Coevolution in simple and complex host-parasite systems

CLUSTER: „Evolutionary genetics of three-spined stickleback – parasite interactions“

Professor Dr. Theo C. M. Bakker

Coevolution between hosts and their parasites is among others dependent on the gene flow between host populations and between parasite populations. The genetic exchange between individuals in parasite populations will be strongly influenced by the complexity of the parasite’s life cycle. The proposed project addresses the coevolution in complex and simple host-parasite systems using three-spined sticklebacks (Gasterosteus aculeatus) and its parasites as models. The study system consists of numerous lakes on the island of North Uist, Outer Hebrides, Scotland. The lakes are isolated from each other and the stickleback populations in them have been evolved independently of each other since the last deglaciation. Common parasites are the ectoparasitic monogenean trematode Gyrodactylus spp. with a direct life cycle and the digenean trematode Diplostomum spp. with a complex life cycle. A phylogeographic analysis of stickleback, Gyrodactylus, and Diplostomum populations of a large number of acid and alkaline lakes will be performed using microsatellites. The degree of congruence of the various host-parasite phylogenies will be indicative of coevolutionary processes. Experimental infections using a full-sib/half-sib breeding design will give cues about the evolvability of host resistance and secondary sexual traits (like breeding coloration and courtship) as well as their genetic covariances. This will  give information as to whether sexual selection will be involved in the evolution of host resistance. Immunological tests will give cues about the potential targets of genetic resistance.