During the last Pleistocene glacial advance, ice covered much of the modern day range of the threespine stickleback (Gasterosteus aculeatus). As the glaciers began to retreat about 14,000 years ago, a diversity of freshwater habitats were created and subsequently colonized by the marine threespine stickleback. Today, the resultant freshwater populations are undergoing rapid evolutionary diversification throughout northwestern North America, and in some cases speciation has occurred. This remarkable, recent radiation holds great promise for providing information on the patterns and mechanisms of evolutionary change. It also provides a model for adaptive radiations that have new genera and higher taxa. The proposed research will determine, for the first time, the reproductive behavior patterns exhibited by marine threespine stickleback, and the extent to which they vary among sites. This is essential for interpreting the patterns of change in the radiation because the marine form is thought to have given rise to the divergent freshwater forms observed today. In addition, the diversity of reproductive behavior in twenty or more Alaskan freshwater populations will be documented. These observations will not only provide a first approximation of the range of behavioral diversification among Alaskan freshwater populations, but will enable the investigators to select populations for future research on the evolution of specific behavioral phenotypes.
