Hoverflies and their diet as indicators for agroecological transformation in the agricultural landscape

Abstract: Since 2019, the project FInAL(Facilitating insects in agricultural landscapes) has been investigating ways to transform the agricultural landscape in Germany into more insect-friendly and insect-promoting environment in order to counteract insect decline and to preserve important ecosystem services (https://www.final-project.de/en/). In three typical German landscapes dominated by arable crops, various measures are being implemented in collaboration with farmers in a co-design process and tested in a living lab approach for their effects on indicator insect groups. Hoverflies are known for their important role in pollination and also in biological control. Therefore, we tracked the response of species assemblage and abundance of hoverfly populations in the agroecologically intensified landscape laboratory compared to the untreated reference landscape through regular monitoring with pan traps. A well-known measure to promote hoverflies is to increase flower resources through flower strips or specific flowering crops. To assess whether these introduced floral resources were utilized in the modified landscape laboratories, we examined the pollen profile in the gut of the captured hoverflies by isolating the pollen and identifying the plant species using metabarcoding. The results showed that the hoverflies indeed utilized the floral resources that had been introduced in the respective living labs.