Local populations of a species are often considered to be genetically differentiated in response to local differences in environmental factors that produce divergent forces of natural selection. Most demonstrations of such "adaptive differentiation" are actually not based on local populations but are instead focused on populations that are separated by large geographic distances or are completely unconnected by gene flow. Thus the scale at which adaptive differentiation can occur remains to be delineated. Prior work by Dr. Travis has shown extensive local differentiation in apparent response to physical factors that vary across locations. The next phase of the research will (1) examine the detailed nature of the genetic differences and (2) test the hypotheses for how the physical factors in the environment generate divergent forces of natural selection.
