Genetic variation in resistance against parasite infections is a predominant feature in host-parasite systems. However, mechanisms maintaining genetic polymorphism in resistance in natural host populations are generally poorly known. We explored if differences in natural infection pressure between resource-based morphs of Arctic charr (Salvelinus alpinus) has resulted in differentiation in resistance profiles. We experimentally exposed offspring of two morphs from Lake Þingvallavatn (Iceland), the pelagic planktivorous charr (‘murta’) and the large benthivorous charr (‘kuðungableikja’), to their common parasite, eye fluke Diplostomum baeri, infecting the eye humour. We found that there were no differences in resistance between the morphs, but clear differences among families within each morph. Moreover, we found suggestive evidence of resistance of offspring within families being positively correlated with the parasite load of the father, but not with that of the mother. Our results suggest that the inherited basis of parasite resistance in this system is likely to be related to variation among host individuals within each morph rather than ecological factors driving divergent resistance profiles at morph level. Overall, this may have implications for evolution of resistance through processes such as sexual selection.

The dataset presents data from experimental infection of lab-raised offspring of Arctic charr (Salvelinus alpinus) and the wild-caught parent fish from Lake Þingvallavatn.

The dataset has two sheets. The fist sheet contains infection data for lab-raised offspring of Arctic charr (Salvelinus alpinus) with variables indicating the fish morph (planktivorous and benthivorous), fish family, adult wild-caught females and males used to produce the families, and total length and parasite numbers of the offspring. The second sheet contains the corresponding information for the parent female and male fish.