How does SElfing affect ADaptation: Genetic and demographic effects – SEAD

The ability for a population to adapt to environmental changes depends on several factors such as its size, genetic diversity, or mating patterns, in particular selfing rates. In flowering plants, mating patterns are highly variable from strict outcrossing to predominant selfing and almost a half self-fertilize at various rates. Nevertheless, random mating is a classic assumption and the effect of selfing on adaptation remains largely unresolved: on the one hand, the young age of selfing lineages suggests that selfing species lose the ability to adapt to changing environments; on the other hand, the large proportion of selfers in crops suggests that selfing could facilitate adaptation to human use. Selfing can indeed have multiple and complex effects. It shapes the genetic variance of a population, but also the interaction between selection and drift or migration. Selfing is also likely to alter population’s demography, because inbreeding and outbreeding depressions affect the vital rates of individuals. Both these genetic and demographic impacts bear upon the probability of adaptation to environmental variation, which depends on a race between the speed of the adaptive process and the speed of population decline. A refined understanding of these impacts is therefore essential to predict the fate of selfing species in the current context of global change and to improve conservation and management strategies of both natural and cultivated populations.
In this project, we propose to tackle three main issues regarding the effect of selfing on adaptive processes, through a combination of theoretical developments and fine scale analyses of three species. Our study systems include two predominantly selfing and one partially selfing species, all undergoing adaptation to environmental changes related to human activities. First, we propose to focus on the response to selection within population, by developing models explicitly taking into account the complex genetic architecture of traits and specific selection regimes. This modelling approach will be combined with the temporal monitoring of experimental or natural populations under selection. Secondly, we will examine how selfing affects local adaptation in populations connected by gene flow. To achieve this, we will analyse the interplay between selection, drift and gene flow under partial selfing to predict the rate of phenotypic divergence and to quantify local adaptation to heterogeneous environments. Thirdly, we will investigate how temporal variations in selfing rates modify the dynamics of adaptation, while explicitly taking into account demographic effects (especially inbreeding depression and reproductive assurance). This proposal unites research groups that have long been addressing related questions and have complementary expertise (e.g. ecology, demography, population and quantitative genetics, evolutionary theory, crop science).