Dynamic changes in infection over a single generation of , across a wide range of resource availability.

bacteria are maternally inherited symbionts that commonly infect terrestrial arthropods. Many reach high frequencies in their hosts by manipulating their reproduction, for example by causing reproductive incompatibilities between infected male and uninfected female hosts. However, not all strains manipulate reproduction, and a key unresolved question is how these non-manipulative persist in their hosts, often at intermediate to high frequencies. One such strain, Suz, infects the invasive fruit pest , spotted-wing drosophila. Here, we tested the hypothesis that Suz infection provides a competitive benefit when resources are limited. Over the course of one season, we established population cages with varying amounts of food in a semi-field setting and seeded them with a 50:50 mixture of flies with and without . We predicted that -infected individuals should have higher survival and faster development than their uninfected counterparts when there was little available food. We found that while food availability strongly impacted fly fitness, there was no difference in development times or survival between -infected and uninfected flies. Interestingly, however, infection frequencies changed dramatically, with infections either increasing or decreasing by as much as 30% in a single generation, suggesting the possibility of unidentified factors shaping infection over the course of the season.