Immunocompetency and oxidative stress resistance of honey bee, Apis mellifera, populations across the urbanization gradient

Urbanization is one of the greatest forces of environmental change affecting the world today.  The impact of urbanization on ecosystem services such as pollination requires particular attention in order to sustain world populations.  The western honey bee, Apis mellifera, is of great importance both ecologically and economically, with recent disease instances demonstrating the necessity for a thorough understanding of their health state. Immunocompetency is the measure of an individual’s ability to resist pathogenic infection, and thus an important component to overall wellness.  Certain factors of urbanization such as urban pesticides and heavy metals have been shown to negatively affect the immunocompetency of some insects, while other factors, such urban heat island effect have had  varied responses.  Oxidative stress may also be influenced by urbanization, particularly associated with pollutants.  The objective of this research is to determine how urbanization affects the immune system and ability to withstand oxidative stress for A.  mellifera.  Bees were collected from feral and managed colonies through an urbanization gradient: urban zone, suburban zone, and rural zone.  Additionally, managed hives were strategically placed to maximize the exposure to each urbanization zone.  Immunocompetency was evaluated via measuring the encapsulation response, phenol oxidase activity, and antimicrobial turbidity analysis.  qPCR was used to determine constitutive and induced response immune activation, as well as the pathogen load for several notable diseases.  This research provides a deeper understanding of the mechanistic impacts of urbanization as they pertain to this highly valued species.