Genomic Footprints of Adaptive Responses - Across Species and Environments

Genome-wide patterns of variation and differentiation provide information about selection and demographic features of populations and species. Using RAD sequencing we have studied two very different systems, 1) Atlantic eels (European [Anguilla anguilla] and American eel [A. rostrata]) and 2) three-spine sticklebacks (Gasterosteus aculeatus), represented by populations in temperate (Denmark) and Arctic (Greenland) environments. We analyze genome-wide divergence between the two Atlantic eel species that are assumed to have diverged a few million years ago and are both characterized by panmixia and high effective population sizes. Moreover, we analyze genomic footprints of selection within European eel sampled in different localities and environments and assess the possibility of spatially and temporally varying selection, in spite of the species being panmictic. In three-spine sticklebacks, we analyze adaptive divergence between freshwater and marine populations in temperate and Arctic settings. Arctic freshwater ecosystems are much simpler and less variable than in a temperate region like Denmark. We therefore test the hypothesis that adaptive responses in different Arctic freshwater lakes are more similar and predictable than in lakes from temperate regions. We discuss the potential for the different species and populations to invoke adaptive genetic responses to environmental change, such as ongoing climate change.