Evolutionary dynamics of mutualists during territorial expansion

• Applicant: Dr. Melanie Mueller
• Subject Area: Bioinformatics and Theoretical Biology
• Term: from 2011 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 201655341

Mutualism is an interaction between organisms of two different species which is beneficial for both. If the exchanged benefits are costly for the providers, mutualism is an example of altruism between non-kin individuals. The widespread existence of such altruism in nature is a prominent problem of evolutionary biology since it appears to contradict the paradigm of survival of the fittest, which in this case seems to be a cheater that exploits the mutualists without providing any benefit. Recent work has shown that spatial structure can stabilize and enhance mutualism. Here, I will go one step further and investigate the effects of territorial expansion on the evolution of mutualist interactions.Since mutualists depend on each other, they must invade a new territory together, and selection during the expansion does not only act on the single species but also on their interaction. While many examples of territorial expansions of mutualists are known, a detailed and quantitative understanding of their population dynamics and evolution of is lacking.Here, I propose to use engineered mutualistic non-mating strains of the budding yeast Saccharomyces cerevisiae expanding on agar surfaces as a model system for expanding mutualist species. I will first study the spatial and genetic patterns during the expansion on short evolutionary time scales. Then I will investigate how these patterns and the parameters characterizing the mutualist interaction evolve on longer time scales when mutations become important. I will complement these experiments with theoretical modeling in order to obtain both intuitive and quantitative understanding of the evolutionary dynamics. This is a step towards understanding real-world territorial expansion of mutualist species, and to inferring information about the migrational and co-evolutionary history of two mutualist species from the distribution of their genetic variability in space.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor David R. Nelson