Consequences of self-fertilization on the adaptive potential of populations ˸empirical, experimental and theoretical approaches ; Conséquences de l'autogamie sur le potentiel évolutif des populations ˸ approches empirique, expérimentale et théorique

Self-fertilization is often described as an evolutionary dead end. Due to their smaller effective population size, increasing the strength of genetic drift, the more efficient purge of deleterious mutations, and predominant genetic associations, selfing populations are expected to harbour less genetic diversity, limiting their adaptive potential. However, there is little empirical data supporting these theoretical expectations, and the dynamics and adaptive potential of selfing populations remain poorly understood. The aim of this thesis is to better understand the evolutionary dynamics of selfing populations, and notably the possible role of residual allogamy in this dynamics and in populations' response to environmental constrains. To do so, I combined theoretical and empirical approaches, using the predominantly selfing species Medicago truncatula. First, I performed a meta-analysis in angiosperm species and showed that if selfing populations have less genetic diversity than their outcrossing counterparts can, the mating system is a poor predictor of the amount of genetic diversity within populations. I then used models to show that even if the amount of genetic variance is smaller in selfing populations, the remobilization by residual allogamy of the genetic variance stored in genetic associations allows a similar level of adaptation as in outcrossing populations. I then showed that the genetic differentiation accumulated between inbred lines, at within- and among-population scales, is deleterious, on average, during hybridization events. This is due to negative dominance effects, but this mechanism of reproductive isolation does not hinder the remobilization of the hidden genetic variance in Medicago truncatula. Finally, we showed that making theoretical models of quantitative traits under stabilizing selection more realistic, by adding directional dominance at the phenotypic scale, could reconcile theory with empirical data that report a weak effect of the mating system on the adaptive potential of ...