Thesis (M.S.)--Mississippi State University. Department of Entomology and Plant Pathology. / Title from title screen. Includes bibliographical references.

Cooperation is pervasive in nature but paradoxically also provides opportunity to cheaters. My dissertation involves the study of both cooperation and conflict in two species of Megalopta bees. Megalopta is a Neotropical genus of halictid bees whose biology is characterized by complex life cycles that can range from solitary to eusocial. These bees nest in dead wood and forage under dim light conditions. Megalopta’s nests are inhabited by an extensive array of organisms and each nest therefore constitutes a miniature ecosystem providing opportunities for cooperation and conflict, both within and between species. I first delineate the social structure of M. genalis and M. ecuadoria nests in several Panamanian populations and integrate the factors that play a role in the behavioral decisions of females when joining a social group or not. Within a kin-selection framework, I discuss how genetic relatedness plays a role in the formation of social nests. Second, I investigate the conflict between host bees and a congener social parasite, and I elucidate reproductive structures that are relevant for understanding the evolution of parasitism. Finally, I describe a cleaning mutualism between Megalopta bees and their mite associates. Bee-mite associations encompass a broad spectrum of interspecific interactions. Some bee-mites are thought to perform cleaning services for their hosts in exchange for suitable environments for reproduction and dispersal. Field observations and experimental manipulation reveal a significant correlation between the presence of mites and the absence of fungi inside the brood cells, as well as between the absence of mites and increased bee mortality. This study therefore provides evidence of the sanitary effect of mites in nests of Megalopta bees. This bee-mite association constitutes one of the few examples of terrestrial cleaning mutualisms. / text

Social insect colonies are complex systems with emergent properties that arise from the cooperation and interaction amongst individuals within colonies. By dividing reproduction and physical labor amongst them, individuals contribute to the growth and ecological success of their colonies, a success that is greater than individuals could achieve on their own. A key characteristic of social insects is a division of labor amongst workers that is determined primarily either by age, morphology, or dominance. Social insects are considered one of the most ecologically successful groups of organisms on earth. Colony life cycles include: 1) growth, in which workers are produced, 2) reproduction, in which queens and males with reproductive capabilities are produced, and 3) senescence. In life history theory, phenotypic plasticity (i.e. a change in phenotype in response to an environmental change), allows organisms to adjust and optimize fitness in response the change in environments. Central to life history theory is the idea that traits have costs and benefits. Using an energetics framework that considers the costs and benefits of traits contributes to our understanding as to why organisms exhibit the sets of traits that they have within their ecological environments. Using the annual bumble bee Bombus impatiens, my dissertation investigates the effects of resource availability on worker production and on the relative allocation of energy towards growth and reproduction within colonies. Bumble bees have a morphological division of labor and concomitantly, they show large intra-colony size variation amongst workers. Because body size is an important life history trait, I also examined the costs and benefits of producing various sized workers. Lastly, I examined the association among worker body size, metabolic rate (a measure of maintenance costs), and lifespan.

Bee declines have been reported globally and habitat loss and degradation due to urbanization and agricultural intensification are two of the primary drivers. Native bees play a critical role in plant reproduction, and declines in abundance and diversity of bees are expected to impact flowering plant biodiversity and productivity of insect pollinated agricultural crops. Habitat restoration can help mitigate declines by increasing the amount and quality of available bee habitat. However, outside of agroecosystems bees are rarely specified in restoration targets and little is known about how they respond to habitat restoration. My thesis addresses this knowledge gap by: (1) documenting the structure and function of the native bee community at a restored wet meadow to establish a baseline for future monitoring activities, (2) comparing the influence of two restoration approaches on the established bee community, and (3) exploring changes in functional groups and pollination function with time since restoration. I sampled bees at degraded, restored, and (semi)natural habitats at 12 sites in four locations in southern Ontario. I used a combination of structural (abundance, richness, and evenness) and functional (guilds based on social and nesting habits and plant-pollinator interaction networks) characteristics to describe and compare bee communities. I collected a total of 10,446 bees from 30 genera and six families representing a range of phenologies, social behaviours, and nesting habits. At Dunnville Marsh, a restored wet meadow, I collected 5,010 bee specimens from 27 genera and six families. The bee community at Dunnville Marsh was diverse and well connected within 4-6 years of restoration, emphasizing the importance of wet meadows as native bee habitat. However, wood nesters and cleptoparasites were relatively uncommon suggesting that the community may be less stable compared to older habitats. Between 2005 and 2008, individual fields at Dunnville Marsh were dug with pits and mounds before planting and seeding or were seeded into weedy ground. Digging pits and mounds did not convey a clear advantage to the establishing bee community, but genus richness was greater in pit and mound sites (p=0.04). As well, the restoration approach used influenced the relative representation of guilds within the community. Ground nesters and wood nesters were significantly more abundant in pit and mound treated sites (p<0.001), perhaps reflecting the larger amounts of bare ground (p<0.001) and the greater potential for sapling survival on mound tops. Stem nesters were more abundant in planted sites (p<0.001), and floral richness and abundance did not differ between the two restoration approaches. Finally, diversity and evenness of guilds based on social and nesting habits increased with age since restoration, indicating that communities in (semi)natural habitats are more functionally diverse than those in restored habitats, but that communities in restored habitats are more functionally diverse than those in degraded habitats. Relative abundance of guilds changed with age since restoration in ways that reflected structural habitat changes associated with succession. Degraded sites had the highest relative abundance of ground nesters, while (semi)natural sites had the highest relative abundance of wood nesters. Plant-pollinator interaction networks did not demonstrate clear trends with respect to age since restoration, but indicated that communities that establish in response to non-targeted restorations can be diverse, robust to extinction, and well connected.

It has been argued that organic farming sustains a higher biodiversity than conventional farming. This might promote the ecosystem services that exist in agricultural landscapes such as pollination and pest control. Here, I examined the effect of farming system (organic vs. conventional) with respect to the time since farming system transition, landscape heterogeneity and plant richness on pollinating and predatory insects. In total, data from 30 farms were used, of which 20 were organic and 10 were conventional. The data were analyzed using general linear models and model averaging. The results show that insect groups responded differently to various factors. Pollinators were more sensitive to landscape complexity, showing an increase of abundance and species richness with an increased heterogeneity. Predators on the other hand reacted to farming system, where there was an increase in abundance and species richness on organic farms.

Membrane diversity associated with variation in body mass and body temperature of hymenopterans was investigated. Body mass of organisms affects most aspects of their biology, including physiological traits. One trait influenced by mass is metabolic rate, but the basis for its variation among organisms remains unclear. Recent work revealed that membrane phospholipid composition varies systematically with body mass: smaller vertebrates with higher mass-specific metabolic rates have more fluid membranes containing more long chains of polyunsaturated fatty acids (PUFA) and less monounsaturated fatty acids (MUFA). This “membrane pacemaker” theory of metabolism has recently been challenged by a lack of link between metabolic rate and membrane composition. To test this relationship, we have quantified the membrane lipid composition of 22 species of Panamanian orchid bees with a 22-fold range in mass. Results incorporating phylogenetic analysis show significant relationships for 18:1 (MUFA) and 18:3 (PUFA) with body mass that are consistent with the “pacemaker” theory, and unexpected relationships with saturated fatty acids (SFA). Moreover, changes in membrane fatty acid composition with temperature are a strategy in ectothermic poïkilotherms that is part of the “homeoviscous adaptation” model. Here, we report systematic variations in fatty acid composition linked with thoracic temperature excess in North American Hymenopterans, a novel discovery in these heterotherms. These findings are discussed in the context of diet, metabolism and lifespan.

Africanized honey bees (AHB) are a hybrid between African and European honey bees (EHB). Compared to the EHB, AHB exhibit more intense, defensive behaviors but nevertheless provide the same important ecosystem service--pollination. AHB have been found in Tucson, AZ. since 1993. It is important to understand the population ecology of AHB for several reasons. Most directly, the behavioral traits retained from African bees present public safety and health risk. AHB are easily agitated; even slight disturbances (e.g., human movements) can provoke attacks. Several hybridized bee traits (e.g., higher colony growth rates, reproduction at a smaller colony size, nesting in a wider range of cavity materials, etc.) also make them more adapted to urban landscapes. The overlap of habitats and resource-using of AHB with human significantly raise the risk of stinging incidents, especially in the areas of bee aggregation. Although the presence of AHB in urban environments may present a public safety and health risk, they do contribute to urban ecosystems substantially through pollination. The fact that AHB is a part of the urban ecosystem suggests a need for a better understanding of the relationship among climate factors, urban landscape characteristics, and AHB population dynamics. The goal of my dissertation was to understand population dynamics of AHB in urban environments using removal records of AHB colonies in water meter boxes. I have demonstrated useful methods and repeatable procedures to process, extract, and synthesize water meter box data which were not collected or sampled specifically for any ecological research. I also examined the spatio-temporal distributions of AHB colony removals in water meter boxes, and evaluated the effects of variations of temperature and precipitation on observed patterns. Then, I investigated the linkage between spatial patterns of AHB colonies and urban landscape characteristics by evaluating densities of water meter boxes, AHB colony abundance, and colony occupancy among different land cover/land use types. Lastly, a conceptual model and quantitative models were developed to illustrate AHB population dynamics, particularly and the interactions among water meter boxes, alternative cavities, and honey bee colonies. Overall, the probabilities of AHB colonies selecting nesting sites can be influenced by: (1) the ratio of water meter boxes and alternative cavities; (2) the difference of vegetative attributes among locations associated with the preference of AHB in selecting new nesting sites. Seasonal variations of precipitation and temperature can affect the development and productivity of AHB population.

In cranberry (Vaccinium macrocarpon Aiton) cultivation, farmers typically rent colonies of honey bee (Apis mellifera) for pollination. However, the efficiency of this bee at pollinating cranberries in Oregon, as in other regions, is questionable. Bumble bees (Bombus sp.) are reportedly effective in other regions, but their impact in Oregon is unknown. My objectives were to: (i) Compare bumble bee and honey bee pollination efficiencies under caged conditions; (ii) Estimate the abundance of bumble bees, honey bees, and other pollinators on an Oregon cranberry farm; and iii) Analyze and compare sources of pollen collected by bumble bees and honey bees in Oregon cranberries. In comparing pollination efficiencies of bumble bees and honey bees under caged conditions, the analysis of variance of data from the cage study indicated that bumble bee and honey bee pollinated plants yielded statistically equivalent average numbers of cranberries (1421 ± 302.5 and 1405 ± 347.6 berries/m², respectively) and weight of berries (11.5 ± 2.42 and 11.5 ± 2.77g/m²). However, bumble bees may have increased fruit set in honey bee treatments. On one occasion, bumble bees were found in the honey bee treatment, and may have contributed to the pollination of flowers in these plots. To estimate the abundance of pollinators, visual observations and were blue vane traps were utilized. Thirty-four timed visual observations in transects of cranberry beds were performed over on four dates during cranberry bloom. Blue vane traps were set-up on five occasions during bloom for two day periods. In the visual observations, honey bees (3.5 ± 0.58/min) were observed more frequently than bumble bees (1.2 ± 0.20/min). Bumble bees of four species made up 69.1% of trapped bees while honey bees made up 16.6% of bees caught in blue vane traps. On an Oregon cranberry farm during bloom periods in 2009, 2010 and 2011, pollen was collected from honey bee colonies using pollen traps. In 2010 and 2011, pollen was hand collected from reared bumble bee (B. vosnesenkii) colonies at the same farm. A total of 2937 honey bee pollen loads and 171 bumble bee pollen samples (137 scopal pollen loads, and 34 samples from with the colony) were individually acetolyzed and compared to a reference collection using light microscopy. Each pollen load was homogenized and 100 pollen grains were identified and counted to determine the percentage of each pollen type. Pollen collected by honey bees consisted of 29.1 ± 1.4% (2009), 18.3 ± 2.4% (2010), and 23.0 ± 1.1% (2011) cranberry pollen. Cranberry pollen contributed a higher percentage (56.0 ± 6.1%, and 70.4 ± 4.3% in 2010, and 2011, respectively) in bumble bee collected pollen. Both bee species collected pollen from non-target plants including those in the following families: Asteraceae, Fabaceae, Ranunculaceae, and Roseaceae. Native bumble bees (B. vosnesenskii) collected more cranberry pollen than pollen from non-target plants, and consistently collected a higher proportion of cranberry pollen than honey bees. The results of these studies suggest that native bumble bees may be adequate for cranberry pollination in Curry County, Oregon. However, the size of bumble bee populations may vary from year to year due to climactic conditions, availability of nesting sites, and forage before and after cranberry bloom. Thus the dependability and consistency pollination services rendered to cranberry crops by bumble bees needs to be further investigated in relation to population fluxuations. / Graduation date: 2012

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2009. / Härtill 4 uppsatser.