title: Parasites as mediators of heterozygosity-fitness correlations in the Great Tit (Parus major).
abstract: Positive correlations between heterozygosity and fitness traits are frequently observed, and it has been hypothesized, but rarely tested experimentally, that parasites play a key role in mediating the heterozygosity-fitness association. We evaluated this hypothesis in a wild great tit (Parus major) population by testing the prediction that the heterozygosity-fitness association would appear in broods experimentally infested with a common ectoparasite, but not in parasite-free broods. We simultaneously assessed the effects of parental and offspring heterozygosity on nestling growth and found that body mass of nestlings close to independence, which is a strong predictor of post-fledging survival, increased significantly with nestling levels of heterozygosity in experimentally infested nests, but not in parasite-free nests. Heterozygosity level of the fathers also showed a significant positive correlation with offspring body mass under an experimental parasite load, whereas there was no correlation with the mothers' level of heterozygosity. Thus, our results indicate a key role for parasites as mediators of the heterozygosity-fitness correlations.
authors.affiliation: Evolutionary Ecology Lab, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland. bvoegeli@gmx.ch
authors.forename: B
authors.initials: B
authors.lastname: Voegeli
authors.forename: V
authors.initials: V
authors.lastname: Saladin
authors.forename: M
authors.initials: M
authors.lastname: Wegmann
authors.forename: H
authors.initials: H
authors.lastname: Richner
mesh_terms: D000818:Animals; D049628:Body Size / Q000502:physiology*; D005260:Female; D056084:Genetic Fitness / Q000235:genetics*; D014644:Genetic Variation; D005838:Genotype; D006579:Heterozygote; D016013:Likelihood Functions; D016014:Linear Models; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D059208:Parasite Load; D046109:Passeriformes / Q000235:genetics / Q000254:growth & development / Q000469:parasitology*; D016133:Polymerase Chain Reaction; D005423:Siphonaptera / Q000502:physiology*; D013557:Switzerland