Grant: Discovery Launch Supplement

We propose the development of new mathematical models of how natural selection changes over time and the consequences for genetic diversity and adaptation. The proposed work has three main components. First, we will model the dynamics of selection in a variety of archetypal scenarios to gain a repertoire of models of time-dependent selection (Objective 1). Second, we will synthesize the behaviours of these models using mathematical approximation techniques (Objective 2). Finally, we will use these models to develop new inference tools designed for time-resolved allele frequency data (Objective 3) - state of the art evolutionary data with the potential to revolutionize our understanding of evolutionary processes. We will disseminate our results in a way that can readily be implemented by other researchers, including the public release of computer code implementing the newly developed inference tools. The proposed work advances knowledge at the heart of evolutionary research. Explaining observed patterns of genetic diversity is a core objective of evolutionary biology because the genetic diversity that we observe today is the outcome of previous evolutionary processes. Consequently, genetic diversity is one of our only sources of knowledge about how evolution has shaped, and continues to shape, the living world. To make sense of genetic diversity, mathematical models of evolution are needed to translate hypotheses about evolutionary processes into predictions that can be compared with evolutionary observations. Evolutionary models have long accounted for the fact that many aspects of evolution are inherently unpredictable. For instance, whether a particular mutation will occur at a given time is a matter of chance. However, the process central to evolutionary adaptation - natural selection - is typically modeled as a steady, deterministic force. This obviously does not accurately represent reality, because the environment is not static. The proposed work substantially advances our understanding of the time dependence of selection and its consequences, addressing fundamental unresolved questions about the influence of natural selection in evolution, the rate of adaptation, and the forces that maintain and structure genetic variation. From a broader societal standpoint, a better scientific understanding of how populations adapt to environmental change will be essential if we hope to minimize humanity's future harm on the biosphere. The species that share planet earth today have already experienced - and survived - a vast history of environmental change. To do so, they have had to adapt by means of natural selection. As humans continue to change the environment in rapid and, in many respects, unpredictable ways, the species on earth will need to adapt again. Mathematical models of evolutionary adaptation in changing environments like those developed in this proposal will be needed to inform the decisions of humanity at this pivotal juncture.