Long-term Research in Environmental Biology (LTREB): Rapid evolution of a Threespine Stickleback Population

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Evolutionary history is generally studied by comparing species that shared a common ancestor thousands to millions of generations ago, but evolutionary processes are studied over relatively few generations. Hence, conclusions from studies on processes must be extrapolated through time and among species to interpret history. This project makes use of a unique study system involving the stickleback fish, in order to directly integrate evolutionary history and process. A sea-run stickleback population colonized an Alaskan lake in the 1980's and subsequently underwent rapid evolution. When first sampled in 1990, it closely resembled sea-run sticklebacks in body shape and size, the shape of the gill cover, armor plates, feeding structures, and the genes that control armor and regulate the salt concentration in body fluids. Annual sampling revealed progressive evolutionary change of every trait towards those of older lake populations, from which it is now almost indistinguishable. This project will continue the long term study of this lake population, and expand the work to study the evolution of fish immunity to disease agents that are prevalent in freshwater lakes. This project also initiates new research on additional sea-run stickleback populations that are at the earliest stages of colonization of freshwater lakes. Evolution of these sea-run populations simulates the history by which countless freshwater populations have evolved since the last ice age. This study has broader relevance to predicting the adaptability of fish species in the face of global climate change and intensive fishing pressure on commercial species. It will also provide valuable information on the evolution of immune response to emerging infectious disease. The project gives undergraduate students hands-on research experience. Data from this project will be posted annually on a publically accessible website, and the time series of fish collections documenting rapid evolution will be deposited in the Yale Peabody Museum for further study.