Understanding patterns of variation in insect abundance, diversity, and foraging activity across a gradient of urbanization

Urbanization is a growing threat to biodiversity, and this environmental disturbance has variable effects on species. While some insect species may respond negatively to urban development, others species can benefit from urbanization, thriving in human-dominated ecosystems. Our work examines patterns of insect abundance, diversity, and foraging activity across a gradient of urbanization in Southeast Michigan. Over several years, we have evaluated insects inhabiting a variety of habitats including community gardens, farms, and nature parks. Overall, we found no relationship between urbanization and overall abundances of arthropod pests, their predators, or pollinators. However, for individual taxonomic and functional groups of insects we observed negative, positive, and no effect of urbanization. For some of these insects, temperature, an ecological correlate of urbanization was a key driver of variation in abundances. Additionally, floral resource availability, including both floral diversity and total bloom cover, were key predictors of insect diversity and abundance. In conclusion, our results suggest that enhancement of floral resource diversity and abundance is certainly an important component of insect conservation, although other context-dependent factors such as climate variability and urban warming are also important drivers of variation in insect communities.