Experimental resistance evolution and its genetic basis in the Diplostomum-Gasterosteus host-parasite system

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

Professor Dr. Erich Bornberg-Bauer

This project uses artificial selection to uncover specificity, variability and genetic basis of innate immune defence in a fish host, the three-spined stickleback (Gasterosteus aculeatus). Model parasite is the digenean trematode (Diplostomum pseudospathaceum), which uses the stickleback eye lens during its 2nd larval phase (metacercaria), induces severe fitness costs, and is attacked primarily by innate immune defence. Because infection by Diplostomum metacercaria can be precisely controlled in the lab, and parasite load can be assessed non-invasively, it is possible to establish selection lines over several generations. Based on preliminary results that show host genotype x parasite genotype-interactions in Diplostomum infectivity we first assess the specificity of imposed resistance selection with a single parasite genotype by infecting lines with homologous vs. heterologous parasite genotypes. Second, we address trade-offs and test the hypothesis that increased resistance against one parasite results in higher susceptibility towards another parasite species, the tapeworm Schistocephalus solidus. Third, we ask how the result of artificial selection compares to the immune traits of populations subjected to locally varying selection by diverging parasite assemblages with and without Diplostomum. In all infection experiments, we examine the underlying gene transcription patterns of infected vs. control animals using a custom made gene expression array (Illumina bead platform ~ 500 genes) carrying all genes plus controls that are involved in innate and adaptive immunity.