3:00 p.m., Friday (January 19, 2007)

MATX 1100

Claus Rueffler
University of Toronto

The evolutionary ecology of resource specialization

In the presence of different resources, when should we expect the evolution of a generalist phenotype versus specialized phenotypes? While this question has a long history in evolutionary ecology the evolutionary dynamics of a single consumer type in the presence of two kinds of renewable resources has not yet been studied in great detail. I will present a model of one evolving consumer feeding on two resources and analyse the evolutionary dynamics of different consumer traits using a set of techniques known as `` adaptive dynamics''. I show that, depending on the type of trait considered, selection is either frequency-independent or frequency-dependent. This difference is explained by the effects different foraging traits have on the consumer-resource interactions. If selection is frequency-dependent, then the population can become dimorphic through evolutionary branching at the trait value of the generalist. Traits with frequency-independent selection follow Levins' classical prediction stating that convex phenotype sets favour generalists while concave phenotype sets favour specialists.

In a second step I extend the model by allowing consumers to choose their diet so as to maximize resource uptake. This version of the model allows for the study of the dynamic interplay between adaptive choice behaviour and the evolutionary dynamics of morphological and physiological foraging traits. The model predicts that flexible diet choice behaviour can guide the direction of evolutionary change in a foraging trait and that flexible behaviour can mediate the coexistence of different consumer types where coexistence would not be possible otherwise. Such polymorphisms can evolve from a monomorphic population at evolutionary branching points and also at points where a small genetic change in a trait can provoke a drastic and non-genetic change in choice behaviour. The added feature of diet choice behaviour can lead to alternative evolutionarily stable communities.

Refreshments will be served at 2:45 p.m. (Math Lounge, MATX 1115).

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