Explaining the wide range of animal colouration in the natural world is a key issue in evolutionary biology. Bumble bees are often brightly coloured and show a range of colours and colour patterns in different species as well as considerable variation within species. The large garden bumble bee, Bombus ruderatus, is highly variable in its degree of black (melanic) colouration, with morphs ranging from the familiar yellow and black bands (banded) through intermediate forms to morphs that are totally melanic. The aim of this research was to determine what might be maintaining the colour polymorphism in populations of B. ruderatus in the South Island, New Zealand. Colouration of worker bees was measured using a digital photography method and found to be significantly different across sample sites. To look at potential adaptive functions of body colour in B. ruderatus, three hypotheses of thermoregulation, desiccation tolerance and Müllerian mimicry were tested by comparing patterns of variation in melanism to patterns of variation in climatic variables (temperature, rainfall, humidity) and abundance of conspecifics. In order to address the possibility that selectively neutral processes were more important than selection, the genetic structure of B. ruderatus populations was characterised and compared to the pattern of variation in melanism. The colouration of individuals from the same population collected at different times in the season was compared to evaluate whether body colour was plastic and any support for the genetic basis of melanism in B. ruderatus was also assessed by determining any relationship between relatedness and degree of melanism. The results suggest that differences in the degree of melanism between populations are greater than the differences expected through selectively neutral forces alone and, therefore, that the pattern of variation in melanism is likely a result of selection and/or phenotypic plasticity in addition to gene flow and genetic drift. Although a global model consisting of four climatic variables and the abundance of conspecifics explained a small proportion of the variation in melanism, no support was found for any specific hypothesis relating to the adaptive function for body colour. Instead the results suggest that some combination of factors, most likely including factors not measured in this study, is influencing the frequency of melanic morphs. In addition, there was evidence that body colour was influenced by phenotypic plasticity and that melanism has a low heritability in B. ruderatus. Taken together, these results imply that patterns of melanism across B. ruderatus populations are complex and it is likely that multiple factors are influencing melanism in concert.

Biological and cultural control tactics are available for many agricultural pests but insecticides still play an important role in the rapid reduction of pest incidence when damage reaches economic levels. Laboratory and field toxicities of the reduced-risk products spinetoram and flubendiamide to Itame argillacearia (blueberry spanworm) was compared to deltamethrin, a conventional synthetic pyrethroid insecticide. In laboratory experiments, I. argillacearia larvae were highly susceptible to spinetoram and flubendiamide, and efficacy in the field was comparable to that of deltamethrin. Lethal and sublethal effects of the biopesticide formulations of Beauveria bassiana and Bacillus subtilis, and spirotetramat, a new tetramic acid insecticide, to bumble bees, Bombus impatiens, were also assessed. When ingested, field rates of spirotetramat caused high mortality after a week, and B. subtilis significantly reduced drone production. Field rates of spirotetramat, when applied topically, reduced drone production, but drone production varied following topical treatments of either biopesticide.

Pollinator-driven selection is thought to drive much of the extraordinary diversity of flowering plants. Plants that produce floral traits preferred by particular pollinators are more likely to receive conspecific pollen and to evolve further adaptations to those pollinators that enhance pollination and ultimately generate floral diversity. Two mechanisms in particular, sensory bias and learning, are thought to explain how pollinator preference can contribute to divergence and speciation in flowering plants. While the preferences of pollinators, such as bees, flies, and birds, are frequently implicated in patterns of floral trait evolution, the role of learning in generating reproductive isolation and trait divergence for different floral types within plant populations is not well understood. Floral color polymorphism in particular provides an excellent opportunity to examine how pollinator behavior and learning might maintain the different floral morphs. In this study we asked if bumble bees showed innate preferences for different color morphs of the pollen-only plant Solanum tridynamum, whether bees formed preferences for the morphs with which they had experience collecting pollen from, and the strength of those learned preferences. Using an absolute conditioning protocol, we gave bees experience collecting pollen from a color polymorphic plant species that offered only pollen rewards. Despite initially-naïve bees showing no apparent innate bias toward human-white versus human-purple flower morphs, we did find evidence of a bias in learning. Specifically, bees learned strong preferences for purple corollas, but learned only weak preferences for hypochromic (human-white) corollas. We discuss how our results might explain patterns of floral display evolution, particularly as they relate to color polymorphisms. Additionally, we propose that the ease with which floral visual traits are learned—i.e., biases in learning—can influence the evolution of floral color as a signal to pollinators.

The astonishing diversity of floral form in angiosperm plants is driven in large part by preferences of pollinators for various floral traits, including learned preferences. Remarkably, almost all of a vast literature on learning and memory in pollinators relates to nectar as a reward, even though bees and many flies, beetles, and butterflies must collect pollen. In this study, we asked if bees formed preferences for plant species from which pollen had been collected successfully. Using absolute conditioning, we gave pollen foraging bees experience with plant species that offered only pollen rewards. Naive bees generally showed modest preferences, whereas experienced bees adopted strong preferences for those species over alternative species not previously experienced. Learned preferences were retained for at least 24 h, consistent with preferences learned with nectar rewards. These experience-mediated changes in preference raised the possibility that bees formed associations between particular floral features and pollen rewards. We therefore asked if learned preferences required that bees successfully collect pollen. Using differential conditioning, we determined that learned preferences were strongly influenced by receipt of a pollen reward. In a final experiment, we characterized the importance of 2 floral features, the corolla and the anther, in the expression of learned preferences. Although experience altered responses to both floral parts, responses to anthers were influenced more strongly. We discuss recent evidence in the literature for associative learning with pollen rewards and propose that learned preferences in the context of pollen collection have played an important role in floral display evolution.

In 2011, several wild North American bumble bee pollinator species were reported to have declined by up to 96% in relative abundance in comparison to historic estimates, and one species was speculated to be extinct. None of these species have yet been documented to have recovered from these declines and additional species are now suggested to be at risk. Imperiled species in particular show increased specificity to narrow climatic envelopes, as opposed to putatively stable species. My dissertation describes patterns of population genetic diversity, structure, and gene flow pathways associated with climate variation and historical biogeography of bumble bees distributed in western North America. The results of my dissertation research suggests that (1) historic climate variability predicts contemporary patterns of population genetic structure and divergence in an economically important species, (2) color variability in bumble bees is likely associated with lineage diversification and phylogeography, (3) bumble bee community structure across evolutionary time is likely driven by Müllerian mimicry at narrow spatial scales, and (4) bumble bees inhabiting specialized ecological niches are associated with high levels of genetic fixation at regional spatial scales in the Pacific Northwest. The results of my research directly contribute to current efforts to effectively manage, conserve, and advocate for wild bumble bee pollinators in the context of global change.

Neonicotinoid exposure has been recognised as potentially impacting upon bee health, but whether realistic exposure scenarios are driving declines in bee health is not known. This thesis contributes new insights and perspectives to this research field investigating the use of molecular, physiological and behavioural endpoints as potential ecotoxicological markers for pesticide risk assessment. The thesis presents experimental data for dietary exposures of the European honey bee, Apis mellifera, and the buff-tailed bumble bee, Bombus terrestris, to one of two neonicotinoid pesticides, imidacloprid and thiamethoxam. The first part of this thesis explores impacts of chronic dietary exposures to neonicotinoid pesticides on bee immunocompetence- the ability to mount an immune response- using an artificial challenge to invoke an immune response in adult workers. Levels of phenoloxidase, an enzyme involved in melanisation and part of the bee’s defence system, were largely constitutive and resilient to exposure in honey bees and bumble bees. In honey bees, transient transcriptional changes in antimicrobial effector genes were observed following neonicotinoid exposure, but the physiological antimicrobial response was unaffected. In bumble bees, the induced antimicrobial response was impaired following neonicotinoid exposure, but only when exposed to concentrations likely higher than realistic environmental exposure scenarios. The next phase of this thesis investigates whether transcriptional, physiological and behavioural endpoints associated with the functioning of the honey bee hypopharyngeal gland were altered by imidacloprid exposure. Imidacloprid exposure led to transcriptional changes in foraging genes (associated with the control of temporal polyethism) and major royal jelly proteins (fed to developing larvae by nurse workers) and enzymatic changes in glucose oxidase (an enzyme involved in social immunity), which I hypothesise are linked with hypopharyngeal gland development. Despite these laboratory observations, no behavioural effects were observed in a field setting, monitored using Radio Frequency Identification transponders. Lastly, using RNA-Sequencing to investigate changes across the honey bee transcriptome, this thesis identified a suite of genes that were differentially expressed in adult workers in response to immune challenge and/or dietary neonicotinoid exposure. Wounding and bacterial-like infection led to upregulation of known immune genes, including a peptidoglycan recognition protein and antimicrobial effectors. Chronic exposure to thiamethoxam and imidacloprid led to downregulation of genes associated with several metabolic pathways, such as oxidative phosphorylation, pyruvate- and purine- metabolic pathways, as well as ribosomal activity. Some of these genes identified provide candidates for further study to elucidate functional effects mechanisms and better understand health outcomes, as well as potential new biomarkers for use in pesticide risk assessment. This thesis presents novel findings and offers opportunities for future research that will be of interest to a wide audience, including risk assessors and policy makers, as well as the broader biological community, including ecotoxicologists, insect physiologists and molecular biologists.

The last decade has seen a pronounced increase in feminist activism and sentiment in the public sphere, which scholars, activists, and journalists have dubbed the “fourth wave” of feminism. A key feature of the fourth wave is the use of digital technologies and the internet for feminist activism and discussion. This dissertation aims to broadly understand what is “new” about fourth wave feminism and specifically to understand how social media intersect with everyday feminist practices in the digital era. This project is made up of three case studies –Bumble the “feminist” dating app, private Facebook groups for women professionals, and the #MeToo movement on Twitter— and uses an affordance theory lens, examining the possibilities for (and constraints of) use embedded in the materiality of each digital platform. Through in-depth interviews and focus groups with users, alongside a structural discourse analysis of each platform, the findings show how social media are used strategically as tools for feminist purposes during mundane online activities such as dating and connecting with colleagues. Overall, this research highlights the feminist potential of everyday social media use, while considering the limits of digital technologies for everyday feminism. This work also reasserts the continued need for feminist activism in the fourth wave, by showing that the material realities of gender inequality persist, often obscured by an illusion of empowerment. / Media & Communication

Body size is a universal property affecting biological structure and function, from cell metabolism to animal behavior. The nervous system, the physical generator of behavior, is also affected by variations in body size; hence potentially affecting the way animals perceive, interpret and react to the environment. When animals join to form groups, such individual differences become part of the structure of the society, even determining social roles. Here, I explore the association between body size, behavior and social organization in honeybees and bumblebees. Focusing on bumblebees, I explore the link between body size, brain allometry and learning and memory performance, within the context of task specialization. I show that body size goes along with brain size and with learning and memory performance, and that foraging experience affects such cognitive and neural features. Next, I explore the association between body size and foraging task specialization in honeybees. Previous evidence showed a link between specialization on pollen or nectar foraging and sensory sensitivity, further associating sensitivity to the quality and/or quantity of resource exploited. I hypothesize that, as in solitary bees, larger body size is associated with higher sensory sensitivity. I test this hypothesis by comparing body size and the quality and quantity of the resource exploited by wild Africanized and European honeybees. I show that nectar foragers are smaller and have fewer olfactory sensilla, which might underlie their lower sensitivity to odors. Also, larger bees collect more pollen (within pollen foragers) and more dilute nectar (within nectar foragers). To further test this `size hypothesis', I compare strains of bees selected to store large ("high strain") or small ("low strain") amounts of pollen surplus. As these strains differ in sensory sensitivity, I predict that the more sensitive high strain bees are larger and have more sensory sensilla. I show that high strain bees are generally bigger, but have fewer sensory sensilla than low strain bees. These results show that in bees, body size is associated with an individual's sensory, neural and cognitive features, further suggesting that body size plays a more important role in the organization of bee societies than generally assumed.

Animals in general vary immensely in body size, which greatly affects their morphology, physiology, survival, and nutritional requirements. The nervous system is also affected by variation in body size, which, in turn, shapes the perception of environmental stimuli and the behavior of animals. Comparative studies of vertebrates suggest that larger brains and their integrative centers comprise more and generally larger neurons (Jerison, 1973; Kaas, 2000), but much less is known about brain - body size relations in invertebrates. Closely related social bee species are well suited to study correlations between body size and brain composition. Different honey bee species vary in body size yet differ little in their ecological requirements and behavior and bumble bees feature a large range of body sizes even within a single colony.

The inadvertent spread of exotic pests and pathogens has resulted in devastating losses for bees. The vast majority of bee disease research has focused on a single species of managed bee, the European honey bee (Apis mellifera). More recently, pathogen spillover from managed bees is implicated in the decline of several bumble bee species (Bombus spp.) demonstrating a need to better understand the mechanisms driving disease prevalence in bees, transmission routes, and spillover events. RNA viruses, once considered specific to honey bees, are suspected of spilling over from managed honey bees into wild bumble bee populations. To test this, I collected bees and flowers in the field from areas with and without honey bee apiaries nearby. Prevalence of deformed wing virus (DWV) and black queen cell virus (BQCV) as well as replicating DWV infections in Bombus vagans and B. bimaculatus were highest in bumble bees collected near honey bee apiaries (χ 12 < 6.531, P < 0.05). My results suggest that honey bees are significant contributors of viruses to bumble bees. Flowers have been suspected as bridges in virus transmission among bees. I detected bee viruses on 18% of the flowers collected within honey bee apiaries and detected no virus on flowers in areas without apiaries, thus providing evidence that viruses are transmitted at flowers from infected honey bees. In controlled experiments using captive colonies in flight cages, I found that honey bees leave viruses on flowers but not equally across plant species. My results suggest that there are differences in virus ecology mediated by floral morphology and/or pollinator behavior. No bumble bees became infected in controlled experiments, indicating that virus transmission through plants is a rare event that is likely to require repeated exposure. The few studies examining viruses in bumble bees are generally limited to virus detection, resulting in little understanding of the conditions affecting virus titers. In honeybees, infections may remain latent, capable of replicating under certain conditions, such as immunosuppression induced by pesticide exposure. I tested whether exposure to imidacloprid, a neonicotinoid pesticide, affects virus titers in bumble bees. In previous honey bee studies, imidacloprid exposure increased virus titers. In contrast, I found that bumble bee exposure to imidacloprid decreased BQCV and DWV titers (χ42 < 20.873, p < 0.02). My findings suggest that virus-pesticide interactions are species-specific and results from honey bee studies should not be generalized across other bee species. Having found that honey bees are significant contributors of viruses to wild bees and flowers, I investigated how honey bee management practices affect disease spread and developed recommendations and tools to lesson the risk of spillover events. Honey bee disease may be exacerbated by migratory beekeeping which increases stress and opportunities for disease transmission. I experimentally tested whether migratory conditions contribute to disease spread in honey bees and found negative yet varying effects on bees suggesting that the effects of migratory practices may be ameliorated with rest time between pollination events. State apiary inspection programs are critical to controlling disease spread and reducing the risk of spillover. However, these programs are often resource constrained. I developed and deployed a toolkit that enables state programs to prioritize inspections and provide a platform for beekeeper education. Using novel data collected in Vermont, I discovered several promising avenues for future research and provided realistic recommendations to improve bee health.