Heritable variation in host tolerance and resistance inferred from a wild host–parasite system
Résumé
Hosts have evolved two distinct defence strategies against parasites: resistance(which prevents infection or limit parasite growth) and tolerance (which alle-viates the fitness consequences of infection). However, heritable variation inresistance and tolerance and the genetic correlation between these two traitshave rarely been characterized in wild host populations. Here, we estimatethese parameters for both traits inLeuciscus burdigalensis, a freshwater fishparasitized byTracheliastes polycolpus. We used a genetic database to constructa full-sib pedigree in a wildL. burdigalensispopulation. We then used univari-ate animal models to estimate inclusive heritability (i.e. all forms of geneticand non-genetic inheritance) in resistance and tolerance. Finally, we assessedthe genetic correlation between these two traits using a bivariate animalmodel. We found significant heritability for resistance (H¼17.6%; 95% CI:7.2–32.2%) and tolerance (H¼18.8%; 95% CI: 4.4–36.1%), whereas wefound no evidence for the existence of a genetic correlation between thesetraits. Furthermore, we confirm that resistance and tolerance are stronglyaffected by environmental effects. Our results demonstrate that (i) heritablevariation exists for parasite resistance and tolerance in wild host populations,and (ii) these traits can evolve independently in populations.