During certain evolutionary scenarios, such as genetic sweeps and range expansions, the driving lineages have an increased competitiveness or experience an absence of competition, which results in a higher tolerance of deleterious mutations. We have named this phenomenon, during which individuals have more freedom to explore their fitness landscape, the “Free-for-All” effect (FFA). We present evidence for the free-for-all effect and discuss some of its implications for evolutionary science. This document summarizes work that we are preparing for publication.

Selection can be described as a filtering process which changes a population over time with regard to the result of some evaluation (i.e. a fitness function). We are interested understanding the relationship between different parameters for altering selection strength and rates of adaptation. In this work we perform a detailed assay exploring the relationship between population size, noisy phenotype evaluation, and tournament size, and their effects on rates of genomic change. We run our model on nearly 4,500 different scenarios. We observe evolution on a smooth fitness landscape as well as nine deceptive landscapes using our model. We show that for the smooth landscape it is always best to have strong selection with noise-free fitness and a large population. For deceptive landscapes, there is an optimum configuration of tournament size and noise that balances exploration and exploitation. Population size, on the other hand, always increases genomic change when larger, because it not only increases selection strength but also maximizes mutational inflow and standing variation. We see that while these parameters for selection strength have similar effects, they each behave in unique ways. Finally, we suggest that evaluation noise is a better proxy for selection strength than population size.