Résumé
Standing genetic variation is considered a major contributor to the
adaptive potential of species. The low heritable genetic variation
observed in self-fertilising populations has led to the hypothesis that
species with this mating system would be less likely to adapt. However, a
non-negligible amount of cryptic genetic variation for polygenic traits,
accumulated through negative linkage disequilibrium, could prove to be an
important source of standing variation in self-fertilising species. To
test this hypothesis we simulated populations under stabilizing selection
subjected to an environmental change. We demonstrate that, when the
mutation rate is high (but realistic), selfing populations are better able
to store genetic variance than outcrossing populations through genetic
associations, notably due to the reduced effective recombination rate
associated with predominant selfing. Following an environmental shift,
this diversity can be partially remobilized, which increases the additive
variance and adaptive potential of predominantly (but not completely)
selfing populations. In such conditions, despite initially lower observed
genetic variance, selfing populations adapt as readily as outcrossing ones
within a few generations. For low mutation rates, purifying selection
impedes the storage of diversity through genetic associations, in which
case, as previously predicted, the lower genetic variance of selfing
populations results in lower adaptability compared to their outcrossing
counterparts. The population size and the mutation rate are the main
parameters to consider, as they are the best predictors of the amount of
stored diversity in selfing populations. Our results and their impact on
our knowledge of adaptation under high selfing rates are discussed.