Graduate Theses & Dissertations

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Fungal pathogen emergence
The emergence of fungal hybrid pathogens threatens sustainable crop production worldwide. To investigate hybridization, the related smut fungi, Ustilago maydis and Sporisorium reilianum, were selected because they infect a common host (Zea mays), can hybridize, and tools are available for their analysis. Hybrid dikaryons exhibited filamentous growth on plates but reduced virulence and limited colonization in Z. mays. Select virulence genes in the hybrid had similar transcript levels on plates and altered levels during infection of Z. mays relative to each parental dikaryon. Virulence genes were constitutively expressed in the hybrid to determine if its pathogenic development could be influenced. Little impact was observed in hybrids with increased expression of effectors known to modify host response and metabolism. However, increased expression of transcriptional regulators of stage specific pathogenic development increased the hybrid’s capacity to induce symptoms. These results establish a base for investigating molecular aspects of fungal hybrid pathogen emergence. Author Keywords: effectors, hybrid pathogenesis assays, Sporisorium reilianum, transcription factors, Ustilago maydis, virulence factors
Developing Social-Emotional Competencies in Youth
Trait Emotional Intelligence (TEI) plays an important role in the health and wellness of children and adolescents. Not surprisingly, the literature on TEI and youth has expanded dramatically. Although the quality of this work continues to be uneven due to the continued proliferation of TEI-related measures with questionable psychometric features. One over-looked TEI measure in the field is the short form developed for the Emotional Quotient Inventory Youth Version (EQ-i:YV-S). The core goal of Study 1 was to examine the overall reliability and validity of the EQ-i:YV-S. The aim of Study 2 was to evaluate the utility of the EQ-i:YV-S as a measure of the effectiveness of a new school-based social and emotional learning program for elementary school students. Results from Study 1 demonstrated that the EQ-i:YV-S had good internal reliability, 6-month test-retest reliability, and convergent validity. Study 2 found that Total EI and most key EI-related dimensions had significant improvement from pretest to post test on the EQ-i:YV-S. These findings have important implications for TEI measurement in youth and the effectiveness of school-based psychoeducational programming for TEI, with the EQ-i:YV-S as a viable option for research in this area. Author Keywords: emotional intelligence, psychoeducational programming, social-emotional competencies
Soil mineralizable nitrogen as an indicator of soil nitrogen supply for grain corn in southwestern Ontario
Soil mineralizable nitrogen (N) is the main component of soil N supply in humid temperate regions and should be considered in N fertilizer recommendations. The objectives of this study were to determine the potentially mineralizable N parameters, and improve N fertilizer recommendations by evaluating a suite of soil N tests in southwestern Ontario. The study was conducted over the 2013 and 2014 growing seasons using 19 field sites across southwestern Ontario. The average potentially mineralizable N (N0) and readily mineralizable N (Pool I) were 147 mg kg-1 and 42 mg kg-1, respectively. Pool I was the only soil N test that successfully predicted RY in 2013. The PPNT and water soluble N (WSN) concentration (0-30cm depth) at planting were the best predictors of fertilizer N requirement when combing data from 2013 and 2014. When soils were categorized based on soil texture, the relationships also improved. Our findings suggest that N fertilizer recommendations for grain corn can be improved, however, further field validations are required. Author Keywords: corn, nitrogen, nitrogen mineralization, soil nitrogen supply, soil N test, southwestern Ontario
Factors affecting road mortality of reptiles and amphibians on the Bruce Peninsula
Road mortality is one of the leading causes of global population declines in reptiles and amphibians. Stemming losses from reptile and amphibian road mortality is a conservation priority and mitigation is a key recovery measure. I developed a model of road mortalities relative to non-­‐mortalities, based on predictors varying across space (road surface type, traffic volume, speed limit, distance to wetland) and time (weather conditions, traffic volume). Herpetofauna road mortalities were recorded during daily bicycle and vehicle surveys to investigate the impact of roads on reptiles and amphibians within the Bruce Peninsula, Ontario in 2012 and 2013. A total of 2541 observations of herpetofauna on roads were recorded, 79% of which were dead. The major factor influencing turtle road mortality was proximity to the nearest wetland and dates early in the season (spring). For the Massasauga, high daily temperatures and low daily precipitation were associated with road mortality. The major factors driving colubrid snake mortality were also high daily temperature, low daily precipitation, as well as low speeds and paved roads. Frog and toad mortality was driven by proximity to wetland and late summer dates. These models will increase our understanding of factors affecting road losses of herpetofauna and serve as a basis for planned, experimental mitigation within the Bruce Peninsula. Author Keywords: amphibians, hotspot, mitigation, reptiles, road ecology, road mortality
Are We All on the Spectrum? Assessing Autistic Traits in the HEXACO Personality Framework
Autistic traits are characterized by difficulties with socialization, preference for order, and rigid and repetitive behaviour patterns. This study evaluated the psychometric properties of two measures of autistic traits, the Autism-Spectrum Quotient (AQ) and the Sub-threshold Autistic Trait Questionnaire (SATQ), and their associations with the HEXACO personality framework. The relationships between self-objectification, Need for Cognition (NFC), and autistic traits were also examined. In a student sample (N = 294), autistic traits were found to be negatively related to eXtraversion, but unrelated to self-objectification and NFC. However, individual subscales of the SATQ and AQ revealed different personality profiles, suggesting a non-unitary composition of the autistic trait measures. The AQ’s subscales failed to be represented in its factor structure. Intercorrelations between SATQ and AQ subscales showed that some subscales were uncorrelated with others. These concerns challenge whether autistic traits should be considered as a downwards extrapolation of Autism Spectrum Disorder. Author Keywords: Autism Spectrum Disorder, Autistic Traits, HEXACO, Need for Cognition, Self-Objectification
Island Syndrome and Stress Physiology of Mice in the Genus Peromyscus
Biological differences between island and mainland conspecifics have been well studied, but few studies have addressed differences in stress physiology. Stressors, such as predation and competition for resources, cause the release of glucocorticoids (GCs). Characteristics of island wildlife, called “island syndrome”, are attributed to low levels of predators and competitors. I tested the hypothesis that island syndrome includes differences in GC levels between island and mainland rodents using two approaches; first, using white-footed mice (Peromyscus leucopus) from a near-shore archipelago (Thousand Islands, Ontario) and the nearby mainland; second, using study-skins of deer mice (Peromyscus maniculatus) from two archipelagos offshore of Vancouver Island, British Columbia. White-footed mice in the near-shore archipelago did not show characteristics of island syndrome, or changes in GC levels (feces and hair); however deer mice from both archipelagos in British Columbia were heavier and had lower hair GCs for their size than Vancouver Island mice. Author Keywords: Glucocorticoids, Island rule, Island syndrome, Peromyscus, Stress physiology
Food Practices in Transition
The onset of the Natufian sees the unfolding of a lasting dietary shift: the transition from foraging to farming. To understand this transition, we have to identify the exploited plants and explain why they were chosen. To that end, I used use-wear and residue analysis to isolate wear patterns distinctive of specific plants. I conducted a series of six grinding experiments on wheat, barley, fenugreek, lentils, roasted wheat, and rinsed/soaked fenugreek. I then examined the tools under multiple levels of magnification using established protocols and descriptive criteria. To ensure that my descriptive criteria are reproducible, a blind test was performed. The experimental data are then compared to previous studies and residue analysis on the tools used to process wheat and lentils was performed. My results have expanded the experimental database and support the idea that there are distinctions between cereals and legumes and differences between types of cereals and legumes. Author Keywords: Blind test, Cereals, Groundstone tools, Legumes, Starch analysis, Use-wear analysis
Reconnecting the Heart and Spirit
This research explores key themes emerging from the question of the meaning Anishinaabe individuals attach to utilizing traditional practices and ceremonies to address their own trauma. The contributors share their stories, which are deeply rooted in relationships. The methodology of this research is also rooted within an Indigenous paradigm; storytelling is a core feature of relationships and knowledge transmission through its ability to weave together and across generations. Indigenous cultures have had a long history of both verbal and visual storytelling, in the forms of pictographs and petroglyphs, wampum belts, bead and quill work, and so on. While stories are often entertaining, they are at their core, the most human of activities. Anishinaabe approaches to ceremony, spirit and the sacred are woven into the language, attitudes and practices that people still engage in, despite the depredations of colonization. The findings of this research explore how identity, found through love, caring, self-awareness, and the (re)claiming of wellness and wholeness, permeates the stories of healing and is rooted in ceremonies. This is relationship with self and self-in-relation to all things: niwiikaniginaa. Land-as-home, culture, family, and love ground people in their sense of self and wellness. Language and thought emerge from the land, the source of well-being or mino bimaadsiwin in the most profound ways. It is through home – land, family, culture, spiritual connection – that healing occurs in ways that cannot be found in clinical systems. Author Keywords: Colonization, First Nations, Healing, Identity, Storytelling, Trauma
Clonal structure and mating patterns in a natural population of Sagittaria latifolia
Increased plant size is expected to have negative consequences for mating by increasing pollen transfer among the same plant. However, recent theoretical studies have demonstrated that this may not be true for clonal plants. Instead, clonal expansion could enhance outcrossing opportunities without increasing selfing by reducing distances to potential mates. I investigated how the spatial structure of clones influences patterns of pollen dispersal, selfing rates and siring success in a natural population of Sagittaria latifolia. I found that pollen dispersal distances typically exceeded the spatial extent of clones and there was a positive association between clone size and the likelihood that clones were intermingled. Together, this resulted in a weak positive association between clone size and selfing rates, and a strong positive association between clone size and outcross siring success. This is the first empirical support for the theoretical expectation that any negative effects of selfing in large clones might be offset by increased siring success. Author Keywords: clonal growth, fitness gain curve, geitonogamy, plant mating, plant reproductive ecology, sex allocation theory
Prey abundance and habitat during the breeding season for Piping Plovers in the Ontario Great Lakes region
Similar to other shorebird trends around the world, the Piping Plover population (Charadrius melodus circumcinctus) is projected to decline if concerted conservation efforts are relaxed. To date, there is insufficient understanding of the connection between habitat type, prey abundance, and chick behaviour of the Piping Plover breeding population in Ontario. The aim of my thesis was to gain knowledge about prey abundance at recent and historic breeding locations, understanding how habitat influences prey abundance and chick behaviour across the Piping Plover breeding range in Ontario’s Great Lakes. The objective of my first study was to understand prey abundance across the breeding region Great Lakes of Ontario from 2018-2019, including occupied and unoccupied sites, and to quantify variation among habitats and periods of reproduction. To evaluate resources, I sampled 17 locations to compare prey abundance using invertebrate traps (n= 3,507). Sampling took place over the reproductive periods of nest initiation, post-hatch, and fledging and in four habitat types of shoreline, wrack, berm, and back dune. Occupied breeding sites had higher prey abundances, and different assemblages of invertebrate prey than unoccupied sites. Additionally, breeding sites had higher prey abundance during nest initiation and supported higher amounts of prey in shoreline and wrack habitat. The objective of my second study was to understand how habitat types influence chick behaviour. To evaluate behaviour-habitat trends, instantaneous chick observations were recorded at the four nest sites from the post-hatch to fledging stages. In total there were 23 fledged chicks that we observed across the two years. Chicks in this study spent 60.9% of their time foraging, 11.9% of the time displaying alert behaviour, 21.4% of their time resting or being brooded, and 5.9% of their time preening. Chicks spent a large proportion of time foraging in the shoreline, resting in the back dune, and alert in berm habitat. The frequency of these alert, defensive behaviours differed among sites, with Sauble Beach chicks spending more time in defensive behaviours compared to other sites. I concluded that in both nesting and brood-rearing periods, habitat is selected non-randomly by adult and young Piping Plovers to maximize access to invertebrate prey for growth and survival. Access by chicks to the most productive habitats should be considered in local management decisions. Author Keywords: chick behaviour, endangered, Great Lakes Region, habitat, Piping Plovers, prey abundance
Fractionation of Mercury Isotopes in an Aqueous Environment
Fractionation of mercury isotopes in an aqueous environment: Chemical Oxidation Dimitri Stathopoulos The study of fractionation patterns for the stable isotopes of mercury is a growing field. The potential for stable isotopes to trace mercury through the environment from pollution sources to sinks make the subject interesting to geochemists and useful to a wider audience. The purpose of this study is to measure the fractionation of mercury as it is oxidized in an aqueous medium. Samples in this study are prepared by chemically oxidizing different proportions of elemental mercury using four different oxidants. The oxidized portion is then separated from the elemental portion and an analysis of the isotope ratios for both portions is performed using a multicollector inductively coupled plasma mass spectrometer MC-ICP/MS. These isotope ratios are measured against the preoxidation isotope ratio to determine what if any change has occurred. From the findings of this work, it is now known chemical oxidation causes both mass dependent and mass independent fractionation. Mass dependent fractionation causes an enrichment of the heavier isotopes in the oxidized portion while the opposite is true for the elemental portion. Mass independent fractionation occurred only in the odd isotopes and causes a depletion of odd isotopes in the oxidized portion and enrichment in the elemental portion. These trends were found to be true for all oxidants tested as the pattern of fractionation does not change with varying oxidants. Author Keywords: Isotope, Mass Dependent, Mass Independent, Mercury, Oxidation
Daphnia pulicaria responses to temperature and nutrients stress
Warming climates have had various consequences on terrestrial and aquatic food webs that are expected to persist. There is evidence suggesting that certain organisms are better equipped to handle changing climates compared to others. Therefore, the purpose of my thesis was to study the adaptability of Daphnia under temperature stress and nutrient limitation. First, to examine the effects of dietary phosphorus limitation and temperature on daphniid life-history and population growth, a series of experiments were conducted in the laboratory. In general, I found that Daphnia body growth rates and life-history traits to food carbon to phosphorus (C:P) ratios change with temperature. Next, I identified a protocol to limit the genomic DNA (gDNA) from ribonucleic acid (RNA) extractions. I found that using a modified phenol-chloroform extraction protocol was the most effective way to remove gDNA from extracted Daphnia RNA samples. Overall, results from this study show that temperature and food quality interactions are more complicated than previously thought. Furthermore, the RNA extraction protocol developed will be useful in future studies examining gene expression responses in Daphnia. Author Keywords: ecological stoichiometry, gene expression, life-history, nutrient limitation, RNA puritiy, temperature

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Graduate student theses produced at Trent University. You may also browse theses and dissertations by year, program, or author.

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1973 - 2033
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