Evolution of genetic variance in complex environments

There is an urgent need to develop realistic predictions of evolutionary and ecological responses to changing environments, particularly in times of accelerating climate change. Due to the complexity of the predicted dynamics, the effects of spatial and temporal variability often tend to be studied in isolation, or under an assumption of fixed genetic variance. Yet, the complex interaction among these factors can result in qualitatively different outcomes, such as abrupt range fragmentation and rapid depletion of genetic variance. This project will develop fundamental theory on how genetic variance and genetic architecture evolve in complex, changing environments. Genetic variance is crucial for evolutionary processes as it determines the rate of adaptation. Genetic variance is, however, not static but constantly evolving as a result of eco-evolutionary dynamics involving mutation, selection, dispersal, and the effects of finite population size (genetic drift). First, we aim to derive predictions for how temporal change in spatially structured populations increases genetic variance, and how this alters the genetic architecture underlying adaptive traits. Second, building on my recent discovery of species` range and niche fragmentation under joint spatial and temporal change, we will examine how joint spatial and temporal variation affects species cohesion, the evolution of reproductive isolation leading to speciation, and species` resilience in changing environments. To develop testable theory, we will combine individual-based simulations with analytical methods such as nondimensionalization, separation of time scales, and branching process theory. We will also relate our theoretical results to the empirical patterns observed in natural and experimental Drosophila populations. In addition to advancing our fundamental understanding of the limits to species range and niche, this project aims to further develop the theoretical foundations of conservation genetics.