Microbiomes of 2024's Periodical Cicada Brood XIII Vary By Species and Location.

The 17-year Periodical cicadas (Magicicada spp.) are long-lived insects that emerge in mass synchronized events after 17 years underground. Their survival and ecological success depend heavily on their microbiomes, which include obligate bacterial symbionts essential for nutrient acquisition, as well as occasional pathogens such as the behavior-altering fungus Massospora cicadina. While the periodical cicada lifecycle is well studied, little is known about how cicada microbiomes vary across species and environments during a single emergence event. During the 2024 emergence of Brood XIII in northern Illinois, 17-year cicadas were sampled from four ecologically distinct forest preserves. Cicadas were identified by species and sex; their microbiomes were assayed using 16S rRNA gene sequencing and tested for the presence of the fungal pathogen M. cicadina DNA in asymptomatic individuals. Sampling sites were characterized by plant community composition, historical disturbance, and potential presence of the antifungal compound juglone. Microbiome composition differed significantly by cicada species and site, but not by sex. The obligate symbionts Hodgkinia cicadicola and Sulcia muelleri dominated microbiome profiles, though other bacteria-including Pantoea agglomerans, a potential pheromone producer-were variably abundant. Cicada species distributions were non-random across sites and correlated with local plant diversity. M. cicadina DNA was detected in 23% of otherwise asymptomatic cicadas, with infection rates varying by location and negatively correlated with microbiome diversity. This study highlights complex interactions between cicada species, their microbial communities, and environmental variables such as plant diversity, soil chemistry, and land use history.