Doctor of Philosophy (PhD), Wright State University, 2018, Environmental Sciences PhD

The invasion of novel habitats by non-native plant species is a worldwide problem with serious economical and ecological implications. Broad biotic and abiotic filters contribute to the overall invasibility of non-native species. Invasive plants have the ability to rapidly establish themselves and outcompete their native counterparts as result of their relationship with herbivorous arthropods. Because invasive plants displace native plants, reduce overall plant diversity, and alter vegetation structure, this can have cascading effects on insect herbivores, particularly those that rely on one or a few food plants, and arthropod predators. The genus Euonymus (Celastraceae) is comprised of 130 species. Euonymus alatus (burning bush) and Euonymus europaeus (spindle tree) are two non-natives that have been introduced to North American. Although these species are recognized as invasive in portions of the United States, very little is known about their invasion status, relationship with native herbivores, or community impacts. We sought to fill these gaps with a particular focus on burning bush. We first investigated the distribution of burning bush in Ohio and biotic and abiotic factors that contribute to its success through a citizen science self-reporting protocol. We then examined the relationship of burning bush and spindle tree to herbivorous arthropods through examining field herbivory, success in no-choice bioassays, and analysis of chemical defenses. Finally, we examined the cascading impacts of burning bush and overabundant deer on environmental characteristics and arthropod communities. Euonymus alatus was present across Ohio but more likely to be successful in locations with greater disturbance and resources. Burning bush and spindle tree are likely experiencing enemy release as both receive significantly less herbivory than a native congener. While both burning bush and spindle tree contained elevated levels of secondary metabolites, a generalist herbivore (open full item for complete abstract)

Committee: Don Cipollini Ph.D. (Advisor); Mary Gardiner Ph.D. (Committee Member); Thomas Rooney Ph.D. (Committee Member); John Stireman III Ph.D. (Committee Member); Thaddeus Tarpey Ph.D. (Committee Member) Subjects: Biology; Conservation; Ecology; Entomology; Environmental Science; Plant Biology

Master of Science (MS), Bowling Green State University, 2017, Biological Sciences

Soil invertebrates play a critical role in the soil food web as some taxa—detritivores— break down dead and decaying material to make it more accessible to the soil microbial community, which in turn leads to further biogeochemical cycling throughout the soil. Micronutrients have been shown to be important drivers of invertebrate activity and community structure in certain environments. In this study we examined how micronutrient additions and forest age affect the soil invertebrate community and their ability to decompose material. Our study was completed using fine and coarse mesh leaf litter bags fertilized with a 1% mixture of calcium, sodium, or zinc in a ~100 year burn chronosequence in a Northern Michigan deciduous hardwood forest. We detected interactive effects between year of burn and micronutrient treatment on macroinvertebrate predator and detritivore abundance. Zinc fertilization appeared to inhibit both detritivore and predator recruitment for forest plots burned in some years but not others. However, this inhibition did not result in changes in decomposition (leaf mass loss). The calcium treatment recruited the most detritivores; however, the calcium treatment had less decomposition than the unfertilized treatment. We suspect that other biotic (e.g., trophic interactions and leaf litter composition) and abiotic factors also affected the activity and abundance of the detritivore communities causing differential results between micronutrient treatment and forest age. Nevertheless, this study demonstrates that certain nutrients can affect soil and leaf litter invertebrate community structure in ways that change the rate of decomposition, and that these impacts vary as forests recover from disturbance.

Committee: Shannon Pelini PhD (Advisor); Paul Moore PhD (Committee Member); Michael Weintraub PhD (Committee Member) Subjects: Biology; Ecology; Entomology

Master of Science, Miami University, 2014, Ecology

This paper reports on two studies describing responses of abundance, diversity, and functional structure of arthropod communities to high-intensity, low-frequency cattle grazing in eastern North American pastures. The first study assessed the state of arthropod communities before and after discrete grazing events. Grazing negatively affected abundance, diversity, and taxonomic richness, but functional diversity and functional evenness were unaffected. Assemblages of spiders and parasitoid wasps characterized pre-grazing communities, while beetles and flies were common after grazing. The second study assessed how these same properties changed with increasing deferment after grazing, and in response to vegetation structure. Longer deferment periods maximized arthropod abundance. Shorter deferment periods optimized taxonomic and functional diversity. Wasps characterized the most diverse community observed after 32 days of deferment. Vegetation height was important to explaining community composition. Height, biomass, and percent litter cover accounted for 11.8% of variance. Landscape variables may also be important to explaining community composition.

Committee: Alan Cady PhD (Committee Chair); Ann Rypstra PhD (Committee Member); A. John Bailer PhD (Committee Member); Thomas Crist PhD (Committee Member) Subjects: Agriculture; Biology; Conservation; Ecology; Entomology; Range Management

MS, University of Cincinnati, 2010, Arts and Sciences: Biological Sciences

The exotic shrub Lonicera maackii is a problematic invader of southwestern Ohio forests. As L. maackii invades the forest interior, it negatively impacts native plant diversity and abundance and changes the structure of understory vegetation by replacing the native shrub layer, which has a patchy distribution of plant species, with a dense shrub layer. Changes in diversity or structure of native shrub layer vegetation caused by L. maackii invasion could, in turn, affect associated arthropod fauna. Our objective was to determine whether L. maackii invasion impacted arthropod community composition and structure in the forest shrub layer. We predicted that by negatively affecting the diversity of native plant species in the shrub layer, L. maackii invasion would decrease diversity and abundance of arthropod taxa, trophic groups, and feeding specialists. Alternatively, we predicted that invasion of forests by L. maackii could increase vertical cover of the shrub layer, which could increase diversity and abundance of arthropod taxa, trophic groups, and feeding specialists. We established paired plots in ten forested locations to compare both arthropod community characteristics and characteristics of the shrub layer vegetation between invaded and uninvaded areas. Within paired plots, we captured arthropods from shrub layer vegetation using fumigants and a beating stick and then identified or classified individuals to order and family, trophic group, and specialist/generalist feeder. Additionally, within paired plots, we measured percent vertical cover of shrub layer vegetation with a profile board and identified all individuals of woody shrub layer plants to species. In areas invaded by L. maackii, we found increased or unchanged values of richness and abundance of all arthropod taxa, trophic groups, and specialist feeders. We also observed increased or unchanged values of Shannon's diversity and evenness of all arthropod taxa and trophic groups and relative abundance of (open full item for complete abstract)

Committee: Guy Cameron PhD (Committee Chair); Stephen Matter PhD (Committee Member); George Uetz PhD (Committee Member); Theresa Culley PhD (Committee Member) Subjects: Ecology