Is (non)parallel evolution driven by (non)parallel selection?

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How predictable is evolution? Given broadly similar environmental conditions, does natural selection always favor similar traits and genes? If evolution is predictable, then humanity will be better able to anticipate evolutionary changes in diseases, agricultural pests, or species we wish to preserve in the face of environmental change. This study will examine the degree to which evolution is predictable. Specifically, the researchers will test whether the repeated evolution of certain traits in many replicate populations is evidence of similar natural selection, as has been widely assumed but never tested in nature. The work has broad scope, integrating environmental, ecological, morphological, immunological, and genomic data, and so will provide a benchmark for future studies of evolution. Moreover, the study organism -- the threespine stickleback fish -- is abundant, diverse, and well-studied, making it an excellent tool for teaching biology to both K-12 science teachers and their students.The study asks the following questions: (1) where we observe repeated evolution, is natural selection also very similar?, (2) do immune traits evolve in a predictable manner?, (3) does parallel natural selection act on the same genomic regions?, (4) how thoroughly can we explain genetic responses to selection? To answer these questions, the researchers will place F2 hybrids between lake and stream fish into enclosures in natural habitats, to measure selection on many traits and genomic loci. By repeating these measures of selection in four independent lake-stream pairs, they can, for the first time, evaluate the relationship between parallel selection and parallel evolution in the wild.