Graduate Theses & Dissertations

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Comparative efficacy of eDNA and conventional methods for monitoring wetland anuran communities
Identifying population declines and mitigating biodiversity loss require reliable monitoring techniques, but complex life histories and cryptic characteristics of anuran species render conventional monitoring challenging and ineffective. Environmental DNA (eDNA) detection is a highly sensitive and minimally invasive alternative to conventional anuran monitoring. In this study, I conducted a field experiment in 30 natural wetlands to compare efficacy of eDNA detection via qPCR to three conventional methods (visual encounter, breeding call, and larval dipnet surveys) for nine anuran species. eDNA and visual encounter surveys detected the greatest species richness, with eDNA methods requiring the fewest sampling events. However, community composition results differed among methods, indicating that even top performing methods missed species detections. Overall, the most effective detection method varied by species, with some species requiring two to three methods to make all possible detections. Further, eDNA detection rates varied by sampling season for two species (A. americanus and H. versicolor), suggesting that species-specific ecology such as breeding and larval periods play an important role in eDNA presence. These findings suggest that optimized monitoring of complex anuran communities may require two or more monitoring methods selected based on the physiology and biology of all target species. Author Keywords: amphibian, anuran, conventional monitoring, eDNA, environmental DNA, species richness
Assessing the Cost of Reproduction between Male and Female Sex Functions in Hermaphroditic Plants
The cost of reproduction refers to the use of resources for the production of offspring that decreases the availability of resources for future reproductive events and other biological processes. Models of sex-allocation provide insights into optimal patterns of resource investment in male and female sex functions and have been extended to include other components of the life history, enabling assessment of the costs of reproduction. These models have shown that, in general, costs of reproduction through female function should usually exceed costs through male function. However, those previous models only considered allocations from a single pool of shared resources. Recent studies have indicated that the type of resource currency can differ for female and male sex functions, and that this might affect costs of reproduction via effects on other components of the life history. Using multiple invasibility analysis, this study examined resource allocation to male and female sex functions, while simultaneously considering allocations to survival and growth. Allocation patterns were modelled using both shared and separate resource pools. Under shared resources, allocation patterns to male and female sex function followed the results of earlier models. When resource pools were separate, however, allocations to male function often exceeded allocations to female function, even if fitness gains increased less strongly with investment in male function than with investment in female function. These results demonstrate that the costs of reproduction are affected by (1) the types of resources needed for reproduction via female or male function and (2) via trade-offs with other components of the life history. Future studies of the costs of reproduction should examine whether allocations to reproduction via female versus male function usually entail the use of different types of resources. Author Keywords: Cost of Reproduction, Gain Curve, Life History, Resource Allocation Patterns, Resource Currencies
Assessing Brook Trout (Salvelinus fontinalis) Seasonal Occupancy in Haliburton County, ON Using Environmental DNA
Brook trout (Salvelinus fontinalis) are declining across Ontario in both numbers and distribution, prompting concern for their future. Here, conventional, emerging, and predictive tools were combined to document brook trout occupation across seasons using streams in Haliburton County, ON as model systems. By using the Ontario Ministry of Natural Resources and Forestry’s (OMNRFs) Aquatic Ecosystem Classification (AEC) system variables with environmental DNA (eDNA) sampling and backpack electrofishing, my research supports the development of species occupancy models (SOMs) and eDNA as tools to document brook trout occurrence. To do this, eDNA sampling was validated in Canadian Shield stream environments by comparison with single-pass backpack electrofishing before seasonally sampling two river systems across their main channel and tributaries to assess occupancy. Streams were classified as potential high, moderate, and low-quality brook trout habitats using indicator variables within the AEC and sampled seasonally with eDNA to quantify occupancy and relate it to habitat potential at the county scale. Results showed eDNA to be an effective tool for monitoring fish across Canadian Shield landscapes and that brook trout occupancy varied seasonally within and across watersheds, suggesting that habitat and fish management strategies need to consider seasonal movement and spatial connectivity. Using these tools will enable biologists to efficiently predict and document brook trout occurrences and habitat use across the landscape. Author Keywords: Aquatic Ecosystem Classification, brook trout, Canadian Shield, connectivity, environmental DNA, seasonal occupation
Diversity, Biogeography, and Functional Traits of Native Bees from Ontario’s Far North and Akimiski Island, Nunavut
Bees (clade Anthophila), are poorly studied in northern Canada, as these regions can be difficult to access and have a short growing season. This study examined bees from two such regions: Ontario’s Far North, and Akimiski Island, Nunavut. I present this study as the largest biogeographical study of bees performed in these remote areas to enhance knowledge of northern native bees. I found 10 geographically unexpected species in Ontario and on Akimiski Island. Rarefaction and the Chao 1 Diversity Index showed that Akimiski is nearly as diverse as the Far North of Ontario, a significantly larger area. I also found, based on log femur length versus latitude, Bombus worker size was consistent with Bergmann’s rule, and there were no apparent statistical differences in the community weighted means of functional traits between the Far North’s Boreal Shield and Hudson Bay Lowlands ecozones. This work provides invaluable knowledge of the native bee species from these regions, which has implications for their future conservation. Author Keywords: Akimiski Island, Bergmann's rule, Chao 1, Community-weighted means, native bees, rarefaction
effects of heat dissipation capacity on avian physiology and behaviour
In endotherms, physiological functioning is optimized within a narrow range of tissue temperatures, meaning that the capacity to dissipate body heat is an important parameter for thermoregulation and organismal performance. Yet, experimental research has found mixed support for the importance of heat dissipation capacity as a constraint on reproductive performance. To investigate the effects of heat dissipation capacity on organismal performance, I experimentally manipulated heat dissipation capacity in free-living tree swallows, Tachycineta bicolor, by trimming feathers overlying the brood patch, and monitored parental provisioning performance, body temperature, and offspring growth. I found that individuals with an enhanced capacity to dissipate body heat (i.e., trimmed treatment) provisioned their offspring more frequently, and reared larger offspring that fledged more consistently. Although control birds typically reduced their nestling provisioning rate at the highest ambient temperatures to avoid overheating, at times they became hyperthermic. Additionally, I examined inter-individual variation in body temperature within each treatment, and discovered that body temperature is variable among all individuals. This variability is also consistent over time (i.e., is repeatable), irrespective of treatment. Further, I found that individuals consistently differed in how they adjusted their body temperature across ambient temperature, demonstrating that body temperature is a flexible and repeatable physiological trait. Finally, I used a bacterial endotoxin (lipopolysaccharide) to examine the regulation of body temperature of captive zebra finches (Taeniopygia guttata) during an immune challenge. Exposure to lipopolysaccharide induces sickness behaviours, and results in a fever, hypothermia, or a combination of the two, depending on species and dosage. I asked what the relative role of different regions of the body (bill, eye region, and leg) is in heat dissipation/retention during the sickness-induced body temperature response. I found that immune-challenged individuals modulated their subcutaneous temperature primarily through alterations in peripheral blood flow, particularly in the legs and feet, detectable as a drop in surface temperature. These results demonstrate that the importance of regional differences in regulating body temperature in different contexts. Taken together, my thesis demonstrates that heat dissipation capacity can affect performance and reproductive success in birds. Author Keywords: body temperature, heat dissipation, tree swallow, zebra finch
Calcium Stress in Daphnia Pulicaria and Exposure to Predator-Derived Cues
In recent decades, declining calcium concentrations have been reported throughout lakes across the southern edge of the Canadian Shield. This raises concern as Daphnia populations have shown to be decreasing as they require calcium not only for survival but to mitigate predation risks. Therefore, the purpose of my thesis was to study the adaptability of Daphnia under calcium limitation and predation risk from Chaoborus. Firstly, I examined the effects of calcium limitation and Chaobours kairomones on daphniid life-history and population growth. I found that low calcium concentrations and Chaoborus kairomones affected Daphnia calcium content, life-history traits, and survival. Next, I focused on how calcium concentrations and Chaoborus abundance affected the calcium content and abundance of daphniids. During this study, I also examined the relationship between the abundance of Daphnia and a competitor Holopedium. I found that calcium concentrations and the abundance of Chaoborus affects daphniid abundance. Overall, results from this study show the importance of considering both predation risk and calcium declines to better determine daphniid losses. Author Keywords: anti-predator responses, Chaoborus, competition , Life-History traits, predator cues, Zooplankton
Biosynthesis and impact of cytokinins on growth of the oyster mushroom, Pleurotus ostreatus
The oyster mushroom, Pleurotus ostreatus, is one of the most widely cultivated edible basidiomycetes. It has gained increased attention for its economic, environmental, and medicinal properties. While a lot is known about cytokinins (CKs) and their actions at the molecular and cellular levels in plants, much less is known about the function of CKs in other kingdoms. Cytokinins, which have been detected in several fungal species, play a role in pathogenic attack against plants or during plant growth promotion by plant beneficial microbes; however, the role of CKs in fungal physiology, separate from plant associations remains largely unknown. This thesis focuses on the occurrence of fungal-derived CKs in P. ostreatus when grown in vitro as submerged or aerial mycelium. Cytokinin profiling by UHPLC-HRMS/MS revealed that P. ostreatus produces CKs and that the tRNA degradation pathway is the main source of these molecules. CK dynamics within fungal growth supported previous evidence, which suggested that tRNA degradation products have a role in the physiological development of fungi for which CKs act as fungal growth regulators. A second component of the thesis demonstrated that P. ostreatus responds to exogenous applications of aromatic and isoprenoid CKs and their effects were dependent on the dose and CK type. N6-Benzyladenine (BAP), Kinetin (KIN), N6-isopentenyladenine (iP), and trans-zeatin (tZ) bioassays revealed hormone-type responses (hormesis: biphasic response). At low doses, mycelium growth could be stimulated, whereas, at high doses only inhibitory effects were observed. This stimulation/inhibition was observed whether the measured response was an increase/decrease of aerial mycelium colony diameter, biomass accumulation or a change in mycelium morphology as compared to the controls. Results indicated there is potential to alter mycelium growth and development of P. ostreatus; thus, CKs may play the role of a “mycohormone” and may be specifically helpful for medicinal fungi by increasing growth and efficiency to produce many biologically active substances with valuable medical and environmental applications. Author Keywords: cytokinins, fungal-derived CKs, hormesis, mycelium, mycohormone, Pleurotus ostreatus
Population Dynamics of Eastern Coyotes in Southeastern Ontario
The ability of animal populations to compensate for harvest mortality provides the basis for sustainable harvesting. Coyote populations are resilient to exploitation, but the underlying mechanisms of compensation and how they inter-relate are not fully understood. Moreover, deficiencies in the quality and quantity of information about eastern coyotes preclude effective management. I combined field work, laboratory work, and genetic profiling to investigate the population dynamics of eastern coyotes in southeastern Ontario. Specifically, I conducted research on coyotes during 2010–2013 in Prince Edward County where coyote hunting and trapping seasons were open all year. First, I investigated their social status dynamics and space-use patterns. Transients exhibited extensive space-use relative to residents, potentially encountering vacant territories and/or breeding positions, and some transients became residents, potentially filling vacant territories and/or breeding positions. Accordingly, the study population demonstrated the potential to compensate for harvest mortality via source-sink dynamics and/or buffering reproductive capacity. Second, I investigated their survival and cause-specific mortality. Residents exhibited greater survival than transients, probably partly because of the benefits of holding a territory, and transients seemingly exhibited greater vulnerability to harvest than residents, probably partly because their movements exposed them to greater cumulative mortality risks over time. Accordingly, harvest mortality disproportionately impacted the non-reproductive segment of the study population and thus may have failed to substantially limit reproduction, and thus recruitment. Third, I investigated their reproduction and breeding histories. Females in the study population exhibited age-specific reproductive rates and litter sizes generally typical of those in exploited coyote populations. Accordingly, increased reproductive rates and increased litter sizes may have offset losses due to harvest mortality. There was at least some breeder turnover in the study population due to harvest mortality, but many breeders survived to reproduce for multiple years and those that died were quickly replaced. My findings have important management implications for eastern coyotes and contribute significantly to better understanding of their resilience to harvest. Indiscriminate killing of coyotes through liberal harvest is unlikely to be effective in reducing their abundance. Management strategies should consider non-lethal alternatives and/or targeted lethal control for dealing with problem coyotes. Author Keywords: Canis latrans var., eastern coyotes, population dynamics, Prince Edward County, southeastern Ontario
White-Tailed Fear
The primary method used to maintain white-tailed deer (Odocoileus virginianus) populations at densities that are ecologically, economically, socially, and culturally sustainable is hunter harvest. This method considers only the removal of animals from the population (the direct effect) and does not conventionally consider the costs imposed on deer as they adopt hunter avoidance strategies (the risk effect). The impact of risk effects on prey can exceed that of direct effects and there is interest in applying this concept to wildlife management. Deer are potential candidates as they have demonstrated behavioural responses to hunters. I explored the potential of such a management practice by quantifying how human decisions around hunting create a landscape of fear for deer and how deer alter their space use and behaviour in response. I used a social survey to explore the attitudes of rural landowners in southern and eastern Ontario towards deer and deer hunting to understand why landowners limited hunting on their property. I used GPS tracking devices to quantify habitat selection by hunters and hunting dogs (Canis familiaris) to better understand the distribution of hunting effort across the landscape. I used GPS collars to quantify the habitat selection of deer as they responded to this hunting pressure. I used trail cameras to quantify a fine-scale behavioural response, vigilance, by deer in areas with and without hunting. Human actions created a highly heterogeneous landscape of fear for deer. Landowner decisions excluded hunters from over half of the rural and exurban landscape in southern and eastern Ontario, a pattern predicted by landowner hunting participation and not landcover composition. Hunter decisions on whether to hunt with or without dogs resulted in dramatically different distributions of hunting effort across the landscape. Deer showed a high degree of behavioural plasticity and, rather than adopting uniform hunter avoidance strategies, tailored their response to the local conditions. The incorporation of risk effects into white-tailed deer management is feasible and could be done by capitalizing on a better understanding of deer behaviour to improve current management practices or by designing targeted hunting practices to elicit a landscape of fear with specific management objectives. Author Keywords: Brownian bridge movement models, hunting, landscape of fear, resource utilization functions, risk effects, white-tailed deer
role of Cln5 in autophagy, using a Dictyostelium discoideum model of Batten disease
This thesis investigated the role of the neuronal ceroid lipofuscinosis protein, Cln5, during autophagy. This was accomplished by performing well-established assays in a Dictyostelium cln5 knockout model (cln5-). In this study, cln5- cells displayed a reduced maximum cell density during growth and impaired cell proliferation in autophagy-stimulating media. cln5- cells had an increased number of autophagic puncta (autophagosomes and lysosomes), suggesting that autophagy is induced when cln5 is absent. cln5- cells displayed increased amounts of ubiquitin-positive proteins but had no change in proteasome protein abundance. During the development of cln5- cells, fruiting bodies developed precociously and cln5- slug size was reduced. Lastly, when cln5- cells were developed on water agar containing ammonium chloride (NH4Cl), a lysosomotropic agent, the formation of multicellular structures was impaired, and the small slug phenotype was exaggerated. In summary, these results indicate that Cln5 plays a role in autophagy in Dictyostelium. The cellular processes that regulate autophagy in Dictyostelium are similar to those that regulate the process in mammalian cells. Thus, this research provides insight into the undefined pathological mechanism of CLN5 disease and could identify cellular pathways for targeted therapeutics. Author Keywords: Autophagy, Batten disease, Cln5, Dictyostelium discoideum, NCL
Shorebird Stopover Ecology and Environmental Change at James Bay, Ontario, Canada
I examined how shorebirds respond to environmental change at a key subarctic migratory bird stopover site, the southwestern coast of James Bay, Ontario, Canada. First, I investigated if the morphology of sandpipers using James Bay during southbound migration has changed compared to 40 years prior. I found shorter, more convex and maneuverable wings for sandpipers in the present-day compared to the historical monitoring period, which supports the hypothesis that wing length change is driven by increases in predation risk. Secondly, I assessed the relationship between migration distance, body condition, and shorebird stopover and migratory decisions. Species that travelled farther distances from James Bay to wintering areas migrated with more characteristics of a time-minimizing migration strategy whereas species that travelled shorter distances migrated with energy minimizing strategies. Body condition impacted length of stay, wind selectivity at departure, groundspeeds, and probability of stopover and detection in North America after departing James Bay. Thirdly, I examined annual variation in dry/wet conditions at James Bay and found that shorebirds had lower body mass in years with moderate drought. In the present-day, drought resulted in lower invertebrate abundance and refuelling rates of shorebirds during stopover, which led to shorter stopover duration for juveniles and a higher probability of stopover outside of James Bay for all groups except white-rumped sandpiper. Finally, I estimated the relative importance of intertidal salt marsh and flat habitats to the diets of small shorebirds and found that semipalmated and white-rumped sandpiper (Calidris pusilla and C. fuscicollis) and semipalmated plover (Charadrius semipalmatus) diets consist of ~ 40 – 75% prey from intertidal marsh habitats, the highest documented in the Western Hemisphere for each species. My research shows that James Bay is of high importance to white-rumped sandpipers, which are unlikely to stop in North America after departing James Bay en route to southern South America. Additionally, intertidal salt marsh habitats (and Diptera larvae) appear particularly important for small shorebirds in the region. My thesis shows that changing environmental conditions, such as droughts, can affect shorebird refuelling and stopover strategies. Author Keywords: body condition, diet, environmental change, migration, ornithology, stopover ecology
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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Format: 2021/12/03