Graduate Theses & Dissertations


Influence of Action Potentiation on the Perception of Objects Presented Near Hand
For currently-debated reasons, perception of visual stimuli is enhanced in near-hand space compared to far-hand space. According to the action potentiation hypothesis, near-hand effects result from automatically generated potential motor responses produced upon viewing objects presented in near-hand space. This hypothesis was tested by crossing hand manipulations with two separate techniques designed to elicit action potentiation. The first series of experiments presented participants with a cueing task where images of handled objects served as the cue, and its handle compatibility was manipulated. A consistent near-hand effect was observed, but there was no evidence that the images potentiated action as there was no handle-compatibility effect. The second experiment used a visuomotor competition reaching task, which required participants to initiate reaches toward a distractor display and adjust their trajectory on the fly so as to end the reach at a later indicated target location. For every distractor presented simultaneous and competing motor responses were generated, and differences in how hand presence influenced the resolution of this competition were examined. Based on predictions made, action potentiation is unlikely to be the root cause of the near-hand effect; however, was not possible to rule out this explanation entirely. The findings of these experiments shed light both on the importance and consistency of the near-hand effect, and the difficulties associated with uncovering its nature in human populations. Author Keywords:
Influence of Canopy Water Partitioning on the Isotopic Signature of Plant Water in a Mixed Northern Forest
This study seeks to clarify the way in which the differing canopy characteristics among tree species influence the partitioning of precipitation, and therefore the source of water available for plant water uptake, in the Plastic Lake catchment near Dorset, ON. Three dominant tree species were compared: red oak (Quercus rubra), eastern white pine (Pinus strobus), and eastern hemlock (Tsuga canadensis). Above-canopy precipitation, throughfall, stemflow, and soil water content were monitored weekly from June 2016 until October 2016 and the 18O and 2H isotopic signatures of each were analyzed. Plant water and bulk soil water samples were also collected from five trees of each species at five stages of the growing season to compare the isotopic signature of xylem water to that of their surrounding soils. Both plant water and bulk soil water displayed evidence of isotopic fractionation; however, plant water was more depleted in δ2H and δ18O than bulk soil water. Water interacting with the tree canopies as throughfall and stemflow did not display significant evidence of isotopic fractionation. This suggests that the vegetation could have accessed an isotopically distinct source of water stored within the soil or that an unknown isotopic fractionation process occurred throughout this study. Author Keywords:
Influence of Habitat on Woodland Caribou Site Fidelity
Site fidelity is the behaviour of individuals to return to the same location; for female woodland caribou it may reflect reproductive success and depend on habitat quality. I investigated the influence of landscape and disturbance conditions on fidelity among three populations in Manitoba and Ontario, Canada. Habitat classifications were based on Forest Resource Inventory (FRI) and Landsat TM landcover maps. A total of 261 sites were ground-truthed to determine mapping accuracy. An amalgamated map incorporating FRI and Landsat TM data was estimated from field measurements to have an overall accuracy of 69.0%. Site fidelity was expressed as the distance between consecutive-year locations of individuals and was investigated during five week-long periods representing calving, early and late post-calving, winter, and breeding. Site fidelity was strongest during the post-calving seasons and weakest during the winter. Habitat had little influence on site fidelity in all seasons, excepting winter, even under highly disturbed conditions, suggesting maintenance of fidelity may be a maladaptive trait. Individual variation proved a strong predictor and cursory mapping indicated that caribou may return to sites visited two or more years earlier. Conservation management and policy should recognize that site fidelity may represent an ecological trap. Author Keywords: calving, disturbance, habitat, movement, Rangifer tarandus caribou, site fidelity
Influence of Nitrogen Deposition on Community Composition in Pinus banksiana Forests Across Northwestern Canada
Anthropogenic atmospheric emissions and subsequent deposition of nitrogen (N) can affect N-sensitive habitats and lead to shifts in plant species community composition. This study assessed the effects of N deposition on plant community composition for Jack pine forests across northwestern Canada and across a smaller subset of sites surrounding the Athabasca Oil Sands Region (AOSR) using ‘gradient forest’ analysis. Predictor influence on community composition varied depending on the scale of the study and relatively distinct thresholds were identified for different plant groups. In the larger scale study, a total deposited nitrogen (TDN) threshold of 1.5 – 3 kg N ha-1yr-1 was well suited to protect predominantly lichen species, consistent with lichen-based critical loads from other studies. Across the smaller scale study, a TDN threshold of 5.6 kg N ha-1yr-1 was primarily associated with vascular species changepoints but did include some important N-indicator lichen and bryophyte species. Author Keywords: critical loads, gradientForest, Jack pine, Nitrogen deposition, species composition
Influence of geodemographic factors on electricity consumption and forecasting models
The residential sector is a major consumer of electricity, and its demand will rise by 65 percent by the end of 2050. The electricity consumption of a household is determined by various factors, e.g. house size, socio-economic status of the family, size of the family, etc. Previous studies have only identified a limited number of socio-economic and dwelling factors. In this thesis, we study the significance of 826 geodemographic factors on electricity consumption for 4917 homes in the City of London. Geodemographic factors cover a wide array of categories e.g. social, economic, dwelling, family structure, health, education, finance, occupation, and transport. Using Spearman correlation, we have identified 354 factors that are strongly correlated with electricity consumption. We also examine the impact of using geodemographic factors in designing forecasting models. In particular, we develop an encoder-decoder LSTM model which shows improved accuracy with geodemographic factors. We believe that our study will help energy companies design better energy management strategies. Author Keywords: Electricity forecasting, Encoder-decoder model, Geodemographic factors, Socio-economic factors
Influence of nitrogen and sulfur on cadmium tolerance in Euglena gracilis
Heavy metal pollution threatens human and ecosystem health. E. gracilis was investigated for its potential use in bioremediation due to its tolerance for heavy metals and ability to sequester them from the environment. E. gracilis can remove metals by producing metal binding compounds enriched in sulfur and nitrogen. In this thesis, E. gracilis cultures that were pretreated with elevated levels of sulfur or nitrogen had increased tolerance to CdCl2 compared to non-pretreated cultures. RNA-sequencing revealed that both pretreatments led to transcript level changes and that exposure to CdCl2 led to further transcript level changes. Gene ontology (GO) enrichment analysis reflected changes in nitrogen and sulfur metabolism as well as physiological processes related to metal binding. The data from this thesis revealed important transcription level changes that occur when E. gracilis is challenged with CdCl2 and helps us understand how organisms adapt to heavy metal pollution in the environment. Author Keywords: bioremediation, Cadmium, Euglena gracilis, GO-enrichment, metal-binding, RNA-Sequencing
Influence of nitrogen deposition on the vegetation community of Irish oak woodlands
In this study, the influence of N deposition on the vegetation community of semi-natural oak woodlands in Ireland was assessed through national and regional scale analysis of forest plot data. At both scales, Canonical Correspondence Analysis suggested that N deposition was a predictor of community composition, although site-specific soil characteristics were the strongest predictors of the species dataset. Threshold Indicator Taxon Analysis suggested that the vegetation community demonstrated the most change at 13.2 kg N ha-1 yr-1. While this change point falls within the current recommended critical load range for nutrient nitrogen for acidophilous oak dominated woodlands (10 to 15 kg N ha-1 yr-1), it is notable that 23% of species recorded had individual change points below this range, and could potentially be lost from this habitat if deposition increases. The results from this study suggest that, for acidophilous oak woodlands, habitat conservation policies should be unified with N emission reduction policies. Author Keywords: community composition, critical load, nitrogen depositioin, oak woodland, species richness, Taxon Indicator Threshold Analysis
Interactome study of the Giardia intestinalis nuclear localized cytochrome b5
Giardia intestinalis is a waterborne enteric parasite that lacks mitochondria and the capacity for heme biosynthesis. Despite this, Giardia encodes several heme proteins, including four cytochrome b5 isotypes (gCYTB5-I – IV) of unknown function. The aim of this thesis is to gain insight into the function of the Giardia cytochrome b5 isotype III (gCYTB5-III) that is found in the nucleus, as first reported by our laboratory using immunofluorescence microscopy experiments with an isotype-III specific antibody. Nuclear localization of isotype-III is supported by two of my experiments: i) immunoblot analysis of crude cytoplasmic and nuclear enriched fractions of Giardia trophozoites; ii) association of gCYTB5-III with the insoluble fraction of Giardia lysates crosslinked with formaldehyde is reversed by DNase I treatment. To gain an understanding of the possible roles of gCYTB5-III, I performed immunoprecipitation (IP) experiments on lysates from Giardia trophozoites to identify its protein partners. Mass spectroscopy analysis of the immunoprecipitate identified proteins localized to the nucleus (RNA polymerase, DNA topoisomerase, histones, and histone modifying enzymes). Intriguingly, over 40% of the known mitosomal proteome, which functions in iron-sulfur (Fe-S) cluster assembly was also associated with gCYTB5-III. One of these proteins, the flavoenzyme GiOR-1, has been shown to mediate electron transfer from NADPH to recombinant gCYTB5-III. These IP results provide evidence that GiOR-1 and gCYTB5-III interact in vivo, and furthermore, suggest that some proteins in the mitosome could interact with those in the nucleus. I also found that DNA stress, caused by low concentrations of formaldehyde (0.1 – 0.2%) resulted in the increased expression of gCYTB5-III. Collectively these findings suggest a role of gCYTB5-III in Giardia's response to DNA stress and perhaps the formation of Fe/S clusters. Author Keywords: cluster, cytochrome, heme, iron, mitosome, nuclear
Interpretation of forest harvest recovery using field-based and spectral metrics in a Landsat time series in Northwestern Ontario
The forestry sector has a well-developed history of using remote sensing to identify structural characteristics of forests and to detect and attribute changes that occur in forested landscapes. Monitoring the recovery of disturbed forests is an important factor in long term forest management. However, forest that is recovered spectrally may not be recovered when considered in terms of a Free to Grow assessment. A Free to Grow assessment is used in Ontario to determine whether a disturbed site will likely achieve a desired future state, i.e., is recovered according to a forestry perspective. The objective of this research was to determine the relationship between a pixel-based Landsat Time Series of spectral recovery and the results of Free to Grow assessments. Spectral trajectories were generated from representative pixels within known harvested forest areas. Results indicate that while Free to Grow sites often achieve spectral recovery (>90%), many non-Free to Grow sites were classified as spectrally recovered, suggesting that improved methods of spectral recovery monitoring are needed. Author Keywords: forest recovery, Free to Grow, Landsat Time Series, LandTrendr, Pixel-based, spectral recovery
Intra-seasonal Variation in Black Tern Nest-site Selection and Survival
Resources and risk are in constant flux and an organism’s ability to manage change may improve their likelihood of persistence. I examined intra-seasonal variation in nest-site selection and survival of a declining wetland bird, the Black Tern (Chlidonias niger surinamensis). I modelled nest site occupancy and survival of early and late-nesting birds as a function of static and dynamic factors. Early-nesting birds selected nest sites based on the degree and direction of habitat change that occurred over the nesting cycle, while late-nesting birds selected sites based on static conditions near the time of nest-site selection. Nest age had the strongest influence on daily survival rate for both early and late-nesting birds, but the shape of this relationship showed intra-seasonal differences. Additionally, early-season survival improved slightly with increasing vegetation coverage and distance between conspecific nests, while late-season survival increased with clutch size. My results suggest that intra-seasonal variation in nest-site selection and survival is driven by changing habitat conditions and predator behavior. Author Keywords: Black Tern, Chlidonias niger surinamensis, daily survival rate, intra-seasonal variation, nest-site selection
Investigating Ecological Niche Differentiation Among Wild Candids Experiencing Hybridization in Eastern North America
Currently there are large areas of the North American landscape that are occupied by Canis spp. hybrids of several varieties, leading to the logical question as to the genetic structure and ecological function of Canis populations across the continent, and to what extent hybrids reflect contemporary landscapes. This study illustrated patterns of niche differentiation between parental canid species and their hybrids using individual high quality genetic profile and species distribution models to support the intermediate phenotype hypothesis. In general, hybrids demonstrated an intermediate habitat suitability compared to its parental species, across most environmental variables used. A similar trend was observed in the niche metric analysis, where we found that hybrids exhibit intermediate niche breadth, with eastern coyotes and eastern wolves exhibiting the broader and narrower niche, respectively. Our results demonstrate that the intermediate phenotype hypothesis is supported even at a large scale and when involving highly mobile large mammal species. Author Keywords: canid, ecological niche modelling, hybridization, intermediate phenotype, microsatellite genotype, niche differentiation
Investigating the regional variation in frequencies of the invasive hybrid cattail, Typha × glauca
Interspecific hybridization rates can vary depending on genomic compatibilities between progenitors, while subsequent hybrid spread can vary depending on hybrid performance and habitat availability for hybrid establishment and persistence. As a result, hybridization rates and hybrid frequencies can vary across regions of parental sympatry. In areas around the Laurentian Great Lakes, Typha × glauca is an invasive plant hybrid of native Typha latifolia and introduced Typha angustifolia. In areas of parental sympatry in Atlantic Canada and outside of North America, T. × glauca has been reported as either rare or non-existent. I investigated whether the low frequencies of hybrids documented in Nova Scotia, Atlantic Canada, are influenced by reproductive barriers that prevent hybrid formation or environmental factors (salinity) that reduce hybrid performance. I identified an abundance of hybrids in the Annapolis Valley (inland) and a scarcity of hybrids in coastal wetlands through preliminary site surveys throughout Nova Scotia. In Annapolis Valley populations, flowering times of progenitor species overlapped, indicating that asynchronous flowering times do not limit hybrid formation in this region. Viable progeny were created from interspecific crosses of T. latifolia and T. angustifolia from Nova Scotia, indicating that there are no genomic barriers to fertilization and germination of hybrid seeds. Typha × glauca germination in high salinity was significantly lower than that of T. latifolia, but there was no difference at lower salinities. Therefore, while germination of hybrid seeds may be impeded in the coastal wetlands where salinity is high, inland sites have lower salinity and thus an environment conducive to hybrid germination. However, I found that once established as seedlings, hybrids appear to have greater performance over T. latifolia across all salinities through higher ramet production. Moreover, I found that T. latifolia sourced from Ontario had reduced germination and lower survivorship in high salinities compared to T. latifolia sourced from Nova Scotia, which could indicate local adaptation by T. latifolia to increased salinity. These findings underline that interactions between environment and local progenitor lineages can influence the viability and the consequent distribution and abundance of hybrids. This, in turn, can help explain why hybrids demonstrate invasiveness in some areas of parental sympatry but remain largely absent from other areas. Author Keywords: flowering phenology, Hybridization, invasive species, physiology, pollen compatibility, salinity tolerance


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Format: 2023/12/04