Dissertation Research: Drivers of community composition, species interactions, and gene flow in urban landscapes

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Animals contribute to the pollination of 90% of all plant species; therefore they are essential for maintaining healthy ecosystems. Of these animals, bees are some of the most effective and important pollinators of wild plants and their service as pollinators to agricultural systems is worth hundreds of billions of dollars each year. In addition to the familiar domesticated European honeybee, there are at least 20,000 other species of wild bees worldwide. Many of these wild bee populations, however, are declining in number due to human-caused landscape changes, including urbanization. This research explores how urban landscapes alter the types of bee species found in cities, how urban bees use and pollinate native plants, and how different-sized bee species move through urban areas. As a part of this project, researchers will make recommendations to land owners to promote healthy pollinator communities. In addition, this project will enrich the scientific community by employing college and high school students from underserved communities as research assistants. The study will investigate the impacts of urban land use patterns on plant-pollinator interactions using a network analysis approach. The plant-pollinator networks across an urban gradient will be developed through observations of floral visits by bees and the examination of pollen diversity collected from bees found along a gradient of urbanization (40 sites ranging in urban coverage from 0-100 %). As previous observations indicate that urbanized areas contain fewer food resources than rural areas, the researchers predict that bees at urban sites may visit a greater variety of floral species, whereas bees in rural sites may be more specialized in their food choices. To investigate dispersal and colonization patterns within urban landscapes, this study will also examine the genetic make-up of two closely related carpenter bee species. These species are similar in nesting behavior, but vary in size and thus their dispersal potential. The researchers predict that the larger species (Xylocopa virginica) will show fewer genetic signatures of population isolation (ex. inbreeding) than the smaller species (Ceratina strenua) because they can disperse farther through urban areas. Ultimately, results from this study will allow inferences on how pollinators can persist in urban landscapes over time.