Graduate Theses & Dissertations

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Reintroducing species in the 21st century
Climate change has had numerous impacts on species' distributions by shifting suitable habitat to higher latitudes and elevations. These shifts pose new challenges to biodiversity management, in particular translocations, where suitable habitat is considered crucial for the reintroduced population. De-extinction is a new conservation tool, similar to reintroduction, except that the proposed candidates are extinct. However, this novel tool will be faced with similar problems from anthropogenic change, as are typical translocation efforts. Using ecological niche modelling, I measured suitability changes at translocation sites for several Holarctic mammal species under various climate change scenarios, and compared changes between release sites located in the southern, core, and northern regions of the species' historic range. I demonstrate that past translocations located in the southern regions of species' ranges will have a substantial decline in environmental suitability, whereas core and northern sites exhibited the reverse trend. In addition, lower percentages (< 50% in certain scenarios) of southern sites fall above the minimal suitability threshold for current and long-term species occurrence. Furthermore, I demonstrate that three popular de-extinction candidate species have experienced changes in habitat suitability in their historic range, owing to climate change and increased land conversion. Additionally, substantial increase in potentially suitable space is projected beyond the range-limits for all three species, which could raise concerns for native wildlife if de-extinct species are successfully established. In general, this thesis provides insight for how the selection of translocation sites can be more adaptable to continued climate change, and marks perhaps the first rigorous attempt to assess the potential for species de-extinction given contemporary and predicted changes in land use and climate. Author Keywords: climate change, de-extinction, ecological niche models, MaxEnt, reintroduction, translocation
Stopover Movement Patterns by Blackpoll and Canada Warblers Across Southeastern Canada During Fall Migration
Stopover ecology is a topic that surges in relevancy as choices made by migrants during stationary periods (stopover sites) may not only have important individuals’ fitness consequences but also can affect population dynamics. I used MOTUS automated telemetry array to study fall stopover duration of Blackpoll Warbler (BLPW) and departure decisions of BLPW and Canada Warbler (CAWA) in relation to various predictors. I affixed radio-transmitters on 55 BLPWs and 32 CAWAs at two banding stations in Ontario in September-October 2014-2015. Radio-tagged individuals were tracked through the MOTUS network across southeastern Canada. I developed models relating age class, fat score, Julian date and stopover movement types to Blackpolls’ stopover duration. I also examined whether there were species-related differences of wind selectivity when resuming migration. No explanatory variable significantly influenced BLPW’s stopover duration. Both species tended to depart under increased tailwind assistance, but with no difference in the effect of wind conditions between the two species. This study provides further evidence supporting the relevance of local wind conditions as a key factor affecting the departure likelihood, especially when migrating birds face an ecological barrier. Author Keywords: Cardellina canadensis, departure decisions, minimum stopover length, MOTUS, overland fall migration, Setophaga striata
Regulation of Cytokinins During Kernel Development in High and Low Yielding Oat and Barley Lines
Cytokinins (CKs) are a family of plant phytohormones responsible for many areas of plant growth and development. There are four free base types of CKs found in higher plants, trans-zeatin (tZ), N6-(∆2-isopentenyl)adenine (iP), cis-Zeatin (cZ) and dihydrozeatin (DZ). CK biosynthesis is regulated by adenosine phosphate-isopentenyltransferase (IPT), which is encoded by a multi-gene family in many plant species. There are two types of IPT pathways responsible for CK production, the tRNA pathway and the AMP (ATP/ADP) pathway. The tRNA pathway putatively produces cZ and the latter predominantly produces iP type nucleotides. CKs have long been studied for their role in stress tolerance, signal transduction, and involvement in many areas of plant growth and development. This study focuses on the role of CKs and CK biosynthesis by IPT during kernel development and comparisons of its regulation in high and low yielding barley and oat lines. The sequence of a putative IPT encoding gene in barley and oat was identified by a blast search of other known IPT gene fragments in closely related species. Quantitative Real time PCR results based on primers designed for the putative barley and oat IPT gene revealed changes in expression of IPT during different stages of kernel development, but no significance difference was associated with yield. Correlation of IPT gene expression in barley with cZ CK profiles measured by HPLC-MS/MS, confirms a putative IPT gene is a tRNA- IPT. HPLC-MS/MS results reveal some CK types, such as benzyladenine, are more predominant in higher yielding lines. This suggests different types of CKs play a role in yield production. Future studies on more IPT genes in the barley and oat IPT gene family will outline a more clear representation of the role of IPT in barley kernel development. Author Keywords: Benzyladenine, Cereal grain, Cytokinin, Isopentenyl Transferase, Mass Spectrometry, Real Time PCR
influence of tree species litterfall on soil chemistry and implications for modelling soil recovery from acidification
Decades of acidic deposition have depleted base cation pools in soil over large parts of eastern north America, including the Muskoka-Haliburton region of central Ontario. This region has also experienced a shift in forest species composition over the past 200 years, favouring sugar maple (Acer saccharum Marsh.) at the expense of species such as white pine (Pinus strobus L.) and eastern hemlock (Tsuga canadensis (L.) Carr.). This shift in species composition may have changed soil chemistry over time due to differences in nutrient and metal inputs in litterfall. An analysis of litterfall and soil chemistry was conducted for five tree species commonly found across central Ontario. Stands were established in the Haliburton Forest & Wild Life Reserve and were dominated by one of balsam fir (Abies balsamea (L.) Mill.), eastern hemlock, white pine, sugar maple, or yellow birch (Betula alleghaniensis Britt.). Analysis of mineral soil oxides suggested that these stands were established on similar parent material. Deciduous dominated stands (maple and birch) had greater litterfall mass compared with conifer stands (fir, hemlock, and pine), generally leading to greater macronutrient inputs to the soil. Elemental cycling through the organic horizons was more rapid in deciduous stands, with base cations having the shortest residence times. This suggests that a change from greater conifer dominance to mixed hardwood forests may lead to more rapid elemental cycling and alter the distribution of elements in soil. Forests in the region are typically mixed and the resulting differences in soil chemistry may influence model predictions of soil recovery from acidification. Laboratory leaching tests indicated that both stand type and the acidity of simulated rainwater inputs influenced soil solution chemistry, with deciduous stands generally having a greater buffering capacity than sites dominated by coniferous species. Changes in soil chemistry were examined for each stand type using the Very Simple Dynamic (VSD) biogeochemical model. Simulations showed that soil base saturation began to increase following lows reached around the year 2000, and similar patterns were observed for all stands. When sulphur (S) and nitrogen (N) deposition were held constant at present rates, soil base saturation recovery (toward pre-1900 levels) was marginal by 2100. With additional deposition reductions, further increases in base saturation were minor at all sites. In conjunction with additional deposition reductions, the elimination of future forest harvesting allowed for the greatest potential for recovery in all stands. Overall, these results suggest that changes in forest cover may influence soil chemistry over time, most notably in the organic soil horizons. However, forecasted recovery from acidification is expected to follow similar patterns among stands, since differences in soil chemistry were less significant in the mineral soil horizons which compose a greater proportion of the soil profile. Author Keywords: base cation decline, forest harvesting, litterfall, mineral weathering, soil acidification, VSD model
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
Natural antisense transcripts to nucleus-encoded mitochondrial genes are linked to Ustilago maydis teliospore dormancy
Ustilago maydis is a basidiomycete smut fungus and the causal agent of common smut of corn. Disease progression and fungal development in this pathogen occur in planta, terminating in the production of dormant teliospores. Dormant spores of many fungi are characterized by reduced metabolic activity, which is restored during spore germination. The transition out of dormancy requires the rapid translation of stored mRNAs, which may be stabilized through natural antisense transcript (NAT)-mediated mechanisms. Transcript analysis revealed that as-ssm1, a NAT to the mitochondrial seryl-tRNA synthetase (ssm1), is detected in the dormant teliospore and absent in haploid cells. Disruption of ssm1 leads to cell lysis, indicating it is essential for cellular viability. Presented data supports the hypothesis that as-ssm1 has a role in facilitating teliospore dormancy through stabilizing ssm1 transcripts, which reduces mitochondrial function. as-ssm1 expression during in planta development begins 10 days post-infection, coinciding with the first appearance of dormant teliospores. To assess the impact of as-ssm1 expression on cell division, virulence and mitochondrial function, as-ssm1 was ectopically expressed in haploid cells, leading to increased ssm1 transcript levels and the formation of double-stranded RNA. These expression mutants are characterized by attenuated growth rate, virulence, mitochondrial membrane potential and oxygen consumption. Together, these findings support a role for NATs in moderating mitochondrial function during the onset of teliospore dormancy. Author Keywords: Dormant teliospore, Mitochondria, mRNA stability, Natural antisense transcripts, Non-coding RNA, Ustilago maydis
Social thermoregulation and potential for heterothermy
Northern and southern flying squirrels (Glaucomys sabrinus and G. volans, respectively) are experiencing a climate change induced increase in range overlap, resulting in recent hybridization. We investigated the occurrence of heterospecific communal nesting, a potential facilitator of hybridization, and aimed to confirm the presence of torpor, a potential barrier to hybridization, in flying squirrels. In wild-caught captive squirrels, we conducted a paired nest choice experiment and found that heterospecific nesting did occur, but in a lower frequency than conspecific nesting. Ambient temperature did not affect the frequency of grouped nesting. We attempted to induce torpor in flying squirrels in a laboratory through cold exposure while measuring metabolic rate and body temperature. Strong evidence of torpor was not observed, and metabolic rate remained unchanged with season. We conclude that torpor is not a barrier to hybridization in flying squirrels, but resistance to heterospecific nesting may indicate the existence of one. Author Keywords: heterospecific group, hybridization, northern flying squirrel, social thermoregulation, southern flying squirrel, torpor
Predictive Digital Mapping of Soils in Kitimat, British Columbia
Soil is an essential natural resource that supports provisioning services such as agriculture, silviculture, and mining. However, there is limited knowledge on forest soil properties across Canada. Digital soil mapping may be used to fill these data gaps, as it can predict soil properties in areas with limited observations. The focus of this study was to develop predictive maps of select soil physicochemical properties for the Kitimat Valley, British Columbia, and apply these maps to assess the potential impacts of sulphur dioxide emissions from an aluminum smelter, on soil properties in the Valley. Exchangeable [Ex.] magnesium, organic matter, pH, coarse fragment, Ex. potassium, bulk density, Ex. calcium, Ex. acidity, and Ex. sodium were all mapped with acceptable confidence. Time to depletion of base cation pools showed that ~240 km2 of the study area had a depletion time of 50 years or less. However, sources of base cations such as atmospheric deposition and mineral weathering were not considered. Author Keywords: acidification, buffering capacity, Digital soil mapping, predictive mapping, regression kriging, soil properties
Investigation of fugitive dust emissions from nepheline syenite mine tailings near Nephton, Ontario
A set of experiments was designed to investigate the factors—atmospheric and surficial—controlling fugitive dust emissions from the tailings ponds of UNIMIN Canada, a mining company that extracts and produces nepheline syenite (feldspar) at two adjacent sites (Nephton and Blue Mountain) located north of Havelock, Ontario. Using wind tunnel measurements, the combined influence of relative humidity and temperature (represented by the absolute matric potential, |Ψ|) on dust emission was quantified and modelled. About 300 experimental runs were conducted under various conditions of wind speed (4.5-6.25 ms-1), temperature (0-30oC) and relative humidity (10-70%). Generally, dust flux decreased as a logarithmic function of matric potential, with dust emission strongly suppressed for RH > 60% or |Ψ|<70 MPa. Field measurements also confirmed the role of relative humidity in suppressing dust emission. Irrigation, which is widely used by mines to control dust emissions, reduced ambient dust concentration at the study site only about 60% of the time, with the highest mitigation efficiencies (average of 90%) occurring when the total depth of water applied intermittently over a few hours was greater than 10 mm. In the absence of emergent vegetation, the terrestrial laser scanning (TLS) technique proved to be a promising method for detecting and estimating both spatial and temporal moisture content changes in the field environment, particularly for the very thin surface layer, which is the most important layer for dust emission. It is hoped that the results from this study will help mines to optimize their dust management programs for the range of climate and topographic conditions found at their sites, and also serve as a source of useful information and input data for atmospheric dispersion models, such as AERMOD and CALPUFF, whose accuracy depends on the quality of the input data such as the emission rate. Author Keywords: dust mitigation efficiency, Fugitive dust, nepheline syenite, relative humidity, tailings, terrestrial laser scanning
Tests of the Invasional Meltdown Hypothesis in invasive herbaceous plant species in southern Ontario
According to the Invasional Meltdown Hypothesis (IMH), invasive species may interact in their introduced range and facilitate future invasions. This study investigated the possibility that Alliaria petiolata, an invasive allelopathic herbaceous plant in Ontario, is facilitating invasions by additional alien species. Two allelopathic focal species were chosen for this study: the native Solidago canadensis and the invasive A. petiolata. Field surveys in southern Ontario that quantified plant biodiversity in plots that included one or both focal species revealed no support for the IMH, although fewer species co-existed with A. petiolata than with S. canadensis. A year-long recruitment experiment in Peterborough, Ontario, also produced results inconsistent with the IMH, although did provide some evidence that A. petiolata limited recruitment of other species. These results collectively show negative impacts on regional biodiversity by A. petiolata, even in the absence of an invasional meltdown. Author Keywords: allelopathy, Alliaria petiolata, co-occurrence surveys, invasional meltdown hypothesis, invasive species, Solidago canadensis
Effect of Attending a Virtual Oncology Camp on Childhood Cancer Patient's Pyshcosocial Functioning and Parental Stress - A Pilot Study
Objectives/purpose: The current study examined whether attending a 1-month virtual oncology camp (VOC) improved resilience and hope in childhood cancer patients and parental/caregiver stress. Methods:Childhood cancer patients/survivors and their parent/caregivers enrolled for VOC, participated in an online anonymous survey: before, after and 3-months after VOC. The survey included the Child and Youth Resilience Measure (CYRM) and the Snyder’s Children’s Hope Scale (CHS) for the childhood cancer patients/survivors and the Pediatric Inventory for Parents (PIP) for parent/caregivers. Results:CYRM scores increased from T1 to T2 (d=0.86). Compared to T1, at T2 CHS scores also increased (d=1.33). Both CHS and CYRM scores remained higher at T3 compared with T1 (d=1.34; d=0.86). There were no changes in PIP scores between any time points. Conclusion and significance: Our study demonstrated that participation in a VOC improved children’s resilience and hope but did not change parental stress. Highlighting the clinical significance of these VOCs and the impacts they have on childhood cancer patients/survivors. Author Keywords: cancer, children, hope, parental stress, resilience, virtual oncology camp
wind tunnel based investigation of three-dimensional grain scale saltation and boundary-layer stress partitioning using Particle Tracking Velocimetry
Aeolian transport of sand particles is an important geomorphic process that occurs over a significant portion of the earth’s land surface. Wind tunnel simulations have been used for more than 75 years to advance the understanding of this process; however, there are still several principles that lack validation from direct sampling of the sand particles in flight. Neither the three-dimensional dispersion of, nor the momentum carried by particles in flight have been properly measured. This has resulted in the inability to validate numerical particle dispersion models and the key boundary-layer momentum partitioning model that serves as the framework for understanding the air-sand feedback loop. The primary impediment to these measurements being made is a lack of tools suited for the task. To this end, this PhD aims to improve existing particle tracking technology, thus enabling the collection of particle measurements during wind tunnel experiments that would address the aforementioned knowledge gaps. Through the design and implementation of the Expected Particle Area Searching method, a fully automated particle tracking velocimetry system was developed with the capability to measure within ½ grain diameter of the bed surface under steady state transport conditions. This tool was used to collect the first 3-D data set of particle trajectories, from which it was determined that a mere 1/8th of sand transport is stream aligned and 95% is contained within ± 45o of the mean wind direction. Particles travelling at increasing spanwise angles relative to the stream aligned flow were found to exhibit different impact and ejection velocities and angles. The decrease in the number of particles with increasing height in the saltation cloud, very close to the bed is observed to transition from a power to a linear relation, in contrast to previous literature that observed an exponential decay with coarser vertical resolution. The first direct measurements of particle-borne stress were captured over a range of wind velocities and were compared with earlier fluid stress measurements taken using Laser Doppler Anemometry. In support of established saltation theory, impacting particle momentum is found to contribute strongly to particle entrainment under equilibrium conditions. In opposition to established theory, however, particle-borne stress was found to reach a maximum above the surface and does not match the change in air-borne stress with increasing distance from the surface. Near surface splashed particles, measured herein for the first time, appear to play a greater role in stress partitioning than previously thought. This study suggests that research is needed to investigate the role of bed load transport on stress partitioning, to differentiate between airborne trajectory types, and to develop particle tracking tools for field conditions. Author Keywords: Aeolian Transport, Eolian Transport, Particle Tracking Velocimetry, Saltation, Stress Partitioning, Wind Tunnel Simulation

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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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