Phylogeny, diet, and geography influence microbiome composition in two Diabrotica species

Insect-associated microbes have the ability to affect plant-insect interactions. Endogenous microbial communities can help the western corn rootworm, Diabrotica virgifera virgifera LeConte (WCR), overcome plant defenses and may aid WCR in resistance to transgenic crops producing Bacillus thuringiensis insecticidal proteins. Despite this functionality, our understanding of how the microbial communities of WCR are influenced by phylogeny, diet, and the environment is minimal. To address this, we compared the bacterial communities of adult WCR and its congener, the northern corn rootworm (NCR; Diabrotica barberi Smith & Lawrence), collected from corn fields across several states. We then reared wild WCR and NCR beetles collected from disparate locations on similar diets in the lab to examine the diet’s effect on bacterial communities. Through the use of 16S amplicon sequencing, we found WCR and NCR beetles harbor significantly different bacterial communities even when grown on similar diets. However, the communities associated with field collected beetles are significantly different than those of beetles reared in the lab. These results demonstrate host species identity, diet, and local environment are important factors that shape microbial communities in Diabrotica. Increasing our understanding of what influences microbiome composition in insects can provide insight into how microbe-mediated effects on plant-insect interactions might have evolved.