Oceans are large, open habitats, and scientists previously believed that their lack of obvious barriers would result in extensive mixing, preventing organisms from genetically adapting to particular habitats. Recent studies have shown, however, that many marine species are subdivided into multiple populations that have evolved to thrive best under contrasting local environmental conditions.

One example is Atlantic silverside (Menidia menidia), a small estuarine fish that exhibits a remarkable degree of local adaptation in growth rates and a suite of other traits tightly associated with climatic variation across latitudes. Decades of research have made the Atlantic silverside one of the best understood marine species in terms of evolutionary tradeoffs among traits and drivers of selection and adaption. Yet, the underlying genomic basis is completely unknown.

Nina Overgaard Therkildsen, Natural Resources, and her team are working to integrate whole genome sequencing data from wild fish sampled across the distribution range, with breeding experiments in the laboratory, to decipher these genomic underpinnings. With a focus on gene flow—how genetic variation transfers between populations—the findings will have broad implications and will significantly advance understanding of the role genomic architecture plays in modifying the balance between gene flow and selection within coastal environments. The project will provide one of the most comprehensive assessments of the genomic basis for local adaptation in the oceans to date, generating insights that are urgently needed for better predictions about how species can respond to rapid environmental change.