Bumble bees and other wild pollinators are crucial to the support of both natural and agricultural ecosystems. However, unprecedented declines of pollinator populations have been observed all over the world, raising concerns of a looming threat to both the human food supply, as well as sustainability of the biodiversity in local ecological niches. Though declines are well described, the cause behind these still evades scientists. Proposed contributors include anthropogenic-mediated environmental stress, including application of xenobiotics for pest control, and increase of pathogen diversity and abundance due to the shipment of infection human-managed colonies. This research examined these theories and attempted to quantify the threats they may pose. Through development of a chronic, oral toxicity experiment, susceptibility of all Bombus impatiens castes to clothianidin exposure was examined. This exposed a substantial increase in vulnerability of male bumble bees to realistic concentrations of neonicotinoid pesticides, highlighting the crucial need to examine all members of wild bumble bee life cycles before determining pesticide regulations. Additionally, sublethal effects on fitness-related foraging behaviors in Bombus impatiens were examined through development of a voluntary task switching assay. The results of this experiment suggest humoral immune stimulation, through pathogenic infection, leads to significant impairment of cognitive flexibility. Taken together, this data suggests that pesticides and pathogens are capable of causing severe detrimental effects, both lethally and sublethally, in wild bumble bees. I hope this data will eventually contribute to reassessment of environmental regulations and establishment of effective conservation strategies in order to sustain the critical populations of wild bumble bees.

Land use change is a major driver of species loss worldwide, the extent and intensity of agricultural land use poses particular pressures for biodiversity and the ecosystem services it provides. In recent years, agroecosystems have seen the introduction of 2nd generation bioenergy crops in order to tackle anthropogenic climate change, providing a renewable alternative to fossil fuels. In this thesis I study the impact of cultivating two commercial perennial energy crops (PECs), Miscanthus x giganteus and willow short-rotation coppice, when compared to the cereal crops they replace. I investigate processes relevant to the provisioning of pollination and decomposition services and explore patterns of soil element bioaccessibility alongside analyses of the similarity and diversity of soil bacterial communities. When compared to cereals, I find a consistent increase in pollinator (hoverfly, bumblebee and butterfly/moth) wildflower visitation in the margins of willow but not Miscanthus. In Miscanthus, opposing trends arose for different pollinator taxa: butterflies/moths were more frequent flower visitors in Miscanthus margins than cereal margins, while hoverfly flower visits were most frequent in cereal margins. Furthermore, the availability of margin wildflowers was enhanced in willow but not Miscanthus and the seed set of margin phytometers was similar between Miscanthus and cereals. Cultivation of willow, in particular, may therefore yield local conservation benefits for both wildflowers and pollinators. However, there was no evidence for enhancement of pollinator activity in cereals adjacent to either PEC, indicating that the strategic cultivation of these crops is unlikely to enhance pollinator service provision in the wider agri-environment. For investigated soil elements, bioaccessibility in PECs did not differ significantly to cereal controls, and denaturing gradient gel electrophoresis (DGGE) revealed no difference in the diversity of bacterial communities. Similarly, DGGE fingerprint patterns did not indicate the development of crop specific assemblages, demonstrating that the mobility of soil elements and structure of bacterial communities were principally determined by factors other than the identity of the crop cultivated. Investigation of meso-microfaunal decomposition rates in Miscanthus using litter bags demonstrated an impact on decomposition processes, with a significant increase in winter decomposition rates in the PEC when compared to cereals.

Public awareness of declining pollinator populations has increased interest in creating “bee–friendly” urban landscapes. I quantified bee visitation and assemblages of 72 species of flowering woody plants common in urban landscapes. I found strong plant species effects and variation in seasonal activity of particular bee taxa but no overall differences in bee visitation or genus diversity between native versus nonnative species or trees versus shrubs. Analysis of pollen from a subset of these plants revealed small but statistically significant differences in total and essential amino acids between native and nonnative species and trees and shrubs, although each group had species with high quality pollen. Uptake and dissipation of soil–applied imidacloprid and dinotefuran was measured in nectar and leaves of two woody plant species, Ilex × attenuata and Clethra alnifolia to assess concentrations to which pollinators might be exposed in landscape settings. Three application timings were evaluated. Residues in nectar and tissue were analyzed by HPLC–MS/MS in two successive years. Residues in nectar following autumn or spring applications exceed concentrations shown to adversely affect individual and colony–level traits of bees. Summer application mitigated concentrations of imidacloprid (8–31 ng/g), but not dinotefuran (235–1191 ng/g), in nectar.

Aciphylla species (wild spaniard/speargrass) are an iconic component of the Australasian high country flora, but their reproductive system is enigmatic. They are insect-pollinated dioecious mast seeders (synchronous highly variable seed production), which seems maladaptive. The resource supply to pollinators is highly variable, yet dioecious plants are dependent on pollinators, and dioecious masting requires male and female plants to flower synchronously. Floral display in Aciphylla is relatively large, with tall inflorescences bearing thousands of flowers, suggesting that plants would not have the resources to produce such large stalks every year. But why do they have such huge inflorescences in the first place? I tested whether pollinator attraction is providing an economy of scale which favours intermittent production of very large inflorescences, by manipulating floral display size during a high-flowering year and measuring insect visitation rates and seed set (female reproductive success). Using space-for-time substitution and selective removal of male inflorescences, I also tested whether female seed set was affected by distance to flowering male plants (i.e. changes in local pollen availability) to see if flowering asynchrony would reduce pollination success. Bags were used to exclude pollination by insects and test for wind pollination, and hand pollination was done to test for pollen limitation. Insect surveys suggest that Aciphylla has a generalist pollination system (to avoid satiating a specialist pollinator during 'mast' years'). Male inflorescences received significantly more visits than females, and some seeds were set inside bags (although only 20-30%), suggesting wind pollination may occur at low levels. Seed set rate was higher for taller inflorescences with greater flowering length in A. aurea but tall inflorescences with excess flowers led to a decrease in seed set rates in A. scott-thomsonii. Hand pollination significantly increased seed set rates although these effects were not as large as expected (e.g. 10% increases from natural to hand-pollinated inflorescences were typical). There was no evidence for resource limitation in any species. Female plants in dense flowering populations had higher seed set rates, and individual floral display size in females was particularly important when females were 'isolated' from males. Insect visitation rates were generally higher on inflorescences with a larger floral display, suggesting that display size is important for pollinator attraction. Overall, these results suggest that the pollinator-attraction benefits of such a large floral display (at both the plant and population level) are possibly providing an economy of scale, although the relative effects are small.

Várias podem ser as causas da variação local no sucesso reprodutivo de espécies vegetais, sendo a disponibilidade de recursos abióticos, herbivoria, polinização e dispersão de sementes comumente consideradas. Em espécies distílicas, a variação na disponibilidade de recursos abióticos pode determinar diferenças na quantidade e no período de produção das estruturas reprodutivas, e estas por sua vez podem influenciar a interação planta polinizador, modulando o comportamento de forrageio de visitantes florais. Este trabalho teve como objetivos verificar como alguns fatores poderiam determinar variação na fenologia e no sucesso reprodutivo de Psychotria suterella, uma espécie arbórea distílica comum em florestas no sudeste do Brasil. Os fatores experimentalmente investigados foram água, luz, nutrientes inorgânicos e superfície foliar. Além disto, investigamos a resposta de abelhas Bombus, B. brasiliensis e B. morio, à disponibilidade de recursos florais em quatro escalas espaciais. A variação na oferta de recursos não afetou o padrão temporal sincrônico de emissão de botões e desenvolvimento de flores dos tipos florais de P. suterella, mas condicionou alterações na quantidade das estruturas reprodutivas produzidas de forma distinta em cada tipo floral. Plantas com morfologia floral longistila parecem estar se reproduzindo sob condições ambientais limitantes, em função de responderem positivamente ao aumento na disponibilidade de recursos, enquanto plantas com morfologia floral brevistila parecem estar melhor adaptadas às condições ambientais, uma vez que responderam negativamente a todos os tratamentos. Respostas fisiológicas singulares parecem ser as responsáveis por essas diferenças. Não houve variação no número de flores, energia produzida no néctar das flores e freqüência de visitas a flores e plantas para os tipos florais de P. suterella. A oferta de energia por flor e a freqüência de visitas por flor variaram entre plantas. Bombus morio e Bombus brasiliensis responderam à variação na disponibilidade de recursos florais de P. suterella em escala espacias menores que 5m, visitando com mais freqüência plantas com maior oferta de energia, independente da disponibilidade energética na vizinhança. Porém, a freqüência de visitas média por flor não apresentou relação com a quantidade de recursos florais nas plantas, e não foi influenciada pela densidade de energia nas demais escalas, fato que deve estar relacionado à grande variação na produção de néctar entre as flores dentro de uma mesma planta. / Several factors might cause intrapopulational variation in plant reproductive success, being often mentioned abiotic resource availability, herbivory, pollination and frugivory as possible factors. In distylous species, the variation on abiotic resources availability can determine differences in quantity as well as in the moment of emisssion of reproductive structures. Those structures might influence the plant-pollinator interaction, modeling foraging behaviour of floral visitors. The aims of this study were to identify how variation in some abiotic resources change the phenology and reproductive success of Psychotria suterella, a common distylous species from Brazilian southeastern forests. We experimentally changed the amounts of light, water, inorganic nutrients and foliar surface. In addition, we measured the frequency of Bombus, B. brasiliensis and B. morio, in relation to floral density at four spatial scales. The variation in abiotic resources availability did not change the temporal pattern of flowering in both, pin and thrum morphs, although bud and flower number was different. Pin plants seemed to be under restrict environmental conditions because the addition of resources increased the number of reproductive structures. On the other hand, any alteration in environmental resources affected negativelly thrum plants. We did not register variation in flower number, energy production in nectar, plant and flower visitation rates for both P. suterella floral morphs. Energy supply per flower and flower visitation rates varied among plants. Bombus morio and Bombus brasiliensis responded to availabitity of floral resources in spatial scales smaller than five meters, visiting more frequently plants with more energy reward regardless of neighbourhood energetic availability. The flower visitation rate was not related to flower resource availability in P. suterella plants. This result might be determined by the high variation in flower energy production within plant.

Beekeepers help to secure the pollination capacity of bees by mediating bee-stressors. This study argues that beekeeper strategies are best conceptualized as a series of specialized practices for bettering bee-health, which are mobilized by a variety of actors, including those who are not traditionally considered ‘beekeepers’. The aim of this paper is to explore those human beliefs and practices which are most relevant for gaining insight into the current pollinator problem. Farmers, bee-conservationists, bee-researchers and honeybee-keepers all play an important role in securing bee health. The paper draws on the social-ecological perspective to consider alternative definitions of caring for bees, what shapes these conceptualizations and how these are reflected in beekeeper strategies, which inevitably contribute to the overall functioning of human-bee constituted systems. In the context of rising honeybee colony losses in Canada and of wild bee decline around the world, understanding the diversity of approaches for bettering bee-health is exceedingly important for initiating long-term, sustainable and multi-level bee-pollinator conservation.

Observation of floral visitation is an accepted method to describe plant-pollinator interactions despite potential biases. Collecting pollen from pollinators offers new insights on the structure and function of plant-pollinator communities. Furthermore, the strength and frequency of plant-pollinator interactions can vary across temporal scales. However, within-season and within-day (morning vs. evening) variation in plant-pollinator networks has been little studied. By evaluating variation in network structure across these biologically relevant time scales, we will gain a better understanding of the factors that shape plant-pollinator communities. The objectives of this study are to 1) Compare the structure of plant-pollinator networks built on floral visitation and pollen transport data, 2) Evaluate intra-annual variation in plant-pollinator network structure and 3) Evaluate variation in plant-pollinator structure within a single day (i.e. morning vs. evening). Congruence and Temporal Variation of Floral Visitation and Pollen Transport Networks in Southern Appalachia

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The present study deals with ecological impact of giant hogweed (Heracleum mantegazzianum) invasion in Slavkovský les area. Being one of the prominent invasive species with significant impact on human health it has been subjected to a wide research. In spite of that little is known about its impact on the invaded ecosystem. My research was therefore focused on analysis of the ecosystem impact, particulary 1) microclimatic measurements of temperature and soil moisture and their comparisons between invaded and noninvaded vegetation, 2) comparison of germination and survival of model plant species sowed into invaded and noninvaded plots and 3) study of the effect of H. mantegazzianum presence on model species seed production. Results have shown significant alteration of microclimate due to H. mantegazzianum invasion. Further research is needed to resolve what impact it may pose to species in invaded communities. The effect of Heracleum mantegazzianum presence on germination and survival of model species was not significant. Similarly, seed production of model plants was not significantly affected.

Premise of research. The duration and intensity of flowering overlap among plants are the first determiners of the potential for pollinator-mediated plant-plant interactions. Yet, our ability to describe community-wide patterns of coflowering, and thus understand its impact on the structure of plant-pollinator communities, is limited. Methodology. We present a conceptual framework for how network theory can reveal structural properties that are ecologically relevant in diverse coflowering communities. Coflowering modules, in particular, may suggest that groups of species coflower more strongly (clustering) with each other than with other species (over-dispersion) in the community. Such a finding would indicate that competitive and facilitative interactions do not act alone but instead act simultaneously to mediate the assembly of coflowering communities. We illustrate our conceptual framework in four diverse coflowering communities in the serpentine seeps in northern California. Pivotal results. Our coflowering networks vary in size and degree but not in overall connectance, suggesting that both intrinsic community features (species richness) and ecological constraints (length of flowering season) play a role in mediating coflowering community structure (distribution of frequency and intensity of flowering overlap among plant species). We show, for the first time, that groups of species tend to coflower more strongly with each other than with other species in a community, supporting the idea that competition and facilitation are not mutually exclusive processes mediating coflowering community assembly. Our results show that the degree of modularity is not sensitive to the number of coflowering species within each community, suggesting that ecological factors may be more important in driving this pattern. Conclusions. Coflowering networks have the potential to advance our understanding of the causes and consequences of flowering overlap in diverse plant communities by revealing a more in-depth and novel characterization of coflowering community structure. Such characterization will allow for a better understanding of the importance of coflowering patterns in mediating the structure of plant-pollinator interactions.