The impact of goldenrod-feeding insects on the growth and reproduction of individual stems and on field community composition during the course of succession will be studied. Insect populations will be surpressed in plots of newly cleared ground to determine whether feeding by insects affects which plant species become established in these plots. To supplement this holistic approach, more detailed experiments will be performed on two members of the old field community, goldenrod and strawberry, to assess the role herbivores play in mediating the competitive outcome between the two. A second objective is to examine in detail the effect of different types of herbivore feeding damage on the fitness of individual goldenrod stems. Experiments in which herbivore damage is simulated in various ways will allow the investigation of how insect damage disrupts the balance between carbohydrate sources and sinks within the plant. In addition, because different herbivores are attracted to goldenrods growing at different fertility levels, experiments will be conducted to assess the combined effect of soil fertility and insect feeding style on plant fitness. Long-term studies of the spatial and temporal variation in the populations of several insect species that feed on goldenrod will be continued. To gain further insight into the structure of the fauna and the quality of the herbivore load at our various sites, experiments designed to determine the host finding abilities of several insect species will be conducted. These data provide a context for interpreting the more focused experiments by allowing the frequency with which our experimental conditions occur naturally to be determined. They also form the basis for building new hypotheses about the structure of the insect fauna of goldenrods and the interactions between species.
