Many studies have addressed several plant-insect interaction topics at nutritional, molecular, physiological, and evolutionary levels. However, it is still unknown how flexible the metabolism and the nutritional content of specialist insect herbivores feeding on different closely related plants can be. We performed elemental, stoichiometric, and metabolomics analyses on leaves of two coexisting Pinus sylvestris subspecies and on their main insect herbivore; the caterpillar of the processionary moth (Thaumetopoea pityocampa). Caterpillars feeding on different pine subspecies had distinct overall metabolome structure, accounting for over 10% of the total variability. Although plants and insects have very divergent metabolomes, caterpillars showed certain resemblance to their plant-host metabolome. In addition, few plant-related secondary metabolites were found accumulated in caterpillar tissues which could potentially be used for self-defense. Caterpillars feeding on N and P richer needles had lower N and P tissue concentration and higher C:N and C:P ratios, suggesting that nutrient transfer is not necessarily linear through trophic levels and other plant-metabolic factors could be interfering. This exploratory study showed that little chemical differences between plant food sources can impact the overall metabolome of specialist insect herbivores. Significant nutritional shifts in herbivore tissues could lead to larger changes of the trophic web structure.

• Keywords
• herbivory, metabolomics, plant-insect, processionary moth, scots pine, secondary metabolites, stoichiometry,
• MeSH
• Principal Component Analysis MeSH
• Pinus sylvestris metabolism   parasitology   MeSH
• Herbivory MeSH
• Species Specificity MeSH
• Nitrogen analysis   MeSH
• Phosphorus analysis   MeSH
• Mass Spectrometry MeSH
• Host-Parasite Interactions MeSH
• Larva chemistry   physiology   MeSH
• Plant Leaves chemistry   metabolism   parasitology   MeSH
• Metabolome * MeSH
• Metabolomics * MeSH
• Moths growth & development   physiology   MeSH
• Feeding Behavior MeSH
• Chromatography, High Pressure Liquid MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Nitrogen MeSH
• Phosphorus MeSH

Metabolomes, as chemical phenotypes of organisms, are likely not only shaped by the environment but also by common ancestry. If this is the case, we expect that closely related species of pines will tend to reach similar metabolomic solutions to the same environmental stressors. We examined the metabolomes of two sympatric subspecies of Pinus sylvestris in Sierra Nevada (southern Iberian Peninsula), in summer and winter and exposed to folivory by the pine processionary moth. The overall metabolomes differed between the subspecies but both tended to respond more similarly to folivory. The metabolomes of the subspecies were more dissimilar in summer than in winter, and iberica trees had higher concentrations of metabolites directly related to drought stress. Our results are consistent with the notion that certain plant metabolic responses associated with folivory have been phylogenetically conserved. The larger divergence between subspecies metabolomes in summer is likely due to the warmer and drier conditions that the northern iberica subspecies experience in Sierra Nevada. Our results provide crucial insights into how iberica populations would respond to the predicted conditions of climate change under an increased defoliation in the Mediterranean Basin.

• Keywords
• Pinus sylvestris, drought, evolutionary processes, folivory, herbivorous attack, metabolomics, processionary moth, sympatric subspecies,
• Publication type
• Journal Article MeSH