9726648 Whitham Biologists have long considered hybridization to be a major impetus to plant evolution. Mechanisms of how such events influence the ecological performance of a species are largely unexplored. This research will consider how variation created by hybridization affects diverse members of an ecological community. The research will focus on cottonwoods (Populus spp.), which are important trees in riparian habitats of the western US and known to hybridize frequently. One of the goals of this project is to discover whether or not the genetic differences in individuals of hybrid populations in the wild determine the distribution of invertebrate herbivores. Another is to determine if hybrid zone size affects the concentration of herbivores. In addition, common-garden studies will be conducted to determine the underlying mechanisms that affect hybrid resistance and susceptibility to herbivores. These latter experiments will allow the investigators to determine the heritability of traits involved in herbivore resistance. The outcome of this research is likely to provide new insights into how genetic variation resulting from hybridization contributes to community level processes. s
