Graduate Theses & Dissertations

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Hybridization dynamics in cattails (Typha spp.,) in northeastern North America
Interspecific hybridization is an important evolutionary process which can contribute to the invasiveness of species complexes. In this dissertation I used the hybridizing species complex of cattails (Typha spp., Typhaceae) to explore some of the processes that could contribute to hybridization rates. Cattails in northeastern North America comprise the native T. latifolia, the non-native T. angustifolia, and their fertile hybrid, T. × glauca. First, I examined whether these taxa segregate by water depth as habitat segregation may be associated with lower incidence of hybridization. I found that these taxa occupy similar water depths and therefore that habitat segregation by water depth does not promote mating isolation among these taxa. I then compared pollen dispersal patterns between progenitor species as pollen dispersal can also influence rates of hybrid formation. Each progenitor exhibits localized pollen dispersal, and the maternal parent of first generation hybrids captures more conspecific than heterospecific pollen; both of which should lead to reduced hybrid formation. I then conducted controlled crosses using all three Typha taxa to quantify hybrid fertility and to parameterize a fertility model to predict how mating compatibilities should affect the composition of cattail stands. I found that highly asymmetric formation of hybrids and backcrosses and reduced hybrid fertility should favour the maintenance of T. latifolia under certain conditions. Finally, I used a population genetics approach to characterize genetic diversity and structure of Typha in northeastern North America to determine the extent to which broad-scale processes such as gene flow influence site-level processes. I concluded that hybrids are most often created within sites or introduced in small numbers rather than exhibiting broad-scale dispersal. This suggests that local processes are more important drivers of hybrid success than landscape-scale processes which would be expected to limit the spread of the hybrid. Though my findings indicate some barriers to hybridization in these Typha taxa, hybrid cattail dominates much of northeastern North America. My results therefore show that incomplete barriers to hybridization may not be sufficient to prevent the continued dominance of hybrids and that active management of invasive hybrids may be required to limit their spread. Author Keywords: fertility model, genetic structure, Hybridization, invasive species, niche segregation, pollen dispersal
New Interpretations from Old Data
Range contractions and expansions are important ecological concepts for species management decisions. These decisions relate not only to rare and endangered species but to common and invasive species as well. The development of the broad spatiotemporal extent models that are helpful in examining range fluctuations can be challenging given the lack of data expansive enough to cover the time periods and geographic extents needed to fit the models. Archival records such as museum databases and harvest data can provide the spatiotemporal extent needed but present statistical challenges given they represent presence-only location information. In this thesis, I used maximum entropy and Bayesian hierarchical occupancy algorithms fitted with archival presence-only records to develop spatiotemporal models covering broad spatial and temporal extents for snowshoe hare and Canada lynx. These two algorithm types are well suited for presence-only data records and can be adapted to include biological and physical processes, thus improving the ecological realism of the models. Using these modelling methods, I found the extent of occurrence (EOO) and area of occupancy (AOO) varied greatly over time and space for both snowshoe hare and Canada lynx, suggesting that management decisions for these species should include consideration of these variations. While the presence-only data were appropriate for model development and understanding changing values in EOO and AOO, it sometimes lacked the locational accuracy and precision needed to create fine scale ecological analyses, thus resulting in somewhat coarse but potentially relevant conclusions. Author Keywords: Area of occupancy, Bayesian hierarchical models, Canada lynx, Extent of occurrence, Presence-only data, Snowshoe hare
Time to adapt
To better understand species’ resilience to climate change and implement solutions, we must conserve environments that maintain standing adaptive genetic variation and the potential generation of new beneficial alleles. Coding trinucleotide repeats (cTNRs) providing high-pace adaptive capabilities via high rates of mutation are ideal targets for mitigating the decline of species at risk by characterizing adaptively significant populations. Ultimately, adaptive genetic information will inform the protection of biological diversity below the species level (i.e., “Evolutionarily Significant Units” or “ESUs”). This dissertation investigates cTNRs within candidate genes to determine their prevalence and influence under selection in North American mammals. First, I evaluated the potential for somatic mosaicism in Canada lynx (Lynx canadensis), and found that tissue-specific mosaicism does not confound cTNR genotyping success in lynx. Second, I assessed a selection of clock gene cTNRs across characterized mammals and found that these repeats are abundant and highly variable in length and purity. I also identified preliminary signatures of selection in 3 clock gene cTNRs in 3 pairs of congeneric North American mammal species, highlighting the importance of cTNRs for understanding the evolution and adaptation of wild populations. I further evaluated the influence of selection on the NR1D1 cTNR within Canada lynx sampled across Canada using environmental correlation, where I estimated the variation in NR1D1 cTNR alleles explained by environmental and spatial variables after removing the effects of neutral population structure. Although most variation was explained by neutral structure, environment and spatial patterns in eastern lynx populations significantly explained some of the variation in NR1D1 alleles. To examine the role of island populations in the generation and distribution of adaptive genetic variation, I used 14 neutral microsatellites and a dinucleotide repeat within a gene linked to mammalian body size, IGF-1, and found that both genetic drift and natural selection influence the observed genetic diversity of insular lynx. Finally, I estimated the divergence dates of peripheral lynx populations and made recommendations towards the conservation of Canada lynx; high levels of genetic differentiation coupled with post-glacial colonization histories and patterns of divergence at cTNR loci suggest at least 4 ESUs for Canada lynx across their range. Author Keywords: adaptation, Canada lynx, candidate genes, coding trinucleotide repeats, evolution, natural selection
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
Reproductive Fitness of Smallmouth Bass (Micropterus dolomieu) Under Heterogeneous Environmental Conditions
Identifying the biotic and abiotic factors that influence individual reproductive fitness under natural conditions is essential for understanding important aspects of a species’ evolutionary biology and ecology, population dynamics, and life-history evolution. Using next generation sequencing technology, I developed five microsatellite multiplex reactions suitable for conducting large scale parentage analysis of smallmouth bass, Micropterus dolomieu, and used molecular pedigree reconstruction techniques to characterize the genetic mating system and mate selection in adult smallmouth bass nesting in Lake Opeongo, Ontario, Canada. I used multivariate spatial autocorrelation analysis to indirectly infer the occurrence and extent of natal philopatry among spawning adults, to assess the strength and direction of sex-bias in natal dispersal patterns, and to evaluate the degree of nest site fidelity and breeding dispersal of spawning adults. I also evaluated how differences in littoral zone water temperature caused by wind-induced seiche events influence the relative reproductive success of spawning adults. Lastly, I provide a synopsis of potential future research aimed at further exploring factors that influence the reproductive fitness of smallmouth bass in Lake Opeongo. This information will contribute to our understanding of the factors regulating smallmouth bass populations, and provide insight into the factors controlling the variance in individual reproductive success and thus recruitment dynamics in this species. Author Keywords: Dispersal, Fitness, Mate selection, Mating systems, Philopatry
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
silicon sol-gel approach to the development of forensic blood substitutes
The research and development of synthetic blood substitutes is a reported need within the forensic community. This work contributes to the growing body of knowledge in bloodstain pattern analysis by offering a materials science approach to designing, producing and testing synthetic forensic blood substitutes. A key deliverable from this research is the creation of a robust silicon-based material using the solution-gelation technique that has been validated for controlled passive drip and spatter simulation. The work investigates the physical properties (viscosity, surface tension and density) of forensic blood substitute formulations and describes the similarity in the spreading dynamics of the optimized material to whole human blood. It then explores how blood and other fluids behave in impact simulation using high-speed video analysis and supports the use of the optimized material for spatter simulation. Finally, the work highlights the practical value of the material as an educational tool for both basic and advanced bloodstain experimentation and training. Author Keywords: bloodstain pattern analysis, forensic blood substitutes, high-speed video analysis, silicon solution-gelation chemistry, thin-film deposition, training and education
Conservation Genetics of Woodland Caribou in the Central Boreal Forest of Canada
Maintaining functional connectivity among wildlife populations is important to ensure genetic diversity and evolutionary potential of declining populations, particularly when managing species at risk. The Boreal Designatable Unit (DU) of woodland caribou (Rangifer tarandus caribou) in Ontario, Manitoba, and Saskatchewan has declined in southern portions of the range because of increased human activities and has been identified as 'threatened' by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). In this dissertation, I used ten microsatellite DNA markers primarily from winter-collected fecal samples to delineate genetic structure of boreal caribou in declining portions of the range and increase understanding of the potential influence of the non-threatened Eastern Migratory DU of woodland caribou on genetic differentiation. Eastern migratory caribou are characterized by large home ranges compared to boreal caribou and migrate seasonally into portions of the Boreal DU range. A regional- and local-scale analysis using the spatial Bayesian clustering algorithm in program TESS delineated four regional clusters and 11 local clusters, with the majority of local clusters occurring along the southern periphery of the range. One of those clusters in Ontario corresponded spatially with the seasonal overlap of boreal and eastern migratory caribou and was characterized by substantial admixture, suggesting that the two DUs could be interbreeding. Next, I decoupled the impacts of historical and contemporary processes on genetic structure and found that historical processes were an important factor contributing to genetic differentiation, which may be a result of historical patterns of isolation by distance or different ancestry. Moreover, I found evidence of introgression from a currently unsampled population in northern Ontario, presumably barren-ground caribou (R. t. groenlandicus). Finally, because our analysis suggested recent processes were also responsible for genetic structure, I used a landscape genetics analysis to identify factors affecting contemporary genetic structure. Water bodies, anthropogenic disturbance, and mobility differences between the two DUs were important factors describing caribou genetic differentiation. This study provides insights on where conservation and management of caribou herds should be prioritized in threatened portions of the boreal caribou range and may have implications for future delineation of evolutionarily significant units. Author Keywords: boreal forest, genetic structure, landscape genetics, microsatellite DNA, Rangifer tarandus, woodland caribou
Comparative phylogeography in conservation biology
Phylogeographic histories of taxa around the Great Lakes region in North America are relevant to a range of ongoing issues including conservation management and biological invasions. In this thesis I investigated the comparative phylogeographic histories of plant species with disjunct distributions and plant species with continuous distributions around the Great Lakes region; this is a very dynamic geographic area with relatively recent colonisation histories that have been influenced by a range of factors including postglacial landscape modifications, and more recently, human-mediated dispersion. I first characterized four species that have disjunct populations in the Great Lakes region: (Bartonia paniculata subsp. paniculata, Empetrum nigrum, Sporobolus heterolepis, and Carex richardsonii). Through comparisons of core and disjunct populations, I found that a range of historical processes have resulted in two broad scenarios: in the first scenario, genetically distinct disjunct and core populations diverged prior to the last glacial cycle, and in the second scenario more recent vicariant events have resulted in genetically similar core and disjunct populations. The former scenario has important implications for conservation management. I then characterized the Typha species complex (T. latifolia, T. angustifolia, T. x glauca), which collectively represent species with continuous distributions. Recent microevolutionary processes, including hybridization, introgression, and intercontinental dispersal, obscure the phylogeographic patterns and complicate the evolutionary history of Typha spp. around the Great Lakes region, and have resulted in the growing dominance of non-native lineages. A broader geographical comparison of Typha spp. lineages from around the world identified repeated cryptic dispersal and long-distant movement as important phylogeographic influences. This research has demonstrated that comparisons of regional and global evolutionary histories can provide insight into historical and contemporary processes useful for management decisions in conservation biology and invasive species. Author Keywords: chloroplast DNA, conservation genetics, disjunct populations, invasive species, phylogeography, postglacial recolonisation
Elemental Variation in Daphnia
Environmental variation can affect consumer trait expression and alter ecological and evolutionary dynamics in natural populations. However, although dietary nutrient content can vary by an order of magnitude in natural ecosystems, intra-specific differences in consumer responses to food quality have not been thoroughly investigated. Therefore, the purpose of my dissertation was to examine the influence of dietary nutrition and other environmental factors on consumer phenotypic variation using the freshwater cladoceran Daphnia. I conducted a series of complementary laboratory and field studies where I examined the effects of dietary phosphorus (P) content and additional biological/environmental variables (multi-elemental limitation, genetic variation, and temperature) on daphnid life-history, biochemistry, body elemental composition, and population growth. In general, phenotypic expression within a species varied significantly in response to all experimental variables, but the relative influence of each was highly context dependent. In my first chapter, I found that dietary P content and environmental calcium (Ca) concentrations both altered Daphnia body Ca:P ratios and growth rates of individuals and affected intrinsic rates of increase at the population level. However, food quality appeared to have a much larger effect on trait expression, and body Ca:P ratios were highly sensitive to other forms of dietary nutrient limitation. Next, I documented significant quantitative genetic variation and phenotypic plasticity in daphnid P content, growth, and P use efficiency of field collected animals grown across dietary P gradients. Trait expression was also influenced by genotype X diet interactions suggesting that consumer responses to dietary nutrient limitation can be heritable and may be adaptive in different nutrient environments. Finally, I found that temperature appeared to override food quality effects and decouple P metabolism in natural Daphnia populations, but total biomass production was affected by both dietary P content and temperature, depending on the nutrient content of the lake. Overall, my dissertation shows that consumer responses to nutrient limitation can vary significantly within a species and that changes in trait expression may be modified by other environmental variables. These results should be incorporated into existing stoichiometric models and used to investigate the eco-evolutionary consequences of consumer phenotypic variation in response to nutritional stress. Author Keywords: ecological stoichiometry, evolution, life-history, nutrient limitation, nutrient metabolism, zooplankton
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
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

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