Résumé
Hosts have evolved two distinct defence strategies against parasites:
resistance (which prevents infection or limit parasite growth) and
tolerance (which alleviates the fitness consequences of infection).
However, heritable variation in resistance and tolerance and the genetic
correlation between these two traits have rarely been characterized in
wild host populations. Here, we estimate these parameters for both traits
in Leuciscus burdigalensis, a freshwater fish parasitized by Tracheliastes
polycolpus. We used a genetic database to construct a full-sib pedigree in
a wild L. burdigalensis population. We then used univariate animal models
to estimate inclusive heritability (i.e. all forms of genetic and
non-genetic inheritance) in resistance and tolerance. Finally, we assessed
the genetic correlation between these two traits using a bivariate animal
model. We found significant heritability for resistance (H = 17.6%; 95%
CI: 7.2–32.2%) and tolerance (H = 18.8%; 95% CI: 4.4–36.1%), whereas we
found no evidence for the existence of a genetic correlation between these
traits. Furthermore, we confirm that resistance and tolerance are strongly
affected by environmental effects. Our results demonstrate that (i)
heritable variation exists for parasite resistance and tolerance in wild
host populations, and (ii) these traits can evolve independently in
populations.