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

A One-Health Model for Reversing Honeybee (Apis mellifera L.) Decline

Global insect decline impacts ecosystem resilience; pollinators such as honeybees (Apis mellifera L.) have suffered extensive losses over the last decade, threatening food security. Research has focused discretely on in-hive threats (e.g., Nosema and Varroa destructor) and broader external causes of decline (e.g., agrochemicals, habitat loss). This has notably failed to translate into successful reversal of bee declines. Working at the interdisciplinary nexus of entomological, social and ecological research, we posit that veterinary research needs to adopt a “One-Health” approach to address the scope of crises facing pollinators. We demonstrate that reversing declines will require [1] integration of hive-specific solutions, [2] a reappraisal of engagement with the many stakeholders whose actions affect bee health, and [3] recontextualising both of these within landscape scale efforts. Other publications within this special issue explore novel technologies, emergent diseases and management approaches; our aim is to place these within the “One-Health” context as a pathway to securing honeybee health. Governmental policy reform offers a particularly timely pathway to achieving this goal. Acknowledging that healthy honeybees need an interdisciplinary approach to their management will enhance the contributions of veterinary research in delivering systemic improvements in bee health

Gut microbial community supplementation and reduction modulates African armyworm susceptibility to a baculovirus

Gut microbiota stimulates the immune system and inhibits pathogens, and thus, it is critical for disease prevention. Probiotics represent an effective alternative to antibiotics used for the therapy and prevention of bacterial diseases. Probiotic bacteria are commonly used in vertebrates, although their use in invertebrates is still rare. We manipulated the gut microbiome of the African Armyworm (Spodoptera exempta Walker) using antibiotics and field-collected frass, in an attempt to understand the interactions of the gut microbiome with the nucleopolyhedrovirus, SpexNPV. We found that S. exempta individuals with supplemented gut microbiome were significantly more resistant to SpexNPV, relative to those with a typical laboratory gut microbiome. Illumina MiSeq sequencing revealed the bacterial phyla in the S. exempta gut belonged to 28 different classes. Individuals with an increased abundance of Lactobacillales had a higher probability of surviving viral infection. In contrast, there was an increased abundance of Enterobacteriales and Pseudomonadales in individuals dying from viral infection, corresponding with decreased abundance of these two Orders in surviving caterpillars, suggesting a potential role for them in modulating the interaction between the host and its pathogen. These results have important implications for laboratory studies testing biopesticides

Honeybee nutrition is linked to landscape composition

Declines in insect pollinators in Europe have been linked to changes in land use. Pollinator nutrition is dependent on floral resources (i.e., nectar and pollen), which are linked to landscape composition. Here, we present a stratified analysis of the nutritional composition of beebread in managed honeybee hives with a view to examining potential sources of variation in its nutritional composition. Specifically, we tested the hypothesis that beebread composition correlates with local land use and therefore available floral resources. The results demonstrated that the starch, lipid, and moisture contents of beebread are all highly conserved across hives, whereas levels of protein and nonreducing sugar increased as the year progressed, reducing sugars, however, decreased during the first half of the year and then increased toward the end. Local land use around hives was quantified using data from the Countryside Survey 2007 Land Cover Map. Bee-bread protein content was negatively correlated with increasing levels of arable and horticultural farmland surrounding hives and positively correlated with the cover of natural grasslands and broadleaf woodlands. Reducing sugar content was also positively correlated with the amount of broad-leaved woodland in a 3Km(2) radius from the hives. Previous studies on a range of invertebrates, including honeybees, indicate that dietary protein intake may have a major impact on correlates of fitness, including longevity and immune function. The finding that beebread protein content correlates with land use suggests that landscape composition may impact on insect pollinator well-being and provides a link between landscape and the nutritional ecology of socially foraging insects in a way not previously considered

A little does a lot:Can small-scale planting for pollinators make a difference?

Insect pollinators are declining globally as a result of the anthropogenic pressures that have destroyed native habitats and eroded ecosystems. These declines have been associated with agricultural productivity losses, threatening food security. Efforts to restore habitat for pollinators are underway, emphasizing large-scale habitat creation like wildflower strips, yet ignoring the impact of smaller or more isolated patch-creation. A meta-analysis of 31 independent published studies assessed the effect of scale of pollinator planting interventions (herbaceous strips, hedgerows, fertiliser/grazing/mowing control). We assessed pollinator species richness and abundance against size of intervention and type. Pollinator conservation interventions increased species richness and abundance in almost all of the studies examined, with the greatest increases in pollinator ecological metrics seen from hedgerows covering 40 m² and herbaceous interventions at 500 m². We then analysed results from a 5-year study that deployed small pollinator habitats (30 m²) at community gardens and farms (150,000 m²). Together, we show that small interventions (∼500 m²) can significantly benefit pollinators, but only when sufficiently densely distributed at a landscape level. Though we understand the effects of single interventions at various scales, future research is needed to understand how these relatively small interventions act cumulatively at a landscape scale, and within this context whether larger areas are still needed for some species. Nonetheless, these preliminary data are promising, and may play an important role in convincing smaller landowners to act to preserve insect pollinators

Global insect decline is the result of wilful political failure:A battle plan for entomology

The Millennium Ecosystem Assessment assessed ecosystem change, human wellbeing and scientific evidence for sustainable use of biological systems. Despite intergovernmental acknowledgement of the problem, global ecological decline has continued, including declines in insect biodiversity, which has received much media attention in recent years. Several roadmaps to averting biological declines have failed due to various economic and political factors, and so biodiversity loss continues, driven by several interacting human pressures. Humans are innately linked with nature but tend to take it for granted. The benefits we gain from the insect world are broad, yet aversion or phobias of invertebrates are common, and stand firmly in the path of their successful conservation. Providing an integrated synthesis for policy teams, conservation NGOs, academic researchers and those interested in public engagement, this article considers: (1) The lack of progress to preserve and protect insects. (2) Examples relating to insect decline and contributions insects make to people worldwide, and consequently what we stand to lose. (3) How to engage the public, governmental organizations and researchers through “insect contributions to people” to better address insect declines. International political will has consistently acknowledged the existence of biodiversity decline, but apart from a few narrow cases of charismatic megafauna, little meaningful change has been achieved. Public values are reflected in political willpower, the progress being made across the world, changing views on insects in the public should initiate a much-needed political sea-change. Taking both existing activity and required future actions, we outline an entomologist's “battle plan” to enormously expand our efforts and become the champions of insect conservation that the natural world needs

Asymptomatic Phytoplasma Reveal a Novel and Troublesome Infection

Asymptomatic infections are by their nature challenging to study and even more difficult to monitor across broad geographical ranges, particularly as methods are reliant on expensive molecular techniques. The plant pathogen that causes Witches’ Broom disease of lime (Candidatus Phytoplasma aurantifolia) is a major limiting factor in lime production across the Middle East and was recently detected in Brazil, but without the typical symptoms from the Middle East. Here, we discuss the difficulty of monitoring asymptomatic infections and highlight the threat posed by highlight future outbreaks. Asymptomatic infections have important implications for understanding the evolution of pathogens within perennial hosts. We use three model systems of asymptomatic infections: (i) a Phytoplasma and (ii) a bacterial infection of lime (Citrus aurantifolia) and (iii) an “out-group” Phytoplasma of Cassava (Manihot esculenta) to demonstrate consistency across divergent hosts. We found that although all plants in the study were intentionally infected, assays typically did not confirm this diagnosis. Emergent technologies monitoring gene expression could be used to both study novel biology associated with asymptomatic infections and develop monitoring technologies. We highlight the difficulty of monitoring asymptomatic infections in possible future outbreaks and have important implications for understanding the evolution of pathogens within perennial hosts