Costs and genomic aspects of Drosophila immunity to parasites and pathogens

This chapter begins by focusing on the parasites and pathogens known to attack or infect D. melanogaster (or other Drosophila species), from macroparasites, such as parasitoids and mites to microbial (fungal and bacterial) pathogens to viruses. It concentrates on the main selection pressures for and against resistance against these parasites and pathogens. High resistance is selected for when the benefits it incurs outweigh its costs. For each parasite/pathogen, the chapter summarizes the existing knowledge on abundance in the field, fitness effects of parasitism/infection, and costs of resistance, where it distinguishes between costs of actual resistance and costs of the resistance mechanism. The second section of the chapter shifts the focus to the genomic level. Over the last few years several papers have been published where microarrays have been used to investigate D. melanogaster resistance to parasites and pathogens. The chapter considers what these studies are telling us about Drosophila resistance mechanisms and about the associated costs.