Sexual success of infected versus uninfected males
To determine whether infection has any effect on male sexual success, we compared the competitive paternity success of infected and sham-treated males (infection protocol described below). Because the infected and uninfected males came from the same population, we would not be able to distinguish paternity in direct competitions. We therefore competed each against males from a reference population homozygous for theebony marker.
Each replicate consisted of five focal males (either infected (N = 38) or sham-treated (N = 39)) and five ebony males competing for fiveebony females. These flies were allowed to interact for 48 hours before being discarded. The resulting offspring were scored upon emergence as adults. The recessive ebony mutation enabled us to distinguish offspring sired by the focal males (which would have wild type cuticles) and those sired by the reference males (which would have dark cuticles). The proportion of wild type offspring was then used as a measure of sexual success of the infected versus non-infected focal males. Even though the fraction of wild type offspring may deviate from the actual fertilization success of focal males because of differences in egg-to-adult survival of wild type and ebony offspring, this would affect the estimates for the two types of males in the same way.