Graduate Theses & Dissertations

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THE LIFE HISTORY STRATEGY, GROWTH, BODY CONDITION, AND DIET OF STOCKED AMERICAN EEL (Anguilla rostrata) IN THE UPPER ST. LAWRENCE RIVER AND LAKE ONTARIO
My study was primarily focused on the comparison of life history traits between stocked American eel and their naturally recruited conspecifics in Lake Ontario and the upper St. Lawrence River (USLR/LO). I found that stocked eels experienced faster annual growth than their naturally recruited conspecifics and were comprised of a greater proportion of males. These findings indicate that the life history patterns of American eel may be genetically predisposed. Additionally, my study served to characterize the diets of stocked American eel and examine possible associations between eel and prey size. The eels consumed a number of macroinvertebrate prey orders as well as fishes and macrocrustaceans, with the latter prey items being more prevalent in the diets of larger eel specimens. A disparity in eel growth and body condition was observed between two primary stocking locations and were likely attributable to differences in available forage and habitat. Lastly, growth, body condition, and stocked eel diet were compared between lentic and lotic habitats. Eels from lotic streams experienced slower annual growth and had reduced body condition, and their diets were comprised of smaller prey items. The results of this study suggest that the current stocking methods employed in the USLR/LO are not suitable to restore the natural recruitment of individuals that will exhibit desired life history traits. Author Keywords:
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
HABITAT SELECTION AND LIFE-HISTORY TRAITS OF BREEDING BIRDS IN THE BOREAL-TUNDRA ECOTONE, WITH SPECIAL ATTENTION TO THE AMERICAN ROBIN (TURDUS MIGRATORIUS)
I investigated biodiversity of birds and vegetation associations along the boreal-tundra ecotone in Ivvavik National Park, Yukon Territory, and breeding adaptations used by American Robins (Turdus migratorius) at high latitudes. Twenty bird species were detected over three years using point-count surveys. Densities of American Robin, Dark-eyed Juncos (Junco hyemalis), and Yellow-rumped Warbler (Dendroica coronata) had positive relationships with tree and shrub density, whereas density of White-crowned Sparrows (Zonotrichia leucophrys) was negatively related to tree density. American Robins at this latitude raised only one brood, but females laid slightly larger clutches, the young fledged earlier, and pairs experienced higher nest-success than American Robins at more southerly latitudes. American Robins selected nest sites with high vegetation volume, at both the nest-site, and the nest-patch. This study is important for the first description of the bird community at this high latitude location, and describing how a species at the northern limit of the boreal forest has adapted to living with short-breeding seasons. Author Keywords: American Robin, Ivvavik National Park, Life History, Nest-stie selection, Northern limit
Equilibria and distribution models of ionizing organic chemical contaminants in environmental systems
Ionizing organic chemicals are recognized as constituting a large fraction of the organic chemicals of commerce. Many governments internationally are engaged in the time-consuming and expensive task of chemical risk assessment for the protection of human and environmental health. There are standard models that are consistently used to supplement experimental and monitoring data in such assessments of non-ionizing organics by both government regulators and industry stakeholders. No such standard models exist for ionizing organics. Equilibrium distribution models, the foundational equations within multimedia environmental fate models for non-ionizing organics, were developed for the standard series of biphasic systems: air-water, particle-water, air-particle and organic-aqueous phases within living tissue. Multiple chemical species due to the ionization reaction were considered for each system. It was confirmed that, under select conditions, the properties of the neutral parent are sufficient to predict the overall distribution of the organic chemical. Complications due to biotransformation and paucity of identifiable equilibrium distribution data for ionizing organics limited the development of the model for living tissues. However, the equilibrium distributions of ionizing organics within this biotic system were shown to correlate with the abiotic sediment-water system. This suggests that the model developed for particle-water systems should be adaptable to the biotic system as model input and test data become available. Observational data for soil- and sediment- water systems, i.e., particle-water systems, allowed the development of a primarily non-empirical distribution equation for mono-protic acids; this model was almost entirely theoretically derived. The theoretical approach to model development allowed a quantitative assessment of the role of the neutral ion pair, resulting from the complexation of the organic anion with metal cations. To demonstrate the model's potential usefulness in governmental screening risk assessments, it was applied to a broad range of mono-protic organics including drugs and pesticides using standard property estimation software and generic inputs. The order-of-magnitude agreement between prediction and observation typical of the existing models of non-ionizing organics was generally achieved for the chemicals tested. The model was sensitive to the octanol-water partition coefficient of the most populous species. No calibration set was used in the development of any of the models presented. Author Keywords: bioconcentration, chemical equilibrium, environmental modelling, ionizing organic, sorption
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
Scarring, sex assignment, and sex-specific sociality of Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary and eastern Taiwan Strait
The Pearl River Estuary (PRE) and eastern Taiwan Strait (ETS) populations of Indo-Pacific humpback dolphins (Sousa chinensis) contain ~600 and 100 catalogued individuals, respectively. Population demography is important for conservation actions but few animals have been sexed by conventional methods. Longitudinal analysis of tooth-rake scars on dorsal fins showed scars disappear within 7 months; sexing adults by scarring is likely not impacted by juvenile scarring. Using dorsal fin photographs, sex assigned for 87% of catalogued PRE adults (n=300) and for 93% of ETS adults (n=60), using scars hypothesized from male-male competition, was in concordance with sex assigned by DNA, calf association, and ventral photographs. Scarring was higher in presumed males than females and in PRE females than ETS females. Female:male sex ratios were 3:2 (PRE) and 2:1 (ETS), though this likely results from biases in photo-identification methods. Social analysis with presumed sexes showed strong female-female associations in both populations but stronger female-male and male-male associations in PRE. These results support sex differentiation by scarring, which was a non-invasive approach, and sex assignment for many PRE and ETS individuals. Author Keywords: Indo-Pacific humpback dolphins, photo-identification, scarring, sex differentiation, sexes, social structure
Ecological and morphological traits that affect the fitness and dispersal potential of Iberian pumpkinseed (Lepomis gibbosus)
The Pumpkinseed (Lepomis gibbosus) is a sunfish that is endemic to eastern portions of Canada and the United States. During the late 19th century, the species was introduced into Europe, and it is now present in over 28 countries. Previous attempts to determine the characteristics that can predict the spread of non-indigenous species have been largely unsuccessful, but new evidence suggests that phenotypic plasticity may help to explain the dispersal and range expansion of some organisms. Experimental comparisons on lower-order taxa have revealed that populations from areas outside of their native range are capable of exhibiting stronger levels of phenotypic plasticity than counterparts from their source of origin. Using Pumpkinseed, I conducted the first native/non- native comparison of phenotypic plasticity in a vertebrate. Progeny from adult Pumpkinseed collected in Ontario, Canada and the Iberian Peninsula (Spain) were reared under variable water velocities, habitat type and competitive pressures, three ecological factors that may affect the dispersal potential of fishes introduced into novel aquatic systems. Differences in phenotypic plasticity, assessed from a morphological perspective, were compared among populations using a traditional distance-based approach. All populations exhibited divergent morphological traits that appeared to be inherited over successive generations. In each experiment, all populations responded to environmental change by developing internal and external morphological forms that, in related taxa, enhance and facilitate foraging and navigation; however, non-native populations always exhibited an overall lower level of phenotypic plasticity. Pumpkinseed from non-native areas may have exhibited a reduction in phenotypic plasticity because of population-based differences. Nevertheless, all Pumpkinseed populations studied were capable of exhibiting phenotypic plasticity to novel environmental conditions, and develop morphological characteristics that may enhance fitness and dispersal in perturbed areas. Author Keywords: Invasive species, Morphology, Phenotypic plasticity, Pumpkinseed sunfish, Reaction norm
Novel Silica Sol-Gel Passive Sampler for Mercury Monitoring in Aqueous Systems
A novel passive sampler for mercury monitoring was prepared using organosilica sol-gel materials. It comprises a binding layer with thiol groups for mercury complexation and a porous diffusive layer through which mercury can diffuse and arrive at the binding layer. Our study demonstrated that this new sampler follows the principle of passive sampling. The mass of mercury accumulated in the binding layer depends linearly on the mercury concentration in solution, the sampling rate and the exposure time. A typical sol-gel sampler is characterized by a diffusive layer of 1.2 &mum, in which mercury ions diffuse with a coefficient of D = 0.09~10-6 cm2/s. The capacity for mercury uptake is approximately 0.64 &mug/cm2. Mercury diffusion and binding in the passive sampler are independent of the type of mercury-chloride complex. Its sampling rate increases with increasing water turbulence and decreases with increasing DOM amount. The field trial of sol-gel sampler in Miller Creek shows the concentration gained from the sol-gel passive sampler is slightly lower than that from the spot sampling. Author Keywords:
SPATIAL AND TEMPORAL GENETIC STRUCTURE OF WOLVERINE POPULATIONS
Habitat loss and fragmentation can disrupt population connectivity, resulting in small, isolated populations and low genetic variability. Understanding connectivity patterns in space and time is critical in conservation and management planning, especially for wide-ranging species in northern latitudes where habitats are becoming increasingly fragmented. Wolverines (Gulo gulo) share similar life history traits observed in large-sized carnivores, and their low resiliency to disturbances limits wolverine persistence in modified or fragmented landscapes - making them a good indicator species for habitat connectivity. In this thesis, I used neutral microsatellite and mitochondrial DNA markers to investigate genetic connectivity patterns of wolverines for different temporal and spatial scales. Population genetic analyses of individuals from North America suggested wolverines west of James Bay in Canada are structured into two contemporary genetic clusters: an extant cluster at the eastern periphery of Manitoba and Ontario, and a northwestern core cluster. Haplotypic composition, however, suggested longstanding differences between the extant eastern periphery and northwestern core clusters. Phylogeographic analyses across the wolverine's Holarctic distribution supported a postglacial expansion from a glacial refugium near Beringia. Although Approximate Bayesian computations suggested a west-to-east stepping-stone divergence pattern across North America, a mismatch distribution indicated a historic bottleneck event approximately 400 generations ago likely influenced present-day patterns of haplotype distribution. I also used an individual-based genetic distance measure to identify landscape features potentially influencing pairwise genetic distances of wolverines in Manitoba and Ontario. Road density and mean spring snow cover were positively associated with genetic distances. Road density was associated with female genetic distance, while spring snow cover variance was associated with male genetic distance. My findings suggest that northward expanding anthropogenic disturbances have the potential to affect genetic connectivity. Overall, my findings suggest that (1) peripheral populations can harbour genetic variants not observed in core populations - increasing species genetic diversity; (2) historic bottlenecks can alter the genetic signature of glacial refugia, resulting in a disjunct distribution of unique genetic variants among contemporary populations; (3) increased temporal resolution of the individual-based genetic distance measure can help identify landscape features associated with genetic connectivity within a population, which may disrupt landscape connectivity. Author Keywords: conservation genetics, Holarctic species, landscape genetics, peripheral population, phylogeography, wolverine
Mixed methods approaches in marine mammal science
This thesis explored the contribution of mixed methods approaches to marine mammal science through the use of concurrent and sequential designs to study distribution and feeding ecology of bowhead whales (Balaena mysticetus) in the Arctic region of Nunavik, Quebec, Canada. The study combines Inuit knowledge (IK), collected through semi-directed interviews with Inuit harvesters, and analyses of stable isotopes and trace elements (SI/TE) in baleen plates. A systematic literature review found that mixed methods are increasingly used in marine mammal ecology studies in remote locations, yet are still relatively rare and face a number of challenges. Both IK and SI/TE, indicated that bowhead whales have a seasonal pattern in their distribution and feeding ecology. They are most commonly present in productive nearshore areas in summertime, feeding in areas of great prey diversity, and moving to offshore areas in winter to fast. Mixed methods approaches used in this case study enabled the collection of complementary knowledge about bowhead whale ecology important for local management in a changing climate. This study also shows the value of mixed methods approaches for future marine mammal studies in Nunavik and elsewhere. Author Keywords: Arctic, bowhead whale, distribution, feeding ecology, mixed methods, traditional ecological knowledge
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
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

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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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