Detecting directional epistasis and dominance from cross-line analyses in alpine populations of Arabidopsis thaliana
Résumé
The contribution of non-additive genetic effects to the evolutionary potential of populations has been a topic of theoretical and empirical interest for a long time. Yet, the empirical study of these effects in natural populations remains scarce, perhaps because measuring dominance and epistasis relies on heavy experimental line crosses. In this study, we explored the contribution of dominance and epistasis in natural alpine populations of Arabidopsis thaliana, for two fitness-related traits, the dry weight and the number of siliques, measured in a greenhouse. We first found that, on average, crosses between inbred lines of A. thaliana led to mid-parent heterosis for the dry weight, but outbreeding depression for the number of siliques. While heterosis for the dry weight was due to dominance, we found that outbreeding depression for the number of siliques could be attributed to the breakdown of epistasis. We simulated and discussed the implication of these results for the adaptive potential of the studied populations, as well as the use of line-cross analyses to detect directional non-additive genetic effects.