Simple regulatory mechanisms based on the idea of the saturable 'common stomach' can control the regulation of protein foraging and protein allocation in honeybee colonies and colony-level responses to environmental changes. To study the economic benefits of pollen and nectar foraging strategies of honeybees to both plants and honeybees under different environmental conditions, a model was developed and analyzed. Reallocation of the foraging workforce according to the quality and availability of resources (an 'adaptive' strategy used by honeybees) is not only a successful strategy for the bees but also for plants, because intensified pollen foraging after rain periods (when nectar quality is low) compensates a major fraction of the pollination flights lost during the rain. The 'adaptive' strategy performed better than the'fixed' (steady, minimalistic, and non-adaptive foraging without feedback) or the 'proactive' (stockpiling in anticipation of rain) strategies in brood survival and or in nectar/sugar economics. The time pattern of rain periods has profound effect on the supply-and-demand of proteins. A tropical rain pattern leads to a shortage of the influx of pollen and nectar, but it has a less profound impact on brood mortality than a typical continental rainfall pattern. Allocating more bees for pollen foraging has a detrimental effect on the nectar stores, therefore while saving larvae from starvation the 'proactive' strategy could fail to collect enough nectar for surviving winter.

Flowering plants require conspecific pollen to reproduce but they often also receive heterospecific pollen, suggesting that pollinators carry mixed pollen loads. However, little is known about drivers of abundance, diversity or composition of pollen carried by pollinators. Are insect-carried pollen loads shaped by pollinator traits, or do they reflect available floral resources? We quantified pollen on 251 individual bees and 95 flies in a florally diverse community. We scored taxonomic order, sex, body size, hairiness and ecological specialization of pollinators, and recorded composition of available flowers. We used phylogenetically controlled model selection to compare relative influences of pollinator traits and floral resources on abundance, diversity and composition of insect-carried pollen. We tested congruence between composition of pollen loads and available flowers. Pollinator size, specialization and type (female bee, male bee, or fly) described pollen abundance, diversity and composition better than floral diversity. Pollen loads varied widely among insects (10–80,000,000 grains, 1–16 species). Pollen loads of male bees were smaller, but vastly more diverse than those of female bees, and equivalent in size but modestly more diverse than those of flies. Pollen load size and diversity were positively correlated with body size but negatively correlated with insect ecological specialization. These traits also drove variation in taxonomic and phylogenetic composition of insect-carried pollen loads, but composition was only weakly congruent with available floral resources. Qualities of pollinators best predict abundance and diversity of carried pollen indicating that functional composition of pollinator communities may be important to structuring heterospecific pollen transfer among plants.

Animal pollination is responsible for the majority of the human food supply. Understanding pollination dynamics in agricultural systems is thus essential to help maintain this ecosystem service in the face of human disturbances. Surprisingly, our understanding of plant–pollinator interactions in widely distributed smallholder agricultural systems is still limited. Knowledge of pollination dynamics in these agricultural systems is necessary to fully assess how human disturbances may affect pollination services worldwide. In this study, we describe the structure of a plant–floral visitor network in a smallholder Cucurbitaceae agricultural system. We further identify the main floral visitors of these crops and tested their importance by simulating how their extinction affected network structure and robustness. The observed network was highly connected and generalized but it was neither nested nor compartmentalized. Our results suggest that the structure of agricultural plant–pollinator networks could be inherently different from those in natural communities. These differences in network structure may reflect differences in spatial distribution of floral resources between agricultural and natural systems. We identified Augochlora nigrocyanea and Peponapis limitaris as the two most frequent floral visitors. However, removal of these species did not affect network structure or its robustness, suggesting high levels of interaction rewiring. To our knowledge, this is one of the first studies to describe the structure of a plant–floral visitor network in diverse agricultural systems in the tropics. We emphasize the need for more studies that evaluate network structure in agricultural systems if we want to fully elucidate the impact of human disturbances on this key ecosystem service.

The goal of this thesis was to examine the breeding system and natural history of the Maguire primrose (Primula cusickiana var. maguirei). Maguire primrose is an endemic, threatened subspecies found only along a narrow corridor within Logan Canyon in northern Utah, USA. This plant displays distinct flower distyly, with clear distinction of pin and thrum morphologies (morphs). The timing of Maguire primrose flower blooms was disparate between upper and lower canyon populations, and the flowers experienced cool temperatures occasionally. I captured eight different species of flying insects visiting Maguire primrose flowers, and made 67 observations of insect visitation. Inter-morph outcrossing hand pollinations were the most successful hand pollinations performed, but were usually not as successful as those that were naturally pollinated. Selfing rates were quite low compared to outcrossing reproductive scenarios. Morph-specific fecundity differences were detected in my hand pollinations, but not in the naturally pollinated maternal plants. I did not observe clear fecundity differences based on the canyon location of Maguire primrose.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18113号 / 理博第3991号 / 新制||理||1576(附属図書館) / 30971 / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 酒井 章子, 教授 山内 淳, 准教授 永益 英敏 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20958号 / 理博第4410号 / 新制||理||1633(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 川北 篤, 教授 工藤 洋, 教授 永益 英敏 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Increased growth rates, wood quality, and disease resistance have been accomplished within loblolly pine (Pinus taeda L.) through genetic selection and improved management practices. Genetic engineering of trees has the potential to further improve these selections but also needs to be tested. Two studies were conducted. Study one compares three levels of genetic improvement: Mass-Control Pollinated (MCP), Second Generation Op (2nd gen), and Varietal Material. After three years the MCP material had larger mean heights, mean diameters, and mean volume than the other two genetic entities. However the top five performing varietals were about 0.5 feet taller than the MCP material. Study two tested two contrasting loblolly pine ideotypes across different spacings and management intensities. After two years the crop tree ideotype and the intensive management plots had larger mean heights, mean ground-line diameters, mean volumes, and mean crown widths. Mean branch angle differed significantly between the two crown ideotypes.

Honey bees play an important role in pollination ecology but the conditions of health and genetic purity in North Sweden are not very clear because most honey bees are not native to boreal environments. Emerging studies on insect microbiomes are focusing on the role of lactobacillus as a health factor, given its connection with nectar digestion processes. The aim of this thesis is an assessment of the genetic purity of the western honey bee (Apis mellifera mellifera) and the understanding of implications between non-pathogenic microorganisms and the honey bee's health status. Additionally, the relationships between hive’s colony size, environment, and health status are tested to understand any possible linkages, following the idea that different environments might affect the quantity of lactobacillus and thus immunity and resistance patterns in honey bees. For this project, 15 beehives were sampled in the region of Västerbotten in the summer of 2019/2020, in different types of habitats, with different purposes: analyzing the genetic purity with the wing morphometry method, cultivating the microorganisms that are present in the guts of bees, and comparing the results between urban and agricultural environments. The wing morphometry genetic assessment results showed that up to 80% of the bee keepers who took part in this study breed the subspecies A. mellifera mellifera with no significant level of hybridization with other subspecies. Therefore, honey bee purity status depends on the beekeeper’s choices. Microscopy and the analysis of the microbiomes showed the presence of lactobacillus and minor microorganisms. Cultivable lactic acid bacteria are more present in healthy honey bees in locations with higher plant biodiversity. In fact, the bacillus microbiomes are present in both agricultural and semi-urban areas but are more abundant and diverse in long-lived honey bees from hives in semi-urban area. This could depend on the higher plant diversity in these sites. Finally, the purity of subspecies does not influence adaptive responses or resistance in boreal environments.

More than 60% of plant populations experience low pollen availability which limits seed production (pollen limitation). Pollen limitation occurs due to low quantity or quality of pollen delivered to stigmas. Despite its ubiquity in nature, to date we still have limited understanding of the drivers of pollen limitation in plant communities. Plants typically occur in diverse communities where pollinator sharing is common and can influence quality and quantity aspects of pollen limitation. Co-flowering species can attract larger numbers of pollinators or they can compete for pollinators affecting pollen loads on stigmas. Pollinator competition may also lead to higher rates of self-pollination, reducing pollen quality. Knowledge on the relative contribution of pollen quantity and quality to overall pollen limitation, and how it varies with increasing co-flowering diversity, is central for understanding the factors that determine plant reproductive success. Here, we used populations of four Clarkia species to evaluate how changes in co-flowering community diversity impact the contribution of pollen quantity and quality in limiting plant reproduction. We sampled twenty-five communities of 1-4 species. We collected 29-100 styles per site/species (2400 total). Styles were processed and the amount of pollen grains and pollen tubes were counted under a microscope. Differences in the amount of pollen grains received (pollen quantity) and proportion of pollen tubes produced (pollen quality) were estimated across species and populations. The amount of pollen received increased with increasing number of co-flowering species only for C. unguiculata, suggesting pollinator facilitation. The proportion of pollen tubes was not affected by the number of co-flowering species present. All Clarkia species differ in the amount of pollen grains received and the proportion of pollen tubes produced. C. xantiana, received the least amount of pollen but produced the highest amount of pollen tubes. C. speciosa received the highest amount of pollen grains but produced the fewest number of tubes. Pollen quantity and quality varied widely among individuals within a population compared to individuals across populations or species. Pollen quality and quantity are limiting factors in the reproductive success of Clarkia species, however their relative contribution depends on species identity. Overall, differences in pollen limitation may depend on intrinsic species characteristics rather than aspects of the surrounding co-flowering community. Specifically, quantity and quality components of pollen limitation may vary depending on differences in pollinator community composition, level of specialization and efficiency, and differences in plant mating system (self vs outcrossed). This study emphasizes the need to fully evaluate all aspects of pollen limitation and how these vary across space and species. This knowledge is key to understand the processes that mediate plant reproductive success in nature and how plants will respond to human disturbances.

Urbanization, the conversion of natural habitat into area fit for human exploitation, is the greatest contemporary threat to natural ecosystems. With urbanization only projected to increase in magnitude as human populations continue to grow it is becoming increasingly important to evaluate the potential negative impacts urbanization can have on vital ecosystem functions and services. One such important ecosystem service is pollination. Roughly 87.5% of flowering plants are animal pollinated, with pollination contributing over $175 billion dollars to the global economy each year. The fundamental ecologic and economic importance of pollination, coupled with the growing threat of urbanization, makes it important to better understand how pollination success may be impacted by urban development. Though, studies on the impact of urbanization on pollination success vary wildly in their findings, with some studies finding a negative impact of urbanization, while others find a negligible or even positive impact. This discordance in past studies is likely due to the fact that pollination studies typically focus on just one aspect of the pollination process, whether that be pollinator community, pollen removal/deposition, or fruit/seed production. Urbanization, however, may induce differential impacts across different stages of the pollination process. Focusing on just one pollination aspect may limit our understanding of the potential underlying mechanisms urbanization may impart on different stages of the pollination process. The goal of this study was to evaluate multiple aspects of pollination success across an urbanization gradient. Specifically, pollinator community (in terms of visitation rate and community composition), pollen removal/deposition, and fruit/seed production were surveyed across 12 common milkweed (Asclepias syriaca) populations, six of which were in natural habitats and six of which were in areas of moderate urbanization. By evaluating all pollination aspects together we can pinpoint which step(s) of the pollination process are impacted by urbanization, which will inform decisions on how to best conserve the integrity of pollination in anthropogenically disturbed environments. Overall, urbanization increased pollinator visitation rate (0.151 visits per minute per flower in urban populations, compared to 0.067 at natural populations), and altered pollinator composition, with more small bees and beetles present in more urbanized areas. Pollen removal also increased with urbanization (2.00 pollen removals per flower in urban populations, compared to 1.41 at natural populations), while pollen deposition, fruit production, and seed production were unchanged by urbanization. Thus, suggesting that the more abundant pollinators in more urbanized areas were effective at removing pollen, but ineffective at depositing pollen, resulting in no change in reproductive output (i.e., equal fruit and seed production). The results of this study suggest that increased urbanization can variably impact various steps in the pollination process, thus stressing the importance of studying multiple pollination aspects in tandem.