Honey bees utilize their circadian rhythms to accurately predict the time of day. This ability allows foragers to remember the specific timing of food availability and its location for several days. Previous studies have provided strong evidence toward light/dark cycles being the primary Zeitgeber for honey bees. Work in our laboratory described large individual variation in the endogenous period length of honey bee foragers from the same colony and differences in the endogenous rhythms under different constant temperatures. In this study, we further this work by examining the temperature inside the honey bee colony. By placing temperature and light data loggers at different locations inside the colony we measured temperature at various locations within the colony. We observed significant oscillations of the temperature inside the hive, that show seasonal patterns. We then simulated the observed temperature oscillations in the laboratory and found that using the temperature cycle as a Zeitgeber, foragers present large individual differences in the phase of locomotor rhythms for temperature. Moreover, foragers successfully synchronize their locomotor rhythms to these simulated temperature cycles. Advancing the cycle by six hours, resulting in changes in the phase of activity in some foragers in the assay. The results are shown in this study highlight the importance of temperature as a potential Zeitgeber in the field. Future studies will examine the possible functional and evolutionary role of the observed phase differences of circadian rhythms.

Bees are the most important pollinators of flowering plants and are necessary for pollinating both wild plants and many of the crops that produce the food we eat. There are many different species of bees, with about 20,000 species worldwide and 4,000 species in the United States. Even though bees are important pollinators, there is still much we do not know about how many species there are and their biology. In order to better understand the species and their biology, I performed three projects that help fill these gaps by reviewing the species of a poorly known bee group, examining the different ways bees carry pollen, and then reviewing how bees gather pollen from flowers. To better understand bee diversity, I examined a group of species in the subgenus Heteroperdita in the genus Perdita (Andrenidae). I described nine species that were new to science, found the opposite sex of three species, and found that one species was a duplicate of a previously described species. This work increased the number of species in Heteroperdita to 22 and increased the number of species in the genus Perdita to 636. I then explored how pollen is carried back to the nest in two distantly-related bee groups, the genera Perdita and Hesperapis (Melittidae). I found that different species can carry pollen in one of three different ways: moist, dry, or glazed. Interestingly, how the bees carry pollen appears to depend on the shape and stickiness of the pollen grains that the bees prefer. I then reviewed how bees gather pollen from flowers. I combined previous research and my own observations of bees to classify the different pollen gathering behaviors into seven different types. I then examined why bees use different pollen gathering behaviors and provided a set terminology to refer to each behavior. Overall, this dissertation advances our knowledge of the diversity of bees and their relationships with flowers, which will support efforts to understand and conserve these important pollinators.

Chapter 1 – General Introduction One of the greatest challenges of ecological research is to predict the response of ecosystems to global change; that is to changes in climate and land use. A complex question in this context is how changing environmental conditions affect ecosystem processes at different levels of communities. To shed light on this issue, I investigate drivers of biodiversity on the level of species richness, functional traits and species interactions in cavity-nesting Hymenoptera. For this purpose, I take advantage of the steep elevational gradient of Mt. Kilimanjaro that shows strong environmental changes on a relatively small spatial scale and thus, provides a good environmental scenario for investigating drivers of diversity. In this thesis, I focus on 1) drivers of species richness at different trophic levels (Chapter 2); 2) seasonal patterns in nest-building activity, life-history traits and ecological rates in three different functional groups and at different elevations (Chapter 3) and 3) changes in cuticular hydrocarbons, pollen composition and microbiomes in Lasioglossum bees caused by climatic variables (Chapter 4). Chapter 2 – Climate and food resources shape species richness and trophic interactions of cavity-nesting Hymenoptera Drivers of species richness have been subject to research for centuries. Temperature, resource availability and top-down regulation as well as the impact of land use are considered to be important factors in determining insect diversity. Yet, the relative importance of each of these factors is unknown. Using trap nests along the elevational gradient of Mt. Kilimanjaro, we tried to disentangle drivers of species richness at different trophic levels. Temperature was the major driver of species richness across trophic levels, with increasing importance of food resources at higher trophic levels in natural antagonists. Parasitism rate was both related to temperature and trophic level, indicating that the relative importance of bottom-up and top-down forces might shift with climate change. Chapter 3 – Seasonal variation in the ecology of tropical cavity-nesting Hymenoptera Natural populations fluctuate with the availability of resources, presence of natural enemies and climatic variations. But tropical mountain seasonality is not yet well investigated. We investigated seasonal patterns in nest-building activity, functional traits and ecological rates in three different insect groups at lower and higher elevations separately. Insects were caught with trap nests which were checked monthly during a 17 months period that included three dry and three rainy seasons. Insects were grouped according to their functional guilds. All groups showed strong seasonality in nest-building activity which was higher and more synchronised among groups at lower elevations. Seasonality in nest building activity of caterpillar-hunting and spider-hunting wasps was linked to climate seasonality while in bees it was strongly linked to the availability of flowers, as well as for the survival rate and sex ratio of bees. Finding adaptations to environmental seasonality might imply that further changes in climatic seasonality by climate change could have an influence on life-history traits of tropical mountain species. Chapter 4 – Cryptic species and hidden ecological interactions of halictine bees along an elevational Gradient Strong environmental gradients such as those occurring along mountain slopes are challenging for species. In this context, hidden adaptations or interactions have rarely been considered. We used bees of the genus Lasioglossum as model organisms because Lasioglossum is the only bee genus occurring with a distribution across the entire elevational gradient at Mt. Kilimanjaro. We asked if and how (a) cuticular hydrocarbons (CHC), which act as a desiccation barrier, change in composition and chain length along with changes in temperature and humidity (b), Lasioglossum bees change their pollen diet with changing resource availability, (c) gut microbiota change with pollen diet and climatic conditions, and surface microbiota change with CHC and climatic conditions, respectively, and if changes are rather influenced by turnover in Lasioglossum species along the elevational gradient. We found physiological adaptations with climate in CHC as well as changes in communities with regard to pollen diet and microbiota, which also correlated with each other. These results suggest that complex interactions and feedbacks among abiotic and biotic conditions determine the species composition in a community. Chapter 5 – General Discussion Abiotic and biotic factors drove species diversity, traits and interactions and they worked differently depending on the functional group that has been studied, and whether spatial or temporal units were considered. It is therefore likely, that in the light of global change, different species, traits and interactions will be affected differently. Furthermore, increasing land use intensity could have additional or interacting effects with climate change on biodiversity, even though the potential land-use effects at Mt. Kilimanjaro are still low and not impairing cavity-nesting Hymenoptera so far. Further studies should address species networks which might reveal more sensitive changes. For that purpose, trap nests provide a good model system to investigate effects of global change on multiple trophic levels and may also reveal direct effects of climate change on entire life-history traits when established under different microclimatic conditions. The non-uniform effects of abiotic and biotic conditions on multiple aspects of biodiversity revealed with this study also highlight that evaluating different aspects of biodiversity can give a more comprehensive picture than single observations. / Kapitel 1 – Allgemeine Einführung Eine der größten Herausforderungen der ökologischen Forschung ist es, die Reaktion der Ökosysteme auf den globalen Wandel, d.h. auf Veränderungen von Klima und Landnutzung, vorherzusagen. Eine komplexe Frage in diesem Zusammenhang ist, wie sich verändernde Umweltbedingungen auf die Ökosystemprozesse auf verschiedenen Ebenen von Gemeinschaften auswirken. Um dieses Thema näher zu beleuchten, untersuche ich die Triebkräfte der Biodiversität auf der Ebene des Artenreichtums, der funktionellen Eigenschaften und der Wechselwirkungen zwischen Arten bei Hautflüglern, die in Hohlräumen nisten. Zu diesem Zweck nutze ich den steilen Höhengradienten des Kilimandscharo, der starke Umweltveränderungen auf relativ kleinem Raum mit sich bringt und somit ein gutes System für die Untersuchung von Triebkräften der biologischen Vielfalt bietet. In dieser Arbeit konzentriere ich mich auf 1) Triebkräfte des Artenreichtums auf verschiedenen trophischen Ebenen (Kapitel 2); 2) saisonale Muster in der Nestbauaktivität, lebensgeschichtliche Merkmale und ökologische Raten in drei verschiedenen funktionellen Gruppen und in verschiedenen Höhenlagen (Kapitel 3) und 3) Veränderungen in kutikulären Kohlenwasserstoffen, Pollenzusammensetzung und Mikrobiomen bei Lasioglossum Bienen, die durch klimatische Faktoren verursacht werden (Kapitel 4). Kapitel 2 – Klima und Nahrungsressourcen prägen den Artenreichtum und die trophischen Wechselwirkungen von hohlraumnistenden Hautflüglern Die Triebkräfte des Artenreichtums werden seit Jahrhunderten erforscht. Temperatur, Ressourcenverfügbarkeit und Top-Down-Regulierung sowie die Auswirkungen der Landnutzung werden als wichtige Faktoren für die Bestimmung der Insektenvielfalt angesehen. Die relative Bedeutung jedes dieser Faktoren ist jedoch unbekannt. Mit Hilfe von Nisthilfen entlang des Höhengradienten des Kilimandscharo versuchten wir, die Triebkräfte des Artenreichtums auf verschiedenen trophischen Ebenen zu enträtseln. Die Temperatur war der Hauptfaktor für den Artenreichtum auf allen trophischen Ebenen, wobei die Bedeutung der Nahrungsressourcen auf den höheren trophischen Ebenen der natürlichen Antagonisten zunahm. Die Parasitierungsrate wurde sowohl durch die Temperatur als auch durch die trophische Ebene bestimmt, was darauf hindeutet, dass sich die relative Bedeutung der Bottom-up- und Top-down-Kräfte mit dem Klimawandel verschieben könnte. Kapitel 3 – Saisonale Schwankungen in der Ökologie von tropischen hohlraumnistenden Hautflüglern Natürliche Populationen schwanken mit der Verfügbarkeit von Ressourcen, dem Vorhandensein natürlicher Feinde und klimatischen Schwankungen. Die Saisonalität ist jedoch auf tropischen Bergen noch nicht gut untersucht. Wir untersuchten saisonale Muster in der Nestbauaktivität, funktionale Merkmale und ökologische Raten bei drei verschiedenen Insektengruppen in niedrigeren und höheren Höhenlagen. Insekten wurden mit Nisthilfen gefangen, die während eines Zeitraums von 17 Monaten, der drei Trocken- und drei Regenzeiten umfasste, monatlich überprüft wurden. Die Insekten wurden nach ihren funktionalen Gilden eingeteilt. Alle Gruppen zeigten eine starke Saisonalität im Nestbau, die in niedrigeren Lagen höher war und dort zwischen den Gruppen stärker synchronisiert war. Die Saisonalität im Nestbau von Raupen- und Spinnen- jagenden Wespen war mit saisonalen Klimaschwankungen verbunden, während sie bei Bienen stark von der Verfügbarkeit von Blüten abhing, genauso wie die Überlebensrate und das Geschlechterverhältnis der Bienen von der Blütenmenge abhing. Die Anpassung an die Saisonalität der Umwelt könnte bedeuten, dass weitere Veränderungen der saisonalen Klimaschwankungen durch den Klimawandel einen Einfluss auf die lebensgeschichtlichen Merkmale tropischer Bergarten haben könnten. Kapitel 4 – Kryptische Arten und versteckte ökologische Wechselwirkungen bei Schmalbienen entlang eines Höhengradienten Starke Umweltgradienten, wie sie an Berghängen auftreten, stellen für Arten eine Herausforderung dar. Versteckte Anpassungen oder Interaktionen wurden in diesem Zusammenhang selten berücksichtigt. Als Modellorganismen haben wir Bienen der Gattung Lasioglossum verwendet, da Lasioglossum die einzige Bienengattung ist, die über den gesamten Höhengradienten am Kilimandscharo weit verbreitet ist. Wir fragten, ob und wie (a) kutikuläre Kohlenwasserstoffe (CHC), die als Barriere gegen Austrocknung wirken, sich in ihrer Zusammensetzung und Kettenlänge entlang von Temperatur- und Feuchtigkeitsänderungen verändern; (b) Lasioglossum Bienen ihre Pollennahrung mit wechselnder Ressourcenverfügbarkeit ändern; (c) Änderungen von Darm-Mikrobiota mit Pollennahrung und Klimabedingungen und Änderungen von Oberflächen-Mikrobiota mit CHC und Klimabedingungen zusammen hängen, und ob die Veränderungen eher durch den Wechsel von Lasioglossum Arten entlang des Höhengradienten beeinflusst werden. Wir fanden physiologische Anpassungen an das Klima in CHC, sowie Veränderungen in der Zusammensetzung von Pollennahrung und Mikrobiota, die auch miteinander korrelierten. Diese Ergebnisse deuten darauf hin, dass komplexe Wechselwirkungen und Rückkopplungen zwischen abiotischen und biotischen Bedingungen die Artenzusammensetzung in einer Gemeinschaft bestimmen. Kapitel 5 – Allgemeine Diskussion Abiotische und biotische Faktoren förderten die Artenvielfalt, Eigenschaften und Wechselwirkungen von Arten und sie wirkten unterschiedlich, je nachdem, welche funktionelle Gruppe untersucht wurde und ob räumliche oder zeitliche Einheiten berücksichtigt worden sind. Es ist daher wahrscheinlich, dass im Lichte des globalen Wandels verschiedene Arten, Merkmale und Wechselwirkungen unterschiedlich betroffen sein werden. Darüber hinaus könnte eine zunehmende Landnutzungsintensität zusätzliche Auswirkungen oder Wechselwirkungen mit dem Klimawandel auf die Biodiversität haben, auch wenn die potenziellen Landnutzungseffekte am Kilimandscharo noch gering sind und bis jetzt die hohlraumnistenden Hautflüglern nicht beeinträchtigen. Weitere Studien sollten sich mit Nahrungsnetzwerken befassen, die empfindlichere Veränderungen aufzeigen könnten. Nisthilfen bieten dafür ein gutes Modellsystem, um die Auswirkungen des globalen Wandels auf mehreren trophischen Ebenen zu untersuchen, und können auch direkte Auswirkungen des Klimawandels auf ganze lebensgeschichtliche Merkmale aufzeigen, wenn sie unter verschiedenen mikroklimatischen Bedingungen etabliert werden. Die nicht einheitlichen Auswirkungen abiotischer und biotischer Bedingungen auf mehrere Aspekte der Biodiversität, die in dieser Studie gezeigt wurden, zeigen auch, dass die Untersuchung verschiedener Aspekte der Biodiversität ein umfassenderes Bild vermitteln kann als Einzelbetrachtungen.

Due to the rise of monoculture in agricultural production, insect biodiversity has sharply declined in agroecosystems due to the reduction in host plant biodiversity. This includes declines in populations of native pollinators, which reduces the ambient pollination services received by crops and increases the reliance on managed pollinators like European honeybees (Apis mellifera). One way to combat this decline in pollination services is to develop crop varieties that have high attraction to pollinators, this can have a dual effect of inducing native pollinators to move deep into agricultural fields from adjacent habitats like woodland or meadow strips, as well as retaining managed honeybees within crop fields and improving their efficacy. Attraction can be determined by many traits including floral morphology, pigmentation, and chemical cues like fragrance. Under higher ambient temperature the floral temperature rises, resulting in several potential effects. A warmer flower is likely to emit a larger volume of volatile compounds, as well as to be an attractive resting place for ectothermic pollinators, and yet high floral temperature may reduce pollen viability. The goal of this study is to first assess the effects of floral traits, particularly morphology and pigmentation, on floral temperature relative to ambient conditions, and secondarily, how flower temperature differentials alongside floral traits may affect pollinator foraging preferences. Our findings indicate that floral morphology and pigmentation both influence floral temperature differentials, and that floral morphology, pigmentation, and temperature differentials influence visitation by native pollinators (bumblebees and sweat bees). Floral traits and their influence on temperature are potentially important targets for the improvement of pollinator visitation to sunflower cultivars and the improvement of yields.

My research findings have implications for applied ecology and restoration policy in Ontario. I my discussions, and final chapter, I offer suggestions for the practitioner. / Restoration practitioners are tasked with recreating ecosystems using appropriate plant material that will provide ecological goods and services. However, best-practices for this type of intervention are not well developed for the southern Ontario landscape. Therefore, we evaluated approaches from four different aspects of seed-based restoration. First, we quantified the impact of seeding rate and application method on the success of grassland recreation. We also measured the impact of this restoration on the local bee community. Next, we compared a suite of native and nearly native wetland plants for their potential to prevent the establishment of invasive Phragmites australis. We measured the effect of competition on Phragmites across soil moisture and salinity gradients. Finally, we sought evidence for local specialization in a grassland forb, Monarda fistulosa, that would warrant policies to prevent the transfer of grassland seed for revegetation. In re-creating grasslands from seed, we found an interaction between seeding rate and application method. At a high rate, both methods had the same outcome, but at a low rate, a two-phase application method produced better results than a single-phase method. However, we also found that a single-phase method produced target plant cover with a higher floristic quality index after three years. In one study region, restored sites supported a greater bee abundance than un-restored sites, but bee abundance did not change after restoration in all regions. Of all the native species tested, Phragmites was supressed most by Bidens frondosa, a fast growing annual. We also found evidence that Phragmites may be less competitive at low soil moisture, and more competitive at high soil salinity. Finally, we found no evidence of local adaptation in M. fistulosa at the watershed scale; instead, we see independent effects of site and seed origin. This implies that current site conditions may not be favorable to the offspring of relic populations, and that local genotypes may not always be the best choice for restoration. / Dissertation / Doctor of Philosophy (PhD) / I tested four approaches to seed-based restoration. First I found that a two-phase hydroseeding method can be more efficient at a low seeding rate. Second, I found that the response of the bee community to local restoration may depend on broader landscape factors. Next, I found that Monarda fistulosa is not locally adapted at a watershed scale. Finally, I found that native annuals may be best at resisting invasion from Phragmites, and that some native species actually can facilitate invasion.

The honey bee is one of the most important crop pollinating insects in the world. Researchers have recently identified a disease that has begun to impact the honey bee population. Colony Collapse Disorder results in the death of many bee colonies every year, but the cause for this remains unknown. Investigating the cause, harmonic radars are being considered to track the foraging patterns of honey bees. This research endeavors to find an optimized waveform for use in tracking foraging bees. Harmonic oscillators were developed for a transmit frequency of 1.2 GHz and various waveforms were tested against the oscillators. Ultimately, the waveform was found to be arbitrary. The amount of power that the harmonic oscillator receives is the determining factor. Given this, a general pulsed waveform can be developed that attempts to provide the maximum possible return for a predetermined maximum range of interest.

No description available.

Recent concerns of declining bee populations have highlighted the importance of monitoring wild bees, but bee community assessments are hampered by species complexes that are difficult to identify. Bees in the genus Melissodes are often considered challenging to identify to species, with two widespread North American species, M. agilis Cresson and M. trinodis Robertson, being particularly difficult due to similar morphology, geographic ranges, and preferred floral hosts. These two species exhibit characteristics of cryptic species complexes, raising the possibility that our current understanding of their taxonomy is incomplete. We conducted a study to clarify the species boundaries within this complex, and to test if geometric morphometrics could be used to differentiate its member taxa. We sequenced fragments of the mitochondrial COI gene from 112 M. agilis/trinodis specimens, and integrated them into a phylogeny based on published reference sequences of over 70 Melissodes species. We additionally landmarked forewing venation for 102 of these specimens, tested if forewing morphometrics was associated with sex and phylogenetic clade, and tested if forewing morphometrics could accurately assign specimens to their proper clade and sex. Phylogenetic reconstructions resulted in nearly all specimens being assigned to three primary clades, with one clade containing reference sequences for M. agilis and M. trinodis, and two clades appearing to be undetermined cryptic taxa. Forewing morphometrics differed between clades and sexes, and was able to assign specimens to their proper clade or sex with over 80% accuracy, although accuracy of classification to clade declined to between 33-93% after cross-validation. Our results suggest the existence of cryptic diversity within M. agilis and M. trinodis, and indicate that forewing morphometrics can characterize some of this diversity. M. agilis and M. trinodis may comprise a complex of 3-5 cryptic species, but whether these are described or undescribed species is unknown. Also unclear is the degree to which the potential cryptic species contribute to the economically important sunflower pollination services currently considered to be conducted by M. agilis and M. trinodis. We encourage additional study of this complex to determine the nature of this cryptic diversity and resolve the taxonomic questions this study has raised.

Through pollination, bees are responsible for the persistence of many biological systems on our planet. Bees have also been used for thousands of years in agriculture to improve crop quality and yield. Recently, there have been declines in honeybees worldwide. This decline is concerning because it threatens food supplies and global biodiversity. An alternative to alleviating the effect of a honey bee shortage could be to use native bees. Problems with adoption of native bees in agriculture occur because of a lack of large scale analysis methods for native bees, regional species lists and management knowledge. This research explores the use of GIS in modeling native bee habitat to provide a landscape scale analysis method for native bees and develop a systematic sampling method for regional species list development. Raster GIS modeling, incorporating decision support and Poisson statistical methods were used to develop a native bee habitat model. The results show landscape composition is important to bee abundance and diversity. In addition, habitat fragmentation may not be as detrimental to bees as previously thought. Bees are most sensitive to landscape composition at a scale of 250 m, but require large patches of floral resources. GIS proved to be very useful in modeling bee habitat and provides an opportunity to conduct landscape scale bee population analysis. / Master of Science

Over the past several decades, native and managed bee populations have decreased in the United States and worldwide. Although bee decline is attributable to several factors, habitat loss is the primary driver. Simultaneously, cattle producers in the eastern U.S. rely primarily on cool-season forages that peak in biomass production in late spring, leading to a lack of forage in the summer months and increasing the costs of cattle production. Seeding pastures with a mix of native warm-season grasses and native wildflowers could increase forage availability while also increasing available resources for bees. In this study, a mix of three native warm-season grasses (NWSGs) and 15 wildflower species was planted at the Virginia Tech Shenandoah Valley Agricultural Research and Extension Center (SVAREC). The objectives of this project were to document the establishment and species composition of NWSG + wildflower pasture mixtures, compare the attractiveness of wildflowers and weedy species to bees, and compare the bee community between NWSG + wildflower pastures and more typical cool-season grass pastures. The wildflowers in the NWSG + wildflower pastures dominated over grasses. All wildflower species that established were attractive to bees, as were some weedy species. The NWSG + wildflower treatments had the highest abundance of bees collected, with an average of 14.8 bees collected per pasture per sampling date in 2018, and an average of 12.4 bees collected per pasture per sampling date in 2019. These results indicate that with modification of establishment methods so that more grasses are present, this pasture system could be beneficial from both a cattle production and bee conservation standpoint. / Master of Science in Life Sciences / Over the past several decades, there has been a decline in bee populations in the U.S. and around the world. Bees play an important role in pollinating many food crops, including most fruits and vegetables. Habitat loss is the biggest contributor to their decline. There are also issues with cattle production in the eastern U.S. Most farmers rely on grasses that are the most productive in the late spring and early summer, meaning that by mid- and late summer, there is little grass available for cattle. Planting pastures with native grasses designed to be the most productive in the late summer and native wildflowers could increase food available for cattle as well as provide more pollen and nectar for bees. In this experiment, we planted a mix of three grasses and 15 wildflowers. We documented how well the grasses and wildflowers established. We also examined how attractive wildflowers and weeds were to bees and compared the number and types of bees collected between the new pastures and traditional pastures. We found that the wildflowers, instead of the grasses, dominated the pastures. All wildflowers that established, as well as some weeds, attracted bees and provided resources. Higher numbers of bees were collected in the pastures with wildflowers than standard grass pastures, but there were not necessarily more bee species present. These results suggest that, with some modifications, planting native grasses and wildflowers in pastures could help conserve bees as well as benefit cattle farmers.