Optimization of the immune system by natural and sexual selection

One of the greatest mysteries in evolutionary biology to date is the widespread occurrence of sexual reproduction. A key role in its evolution and maintenance is assumed for the dynamic co-evolutionary cycles of parasites and their hosts. Using the three-spined stickleback as a model organism in laboratory and field experiments, the importance of parasite-mediated natural but also sexual selection on reproductive success and thus on Darwinian fitness can be investigated. This in turn will help to better understand the widespread evolution of sexual reproduction.