Microbial Community Dynamics in Natural Drosophila melanogaster Populations Across Seasons.

Many insects benefit from gut microbes that contribute to digestion, detoxification, nutrient supplementation or defence. Although abiotic and biotic factors are known to shape insect-associated microbial communities, the seasonal dynamics and their potential impact on host fitness remain poorly studied. Here we investigated the temporal changes in bacterial and fungal communities associated with the model organism Drosophila melanogaster over 5 months. Our results reveal high inter-individual variation, but also consistent changes in microbial communities of three wild D. melanogaster populations from early spring to late summer. These changes were driven by specific indicator species, particularly Acetobacteraceae bacteria (Gluconobacter and Komagataeibacter) and Saccharomycetales yeasts (Pichia, Starmerella, Kregervanrija, Hanseniaspora, Saccharomycopsis, Priceomyces and Dipodascopsis). The temporal dynamics were not accompanied by differences in the total bacterial or fungal abundance, and alpha-diversity only changed across sampling months for the fungal but not the bacterial communities. While the changes in D. melanogaster-associated microbial communities are likely driven by the exposure to seasonally changing microbial environments and diets, they may have important impacts on host fitness. Elucidating the potential adaptive value of seasonally changing microbial communities will enhance our understanding of how symbiotic microbes may contribute to ecological niche shifts and geographic range expansions in insects.