This project will test whether density-dependent natural selection (natural selection that operates differently at different levels of crowding) is responsible for a major life-history divergence in a small north Florida fish. One facet of the work will examine long-term numerical dynamics of two fish populations and the species in their communities. The other facet will be an experimental study of whether natural selection at different levels of crowding will re-sort the genes responsible for different life histories in different populations.
Density-dependent selection for life histories, the idea that populations that experience characteristically different regimes of crowding ought to exhibit characteristically different life histories, is fundamental to population biology. The concept was once hypothesized to account for much natural life-history diversity; it has also been the foundation for ideas about whether stable population dynamics can evolve or whether exploitation of fisheries by reducing fish density will alter the life history of the fishery species. Yet the empirical support for the entire concept is weak and circumscribed. This study will develop a model system from natural populations for testing the concept and understanding how it works (if indeed it does) and how it can be used in a variety of applications.
