Metabolomic insights into host specialization and nutritional adaptation in a specialist root-feeding insect

Nutritional ecology plays a pivotal role in shaping the evolution and host specialization of insect herbivores. Specialist herbivores often rely on a narrow range of host plants that provide essential nutrients required for development and reproduction. The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is a root-feeding herbivore that specializes exclusively on maize (Zea mays), causing an estimated $2 billion in annual yield losses and control costs in the United States and parts of Europe. To investigate the metabolomic responses underlying WCR host specialization, we performed global metabolomic profiling of WCR larvae and adults fed on maize, wheat, wheatgrass, and oats. Additionally, we characterized the nutritional landscape of maize roots across four developmental stages (V2, V7, V18, and R2). No larvae survived on oats, and fewer larvae and adults survived in wheat and wheatgrass compared to maize. Larval and adult tissues were extracted using methanol and analyzed via ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) interfaced with a heated electrospray ionization (HESI-II) source and Orbitrap mass analyzer, resulting in the detection of over 700 unique metabolites, ~80% of which were confirmed using authentic standards. Comparative analyses revealed distinct metabolic profiles associated with maize feeding, including amino acids, carbohydrates, sterols, vitamins, and trace minerals critical for WCR development. Several maize-specific compounds and key nutritional pathways were identified as potential determinants of WCR specialization. These findings provide insights into the nutritional constraints and evolutionary ecology of a major agricultural pest and provide a foundation for designing targeted, nutrition-based control strategies.