Bee communities throughout the St. Louis metropolitan area: Time, area and management

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Emily G. Morris, Biology, Saint Louis University, Saint Louis, MO and Gerardo R. Camilo, Biology, Saint Louis University, St. Louis, MO

Background/Question/Methods
Historically, studies have shown that cities support lower diversity of many animal and plant groups than rural and natural areas. Yet, emerging data suggests that bee communities can deviate from this pattern, resulting in high bee species diversity in cities. In the city of St. Louis, MO, USA, we have identified over 200 species of bees, representing over 45% of the species in the state, and 55% of the regional species pool. With current pollinator declines, it is increasingly important to understand the drivers of urban bee diversity. Therefore, we are interested in why St. Louis harbors such high levels of bee diversity. We hypothesize that local bee diversity is influenced not only by habitat size and time since establishment but also by the site’s management type. Community assemblages were determined from specimens in the Saint Louis University insect collection. Sites selected for analysis were sampled a minimum of five times between 2014 and 2017 and had over 100 specimens. We used cluster analysis to determine community similarities and species turnover across locations. We then applied non-metric multidimensional scaling (NMDS) to ascertain the correlations among management types (urban farm, community garden, and native vegetation) and species.
Results/Conclusions
We identified 122 species within five families from 7,771 bee specimens collected across seventeen sites. Local species richness ranged from 20 to 59, with the social sweat bee, Halictus ligatus, and the Eastern carpenter bee, Xylocopa virginica, being the most common species.
Management type accounted for the greatest dissimilarity between bee communities, with urban farms having a higher species richness than the other management types. Area and age since establishment also led to dissimilarity, as urban farms were typically older and larger while community gardens and areas of native vegetation were smaller and more recently established. Two exceptions existed––a remnant prairie and a large community garden––with both being more similar to urban farms. Geography also appeared to account for further dissimilarities among urban farms and between community gardens and native vegetation sites.
While this study is preliminary, the results point towards the importance of site management and size for a taxonomically diverse bee community. This knowledge will guide my work as I seek to understand and explain why high bee community diversity is possible in urban areas.