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.

富营养化与全球化促进了全球水生生态系统中外来植物的优势地位。水生杂食动物可对植物入侵产生生物抗性，但目前对专性水生植食动物是否具备同等能力仍知之甚少。诸如昆虫类的植食动物可大量损毁水生植被，但由于其取食特性或多或少存在特化，可能无法取食外来植物。本研究以水生昆虫水螟蛾（Parapoynx stratiotata）的幼虫为研究对象，通过实验探究其对11种分别源自本土与外来的沉水植物的取食行为；同时检测了昆虫植食作用是否会促进营养物质与有机质的释放，进而对水质产生影响。结果显示，水螟蛾幼虫可取食11种植物中的7种，其生长速率与植物的营养成分含量及化学计量特征密切相关。但幼虫对本土或外来大型水生植物并无取食偏好，且其取食偏好与所测定的植物性状并无关联，推测其偏好可能由次生代谢产物驱动。幼虫通过取食植物可诱导水体发生褐变并促进磷酸盐释放，该效应的强度因植物物种而异，但在本土与外来植物间并无显著差异。综上，水螟蛾幼虫表现出显著的取食偏好，这表明水生昆虫可通过直接与间接途径改变水质与植被群落组成。