Graduate Theses & Dissertations


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
Comparing Biological Responses to Contaminants in Darters (Etheostoma spp.) Collected from Rural and Urban Regions of the Grand River Watershed, Ontario
Urban and agricultural activities may introduce chemical stressors, including contaminants of emerging concern (CECs) and current use pesticides (CUPs) into riverine systems. The objective of this study was to determine if fish collected from sites in a river show biomarkers of exposure to these classes of contaminants, and if the biomarker patterns vary in fish collected from urbanized and agricultural sites. The watershed selected for this study was the Grand River in southern Ontario, which transitions from areas dominated by agricultural land use in the north to highly urbanized locations in the southern part of the watershed. Rainbow darters (Etheostoma caerluem) and fantail darters (Etheostoma flabellare) were collected from the Grand River in June, 2014 for biomarker analysis from two urbanized sites and three agricultural sites (n=20 per site). Over the same period of time, Polar Organic Chemical Integrative Samplers (POCIS) were deployed for 2 weeks at each site to monitor for the presence of CUPs and CECs. The amounts of the target compounds accumulated on POCIS, determined using LC-MS/MS were used to estimate the time weighted average concentrations of the contaminants at each site. Data on the liver somatic index for darters indicate site-specific differences in this condition factor (p<0.05). Significant differences in the concentrations of thiobarbituric acid reactive substances (TBARS) in gill tissue (p<0.05) indicate differences in oxidative stress in fish collected from the various sites. Measured concentrations of ethoxyresorufin-O-deethylase (EROD) in liver tissue were significantly different between sites (p<0.05), indicating differences in CYP1A metabolic activity. Finally, acetylcholinesterase (AChE) activity in brain tissue was significantly different between fish from rural and urban sites (p<0.05). The analysis of these biomarkers indicates that fish may be experiencing different levels of biological stress related to different land uses. These data may be useful in developing mitigation strategies to reduce impacts on fish and other aquatic organisms in the watershed. Author Keywords: AChE, Biomarker, Darter, EROD, POCIS, TBARS
Comparison of the Optical Properties of Stratiotes aloids and the Local Plant Community
As part of a mandate to control the spread of Stratiotes aloides (WS; water soldier) in the Trent Severn Waterway, the Ministry of Natural Resources (MNR) created a management plan to eradicate WS. However, one of the biggest challenges in eradicating WS or any invasive aquatic plant is the ability to estimate the extent of its spread and detect new populations. While current detection methods can provide acceptable detection, these methods often require extensive time and effort. The purpose of this thesis was to assess the use optical properties of WS and WS exudates for detection, in order to improve on current detection methods. The optical properties of WS were sampled at three different sites during three different seasons (spring, summer, and fall) by a) randomly sampling tissue from WS and the local plant community at each site, and recording the reflectance properties in a laboratory setting b) collecting dissolved organic matter (DOM) samples from plant incubations and river water in the field. Significant differences in the reflectance properties of WS were observed among samples from different sites and different sampling times; however, changes in fluorescence properties were only seasonal. Despite spatial differences in WS reflectance; WS was detectable using both hyperspectral and multispectral reflectance. When hyperspectral reflectance was used, significant differences between WS and the local plant community were found in June using two bands (i.e. bands 525 and 535, R 2 = 0.46 and 0.48, respectively). Whereas multispectral reflectance was significant different in October using the coastal and blue band. While WS produced a unique signal using both reflectance types, multispectral reflectance had a greater potential for detection. Its greater potential for detection was due to the reduced noise produced by background optical properties in October in comparison to June. DOM derived from WS was also characterized and compared with whole-river DOM samples in order to find unique markers for WS exudates in river samples. While similarities in DOM concentrations of WS exudates to Trent River water limited the ability to detect WS using compositional data, the ratio of C4/C5 components were compared in order to find components that were proportionally similar. Based on the results of this study multispectral and fluorescence techniques are better suited for the detection of a unique WS signature. The results derived from this work are intended to have practical applications in plant management and monitoring, DOM tracing, as well as remote sensing. Author Keywords: Dissolved organic matter, Hyperspectral reflectance, Invasive species management, Multispectral reflectance, PARAFAC, Stratiotes aloides
Complex niche determinants in terrestrial salamanders
I assessed how organisms having multiple biotic attributes may have conflicting niche determinants, and whether the realized niche reflects single or multiple attributes. All-female salamanders engage in two biotic states: hybridism and reproductive parasitism. Hybrids should occupy areas transitional to those used by parental species, whereas parasites that engage in competition with hosts should occupy habitats moderately suitable for hosts. Using niche models, I predicted realized niches for unisexual Ambystoma via a hybrid model (environmental predictors) and a parasite model (host suitability predictors). The hybrid model predicted that the unisexual niche would indeed be transitional between parental Ambystoma spp. The parasite model demonstrated unisexual salamanders occupied habitats moderately suitable for hosts, though model validation did not fully corroborate its predictive power. The hybrid model was more descriptive of unisexual occurrence than the parasite model. When species have competing ecological roles a primary biotic attribute may largely derive the realized niche. Author Keywords: Ambystoma, hybrid, niche, parasite, range, unisexual
Composition and Transformation of Dissolved Organic Matter in Hudson Bay, Canada
The Hudson Bay region is a sensitive environment, where anthropogenic (e.g., dams, diversions, and/or reservoirs) impacts have increased in recent decades, potentially influencing the functioning of the ecosystem. Dissolved organic matter (DOM) entering Hudson Bay comes from both terrestrial (allochthonous) and aquatic (autochthonous) sources. The chemical composition of DOM is important, as it controls carbon biogeochemistry, nutrient cycling, and heat exchange. In rivers, estuaries, and oceans, photochemical processes and microbial degradation play a significant role in the chemical composition of DOM. Yet, our knowledge is scarce into how photochemical and microbial processes effect DOM composition specifically in Arctic aquatic systems making it difficult to predict how the carbon cycle will respond to a changing environment. This Ph.D. thesis addresses: (1) the composition of photochemically altered autochthonous and allochthonous DOM; (2) the photochemical transformations of DOM in surface waters of Hudson Bay; and (3) the microbial transformations of DOM in Hudson Bay surface waters. Using multiple analytical techniques, this work demonstrated that photochemical and microbial effects were different for light absorbing DOM compounds and ionisable DOM analyzed by Fourier transform-ion cyclotron-resonance-mass spectrometry (FT-ICR-MS). Based on FT-ICR-MS analysis, microbial processes had a greater impact on the molecular composition of allochthonous DOM originating from riverine sources and estuary whereas photochemical processes were the dominant mechanism for degradation of autochthonous DOM in Hudson Bay. Photochemical processes significantly decreased colored dissolved organic matter (CDOM) and fluorescence dissolved organic matter (FDOM) loss whereas microbial degradation was minimal in Hudson Bay river, estuary, and coastal waters. The results of this thesis highlight the importance of photochemical and microbial alteration of DOM in Arctic regions, two processes that are expected to be enhanced under climate change conditions. Author Keywords: Carbon cycle, Field flow fractionation, Microbial transformation, Optical properties, Photochemical degradation
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
Conservation genetics of Redside Dace (Clinostomus elongatus)
Recent range reductions of endangered species have been linked to urban development, increased agricultural activities, and introduction of non-native species. I used Redside Dace (Clinostomus elongatus) as a focal species to examine the utility of novel monitoring approaches, and to understand historical and contemporary processes that have influenced their present distribution. I tested the efficacy of environmental DNA (eDNA) to detect Redside Dace, and showed that eDNA was more sensitive for detecting species presence than traditional electrofishing. Parameters such as season, number of replicates, and spatial versus temporal sampling need to be accounted for when designing an eDNA monitoring program, as they influence detection effectiveness and power. I also assessed the species’ phylogeographic structure using both mitochondrial and microsatellite DNA analysis. The data from the microsatellite markers indicate that Redside Dace populations are genetically structured, with the exception of several populations from the Allegheny River basin. Combined sequence data from three mitochondrial genes (cytochrome b, ATPase 6 and ATPase 8) indicated that Redside Dace persisted within three Mississippian refugia during the last glaciation. Secondary contact between two lineages was indicated by both mitochondrial and microsatellite data. The combined results from the eDNA and conservation genetics studies can be used to inform Redside Dace recovery efforts, and provide a template for similar efforts for other aquatic endangered species. Author Keywords: eDNA, endangered, genetics, phylogeography
Constraints on phenotypic plasticity in response to predation risk
Inducible defenses are plastic responses by an organism to the perception of predation risk. This dissertation focuses on three experiments designed to test the hypothesis that plastic ability is limited by energetic constraints. Chapter 1 provides a general introduction to phenotypic plasticity research and the theoretical costs and limitations affecting the expression of plastic traits. In Chapter 2, I tested the hypothesis that costs of early plasticity may be manifested by a reduced response to risk in later life stages. I found that amphibian embryos are able to detect and respond to larval predators, but that the energetic cost of those plastic responses are not equivalent among behavioural, growth, and morphological traits, and their expression differs between closely-related species. Chapter 3 explicitly examines the relationship between food resource availability and plasticity in response to perceived predation risk during larval development. Food-restricted tadpoles showed limited responses to predation risk; larvae at food saturation altered behaviour, development, and growth in response to predation risk. Responses to risk varied through time, suggesting ontogeny may affect the deployment of particular defensive traits. Chapter 4 examines the influence of maternal investment into propagule size on the magnitude of the plastic responses to predation risk in resulting offspring. I found that females in better body condition laid larger eggs and that these eggs, in turn, hatched into larvae that showed greater morphological plasticity in response to predation risk. Maternal investment can therefore affect the ability of offspring to mount morphological defenses to predation risk. Last, Chapter 5 provides a synthesis of my research findings, identifying specific factors constraining the plastic responses of prey to perceived predation risk. Overall, I found constraints on plastic responses imposed by the current environment experienced by the organism (resource availability), the prior experience of the organism (predator cues in the embryonic environment), and even the condition of the previous generation (maternal body condition and reproductive investment). Together, these findings both provide new knowledge and create novel research questions regarding constraints limiting phenotypic variation in natural populations. Author Keywords: behaviour, inducible defense, Lithobates pipiens, morphometrics, phenotypic plasticity, predation risk
Contributions of Mayflies (EPHEMEROPTERA
Walleye (Sander vitreus) are an ecologically and economically significant fish harvestedby recreational and commercial fisheries across Ontario. Adult Walleye are piscivores, but anecdotal evidence from anglers suggests that Walleye often target aquatic insects such as mayfly larvae (Ephemeroptera). My research examined the diet of Walleye caught from May to September in Lake St. Joseph in northern Ontario. I examined the stomach contents of angle harvested Walleye to identify the prey over two summers. Through morphological analysis of stomach contents, mayflies were found to be a significant prey source for Walleye, during larval emergence events in early summer, and to a lesser extent throughout the rest of the summer season. These findings are important for long term management of Walleye populations and associated resources. I also assess the potential and problems of Walleye management and research from my experiences of having worked with industry, government, and university partners on this project. Author Keywords: alternative prey, Food web interactions, invertebrate, piscivore, Predator prey interactions
Cytokinin Oxidase/Dehydrogenase (CKX) Gene Family in Soybeans (Glycine max)
Glycine max (soybean) is an economically important plant species that registers a relatively low yield/seed weight compared to other food and oil seed crops due to higher rates of flower and pod abortion. Alleviation of this abortion rate can be achieved by altering the sink strength of the reproductive organs of soybeans. Cytokinin (CK) plays a fundamental role in promoting growth of sink organ (flowers and seeds) by increasing the assimilate demand. Cytokinin oxidase/dehydrogenase (CKX) is an enzyme that catalyses the irreversible breakdown of active CKs and hence reduce the cytokinin content. The current thesis uncovers the members of CKX gene family in soybeans and the natural variations among CKX genes within soybean varieties with different yield characteristics. The identification of null variants of OsCKX2 that resulted in large yield increases by Ashikari et al. (2005) provided a rationale for current thesis. The soybean CKX genes along with the ones from Arabidopsis, Rice and Maize were used to construct a phylogenetic tree. Using comparative phylogeny, protein properties and bioinformatic programs, the potential effect of the identified natural variations on soybean yield was predicted. Five genes among the seventeen soybean CKXs identified, showed polymorphisms. One of the natural variations, A159G, in the gene GmCKX16 occurred close to the active site of the protein and was predicted to affect the activity of enzyme leading to higher accumulation of CKs and hence increased seed weight. Use of such natural variations in marker assisted breeding could lead to the development of higher yielding soybean varieties. Author Keywords: CKX, Cytokinins, Seed weight, Seed Yield, SNPs, Soybeans
Cytokinin biosynthesis, signaling and translocation during the formation of tumors in the Ustilago maydis-Zea mays pathosystem
Cytokinins (CKs) are hormones that promote cell division. During the formation of tumors in the Ustilago maydis-Zea mays pathosystem, the levels of CKs are elevated. Although CK levels are increased, the origins of these CKs have not been determined and it is unclear as to whether they promote the formation of tumors. To determine this, we measured the CK levels, identified CK biosynthetic genes as well as CK signaling genes and measured the transcript levels during pathogenesis. By correlating the transcript levels to the CK levels, our results suggest that increased biosynthesis and signaling of CKs occur in both organisms. The increase in CK biosynthesis by the pathosystem could lead to an increase in CK signaling via CK translocation and promote tumor formation. Taken together, these suggest that CK biosynthesis, signaling and translocation play a significant role during the formation of tumors in the Ustilago maydis-Zea mays pathosystem. Author Keywords: Biosynthesis, Cytokinins, Signaling, Translocation, Ustilago maydis, Zea mays
Cytokinins in nematodes
To investigate cytokinins (CKs) in nematodes, CK profiles of a free-living Caenorhabditis elegans and a plant parasitic Heterodera glycines (soybean cyst nematode, SCN) were determined at the egg and larval stages. SCN had higher total CK level than C. elegans; however, CKs in SCN were mostly inactive precursors, whereas C. elegans had more bioactive forms. This is the first study to show that methylthiols are present in nematodes and may affect plant infection. In infectious SCN larvae, methylthiol levels were much higher than in eggs or C. elegans larvae. Furthermore, The CK profiles of SCN-susceptible and resistant Glycine max cultivars at three developmental stages revealed that, regardless of the resistance level, SCN infection caused an increase in root CKs. One resistant cultivar, Pion 93Y05, showed significantly high levels of bioactive N6-isopentenyladenine (iP) in the non-infected roots which indicated a potential role of CKs in soybean resistance to SCN. Author Keywords: Cytokinins, HPLC-MS/MS, Nematode, SCN resistance, Soybean


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