Résumé
When pollution occurs in an environment, populations present suffer
numerous negative and immediate effects on their life history traits.
Their evolutionary potential to live in a highly stressful environment
will depend on the selection pressure strengths and on the genetic
structure, the trait heritability, and the genetic correlations between
them. If expression of this structure changes in a stressful environment,
it becomes necessary to quantify these changes to estimate the
evolutionary potential of the population in this new environment. We
studied the genetic structure for survival, fecundity, and early and late
growth in isogenic lines of a Caenorhabditis elegans population subject to
three different environments: a control environment, an environment
polluted with uranium, and a high salt concentration environment. We found
a heritability decrease in the polluted environments for fecundity and
early growth, two traits that were the most heritable in the control
environment. The genetic structure of the traits was particularly affected
in the uranium polluted environment, probably due to generally low
heritability in this environment. This could prevent selection from acting
on traits despite the strong selection pressures exerted on them.
Moreover, phenotypic traits were more strongly affected in the salt than
in the uranium environment and the heritabilities were also lower in the
latter environment. Consequently the decrease in heritability was not
proportional to the population fitness reduction in the polluted
environments. Our results suggest that pollution can alter the genetic
structure of a C. elegans population, and thus modify its evolutionary
potential.