Pre-copulatory reproductive behaviours are preserved in Drosophila melanogaster infected with bacteria

Abstract

Reproduction and immunity are crucial traits that determine an animal's fitness. Terminal investment hypothesis predicts that reproductive investment should increase in the face of a mortality risk caused by infection. However, due to competitive allocation of energetic resources, individuals fighting infections are expected to decrease reproductive efforts. While there is evidence for both hypotheses, the factors that determine the choice between these strategies are poorly understood. Here, we assess the impact of bacterial infection on pre-copulatory behaviours in the fruit fly Drosophila melanogaster. We found that male flies infected with six different bacteria, including pathogenic and non-pathogenic strains, show no significant differences in courtship intensity and mating success. Similarly, bacterial infections did not affect sexual receptivity in female flies. Our data suggest that pre-copulatory reproductive behaviours remain preserved in infected animals, despite the huge metabolic cost of infection.