Bringing together evolution and ecology through the Red Queen Perspective

Our project addresses the question how important biotic influences are, as for example competition between organisms for food or space, compared to changes in the physical environment, as for example a change in ambient temperature, in driving the evolutionary process. The idea that the interactions between organisms alone suffice for evolution to go on and on without ever settling was termed the 'Red Queen hypothesis' and is a classical hypothesis in evolutionary biology, first formulated by Leigh Van Valen in 1973. Although this hypothesis is not new, it is still poorly understood how important interactions between organisms are in driving evolution. In this project we address this question from two angles. We work with bacterial systems and conduct long-term in vitro experiments where we can trace the ecological as well as the evolutionary dynamics at the same time. Additionally, we work with mathematical models that describe the relevant aspects of the bacterial communities to evaluate which kinds evolutionary dynamics are possible under which circumstances. In the empirical part of our project, a batch-culture approach has been successfully set up and is in use. In this set up, a sample of an initial bacterial community is added to a flask containing growth medium and in fixed intervals, samples of the community are transferred to a flask with fresh medium. In this way, we will produce an artificial 'fossil record' of our bacterial communities for further analysis. The experimental setup is close to being fully operational, which means we will soon be able to study rates of adaptation in the bacterial community. Theoretical work inspired by the results from the empirical system has been developed. A new paper that we recently published provides a population and natural selection based model for investigating Red Queen dynamics. The main finding is that only symmetric ecological interaction will make evolution stop. However, trophic interaction is by nature asymmetric, and the model finds that asymmetric interactions will result in ongoing evolution.

It has long been recognized that both biotic and abiotic factors play an essential role in driving the evolutionary dynamics of a multispecies community. While acknowledging the importance of abiotic forces, Van Valen (1973) suggested in his 'Red Queen Hy pothesis' that biotic effects alone suffice to force species in a continued evolutionary race. Though long-standing, the validity of his hypothesis remains unclear. Adopting a Red Queen Perspective, the proposed project aims at evaluating Van Valen?s hypo thesis, and furthermore at increasing our understanding of the relative importance of abiotic and biotic forces on the evolutionary process as well as of their interplay. We will combine theory and experiment to address these questions. Mathematical model s will be developed that extend the theory of evolution within multispecies communities and that incorporate population dynamics, speciation and extinction. Multispecies microbial systems will be set up that allow us to track long-term ecological and evol utionary dynamics. Knowledge gained in the empirical part of the project will influence the development of the theoretical work, and vice versa.