The limits of evolutionary adaptation in ecological time: experimental evolution and ecology.

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My research program uses laboratory experiments to investigate fundamental processes in ecology and evolution. Populations of unicellular yeasts and algae are easily maintained in the laboratory, and by virtue of their very large size (billions of individuals in a small flask) and rapid turnover (generation times of a few hours) they make it possible to study large-scale processes in real time. I shall use these laboratory microcosms to study three kinds of process. The first project explores the limits of adaptation by showing how radically different ways of life can evolve within short periods of time. I shall trace the series of modifications that enable an alga that grows in the light by photosynthesis (like a green plant) to evolve into types that can grow in complete darkness, using an organic chemical as a food source (like a fungus). The second project investigates the specificity of adaptation. Different strains of bacteria or yeast can each metabolize a certain range of substrates, just as animals consume only a limited range of foodstuffs. I will document how diet of yeast populations evolves when they are offered a complex mixture of substrates, such as they encounter in natural environments. The goal of these experiments is to show that the degree of dietary specialization that evolves in laboratory populations can be predicted from biochemical principles involving the structure of metabolic pathways. The third project extends the experimental approach to whole communities to discover how they can respond to severe stress. This introduces two novel techniques. The first is gradient selection with dispersal, which contrives the gradual emergence of a resistant community by successive adaptation to increasing levels of stress. The second is the accumulating bioreactor, which is designed to discover very rare types in natural communities that are capable of performing some defined task, such as degrading a particular toxin. These techniques can be applied both to fundamental processes of community assembly and to practical problems such as the bioremediation of polluted soil and water.