The role of the microbiome in eco-evo feedbacks in natural settings

Rising water temperatures and increasing eutrophication are disrupting the well-functioning of our aquatic systems, amongst others stimulating the growth of toxic cyanobacterial blooms. These blooms pose an important threat to human health, drinking water supplies, livestock, recreational activities, ecosystem functioning and food web structure. Daphnia spp. are pivotal interactors in pond and lake ecosystems, and their strong grazing capacities are important in the prevention and perhaps control of cyanobacteria blooms. Genotype x genotype interactions are thought to be important determinants of the outcome of interactions between Daphnia and cyanobacteria strains, and ultimately may affect top-down control of toxic blooms. The study of Daphnia/cyanobacteria interactions thus provides an interesting perspective of eco-evolutionary dynamics, especially as it has been shown that microbiome adaptation may also impact interactions. The system thus provides a highly interesting setting to test for genotype x microbiome x environment interactions. Previous research on eco-evolutionary dynamics has largely focused on providing proof-of-principle using relatively simple experiments in laboratory environments. There is a need to quantify eco-evolutionary dynamics in more realistic, natural settings. Seasonal and annual changes, as well as the consideration of multiple species are examples of additional levels of complexity that need to be included. Moreover, the microbiome is thought to have a major influence on a variety of processes within natural systems, including at the levels of the individual, the population and the (meta)community. It was shown to be important in mediating Daphnia tolerance towards toxic cyanobacteria, and as such might influence the outcome of eco-evolutionary dynamics. This doctoral thesis aims to disentangle the influence of evolution and the Daphnia microbiome in shaping Daphnia/cyanobacteria-interactions, top-down control, priority effects and eco-evolutionary dynamics in natural settings. We will use Daphnia and algal communities from natural systems like Langerodevijver (Heverlee) and the Bellefroid lakes (Wilsele). The latter systems also provide a valuable opportunity to study these processes under the influence of restoration management. In addition to seasonal and among-year variation, we will also employ a resurrection ecology approach to study temporal adaptation of the key players over the past decades.