Plant defense influence the gut microbiome of a specialist herbivore and its interaction with parasitoids

The gut bacterial assemblages of lepidopteran larvae are susceptible to changes in their diet and environmental factors. Recent studies have demonstrated that diet quality influences the establishment and proliferation of gut bacteria. Furthermore, parasitism may disrupt the gut microbiome of caterpillars. However, we still do not know how phytochemicals shape the bacterial assemblage of caterpillars and whether these changes influence natural enemy performance. To fill this knowledge gap, we assess how different levels of jasmonate defenses in tomato plants (low, intermediate, and high resistance) alter the composition and diversity of the gut microbiome in Manduca sexta. Then, we evaluate how changes in the gut microbiome of a caterpillar influence performance of a parasitoid (Cotesia congregata). We will measure caterpillar performance in response to plants varying in resistance by measuring weight, size, and development time, and assess the changes in composition and diversity of their gut microbiome. To investigate the effects on parasitoid (Cotesia congregata) performance, we will record the number of parasitoid eggs on caterpillars and monitor the emergence of parasitoids. We predict that jasmonate tomato defenses will alter the composition and diversity of M. sexta gut microbiome. We expect that high-resistant plants will reduce the performance of caterpillars, reducing their body mass and slowing their developmental time. Furthermore, we expect that parasitoids will opt for caterpillars feeding on low-resistant plants, as phytochemicals impact the immune system of time caterpillars. Our research findings will disentangle the multitrophic relationship among plants, herbivores, natural enemies, and microorganisms.