Causes and consequences of variation in the nutrition and endemic microflora of food stores in managed honey bees (Apis mellifera L.)

Honey bees are pollinators, accounting for around 90% of commercial pollination of animal-pollinated plants and approximately 35% of global food production. Global populations of honey bees have declined significantly recently with heavy losses attributed to Colony Collapse Disorder, pesticides, parasites and pathogens. One of the factors that may be contributing to an increase in susceptibility to these stresses is the quality of food available in a hive. This thesis focuses on the interactions between honey bee nutrition, microbial communities and fitness. In Chapter 2 the nutritional composition of bee bread (pollen stored inside hives) was studied. The composition in terms of protein and reducing sugar was found to vary both spatially and temporally; lipid and starch content was found to vary temporally through the season. The spatial trends in protein content were found to be associated with changes in landscape composition, as estimated by the Countryside Survey database. The implications for these findings are that certain landscape types may produce higher quality diets for honey bees. In Chapter 3, the link between nutritional composition of bee bread and the species of plant that comprise it was investigated. Previous research indicates that pollens vary in their nutritional content and using molecular tools, we investigated the impact of complex plant communities in this system. The number of plant species in bee bread was positively correlated with increasing protein levels, and specifically certain individual plant species were found to be driving this pattern. These results indicate that a more diverse diet of plants will benefit honey bees by increasing their dietary protein intake. The conversion of pollen to bee bread requires the activity of certain microorganisms. In chapter 4, we again used molecular tools to study the microbial community found associated with bee bread. We found a community that was not significantly different between hives located in different areas, but which varied significantly in is composition through the beekeeping season. This suggests that the environment does not determine the bacterial communities in honey bee hives; rather it is being determined by seasonal changes. Finally, in chapter 5 the relationship between the nutritional composition of bee bread and the immunocompetence of larval and adult honey bees was examined. The results showed that dietary protein and carbohydrate is significantly correlated with the overall fitness of a hive in terms of expression a constituent immune response. The link between landscape composition and nutrition established in chapter 2 was used to predict honey bee nutrition across the UK, and then was used to predict immune response for all UK bees. These predictions were comparable to honey bee disease records maintained by UK government. This thesis provides a detailed examination of the effects of landscape composition on honey bee nutrition and immunity. The results presented here have implications for understanding spatial patterns in bee fitness and bee disease epidemiology.