Doctor of Philosophy, The Ohio State University, 2022, Entomology

Metal contamination, resulting from industrial, mining, transportation, and incineration activities, is ubiquitous in urban and other human dominated areas and poses an understudied yet potentially impactful challenge to pollinator communities. Legacy cities, concentrated in post-industrial regions, are cities that experienced a dramatic economic decline, followed by an exodus of residents which led to an abundance of vacant infrastructure and land that is oftentimes contaminated with metals. Increasing interest in reimagining unused urban land as habitat for bees and other beneficial species has created an urgent need to identify and isolate the impacts of metal exposure on these pollinators. Bees are exposed to and accumulate metals while searching for food and resources within contaminated regions, yet, they and other organisms are readily found within contaminated landscapes despite the potential negative effects of metal exposure. Therefore, the overarching goals of this dissertation research were to determine the lethal limits of metal exposure for bees, investigate the impacts of field relevant concentrations of common urban metals on bumble bee colony health, and asses any sublethal effects of metal exposure on bumble bee foraging behavior. Focusing first on legacy cities' unique opportunities for urban bee habitat with a potential for unintended metal exposure, the first objectives of this research were to review the literature on potential metal exposure routes for pollinators, and if bees are exposed, the impacts of metals on wild bee health, fitness, and behavior (Chapter 1). My next objective was to identify if, and at what concentrations, metal exposure results in forager bee mortality and if bees bioaccumulate any metals within their bodies (Chapter 2). Next, I wanted to identify how exposure to environmentally relevant concentrations of metals arsenic, cadmium, chromium, and lead that bees encounter in cities influence overall Bombus impatiens co (open full item for complete abstract)

Committee: Frances Sivakoff (Committee Member); Roman Lanno (Committee Member); Reed Johnson (Committee Member); Mary Gardiner (Advisor) Subjects: Entomology

Master of Science, University of Akron, 2019, Biology

Pollinators provide the essential ecosystem service of animal-facilitated pollination. Recent studies have presented a novel and surprising avenue for future pollinator conservation, urban pollinator habitat. One group of pollinators, bumble bees (Hymenoptera: Apidae: Bombus), might be especially well suited to utilize the heterogeneous landscape of urban environments. A defining feature of urban environments is their large amounts of impervious surface. In this study we investigated the influence of urbanization on bumble bee communities by surveying bee and flower abundance and diversity in weedy margins nestled within impervious surfaces along an urban gradient. We first quantified and defined an urban gradient by creating an “intensely developed” land cover category with > 50% impervious surface using the USGS NLCD. To choose our survey sites we analyzed the land use information above to identify likely sites distributed across the urban gradient. We conducted surveys from mid – June – early – August 2018 between the hours of 10:00 and 17:00, when bees are most active. To quantify the bee abundance and diversity, on each site visit we conducted timed surveys in which a single observer (the same observer at all sites) walked freely throughout the site and identified all bees for a total of 15 minutes. Following the bee survey, we then surveyed the floral community. During the summer of 2018 we observed 2776 total bees. Bumble bee abundance was not significantly affected by the proportion of intensely developed land in the local landscape or floral richness. There was a difference in relative abundance of the three bee groups, with bumble bees significantly more abundant than both honeybees and “other” bees. During our floral surveys we documented 66 different floral taxa across all 33 sites; natives made up less than 10% of the total floral abundance. Our findings affirmed both of our predictions: (1) that bumble bees would be unaffected by the degree of intens (open full item for complete abstract)

Committee: Randy Mitchell Dr (Advisor); Jessie Lanterman Dr (Committee Member); Todd Blackledge Dr (Committee Member) Subjects: Ecology

Master of Science, The Ohio State University, 2023, Entomology

Bumble bees (Bombus) are essential pollinators for wildflowers and crops worldwide, but many species are currently in decline. Habitat loss and fragmentation are leading factors in these declines. Urbanization is a source of habitat loss and fragmentation; however, robust and abundant bumble bee populations are often found in metropolitan areas. Though prior research has broadly examined bumble bee abundance and diversity in urban areas, little work has focused on individual abundances of different species, which may differ in their relationships with urban land. Furthermore, the potential impacts of urban land on gene flow and other genetic health factors in bumble bees remain largely unknown. The first goal of this research was to evaluate and compare the abundances of three target species—Bombus impatiens Cresson, 1863, B. griseocollis De Geer, 1773, and B. bimaculatus Cresson, 1863—along an agricultural-to-urban gradient in Madison, WI, USA. Bumble bees were collected from 16 sites during the summer of 2019 and 19 sites during the summer of 2020. The second goal was to evaluate genetic differentiation, heterozygosity, allelic richness and colony numbers among populations of these species along the same gradient. Percentage of impervious surface cover was used as a metric for urbanization, and this percentage was measured within both 500 m and 1500 m buffers around each study site to account for both local-scale and landscape-scale effects. Impervious surface cover showed no relationship with abundances of B. impatiens or B. griseocollis, but showed a positive relationship with abundance of B. bimaculatus. Impervious surface cover also showed no relationship with genetic differentiation, allelic richness or colony number for all three species in both years, and no relationship with heterozygosity for any species in 2019. In 2020, heterozygosity was negatively correlated with impervious surface cover for B. impatiens at the 500 m buffer but not the 1500 m buffer. (open full item for complete abstract)

Committee: Jamie Strange (Advisor); Andy Michel (Committee Member); Mary Gardiner (Committee Member) Subjects: Entomology