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.