Insects often face multiple simultaneous challenges that threaten their ability to grow and reproduce. For instance, insect herbivores encounter challenging diets where they must acquire enough nutrients while also contending with potentially toxic components of their diet. Plant defenses can target the digestive tract, where they can have direct and indirect impacts on herbivore. In this presentation, I will discuss the ways in which plant antiherbivore toxins against caterpillars are amplified by herbivore gut microbiota. Using fall armyworm as an experimental model, I investigated how different plant defenses enable opportunistic infections by otherwise commensal bacteria. Both the type of plant defense and the specific microbes present in the system altered the magnitude of this effect, enhancing the effect of the plant defenses on the herbivore. I will then discuss hypothesis as to why gut bacteria may be present in the fall armyworm, and why they possess a suite of microbes that may be construed as parasitic. Collectively, the findings from these studies illustrate a complex picture, and demonstrates that host-diet interactions can drive the dynamic functions and ultimate outcomes of herbivore gut microbiomes.
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