Insects associated with sweet fennel: beneficial visitors attracted by a generalist plant

Insects provide key ecosystem services such as pollination, dung burial, soil enhancement, and pest control. Global insect decline requires restoration of the plant-insect mutualistic interactions. By using magnet plants, it is possible to supply beneficial insects with better resource availability and create more sustainable habitats. Current management practices recommend using Umbellifers (Apiales, Apiaceae) in restoration projects. However, analyses of the structure and dynamics of entomofauna associated with this plant family is needed to facilitate practical actions. Here the attention is focused on species composition and seasonal dynamics of beneficial insects associated with sweet fennel Foeniculum vulgare (Apiaceae, Umbelliferae) in Crimea. A 2-year sampling campaign identified 60 insect species from 40 genera across 20 families and four orders: Hymenoptera, Diptera, Coleoptera, and Neuroptera. These insects represented the groups such as social wasps, bees, ants, bumble bees, potter wasps, beetles, lacewings, mud daubers, tachinid flies, and hoverflies. Social wasps and hoverflies dominated in sample collections. Most of insects collected benefit ecosystems and provide essential ecosystem services. During fennel's flowering season, the number of visits by bumble bees, beetles, bees. and wasps decreased. Contrastingly, dipterans visitation increased towards the end of the season. Such trends might be explained with fennel's functional protandry, bias in nectar production between male and female flower stages, and insects' feeding preferences. F. vulgare attracts a diverse assemblage of beneficial insects and consequently can be recommended as a magnet species. When aiming to attract specific insect groups, the seasonal dynamics of fennel's associated entomofauna should be considered.