COLLABORATIVE RESEARCH: Ecological and evolutionary dynamics of secondary contact

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Rivers and streams across the country are being restored to their original flow patterns by the removal of dams, many of which were constructed centuries ago to provide energy for small mills that formed the basis of colonial economies. This project takes advantage of planned dam removals that will connect fish populations that have been separated for nearly four centuries, in order to study the ecological and evolutionary consequences of secondary contact between these recently divergent fish populations, which may interbreed but also may compete. Results from this work will contribute to the conservation and management of migratory alewife fish, a critical resource in coastal freshwater and marine habitats and the focus of intensive restoration and conservation efforts. Researchers will work collaboratively with state managers, the Connecticut Department of Energy and Environmental Protection, lake associations, and land trusts to determine the consequences of restoring migratory populations, provide information vital to alewife recovery, and educate local communities on the consequences of river restoration. The project will train a postdoctoral researcher along with graduate and undergraduate students in an interdisciplinary project that relies on advanced genetics techniques, field sampling, and manipulative field and laboratory experiments. An existing program at Yale University will support involvement of underrepresented minority undergraduate students in summer research. Training will include the broader scientific context of the research, research methods, data analysis, written and oral project reports, and direct involvement with the public to present the societal benefits of the research. This project takes advantage of whole-lake restoration projects to understand the ecological and evolutionary dynamics of secondary contact between recently diverged lineages of alewife. Isolation caused by construction of dams has resulted in two divergent alewife life history forms: the ancestral anadromous form that moves between lakes and the coastal ocean and a landlocked form that is resident in lakes. This project will combine advanced genomics, small-scale experiments, and whole-lake observations and experiments to document and understand the consequences of secondary contact, when dam removal allows reintroduction of anadromous alewife into lakes that contain the land-locked form. Close collaboration with the state agency that removes dams will allow the investigators to study secondary contact from its initiation. The project addresses three stages in response to secondary contact: rapid ecological change in planktonic communities and nutrient flux, rapid evolutionary responses in invertebrate populations in response to novel ecological conditions, and interactions between the two alewife morphs that may result in hybridization and, over the longer-term, alewife evolution and local adaptation. The first of these responses - ecological changes in lacustrine communities - is essential in order to interpret the evolutionary changes that result. The project is unique in its ability to capture the consequences of secondary contact on both time scales. Results will provide rare insight into feedbacks between ecological and evolutionary processes in field populations following secondary contact with important implications for ecosystem function and the maintenance of biodiversity in restored ecosystems.