Immune defense in Drosophila melanogaster depends on diet, sex and mating status

Post-mating immunosuppression has been widely accepted as a female trait in Drosophila melanogaster . Our results challenge this notion by presenting a mating-immunity trade-off in males as well as in females. When inoculated with the fungal pathogen, Beauveria bassiana , both males and females die faster compared to inoculated virgins, and survival is lower when inoculated flies are continuously mated compared to a single day of mating. Past studies with Beauveria bassiana have shown females to be more susceptible to infection than males. Our results challenge this finding as well, showing that the direction of sexual dimorphism in immune defense depends on mating status, specific Beauveria bassiana strain, and fly genotype. Moreover, we show that survival after fungal infection is largely influenced by diet, and that post-infection dietary improvements can help enhance survival. Post-mating suppression in Drosophila survival of B. bassiana infection presents study opportunities with potential applications for biological control of insect vectors of human disease and insect crop pests. ### Competing Interest Statement The authors have declared no competing interest.