Why are some individuals more susceptible to infection by parasites than others? Parasites by definition harm the fitness of individuals (hosts), and thus are expected to have a powerful influence on host abundance, population cycles and the evolution of their defenses. This research will identify how genetic variation in host defenses is maintained and thus how hosts evolve to reduce the effects of parasites. The research uses two species of fruit flies, Drosophila species, and their mite parasites as a model. The research outcomes will inform the development of improved pest control strategies in agricultural settings, and new methods to control disease vectors that are of significance to human health and wellbeing. Research outcomes will be integrated into educational outreach programs involving high school students and the general public.
A major hypothesis for the maintenance of genetic variation in defensive traits, and hence for the enormous evolutionary potential of parasitism, involves costs of resistance. Costs are expressed as trade-offs between host resistance and other fitness-related traits, such as reproductive output, in the absence of parasites. There are few data available for animal host-parasite systems on the genetic and physiological bases of costs of resistance, despite their widespread importance. The researchers will bridge studies of host molecular, metabolomic, and physiological processes, with whole-organism fitness functions, to understand the mechanistic bases of costs of parasite resistance. Using two naturally occurring host-parasite systems, three interrelated aims will be achieved. 1) Test for trade-offs between evolved ectoparasite resistance and major life-history traits in D. melanogaster. 2) Determine and compare the causal molecular and metabolomic factors of ectoparasite resistance and of trade-offs in the two systems. 3) Identify the physiological and anatomical mechanisms underlying fitness costs. The results will be unique to animals, and will complement studies in plant and microbial systems. The research will thus contribute to the development of a unified theory of resistance evolution.
