Polak 9726903 The goals of the proposed work are to elucidate the mechanistic and genetic bases of resistance against parasitism in an insect host. Previous ecological research has shown that the parasite (a macrochelid mite) damages multiple reproductive traits of its host (a drosophilid fly), providing the rationale for asking specific questions about the evolutionary potential of parasitism in this natural system. Laboratory experiments, using genetically distinct resistant and control lines of flies and integrated behavioral and physiological techniques, are proposed to determine (1) the magnitude of genetic variability underlying resistance in the natural host population, (2) constraints on the evolution of resistance, (3) effects of loss of genetic variability (through controlled host inbreeding) on rates of parasitism, and (4) traits of the host that confer resistance. Most of what is known about patterns of genetic variability in resistance against parasites and pathogens, and their effect on the distribution of disease in nature, comes from studies of plants and their natural enemies. Only by acquiring the requisite information in animal hosts can we begin to develop a general theory of the evolution of parasite resistance, and sound approaches to disease control. The proposed study is aimed at attaining this goal using an insect-ectoparasite model whose ecology is well known. The results should have broad-ranging implications because ectoparasites are ubiquitous, are know vectors or transmissible parasitic disease in numerous species, and because the mechanisms expected to mediate susceptibility to ectoparasitism in the present system have strong parallels with that in other taxa including birds, mammals and other invertebrates.
