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Two Daphnia magna from a rock pool population in Finland. The left female is infected with Spirobacillus cienkowskii.
The main focus of the group is evolution, genetics and ecology of host-parasite and host-mutualist interactions, with an emphasize on rapid evolutionary change. Central to this work is the link between phenomena observed in the field and the elucidation of the evolutionary mechanisms behind them.
We ask questions about the adaptive significance of parasite virulence (Why do hosts get sick? Is virulence adaptive for the parasite?), the mechanisms of host-symbiont coevolution and the adaptive significance of genetic variation and sexual recombination (What is sex good for?). We explore host associated microbiota and ask questions related to their ecology and evolution (How are microbiota transmitted? Are microbiota friend or foe? Do microbiota interact with parasitism of their host?). Our work also includes the study of inbreeding and inbreeding depression and its relationship to parasites and microbiota. We conduct our research in the laboratory and at field sites in Switzerland and Finland. Methods include experimental epidemiology, experimental evolution, manipulation of natural populations, evolutionary genomics and evolutionary genetics.
Our main study organisms are microparasites (viruses, bacteria and microsporidia) and the diverse members of the microbiota, as well as their hosts, waterfleas of the genus Daphnia. This system allows us to estimate fitness components of hosts and symbionts, which is essential for the quantification of costs and benefits in both partners. We also use genomic approaches to understand the evolution of host and parasite evolution and combine them with QTL studies and GWAS. We aim for the identification of regions in the genome with ecologically relevant functions with the goal to understand how natural selection shapes the genome and how the genetic architecture shapes the response to selection.
Most of our field work takes place in South-Western Finland, in a large Daphnia metapopulation on the Skerry islands of Tvärminne archipelago. We chose this field site because we can find thousands of small rock pools there, many of which have Daphnia populations. This situation allows work on entire populations, with populations being the unit of replicaton. We study the ecology of this metapopulation system and conduct experiments including manipulaton of entire populations, experimental evolution and experimental epidemiology. Since 2010 we also monitor the host and parasite dynamics in a large pond in Switzerland, the "Swiss pond project".