Genomic, physiological, and chemical analysis of the impacts of environmental stressors on honey bee (Apis mellifera L.) workers and queens

Honey bee (Apis mellifera L.) populations are experiencing worldwide declines, averaging over 30% mortality each winter. In the US alone, honey bees account for over ;First, I examined the impact of coumaphos (organophosphate) and fluvalinate (pyrethroid), common in-hive miticides used for Varroa mite control, on the queen pheromone production and queen-worker pheromone-mediated communication. My analysis revealed that pesticide exposure had a minor impact. Next, I examined the impact of feeding single source (almond) and multisource (wildflower) pollen on colony growth, juvenile hormone (JH) endocrine pathways, protein levels, queen chemistry, and queen-worker pheromone-mediated communication. I found no impacts of pollen source on colony growth, endocrine pathways, protein levels, or queen-worker interactions. However queens fed wildflower pollen had significantly increased homovanillyl alcohol (HVA, queen pheromone component) content of the queen mandibular glands. It is uncertain what contribution increased levels of HVA is having on the colony; however previous findings have linked HVA with learning and the prevention of aversive behaviors in young workers. Lastly, I conducted a whole-genome microarray study to investigate the impact of coumaphos and fluvalinate on the genomic phenotype and physiology of workers. My analysis revealed a significant change in expression patterns in response to pesticide exposure, including the upregulation of several detoxification genes. Furthermore, pesticide exposure significantly impacted expression of genes associated with behavioral maturation. Subsequent analysis on JH pathways (known to impact behavioral maturation) revealed no change in circulating levels of JH, although I found a significant decrease in the JH precursor methyl farnesoate (MF) in response to pesticide exposure, but the role of MF is unclear. Furthermore, pesticide exposure significantly altered expression of genes associated with honey and pollen consumption. Subsequent nutritional bioassays and molecular analysis found that bees fed pollen had had a significant upregulation of genes whose expression was upregulated by pesticide exposure. Additionally, pollen was found to increase survival when challenged with pesticides compared to bees fed only sucrose. These research findings strengthen our understanding of pesticide and nutritional stress on honey bee health and impact current honey bee management practices. Our understanding of the physiological and behavioral mechanisms of pollen consumption and pesticide exposure will aid in our preservation of further declines in the honey bee population.