PNNL

Abstract

Many studies have already addressed different plant-insect interaction questions at nutritional, molecular, physiological, and evolutionary levels. However, it is still unknown how flexible is the metabolism and the nutritional content of specialist insect herbivores feeding on different closely related plants. We performed elemental, stoichiometric and metabolomics analyses on leaves of two coexisting Pinus sylvestris subspecies and their main insect herbivore; the caterpillar of the processionary moth (Thaumetopoea pityocampa). The caterpillars feeding on distinct pine subspecies presented different overall metabolome structure. Although plants and caterpillars had very distinctive metabolomes, caterpillars showed a certain grade of resemblance to their subspecies-host metabolome. Related to this result, some plant-related secondary metabolites that could potentially be used for self-defense accumulated in caterpillar tissues. In addition, caterpillars feeding on N and P richer pine needles had lower N and P content, and higher C:N and C:P ratios, suggesting that nutrient transfer is not necessarily linear through trophic levels and other plant-metabolic factors should be interfering. We showed how slightly distinct foliar chemical composition between pine subspecies can impact the overall metabolome of specialist caterpillars. Nutritional changes in herbivores could lead to trophic web structure changes.