PS 49-156 - Distribution of bees, wasps and flower flies within anthropogenic habitats: Impact of land use and site maintenance

Background/Question/Methods

Land use change and intensive vegetation management practices are major drivers of shifts in insect communities, including ecologically and economically valuable species. We evaluated the impact of agricultural and urban land use and the respective role of lawns and semi-natural meadows to structure and support communities of bees, wasps, and flower flies. We carried out plants and insect inventories on 18 lawns and 18 herbaceous meadows distributed evenly among agricultural, residential, and industrial land use within the Greater Québec city region (Québec, Canada). Insect sampling was conducted five times using bowl traps and entomological nets from early June to mid-September 2020.

Results/Conclusions

Results indicate taxon-specific responses to land use and site maintenance. Agricultural areas were negatively associated with bees (variable over time) and wasps’ abundance and richness, while industrial areas only negatively influenced wasps' abundance and richness. Bees experienced species composition change related to land use: we identified species more associated with agricultural and industrial settings, while residential areas offered an intermediate composition. Bees and wasps were 3 and 7 times more abundant and 2.5 and 5 times more species-rich, respectively, in meadows than in lawns, while it did not differ significantly for flower flies. Lawns support distinct species composition of bees and flower flies, compared to meadows. Some bees (Lasioglossum sp.) and flower flies (Toxomerus marginatus) were related to lawns, while meadows hosted a more balanced community among genera and supported pollinators with wide-ranging resources requirements. Our results suggest that conservation actions must emphasize on landscape management to conserve central-place foragers such as bees and wasps. Moreover, lawns, despite their aesthetic and recreational role, are detrimental to wasps communities and selectively favor a limited number of bees and flower flies species. Our results point to the importance of conserving intricate herbaceous structures, such as meadows, which act as diverse insect reservoirs.