Urbanization is on the rise worldwide and in the face of global pollinator declines, can have a big impact on ecosystem functioning and services. Yet, little is known about how bee species respond to urbanization. A common way to tackle this question is to address it from a taxonomic view, i.e. species diversity. However, while nearly one third of Missouri’s bee fauna is found within the city of St. Louis, the specific aspects of the environment that bees are responding to are unknown
We studied bees’ functional diversity to investigate patterns of distribution within the city of St. Louis. To assess this, we sampled community gardens and urban farms across a range of habitats within the urban core. Sampling was done in a systematic fashion, weekly from mid May to late September 2013, 2014, 2015 and 2016. We sampled at a rate of 0.25 person per hour hectare for all bee species using aerial nets. Specimens were mounted, labeled and identified to species. Species were separated by functional traits including lecty (generalist or specialist forager), nest location, nest architecture and substrate, body size, abundance, flight period, and sociality. We also documented floral diversity and habitat structure within gardens and surroundings.
Results/Conclusions
Over 100 bee species representing 5 families and 31 genera were collected. Early-mid July to late August was the peak of species abundance and diversity. Bee species richness declined from north to south across the city. Highest species richness was found in the north side where empty lots and abandoned houses surrounded many sites. Alternatively, the south side had the lowest species richness, sites were surrounded by inhabited homes with manicured lawns. Bees collected included generalist (53%) and specialist (26%) foragers, as well as kleptoparasitic (21%); origin: native (92%) and non-native (8%); sociality: solitary (84%) and social (16%); nest location: below (60%) and above ground (40%). Early spring bees were missing, which we believe is due to the lack of spring flowering plant taxa in our collection sites. We argue that using functional-trait diversity in addition to taxonomic diversity will reveal general patterns of distribution within urban areas that will improve our understanding of the distribution of bee species within an urban environment. In addition to understanding how bees are responding to changes in environment, our results have significance for understanding community functioning and ecosystem services in an urban landscape.