Data from: Insect herbivory on native and exotic aquatic plants: phosphorus and nitrogen drive insect growth and nutrient release

Eutrophication and globalisation facilitate the dominance of exotic plants in aquatic ecosystems worldwide. Aquatic omnivores can provide biotic resistance to plant invasions, but little is known about whether obligate aquatic herbivores can do the same. Herbivores such as insects can decimate aquatic vegetation, but may not be able to consume exotic plants due to their more or less specialised nature of feeding. We experimentally tested the larval feeding of an aquatic insect, the moth Parapoynx stratiotata, on eleven submerged plant species, from either native or exotic origin. We also tested whether insect herbivory stimulates nutrient and organic matter release, thus affecting water quality. Larvae of P. stratiotata consumed seven out of eleven plant species, and their growth was related to plant nutrient content and stoichiometry. However, larvae had no preference for either native or exotic macrophytes, and their plant preference was not related to the measured plant traits, but was possibly driven by secondary metabolites. Through plant consumption, caterpillars induced brownification and phosphate release, and the intensity thereof varied among plant species, but not between native and exotic plants. In conclusion, P. stratiotata showed strong feeding preferences demonstrating that aquatic insects can directly and indirectly alter water quality and vegetation composition.

富营养化与全球化进程促使外来植物在全球水生生态系统中占据优势地位。水生杂食动物可对植物入侵产生生物抵抗作用，但目前学界对专性水生植食动物是否具备同等能力尚不清楚。昆虫等植食动物可大量消耗水生植被，但由于其摄食习性多具专化性，或许无法取食外来植物。本研究通过实验，针对水生昆虫Parapoynx stratiotata的幼虫取食行为展开测试，供试材料包含11种沉水植物，分属本土与外来起源；同时还检验了该昆虫的植食作用是否会促进营养物质与有机质释放，进而影响水质。实验结果显示，Parapoynx stratiotata的幼虫可取食11种植物中的7种，其生长状况与植物营养含量及化学计量比密切相关。不过，幼虫对本土或外来大型水生植物并无取食偏好，其取食偏好与所测定的植物性状无关，推测可能受植物次生代谢产物驱动。通过取食植物，幼虫可诱导水体发生褐变并促进磷酸盐释放，且该效应的强度因植物种类而异，但在本土与外来植物间未表现出显著差异。综上，Parapoynx stratiotata表现出显著的取食偏好，这表明水生昆虫可直接或间接改变水质与植被组成。