Bacterial and fungal components of the microbiome have distinct roles in Hawaiian reproduction.

The microbiome provides numerous physiological benefits for host animals. The role of bacterial members of microbiomes to host physiology is well-documented. However, much less is known about the contributions and interactions of fungal members, even though fungi are integral components of many microbiomes, including those of humans and insects. Here, we used antibacterial and antifungal drugs to manipulate the gut microbiome of a Hawaiian picture-wing species, , and identified distinct effects for each treatment on microbiome community stability, reproduction, and lipid metabolism. Female oogenesis, fecundity, and mating drive were significantly diminished with antifungal treatment. In contrast, male fecundity was affected by antibacterial but not antifungal treatment. For males and females, simultaneous treatment with both antibacterial and antifungal drugs resulted in severely reduced fecundity and changes in fatty acid levels and composition. Microbial transplants using frass harvested from control flies partially restored microbiome composition and female fecundity. Overall, our results reveal that antibacterial and antifungal treatments have distinct effects on host fecundity, mating behavior, and lipid metabolism, and that interkingdom interactions contribute to microbial community stability and reproduction.