Metabolome and ionome analyses reveal the stoichiometric effects of contrasting geological phosphorus soils on seed-parasitic insects in subtropical oak forests

Abstract

Phosphorus (P)-rich sites develop on phosphate-rock ores, while the soils are generally characterized with P deficiency in subtropical areas, resulting in contrasting nutrient environments for plants and herbivores. It remains unclear how in situ herbivorous insects cope with such two extreme nutrient habitats in terms of metabolome and ionome. Here, we investigated the metabolome and ionome of the weevil larvae (Curculio davidi Fairmaire), which were parasitizing in Quercus variabilis acorns at P-rich and P-deficient sites. Our results showed that there were significant differences in 34 identified metabolites (belonging to sugars, amino acids, lipids, vitamins, nucleosides, etc.) and four chemical elements (P, S, Mg, and Zn) in the two weevil larva populations of the two P-type sites. Moreover, the concentrations of P, Mg, Zn and the identified sugars were significantly higher; however, S, amino acids, and several other N-containing metabolites were lower in the weevil larvae at the P-rich site, in contrast to those at the P-deficient site. Arginine and proline metabolism and glutathione metabolism were the most relevant pathways differentially regulated between the two weevil larva populations at the two contrasting sites. In addition, some metabolites in the weevil larvae were indirectly associated with the P, Mg, Zn, and S concentrations of soils through bottom-up effects. Our results suggested that in situ herbivorous consumers altered their metabolites to a certain extent to adapt to nutrient-varying environments; and there were strong interactions between the nutrients of herbivorous insects and soil elements across variable nutrient sites.