While pollinators and leaf herbivores have been a focus of research for decades, floral antagonists have been studied significantly less. Since floral antagonists can be as common as leaf herbivores and have strong impacts on plant reproduction, it is important to understand the role of floral antagonists in the ecology and evolution of flowers. I conducted four experiments to better understand the relationship between plants, floral traits, floral antagonists, and other plant-insect interactions. First, I manipulated resources (light and soil nutrients) that are known to have impacts on plants and floral traits to test how they affect floral antagonists and other plant-insect interactions. Plentiful resources increased the proportion of floral antagonists to visit flowers, but also increase tolerance of floral antagonists. Second, I manipulated flower bud gallers, a species-specific floral herbivore that destroys flowers, to test how it affected other plant-insect interactions, floral traits, and plant reproduction. Plants with flower bud gallers tended to have more pollinator visits, but this effect is due to a shared preference by gallers and pollinators for similar plants. Third, I manipulated florivory to examine how it affects subsequent plant-arthropod interactions, floral traits, and plant reproduction. Florivory had systemic effects on other plant-insect interactions, including leaf herbivores, and shifted the plant mating system towards more selfing. Additionally, I tested how several floral antagonists respond to floral attractive and defense traits to understand which floral traits are important in mediating antagonisms. Finally, I manipulated florivory, pollination, and nectar robbing to test for effects of multiple floral interactions on subsequent plant-insect interactions, floral traits, and plant reproduction. There were significant many-way interactions between the three treatments on subsequent plant-insect interactions and reproduction, indicating that the effect of one interaction depends on what other interactions are present. Understanding the role that floral antagonists play in plant ecology can help scientists determine which interactions are most important, and may help determine why some floral traits exist in their current state. Together, this work represents some of the most comprehensive research on the community consequences of floral antagonists, as well as the interplay between floral traits and floral interactions.

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Die vorliegende Arbeit befasst sich mit der Charakterisierung der Strahlungsstresstoleranz am Beispiel von Impatiens Genotypen unter Berücksichtigung morphologischer, anatomischer und physiologischer Merkmale. Von 2012 bis 2014 wurden Pflanzen von fünf Impatiens Genotypen bei unterschiedlichem Strahlungsangebot im Gewächshaus kultiviert. Zur Sensibilisierung des Pflanzenmaterials wurde ein Teil der Pflanzen während der Anzucht mit einer herkömmlichen Schattierung stark schattiert (70 % Lichtminderung). Nach 10 Wochen bei unterschiedlichem Strahlungsangebot wurden Blattproben für histologische Untersuchungen entnommen und fünf Pflanzen je Genotyp für Strahlungsstressapplikationen in Pflanzgefäße verpflanzt. Diese Applikationen erfolgten im Freiland unter einem UV-undurchlässigen und einem UV-durchlässigen Foliendach, sowie unter voller Sonne mit und ohne Bewässerung. Während der Stressapplikation wurde die stomatäre Leitfähigkeit und die Chlorophyll-Fluoreszenz gemessen, Thermalbilder erstellt und die Nekrosenintensität täglich dokumentiert. Innerhalb von sieben Tagen waren an schattiert angezogene Pflanzen, im Gegensatz zu unschattiert angezogenen Pflanzen, deutliche Reaktionen an sonnenexponierten Blättern in Form von Nekrosen zu erkennen. Ein zusätzlicher Einfluss von Trockenstress intensivierte diese Reaktion nicht. Zudem wurde deutlich, dass physiologische Messungen während der Stressapplikation nicht mit dem Auftreten der Nekrosen übereinstimmten. Hingegen zeigten Blattquerschnitte und physiologische Messungen nach der Anzucht, dass Blätter, die sich unter hohem Strahlungsangebot entwickelt haben, ein dickeres Palisadenparenchym, mehr Chloroplasten und eine höhere Sättigungskurve der Photosyntheserate aufweisen. Letztendlich zeigt die vorliegende Arbeit, dass die Strahlungsstresstoleranz der Pflanzen stärker von den Anzuchtbedingungen beeinflusst wird, als vom Genotyp, was die Identifikation einer Strahlungsstresstoleranz erschwert. / The aims of the investigation were to characterize the light stress reaction regarding the morphology, anatomy and physiology of five Impatiens varieties. For the trials from 2012 to 2014, plants of each variety were grown in greenhouses at different light conditions. To produce plants with a higher light sensitivity, the light intensity was reduced by using common shading systems (70 % shading). After 10 weeks of pre-treatment at different light conditions, five plants of each variety were transferred into balcony boxes. To determine the anatomical reactions, some leaves were harvested and used for histological investigations. For the light stress treatment, plants were placed outside under UV-impermeable foil, UV-permeable foil and in full sun radiation with and without irrigation. In addition, the stress reaction of plants was evaluated by measuring the stomatal conductance and chlorophyll fluorescence, by using thermal images and by documenting leaf damage daily. Within seven days of light stress the plants subjected to the low light pre-treatment had a significantly higher stress reaction on sun exposed leaves than the plants subjected to the high light pre-treatment. The additional drought stress did not intensify this reaction. Furthermore, the physiological measurements during the stress application were not confirmed by the emergence of leaf damage. But pictures of tissue sections and physiological measurements after pre-treatment illustrated that the leaves developed under high light conditions have more densely packed palisade parenchyma, more chloroplasts and a greater saturation curve of photosynthesis rate compared to the leaves developed in low light conditions. Finally, the results demonstrated that the conditions of plant cultivation influence the light stress adaption stronger than the genotype what makes the identification of light stress tolerant difficult.

Studies performed on natural pathosystems revealed that the spatial structure of the metapopulation plays an important role in the development and spread of disease; phytopathological experimental studies have also revealed a significant effect of climatic factors on the presence of the disease (incidence) and the level of infection (prevalence) in populations. The aim of this study was to explore a natural pathosystem from both sides at the same time and to see which local and spatial environmental factors influence the development of pathosystem. Study focuses on population biology of natural pathosystem Podospaera balsaminae - Impatiens noli-tangere, which has not been investigated yet. In the study area (between the city Sázava (Benešov district) and village Vlkančice) host populations occurred in 78 (64 of them were infected) in 2013 and 82 populations (61 of them were infected) in 2014. Size of host populations had the strongest effect to incidence and prevalence of disease in the pathosystem. In larger populations, the disease occurred more often, developed faster and was higher. The rate of spread of the pathogen territory and the rate of population host connectivity had also strong effect. The abundance of pathogen in the studied area and the level of connectivity of host populations also...

Invasive spread of neophyte Impatiens glandulifera in central Europe started approximatelly eighty years ago. First records of dense cover stands come from belt stands in riparian habitats. The scale of invaded habitats and degree of the dominance of I. glandulifera is more diversified nowadays. This thesis is objected on the dominance and fertility of I. glandulifera within different habitat types and scale of invaded habitats in different parts of invaded range within Europe (i. e. in Czech Republic and Switzerland). The results show that the height and cover (substitutes for biomass and dominance) of this neophyte (i) correlates with the character of invaded vegetation (ii) relates to the degree of hemeroby (a measure of human impact) negativelly, and (iii), of course, both the growth and dominance are positively affected by nutrient content. Fertility does not differ among the types of invaded habitats, but goes up with the height of I. glandulifera and decreases with its cover. Invaded habitats comprises ruderal and riparian vegetation, but also wet maedows, forest clearances, beach and slope forests or weed vegetation.

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.

Plants are under selection to simultaneously attract pollinators while deterring herbivores. This dilemma can lead to tradeoffs in floral traits, which are traditionally thought to be optimized for pollinators. My dissertation addresses the ecological costs and putative functional significance of nectar secondary metabolites, a paradoxical but widespread phenomenon in the angiosperms. I investigate this issue from the pollinator’s perspective using a series of controlled laboratory investigations focused primarily on the bumble bee Bombus impatiens and the nectar alkaloid gelsemine, from Gelsemium sempervirens. I begin by demonstrating that nectar enriched with the alkaloid gelsemine significantly deters visits from bumble bees at a range of natural alkaloid concentrations. However, this aversion can be mitigated by increasing the sucrose concentration such that the alkaloid-rich nectar is more rewarding than its alkaloid-free counterpart. I then demonstrate that the consumption of gelsemine-rich nectar can inhibit oocyte development and protein utilization in bees, but that this effect is limited to bees of suboptimal condition. Continuous consumption of the nectar alkaloid gelsemine also leads to a reduction in the pathogen load of bumble bees infected with Crithidia bombi, but direct interactions between the pathogen and the alkaloid have no impact on infection intensity. Gelsemine also fails to inhibit floral yeast growth, suggesting that nectar alkaloids may not be universally antimicrobial. Finally, I demonstrate that gross nectar cardenolides from the genus Asclepias are strongly correlated with gross leaf cardenolides and that the majority of individual cardenolides found in nectar are a subset of those identified in leaves. This pattern suggests that nectar cardenolides are a consequence of defense for Asclepias; however, they may not be a costly corollary because bumble bees show an overall preference for nectar cardenolides at mean concentrations. Altogether, my dissertation provides a new perspective on the role of chemical defenses against herbivores in plant-pollinator interactions.

Plants are under selection to simultaneously attract pollinators while deterring herbivores. This dilemma can lead to tradeoffs in floral traits, which are traditionally thought to be optimized for pollinators. My dissertation addresses the ecological costs and putative functional significance of nectar secondary metabolites, a paradoxical but widespread phenomenon in the angiosperms. I investigate this issue from the pollinator’s perspective using a series of controlled laboratory investigations focused primarily on the bumble bee Bombus impatiens and the nectar alkaloid gelsemine, from Gelsemium sempervirens. I begin by demonstrating that nectar enriched with the alkaloid gelsemine significantly deters visits from bumble bees at a range of natural alkaloid concentrations. However, this aversion can be mitigated by increasing the sucrose concentration such that the alkaloid-rich nectar is more rewarding than its alkaloid-free counterpart. I then demonstrate that the consumption of gelsemine-rich nectar can inhibit oocyte development and protein utilization in bees, but that this effect is limited to bees of suboptimal condition. Continuous consumption of the nectar alkaloid gelsemine also leads to a reduction in the pathogen load of bumble bees infected with Crithidia bombi, but direct interactions between the pathogen and the alkaloid have no impact on infection intensity. Gelsemine also fails to inhibit floral yeast growth, suggesting that nectar alkaloids may not be universally antimicrobial. Finally, I demonstrate that gross nectar cardenolides from the genus Asclepias are strongly correlated with gross leaf cardenolides and that the majority of individual cardenolides found in nectar are a subset of those identified in leaves. This pattern suggests that nectar cardenolides are a consequence of defense for Asclepias; however, they may not be a costly corollary because bumble bees show an overall preference for nectar cardenolides at mean concentrations. Altogether, my dissertation provides a new perspective on the role of chemical defenses against herbivores in plant-pollinator interactions.

Magistrantūros baigiamojo darbo tyrimų tikslas buvo nustatyti Naujosios Gvinėjos sprigėse (Impatiens hawkeri) plintančias ligas, kenkėjus, ištirti augalų apsaugos produktų ir augalų priežiūrai skirtų produktų efektyvumą jų daromai žalai sumažinti. Bandymai atlikti 2012–2013 m. R. Pauliuko ūkyje Plukių kaime, Panevėžio rajone ir Lietuvos Agrarinių ir Miškų Mokslų Centro filialo Sodininkystės ir daržininkystės instituto (LAMMC SDI) Augalų apsaugos laboratorijoje. Tyrimų objektas: Naujosios Gvinėjos (Impatiens hawkeri) sprigių veislės: ‘Paradise Logia‘,‘Paradise Moores‘ ir ‘Paradise Coiba‘. Tyrimų metodai. Tyrimai atlikti 2-iem etapais. Pirmo etapo 2012 m. tyrimuose nustatėme Naujosios Gvinėjos sprigėse plintančias pagrindines ligas, kenkėjus. Jų apibūdinimui naudojome vizualinį–simptomatinį, ligų sukėlėjų identifikavimui – drėgnų kamerų ir mikroskopavimo metodus. Antro etapo 2012–2013 m. tyrimuose įvertinome biologinių augalų priežiūrai skirtų produktų Mimoten, Funres, Konflic, augimo stimuliatoriaus Florone, augalų apsaugos produktų – fungicido Previcur 607 SL, insekticido Vertimec 018 EC poveikį sprigių ligų, kenkėjų prevencijai ir kontrolei, sprigių augimui ir vystymusi. Tyrimų rezultatai. Tyrimų rezultatai parodė, kad Naujosios Gvinėjos sprigės 'Paradise Logia', 'Paradise Moorea' ir 'Paradise Coiba' R. Pauliuko šiltnamyje buvo pažeistos kekeriniu puviniu, miltlige, netikrąja miltlige, pašaknio puviniais, dėmėtligėmis. Skirtingose sprigių veislėse šios ligos pasireiškė... [toliau žr. visą tekstą] / The main aim of Master studies research was to identify diseases and parasites that can harm New Guinea impatiens (Impatiens hawkeri). Also, investigate effectiveness and efficacy of plant protection and maintenance products. The investigation was conducted in the greenhouse of farmer R. Pauliukas in Plukiai, Panevėžys country and at Agricultural and Forest Sciences Center Gardening Institute Plant protection lab. Object of the research: New Guinea impatiens (Impatiens hawkeri) Breeds: Paradise Logia‘, ‚Paradise Mooera‘ and ‚Paradise Coiba‘. Research methods: Experiments were performed in two phases. First phase was performed in 2012 and major diseases and parasites were identified for New Guinea impatiens. Visual-symptomatic method was used for description of the diseases and parasites. Disease agent was identified with wet camera and microscopy. During a second phase we have evaluated biologically derived agents Mimoten, Funres, Konflic, and growth simulator Florone used in maintentance of plants. Also we have evaluated plant protectants fungicide Previcur, insecticide Vertimec effect on prevention and control of New Guinea impatiens diseases and parasites as well as effect on growth and development of the plant. Research results. The results of this investigation showed that New Guinea impatients ‚Paradise Logia‘, ‚Paradise Moorea‘ and ‚Paradise Coiba‘ in R. Pauliukas greenhouse were affected by gray mould (Botrytis cinerea), mildew (Oidium sp.), downy mildew (Plasmopara... [to full text]

At certain stages of a bumblebee colony life cycle workers lay eggs. Not all workers reproduce, however, since many continue to forage and care for the nest. This leads to questions regarding what differentiates a reproductive worker from a non-reproductive one. It is hypothesized that a form of reproductive competition takes place, where the most behaviourally dominant worker becomes reproductively dominant. The behaviour of orphaned Bombus impatiens pairs was recorded and aggression, social interactions, egg-laying, and ovarian development were identified. Experiment 1 examined the association between aggression and egg-laying. Contrary to the hypothesis, the most aggressive worker did not lay more eggs. When the ovarian development of workers was manipulated and two workers with developed ovaries were paired (Experiment 3), they were more aggressive than pairs with discouraged ovarian development. This provides support for the supposition that aggression and reproduction are related, however, it is only partial support as worker pairs with encouraged ovarian development did not lay more eggs. Since aggression is believed to be only one part of behavioural dominance, Experiment 2 studied the association between social interactions and aggression and reproduction. Results showed that when two socially active bees were paired they were more aggressive than pairs including one or two socially inactive bumblebees. No significant difference in ovarian development between socially active pairs and socially inactive pairs was found. Brood presence was also predicted to affect reproductive control. Experiment 1 found egg-laying and aggression were more likely to co-occur in the absence of brood. Results from Experiment 2 supplemented the first experiment since the absence of brood increased rates of aggression and ovarian development in pairs. Whereas the results confirm aggression has a role in worker reproduction the findings also reveal that behavioural dominance does not equate to reproductive dominance under all conditions. The primary contributions of this thesis were the development of a method to distinguish behavioural dominance from reproductive dominance and determining their relationship under different environments (brood presence) and experimental manipulations (ovarian development). These contributions further define dominance in Bombus impatiens.