Most angiosperms, or flowering plants, need animals to pollinate them. Insects, and particularly bees, do the lion’s share. Because of this, pollinators such as bees are responsible for much biodiversity. However, in urban areas resources, such as flowers and nesting sites, for bees may be limited. In addition, abiotic aspects of urbanization such as pollution and high temperatures, may create conditions that are in hospitable for bees or cause them stress. In our lab we are investigating the effects of urbanization on honey bees and native bees.
The effects of urbanization on honey bee stress and immune function
Bee populations are in decline worldwide, putting at risk ecosystem functioning in natural and human-dominated landscapes. One of the major drivers of bee decline is the increasing pressure from parasites and pathogens on managed and wild bee populations. Graduate student Holden Appler, research associate Elsa Youngsteadt, and postdoctoral researcher Margarita López-Uribe are investigating the effect of urbanization on the pathogen prevalence and immune function of managed (Apis mellifera) and native bees (Bombus impatiens, Xylocopa virginica, Halictus ligatus, Megachile brevis, Agapostemon virescens).
This team is using laboratory assays to compare the immunocompetency of these managed and wild bee species along a gradient of urbanization. Immunocompetency is the measure of an individual’s ability to resist pathogenic infection, and thus an important component to overall health. In addition, they are using next generation sequencing technology to screen for pathogens in bees.
These novel approaches will lead to the discovery of unknown interactions between bacteria, fungi, microsporidians and bees. Certain factors of urbanization such as urban pesticides and heavy metals have been shown to negatively affect the immunocompetency of some insects, thus increasing their susceptibility to diseases. However, other factors associated with urbanization, such as the urban heat island effect, have had varied responses on immune systems and may differentially affect bee interactions with their multiple pathogenic agents. This research will lead to deeper understanding of the mechanistic impacts of urbanization as they pertain to this highly valued group of species.
The effects of urbanization on native bee communities
Graduate student April Hamblin will be investigating native be communities to determine how composition changes along urbanization gradients. More importantly she will be investigating why these communities change and what aspects of the urban environment make some species rare and other common. Native bees provide pollination services for crops and wild plants.
Urban areas have many different characteristics that affect insects and plants. One that our lab has investigated is hotter temperatures due to the Urban Heat Island effect. Because of this, we are sampling cooler and hotter sites to monitor bee populations with the following questions in mind:
- How do environmental factors (temperature, impervious surface, available green space, sunlight, etc.) in urban areas affect bee community structure in Raleigh, NC?
- Which of these factors is the driving cause of the bee community structure?
We are using bee bowls, small (generally 2-4 oz) plastic cups brightly colored blue, white, and yellow with inflorescence to attract bees. Bee bowls attract bees do to their bright colors. The bees get trapped in soapy water where we can collect and identify them. This is the most effective way to sample bee communities.
This research is at its beginning stages and should evolve once baseline data are collected and monitored. Future aspects of this research may include manipulation of study sites and/or different approaches to analyzing data utilizing GIS and other available resources.