Professor Ohio State University, Ohio, United States
Abstract: The Luxury Effect Hypothesis predicts that neighborhoods with a higher median income support a higher plant species richness than lower income areas. This hypothesis suggests that the habitat quality of neighborhoods might vary based on income. We propose that if the Luxury Effect Hypothesis is supported, neighborhoods may vary in habitat quality for insects of conservation concern. Across the US, several species of aphidophagous native lady beetles (Coccinellidae) have exhibited marked declines, coinciding with land use change and the introduction of alien lady beetle competitors over the previous several decades. We have found that populations of many native lady beetle species utilize residential gardens as habitat, where they feed on plant pollen and nectar and forage for prey. Our goal was to determine if the Luxury Effect Hypothesis predicted the species richness and abundance of lady beetles within urban neighborhoods. We predicted that higher income neighborhoods would support a higher species richness and abundance of floral resources and prey, resulting in a greater abundance of lady beetles as compared to lower income neighborhoods. Our approach was to establish 15 greenspace plots across the city of Columbus, Ohio, USA that varied in median household income. Each plot was located at a municipal building such as a school, library or fire station. At each location we collected lady beetles monthly from May-August using unbaited yellow sticky card traps. Each lady beetle collected was counted and identified to species. Vegetation data was collected at each site by randomly selecting two meter squared quadrats and identifying and counting all blooming vegetation in the quadrat. Following our hypothesis, we found total lady beetle abundance was positively associated with socioeconomic status, however this was driven by an abundance of exotic species which followed the same pattern. Native species were exceedingly rare across all sites and had no association to socioeconomic status. Our findings illustrate that the Luxury Effect Hypothesis does extend beyond plant communities to predict the distribution of insects that rely on plants for prey and non-prey foods. In conclusion, our study suggests that wealth is a factor in the ability of insect communities to thrive in urban greenspaces and indicates socioeconomically based inequity in the conservation value of urban greenspaces. Our results suggest that greening investments to support the conservation of lady beetles and other flower feeding insects should focus on lower income neighborhoods within the Columbus, Ohio metropolitan area.
