Across two continents: the genomic basis of environmental adaptation in house mice ( Mus musculus domesticus ) from the Americas.

Since their arrival with European colonizers, house mice have successfully spread throughout the Americas. There is strong evidence that populations in North America have adapted in that time, including parallel evolution of phenotypes across latitude (e.g., body size, behavior) as well as the identification of genes that show signals of selection. Here, we investigate the genetics of environmental adaptation in South America. We find that populations in South America evolve independently of populations in North America. We identify candidate genes for environmental adaptation with links to traits like body size, metabolism, immunity, eye function, and the cardiovascular and renal systems. We then bring together data from three transects across two continents to determine if environmental adaptation is predictable, with parallel genetic changes in response to shared conditions. We find that most evidence of environmental adaptation lies in regulatory regions and that, while most candidate genes are unique to individual transects, many are shared, providing significant evidence of parallel adaptation. We identify a core set of candidate genes independently identified in all three transects that likely contribute to environmental adaptation in the Americas. These results highlight the value of studying wild populations of this genetic model system.