre, Uppsala University, Norbyv. 20, SE-752 36 Uppsala, Sweden,  3Section of Evolution and Ecology, Center for Population Biology, Storer Hall, University of California, Davis, CA 95616, USA and  4Integrative Biology, University of Texas at Austin, 1 University Station, C0930, Austin, TX 78712-0253, USA

Address all correspondence to Richard Svanbäck, Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada. E-mail: svanback@zoology.ubc.ca


Question: Why would individuals that inhabit the same environment choose to feed on different subsets of the available resources?

Mathematical method: We outline a flexible model that combines phenotypic variation with optimal diet theory and population dynamics. We then apply this model to investigate the role of different types of trade-offs, phenotype diversity and level of competition in determining the degree of individual specialization.

Key assumptions: The foragers in the model are omniscient and maximize energy intake per time unit.

Conclusion: Numerical simulations match empirical observations that changes in population density can alter the degree of individual specialization. Forager density and phenotypic variation affected prey densities, which in turn affected forager diet breadth and fitness (energy income). We propose that this feedback can explain the empirical relationship between forager density and the degree of individual specialization in the forager population.

Keywords: density dependence, frequency dependence, individual specialization, inter-individual variation, intra-population variation, niche breadth.

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        © 2005 Richard Svanbäck and Daniel I. Bolnick. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

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