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.

Habitat heterogeneity on feeding habit of two sympatric and congeneric characidae fishes in two tropical reservoirs

“…At this context, diet dissimilarities between the Astyanax species were revealed mainly due to the source of itens consumed. Feeding strategies may differ among environments and omnivory may evolve as a response to high environmental heterogeneity (Chubaty et al, 2014) or food availability.…”

The adaptive evolution of herbivory in freshwater systems

“…However, consuming a plant‐dominated diet is favored in habitats where animal prey are scarce and plant abundance is high (Chubaty et al. ), such as those with frequent disturbance. Furthermore, the palatability of plants is thought to play a key role in structuring herbivore populations (Elger et al.…”

“…Classic optimal foraging theory (i.e., optimal diet) predicts that if a resource is abundant, specializing on that resource is preferred (see Chubaty et al. ). These predictions are supported by early food preference studies, which suggest that herbivores evolved in response to food availability rather than food value (Paine and Vadas ).…”

“…Using an evolutionary simulation model, Chubaty et al. () examined how quality and availability of plant and animal prey shapes the evolution of diet. Results indicate that relative availability of resources can predict an individual's trophic level (Chubaty et al.…”

“…Results indicate that relative availability of resources can predict an individual's trophic level (Chubaty et al. ). More specifically, an increased abundance of plants increases herbivore abundance relative to carnivorous animals (Chubaty et al.…”