Graduate Theses & Dissertations


Environmental structure, morphology and spatial ecology of the five-lined skink (Plestiodon fasciatus) at high latitude range limits
Detecting relevant and meaningful patterns from the complex, interconnected network of relationships between organisms and their environment is a primary objective of ecology. Ecological patterns occur across multiple scales of space and time. In this dissertation, I examine aspects of environmental structure that influence a species’ distribution and are expressed in that species’ population dynamics. I compare the morphology of the five-lined skink (Plestiodon fasciatus) near its high latitude range limits with a lower latitude population and evaluate the economics of their behaviour in the context of its reproductive strategy. I tested the conformity of this species to biogeographical rules postulated by MacArthur, Bergmann, and Rensch. Spatial ecology was investigated in the context of the environmental potential for polygamy proposed by Emlen and Oring (1977) The five-lined skink, Plestiodon fasciatus, conformed to these biogeographic rules. Specifically, abiotic factors were the primary limiting factors affecting distribution at the high latitude range limits of the species; body size was larger in high latitude populations; and the degree of sexual size dimorphism was greater at high latitude than at low latitude. Spatial ecology at the individual scale was influenced by sites with suitable thermal conditions which facilitate the polygynandrous mating system documented in P. fasciatus in high latitude populations. My results confirm the importance of microsites with suitable thermal profiles as key habitat for ectothermic vertebrates at high latitudes. The influence of temperature as a limiting abiotic factor is expressed in population density, body size, spatial ecology, and reproductive strategy of P. fasciatus. Conservation and restoration of high latitude populations of ectothermic vertebrates should focus on ensuring thermal requirements of the species of concern are met before other factors are addressed, as temperature is likely the single most important limiting factor at high latitude range limits. Author Keywords: biogeography, lizard, Plestiodon fasciatus, range limits, sexual size dimorphism, spatial ecology
Carbon Exchange along a Natural Gradient of Deciduous Shrub Coverage in the Low-Arctic
Arctic terrestrial ecosystems have experienced substantial structural and compositional changes in response to warming climate in recent decades, especially the expansion of shrub species in Arctic tundra. Climatic and vegetation changes could feedback to the global climate by changing the carbon balance of Arctic tundra. The objective of this thesis was to investigate the influence of increased shrub coverage on carbon exchange processes between atmosphere and the Arctic tundra ecosystem. In this study a space-for-time substitution was used, referred to as a shrub expansion “chronosequence”, with three sites along a natural gradient of deciduous shrub coverage in the Canadian low Arctic. Leaf-level photosynthetic capacity (Amax) of dominating birch shrub Betula glandulosa (Michx.) was significantly higher (P<0.05) at the site where shrubs were more abundant and taller than at the other sites. For all sites, mean Amax in 2014 was significantly lower than in 2013, in part potentially due to differences in precipitation distribution. Bulk soil respiration (RS) rate was significantly higher (P<0.05) at the site with more shrubs compared with the other sites. The differences in RS across sites appeared to be driven by differences in soil physiochemical properties, such as soil nitrogen and soil bulk density rather than soil microclimate factors (e.g. soil temperature, moisture). The three sites were either annual CO2 sources (NEP<0) to the atmosphere or CO2 neutral, with strongest annual CO2 sources (-44.1±7.0 g C m-2) at the site with most shrubs. Overall this study suggests that shrubs tundra carbon balance will change with shrub expansion and that shrub ecosystems in the Arctic currently act as annual carbon sources or neutral to the atmospheric CO2 and further shrub expansion might strengthen the CO2 emissions, causing a positive feedback to the warming climate. Author Keywords: arctic tundra, carbon exchange, climate change, photosynthetic capacity, shrub expansion, soil respiration
methodological framework for the assessment and monitoring of forest degradation under the REDD+ programme based on remote sensing techniques and field data
In this thesis, a methodological framework for the assessment and monitoring of forest degradation based on remote sensing techniques and field data, as part of the REDD+ programme, is presented. The framework intends to support the implementation of a national Monitoring, Verification and Report (MRV) system in developing countries. The framework proposed an operational definition of forest degradation and a set of indicators, namely Canopy Cover (CC), Aboveground Biomass (AGB) and Net Primary Productivity (NPP), derived from remote sensing data. The applicability of the framework is tested in a sub-deciduous tropical forest in the Southeast of Mexico. The results from the application of the methodological framework showed that the higher rates of forest degradation, 1596-2865 ha·year-1, occur in areas with high population density. Estimations of aboveground biomass in these degraded areas span from 1 to 24 Mg·ha-1, with a rate of carbon fixation ranging from 130 to 246 gC·m2·year. The results also showed that 43 % of the forests of the study area remain with no evident signs of degradation, as detected by the indicators selected, during the period evaluated. The integration of the different elements conforming the methodological framework for the assessment and monitoring of forest degradation enabled the identification of areas that maintain a stable condition and areas that change over the period evaluated. The methodology outlined in this thesis also allows for the identification of the temporal and spatial distributions of forest degradation based on the indicators selected, and it is expected to serve as the basis for operations of the REDD+ programme with the appropriate adaptations to the area in turn. Author Keywords: Forest degradation, Monitoring, REDD+, Remote Sensing, Tropical forest
effects of parasitism on consumer-driven nutrient recycling
Daphnia are keystone consumers in many pelagic ecosystems because of their central role in nutrient cycling. Daphnia are also frequently infected, and the parasites causing these infections may rival their hosts in their ability to regulate ecosystem processes. Therefore, parasitic exploitation of Daphnia may alter nutrient cycling in pelagic systems. This thesis integrates existing knowledge regarding the exploitation of Daphnia magna by 2 endoparasites to predict parasite-induced changes in the nutrient cycling of infected hosts and ecosystems. In chapter 1, I I contextualizing the integration of these themes by reviewing the development of the fields of elemental stoichiometry and parasitology. In chapter 2, we show how the bacterial parasite, Pasteuria ramosa, increased the nitrogen (N) and phosphorus (P) release rates of D. magna fed P-poor diets. We used a mass-balance nutrient release model to show that parasite-induced changes in host nutrient accumulation rates and diet-specific changes in host ingestion rates were responsible for the accelerated nutrient release rates that we observed. In chapter 3, we extended our examination of the nutrient mass balance of infected D. magna to include another parasite, the microsporidian H. tvaerminnensis. We found differences in the effects of these two parasites on host nutrient use as well as support for the hypothesis that parasite-induced changes in Daphnia N release are caused by the effects of infection on Daphnia fecundity. In chapter 4, we examined the relationship between P concentrations and the presence and prevalence of H. tvaerminnensis in rock pools along the Baltic Sea. We found that particulate P concentrations were negatively associated with the prevalence of this parasite, a result that is consistent with the increase in P sequestration of H. tvaerminnensis-infected Daphnia that we observed in chapter 3. I discuss the potential implications of the work presented in chapters 2-4 for other parasite-host systems and ecosystems in chapter 5. Overall, the research presented here suggests that parasite-induced changes in host nutrient use may affect the availability of nutrients in the surrounding environment, and the magnitude of this effect may be linked to parasite-induced reductions in fecundity for many invertebrate hosts. Author Keywords: consumer, ingestion rates, mass-balance, nutrient-recycling, parasitism, phosphorus
Stress Axis Function and Regulation in New World Flying Squirrels
Across vertebrate taxa, the hypothalamic-pituitary-adrenal axis (or the stress axis) is highly conserved, and is central to vertebrate survival because it allows appropriate responses to psychological stressors. Habitat shapes successful physiological and ecological strategies, and to appreciate how individual species respond to stressors in their environment, it is essential to have a thorough knowledge of the basic stress physiology of each species. In this dissertation, I studied the functioning and evolution of the stress physiology of New World flying squirrels. I showed that baseline, circulating cortisol levels in northern (Glaucomys sabrinus) and southern (G. volans) flying squirrels are some of the highest ever reported for mammals, indicating that their stress axes operate at a higher set point than most other species. I also assessed other aspects of their acute stress response, including free fatty acid and blood glucose levels, and indices of immune function, and showed that the flying squirrels’ physiological reaction to stressors may differ from that of other mammals. Using immunoblotting, I found that corticosteroid-binding globulin (CBG) expression levels in flying squirrels appeared to be higher than previously reported using alternative methods. I also concluded however, that these levels did not appear to be high enough to provide their tissues with the protective CBG-bound buffer from their high circulating cortisol concentrations experienced by the majority of vertebrates. Thus, this arm of cortisol regulation within the flying squirrel stress axes may be weak or non-existent. Following this, I focused on southern flying squirrels and showed evidence that the second arm of cortisol regulation — the negative feedback mechanism at the level of the brain — functions effectively, but that this species is glucocorticoid resistant. Their tissue receptors appear to have a reduced affinity for cortisol, and this affinity may change seasonally to allow for the onset of other biological processes required for survival and reproduction. Due to their distinctive stress physiology, northern and southern flying squirrels may provide comparative physiologists with model systems for further probing of the function and evolution of the stress axis among vertebrates. Author Keywords: corticosteroid-binding globulin, flying squirrel, Glaucomys, glucocorticoids, physiological ecology, stress physiology
successful invader in expansion
Researchers have shown increasing interest in biological invasions for the associated ecological and economic impacts as well as for the opportunities they offer to study the mechanisms that induce range expansion in novel environments. I investigated the strategies exhibited by invasive species that facilitate range expansion. Invasive populations exhibit shifts in life-history strategy that may enable appropriate responses to novel biotic and abiotic factors encountered during range expansion. The spatio-temporal scales at which these shifts occur are largely unexplored. Furthermore, it is not known whether the observed dynamic shifts represent a consistent biological response of a given species to range shifts, or whether the shifts are affected by the abiotic characteristics of the new systems. I examined the life-history responses of female round gobies Neogobius melanastomus across fine and coarser spatial scales behind the expansion front and investigated whether invasive populations encountering different environmental conditions (Ontario vs France) exhibited similar life-history shifts. In both study systems, I found an increase in reproductive investment at invasion fronts compared to longer established areas at coarse and fine scales. The results suggest a similar response to range shifts, or a common invasion strategy independent of environmental conditions experienced, and highlight the dynamic nature of an invasive population’s life history behind the invasion front. The second part of my research focused on the development of an appropriate eDNA method for detecting invasive species at early stages of invasion to enable early detection and rapid management response. I developed a simple, inexpensive device for collecting water samples at selected depths for eDNA analysis, including near the substrate where eDNA concentration of benthic species is likely elevated. I also developed a protocol to optimise DNA extraction from water samples that contain elevated concentration of inhibiters, in particular near-bottom samples. Paired testing of eDNA and conventional surveys was used to monitor round goby expansion along its invasion pathway. Round gobies were detected in more sites with eDNA, permitting earlier, more accurate, upstream detection of the expansion front. My study demonstrated the accuracy and the power of using eDNA survey method to locate invasion fronts. Author Keywords: Age-specific reproductive investment, DNA extraction, Energy allocation, Fecundity, Invasion front, Range expansion
Interactome Study of Giardia Intestinalis Cytochromes B5
Giardia intestinalis is an anaerobic protozoan that lacks common eukaryotic heme-dependent respiratory complexes and does not encode any proteins involved in heme biosynthesis. Nevertheless, the parasite encodes several hemeproteins, including three members of the Type II cytochrome b5 sub-group of electron transport proteins found in anaerobic protist and amitochondriate organisms. Unlike the more well-characterized cytochrome b5s of animals, no function has been ascribed to any of the Type II proteins. To explore the functions of these Giardia cytochromes (gCYTB5s), I used bioinformatics, immunofluorescence microscopy (IFM) and co-immunoprecipitation assays. The protein-protein interaction in silico prediction tool, STRING, failed to identify relevant interacting partners for any of the Type II cytochromes b5 from Giardia or other organisms. Differential cellular localization of the gCYTB5s was detected by IFM: gCYTB5-I in the perinuclear space; gCYTB5-II in the cytoplasm with a staining pattern similar to peripheral vacuole-associated protein; and gCYTB5-III in the nucleus. Co-immunoprecipitation with the gCYTB5s as bait identified potential interacting proteins for each isotype. The most promising candidate is the uncharacterized protein GL50803_9861, which was identified in the immunoprecipitate of both gCYTB5-I and II, and which co-localizes with both. Structural analysis of GL50803_9861 using Swiss Model, Phyre2, I-TASSER and RaptorX predicts the presence of a nucleotide-binding domain, which is consistent with a potential redox role involving nicotinamide or flavin-containing cofactors. Finally, the protein GL50803_7204 which contains a RNA/DNA binding domain was identified a potential partner of gCYTB5-III. These findings represent the first steps in the discovery of the roles played by these proteins in Giardia. Author Keywords: Cytochrome b5, Giardia intestinalis, Heme, Interactome, Protein structure prediction
effects of particulate matter on the fate and toxicity of silver nanoparticles
As an emerging contaminant, the antimicrobial agent silver nanoparticles (AgNPs) have been receiving considerable attention to determine their potential effects to aquatic ecosystems. However, estimates of aquatic consumer survivorship and other toxicological endpoints vary considerably among experiments, largely due to the environment in which the test takes place. Throughout this thesis I aim to understand which natural environmental variables impact toxicity to the common aquatic consumer Daphnia. I focus on the effects of particulate matter as it may play a role in animal nutrition as well as interact with AgNPs. I explore particulate matter’s effect on survival in the complex matrices including other natural variables that could impact toxicity. I conduct a series of complimentary field and laboratory studies to understand how particles impact AgNP toxicity and how those interactions vary within whole lake ecosystems. Using laboratory studies, I establish that algal particles mitigate the toxic effects of AgNPs on Daphnia survival through removing Ag from the water column and that phosphorus increases this effect. Using wild Daphnia and lake water, I demonstrate the ability of particulate matter to mitigate toxicity in complex natural settings. It was also one of the major predictors of AgNP toxicity to Daphnia along with dissolved organic carbon and daphnid seasonal health. Finally, using a whole lake AgNP addition experiment, I demonstrate that particles and AgNPs interact variably in the lake. Silver from AgNPs binds to particles and is removed to the sediments through the actions of settling particles without impacting the dynamics of living communities. Overall, I am able to demonstrate that the natural components of lake ecosystems, especially particulate matter, are able to mitigate the effects of AgNPs in lake ecosystems to a point where they likely will be never pose a threat to the survivorship of aquatic consumers such as Daphnia. Author Keywords: Daphnia, ecotoxicity, particulate matter, Silver nanoparticles, whole lake experiment
Fungi and Cytokinins
Cytokinin biosynthesis in organisms aside from plant species has often been viewed as a byproduct of tRNA degradation. Recent evidence suggests that these tRNA degradation products may actually have a role in the development of these organisms, particularly fungi. This thesis examines the importance of cytokinins, a group of phytohormones involved in plant cell division and differentiation as well as the phytohormone abscisic acid, involved in plant response to environmental factors, and their presence and role in fungi. An initial survey was conducted on 20 temperate forest fungi of differing nutritional modes. Using HPLC-ESI MS/MS, cytokinin and abscisic acid were detected in all fungi regardless of their mode of nutrition or phylogeny. The detection of the same seven CKs across all fungi suggested the existence of a common CK biosynthetic pathway and dominance of the tRNA pathway in fungi. Further, the corn smut fungus Ustilago maydis is capable of producing CKs separate from its host and different U. maydis strains induce disease symptoms of differing severity. To determine if CK production during infection alters disease development a disease time course was conducted on cob tissue infected with U. maydis dikaryotic and solopathogenic strains. Dramatic changes in phytohormones including an increase in ABA followed by increases in cisZCKs were detected in tumour tissue particularity in the more virulent dikaryon infection, suggesting a role for CKs in strain virulence. Mining of the U. maydis genome identified a sole tRNA-isopentenyltransferase, a key enzyme in CK biosynthesis. Targeted gene deletion mutants were created in U. maydis which halted U. maydis CK production and decreased pathogenesis and virulence in seedling and cob infections. CK and ABA profiling carried out during disease development found that key changes in these hormones were not found in deletion mutant infections and cob tumour development was severely impaired. These findings suggested that U. maydis CK production is necessary for tumour development in this pathosystem. The research presented in this thesis highlights the importance of fungal CKs, outlines the dominant CK pathway in fungi, identifies a key enzyme in U. maydis CK biosynthesis and reveals the necessity of CK production by U. maydis in the development of cob tumours. Author Keywords: abscisic acid, cytokinins, high performance liquid chromatography-electrospray ionization tandem mass spectrometry, tRNA degradation pathway, Ustilago maydis, Zea mays
Phylogeography and Genetic Structuring of Moose (Alces alces) Populations in Ontario, Canada
Moose are an iconic species, known for their large size and impressive antlers. Eight subspecies are classified in circumpolar regions of the planet - four in North America. Two subspecies are similar in shape and size, the north-western moose (Alces alces andersoni) and the eastern moose (Alces alces americana). It was previously believed that these two subspecies meet in northern Ontario. Earlier genetic population studies used a small number of samples from Ontario, primarily in broad studies covering all of North America. A comprehensive genetic study of moose populations in Ontario has not previously been conducted. We examined the genetic diversity and population structure at 10 polymorphic loci using 776 samples from Ontario, as well as outgroups from representative populations – Manitoba/Cape Breton, representing A. a. andersoni, and New Brunswick/Nova Scotia, representing A. a. americana. Results indicated three genetic populations in the province, in north-western Ontario, north-eastern Ontario and south-central Ontario. RST values, compared against both FST and Jost’s D values for phylogenetic analyses, indicated no phylogenetic pattern which suggests no subspeciation present in the province. Population movement patterns in Ontario were studied. Gene flow was estimated using genetic and spatial data. Isolation by distance was only seen within the first distance class of 100 kilometres and then not seen again at further distances, indicating that moose display philopatry. There were very few migrants travelling across the province, with a greater number moving gradually north and west, towards better habitat and food sources. A forensic database in the form of an allele frequency table was created. Three loci showed very low levels of heterozygosity across all three populations. Probability of identity was calculated for the three populations and quantified. Samples with known geographic origins were run against the database to test for sensitivity, with identification of origin occurring at an accuracy level between 87 and 100%. Within Ontario, there are not two different subspecies, as previously believed, but two different populations of the same subspecies meeting in northern Ontario. The genetic data does not support previous research performed in Ontario. The sample sizes in our research also provide a more comprehensive view of the entire province not seen in any previous studies. The comprehensive research enabled the building of a reliable forensic database that can be used for both management and forensic purposes for the entire province. Author Keywords: Alces alces, Genetic Diversity, Moose, Ontario, Phylogeography, Subspecies
Lipid-derived Thermoplastic Poly(ester urethane)s
Thermoplastic poly(ester urethane)s (TPEU)s derived from vegetable oils possess inferior physical properties compared to their entirely petroleum-based counterparts due to the structural limitations and lower reactivity of the precursor lipid-derived monomers. The present work shows that high molecular weight of TPEUs with enhanced performance can be obtained from lipid-derived monomers via (i) the synthesis of polyester diols with controlled molecular weights, (ii) the tuning of the functional group stoichiometry of the polyester diols and the diisocyanate during polymerization, (iii) the degree of polymerization (iv) the control of the hard segment hydrogen bond density and distribution via the use of a chain extender and (v) different polymerization protocols. Solvent-resistant TPEUs with high molecular weight displaying polyethylene-like behavior and controlled polyester and urethane segment phase separation were obtained. Structure-property investigations revealed that the thermal transition temperatures and tensile properties increased and eventually plateaued with increasing molecular weight. Novel segmented TPEUs possessed high phase separation and showed elastomeric properties such as low modulus and high elongation analogous to rubber. The response of the structurally optimized TPEUs to environmental degradation was also established by subjecting the TPEUs to hydrothermal ageing. TPEUs exhibited thermal and mechanical properties that were comparable to commercially available entirely petroleum-based counterparts, and that could be tuned in order to achieve enhanced physical properties and controlled degradability. Author Keywords: Hydrothermal degradation, Molecular weight control, Polyester diols, Renewable resources, Structure-property relationships, Thermoplastic poly(ester urethane)s
Identification and Quantification of Organic Selenium Species Produced by Microbiological Activity in Freshwater Environments
Despite being an essential nutrient at trace levels, selenium can be devastating to aquatic environments when present in excess. There is no apparent correlation between total aqueous selenium concentrations and observed toxic effects because bioaccumulation varies over several orders of magnitude depending on the chemical species of selenium and the biological species present in the lowest trophic level of the aquatic food chain. Despite being used in toxicity models due to its high bioavailability, free selenomethionine had not been found previously in the environment outside of a biological entity. Here, it is confirmed that selenomethionine is produced during the biological treatment of selenium-contaminated wastewater, and released in the effluent along with other discrete organic selenium species, including selenomethionine oxide. This identification followed the development of a rigorous preconcentration and cleanup procedure, allowing for the analysis of these organic selenium species in high-ionic strength matrices. A newly optimized anion-exchange chromatographic separation was coupled to inductively-coupled plasma mass spectrometry for the simultaneous quantification of these organic selenium species along with the more ubiquitous selenium oxyanions, selenite and selenate. This separation method was also coupled to electrospray tandem mass spectrometry for structural confirmation of selenomethionine and selenomethionine oxide. High resolution orbitrap mass spectrometry was used to identify another oxidation product of selenomethionine – a cyclic species which was tentatively identified, by coelution, in a selenium-contaminated river water sample. The production and release of selenomethionine, selenomethionine oxide, Se-(methyl) selenocysteine, and methyl selenic acid were observed for various laboratory algal cultures. Once the presence of free selenomethionine in a water system was confirmed, factors affecting its uptake into algal cultures were examined. The uptake of selenomethionine into Scenedesmus obliquus was noted to be significantly higher under low nitrate conditions, where it was incorporated into selenium-containing proteins more readily than at higher nitrate conditions where other metabolites were produced. With the increasing popularity of biological treatment systems for the remediation of selenium-contaminated waters, these observations, combined with existing knowledge, could be used to make predictions regarding the potential toxicity of selenium in various environmental scenarios. Author Keywords: bioremediation, electrospray mass spectrometry, inductively-coupled plasma mass spectrometry, selenium, selenoamino acids, selenomethionine


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