An important question in understanding any interspecific interaction is, "how will the interaction change as the interacting species evolve in response to each other?" For many interactions, observations of evolutionary change must be made over decades or centuries. In contrast, infectious diseases typically have short generation times, and because diseases often cause high mortality among their hosts, host-pathogen interactions often have the potential for demonstrating co-evolutionary change between host and pathogen over relatively short time scales. This study will investigate the co-evolution between gypsy moth and its fungal pathogen, Entomophaga. This host-pathogen system shows features of both novel and natural associations. For this host-pathogen interaction, there are host populations in different geographic regions that have had very different lengths of association with the pathogen. Moreover, the sudden appearance of the disease after almost 80 years suggest that there recently have been drastic changes in the fitness of the pathogen. The specific objectives of this project are to determine the introduction history of the pathogenic fungus across the range of the gypsy moth host, to determine the degree of variation in virulence of different strains of the pathogen, and to use this information to begin to assess the co-evolutionary response of this host-pathogen interaction. Overall, this research is strongly tied to the theory of host-pathogen co-evolution, and thus to the study of co-evolution in general, but will also be of practical use in using the fungal pathogen to manage gypsy moth populations.
