title: On the evolution of omnivory in a community context.
abstract: Omnivory is extremely common in animals, yet theory predicts that when given a choice of resources specialization should be favored over being generalist. The evolution of a feeding phenotype involves complex interactions with many factors other than resource choice alone, including environmental heterogeneity, resource quality, availability, and interactions with other organisms. We applied an evolutionary simulation model to examine how ecological conditions shape evolution of feeding phenotypes (e.g., omnivory), by varying the quality and availability (absolute and relative) of plant and animal (prey) resources. Resulting feeding phenotypes were defined by the relative contribution of plants and prey to diets of individuals. We characterized organisms using seven traits that were allowed to evolve freely in different simulated environments, and we asked which traits are important for different feeding phenotypes to evolve among interacting organisms. Carnivores, herbivores, and omnivores all coexisted without any requirement in the model for a synergistic effect of eating plant and animal prey. Omnivores were most prevalent when ratio of plants and animal prey was low, and to a lesser degree, when habitat productivity was high. A key result of the model is that omnivores evolved through many different combinations of trait values and environmental contexts. Specific combinations of traits tended to form emergent trait complexes, and under certain environmental conditions, are expressed as omnivorous feeding phenotypes. The results indicate that relative availabilities of plants and prey (over the quality of resources) determine an individual's feeding class and that feeding phenotypes are often the product of convergent evolution of emergent trait complexes under specific environmental conditions. Foraging outcomes appear to be consequences of degree and type of phenotypic specialization for plant and animal prey, navigation and exploitation of the habitat, reproduction, and interactions with other individuals in a heterogeneous environment. Omnivory should not be treated as a fixed strategy, but instead a pattern of phenotypic expression, emerging from diverse genetic sources and coevolving across a range of ecological contexts.
authors.affiliation: Department of Biological Sciences, Simon Fraser University 8888 University Drive, Burnaby, British Columbia, V5A1S6, Canada.
authors.forename: Alex M
authors.initials: AM
authors.lastname: Chubaty
authors.affiliation: ESSA Technologies Ltd. Vancouver, British Columbia, V6H 3H4, Canada.
authors.forename: Brian O
authors.initials: BO
authors.lastname: Ma
authors.affiliation: Department of Biological Sciences, Simon Fraser University 8888 University Drive, Burnaby, British Columbia, V5A1S6, Canada.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Stein
authors.affiliation: Agriculture and Agri-Food Canada 6947 Highway 7, PO Box 1000, Agassiz, British Columbia, V0M 1A0, Canada.
authors.forename: David R
authors.initials: DR
authors.lastname: Gillespie
authors.affiliation: Department of Zoology, University of Oxford South Parks Road, Oxford, OX1 3PS, UK.
authors.forename: Lee M
authors.initials: LM
authors.lastname: Henry
authors.affiliation: Department of Biological Sciences, Simon Fraser University 8888 University Drive, Burnaby, British Columbia, V5A1S6, Canada.
authors.forename: Conan
authors.initials: C
authors.lastname: Phelan
authors.affiliation: Department of Biological Sciences, Simon Fraser University 8888 University Drive, Burnaby, British Columbia, V5A1S6, Canada.
authors.forename: Eirikur
authors.initials: E
authors.lastname: Palsson
authors.affiliation: Department of Biological Sciences, Simon Fraser University 8888 University Drive, Burnaby, British Columbia, V5A1S6, Canada.
authors.forename: Franz W
authors.initials: FW
authors.lastname: Simon
authors.affiliation: Department of Biological Sciences, Simon Fraser University 8888 University Drive, Burnaby, British Columbia, V5A1S6, Canada.
authors.forename: Bernard D
authors.initials: BD
authors.lastname: Roitberg
keywords: Community structure; density-dependent; diet choice; evolutionary game; frequency-dependent; genotype–environment interaction; omnivory; optimal foraging; phenotype