Environmental heterogeneity may influence the amount of additive genetic variance in traits relevant to performance in a novel environment. This can affect the potential of a population with a given history to track environmental change and to adapt to a new environment. The proposed experiments will measure the effect of environmental heterogeneity on traits under selection by the feature of the environment that is being varied. Liriomyza trifolii, a dipteran leafminer, will be used as a model system in this three phase program. In phase 1, a genetically variable base population of L. trifolii will be established. In phase 2, replicate subpopulations of the base population will be subjected to either uniform or heterogeneous host plant conditions for 20 generations. Then the genetic variances and covariances in each replicate subpopulation for characters related to fitness on a novel plant will be measured. In phase 3, replicate selection lines from each treatment subpopulation will be initiated on the novel plant. Responses to selection on the novel plant will be measured for all lines and compared among the environmental heterogeneity treatments in order to test the effects of population history on evolutionary dynamics. After 10 generations of natural selection on the novel plant, genetic variances and covariances in fitness components will be re- measured. Net selection imposed by the novel plant on these populations during the selection period will be calculated. Qualitative predictions about the evolutionary dynamics of populations with different histories of environmental heterogeneity when faced with a new environment will be tested.
