European oak metabolites shape digestion and fitness of the herbivore <i>Tortrix viridana</i>

Plants harbour a wide range of leaf-feeding insects whose survival and fitness are influenced by both energy-rich molecules phytochemicals in the host foliage. Yet, how leaf chemical diversity insect microbiota—key factors ecological physiological processes—impact nutrition still poorly understood. To study effects metabolic composition on herbivory resistance performance, we fed larvae specialist Tortrix viridana with leaves susceptible resistant Quercus robur trees that characterized contrasting metabolomes. We analysed larval performance mortality, metabolomes plant leaves, insects' saliva faeces non-targeted metabolomics. Using chemometrics, mass difference network analysis metabarcoding, show metabolome changes reactions associated different diets as well their impact gut microbiota. In larvae, secondary metabolites (e.g. flavonoids) persisted more digestion while compounds from primary metabolism were depleted. addition, within indicated degradation pathways used two types (syn. metabotypes), including sulfation sulfonation. feeding oak enriched depleted metabolites, impaired mortality. Although microbiota was slightly upon diets, overall, it fairly stable. Despite chemicals herbivores, generally highly efficient nutrient assimilation (feed conversion ratios 3.3–3.6) able to minimize defences (78% converted, broken down or sequestrated). The comparison metabotypes showed foliar oaks affected influencing digestion. Herbivores less due lower ability metabolize detoxify higher levels phytochemicals, whereas those they could degrade metabolome. This highlights importance specialized herbivore. Read free Plain Language Summary for this article Journal blog.