Microbial Diversity of Two Hawaiian picture wings and their Host Plants; Microbes, Mortality and Epicuticular Hydrocarbons

Abstract

Although the microbiome influences numerous aspects of organismal biology and fitness, the community characterization and role in animal evolution is largely unknown. Microbial communities in insects can have a wide range of interactions from mutualistic to parasitic and can be important in host-plant adaptation. In Drosophila, microbial associations and interactions have been studied for over a century and recently have been shown to influence the fitness and evolution of their host. This study utilizes both traditional culturing methods and high-throughput next generation DNA sequencing to evaluate the bacterial and fungal communities associated with two Hawaiian Drosophila, D. sproati and D. ochracea and their host plants, Cheirodendron trigynum and Freycinetia arborea. The culture-based and high-throughput DNA sequencing approaches provided different but complementary results. Interestingly, we found some overlap between microbiomes of the Hawaiian Drosophila and their host plants. The bacterial family Enterobacteriaceae, as well as a variety of yeasts, consisted of the majority of these shared microbes. This suggests that these microbes may play a role in the fly-host plant interaction. To evaluate the effect of these microbes on Hawaiian Drosophila, we exposed a laboratory population of D. sproati to antibacterial and antifungal treatments to determine the effect on D. sproati survivorship and epicuticular hydrocarbons. Epicuticular hydrocarbons in Drosophila serve a dual function, aiding in desiccation resistance and pheromonal communication. Flies exposed to an antifungal treatment had dramatically reduced survivorship when compared to control flies, while antibacterial treated flies were not affected. This suggests that fungi are essential to Drosophila survival while bacteria are not. However, male flies that were exposed to the antibacterial treatment showed significant changes in two major epicuticular hydrocarbons. One of which, 2MeC28, has been shown to act as a contact pheromone in other insect species. This study shows that changes in microbial communities, specifically bacteria, influence epicuticular hydrocarbon production of D. sproati which can impact multiple levels of fitness.