Graduate Theses & Dissertations

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Spatial Dynamics of Wind Pollination in Broadleaf Cattail (Typha latifolia)
Natural populations of flowering plants rarely have perfectly uniform distributions, so trends in pollen dispersal should affect the size of the pollination neighbourhood and influence mating opportunities. Here I used spatial analysis to determine the size of the pollination neighbourhood in a stand of the herbaceous, wind-pollinated plant (Typha latifolia; broad-leaved cattail) by evaluating patterns of pollen production and seed set by individual cattail shoots. I found a positive correlation between pollen production and seed set among near-neighbour shoots (i.e., within 4 m2 patches of the stand; Pearson's r = 0.235, p < 0.05, df = 77) that was not driven by a correlation between these variables within inflorescences (Pearson's r = 0.052, p > 0.45, df = 203). I also detected significant spatial autocorrelations in seed set over short distances (up to ~ 5 m) and a significant cross-correlation between pollen production and seed set over distances of < 1 m indicating that the majority of pollination events involve short distances. Patterns of pollen availability were simulated to explore the shape of the pollen dispersal curve. Simulated pollen availability fit actual patterns of seed set only under assumptions of highly restricted pollen dispersal. Together, these findings indicate that even though Typha latifolia produces copious amounts of pollen, the vast majority of pollen dispersal was highly localized to distances of ~ 1 m. Moreover, although Typha latifolia is self-compatible and has been described as largely selfing, my results are more consistent with the importance of pollen transfer between nearby inflorescences. Therefore, realized selfing rates of Typha latifolia should largely depend on the clonal structure of populations. Author Keywords: clonal structure, correlogram, dispersal curves, pollination, spatial analysis, Typha latifolia
Calving site selection and fidelity in a restored elk (Cervus elaphus) herd in Bancroft, Ontario, Canada
ABSTRACT Calving site selection and fidelity in a restored elk (Cervus elaphus) herd in Bancroft Ontario, Canada. Michael R. Allan Parturition site selection by ungulates is believed to be influenced by forage abundance and concealment from predators. In 2011 and 2012, I used vaginal implant transmitters and movements to identify calving sites for 23 GPS collared elk (Cervus elaphus) from a restored herd. I tested the hypothesis that maternal elk used sites with higher forage and denser concealment compared to pre-calving sites at micro and macrohabitat levels. I detected no significant microhabitat differences from direct measurements of vegetation. At the macrohabitat scale, based on proximity of landcover classes, mean distances to hardwood forests was significantly less for calving (153 m) than pre-calving sites (198 m). Site fidelity is hypothesized to offer security in terms of familiarity to an area. I tested the hypothesis that females demonstrated fidelity to their previous year's location during pre-partum, parturition, post partum, breeding and winter periods. Elk were more philopatric during parturition and post partum than during breeding. Compared to winter elk were more philopatric during pre-partum, parturition and post-partum periods. Expressed as distance between consecutive-year calving locations, site fidelity varied with 27% of females exhibiting high (<1 km), 18% moderate and 55% (>2.9 km) low fidelity. I measured nearest-neighbour distances at calving time, exploring the hypothesis that females distance themselves from conspecifics. Elk increased the average distances to collared conspecifics during parturition; however, sample sizes were small. This strategy might influence calving site selection. Rapid movement prior to parturition, low site fidelity and spacing-out of females during parturition appear to be strategies to minimize predator risk and detection. Little evidence of selection for vegetation structure suggests this may not be limiting to these elk. Author Keywords: calving, elk, fidelity, movement, parturition, selection
Stoichiometric food quality affects responses of Daphnia to predator-derived chemical cues
While both resource quality and predator-derived chemical cues can each have profound effects on zooplankton populations and their function in ecosystems, the strength and nature of their interactive effects remain unclear. We conducted laboratory experiments to evaluate how stoichiometric food quality (i.e., algal carbon (C):phosphorus (P) ratios) affects responses of the water flea, Daphnia pulicaria, to predator-derived chemical cues. We compared growth rates, body elemental content, metabolic rates, life history shifts, and survival of differentially P-nourished Daphnia in the presence and absence of chemical cues derived from fish predators. We found effects of predator cues and/or stoichiometric food quality on all measured traits of Daphnia. Exposure to fish cues led to reduced growth and increased metabolic rates, but had little effect on the elemental content of Daphnia. Elevated algal C:P ratios reduced growth and body %P, increased respiration, and increased body %C. Most of the effects of predator cues and algal C:P ratios of Daphnia were non-interactive. In contrast, the declines in daphnid survival and related population growth rates that arose because of poor food quality were amplified in the presence of predator-derived cues. Our results demonstrate that stoichiometric food quality interacts with anti-predator responses of Daphnia, but these effects are trait-dependent and appear connected to animal life-history evolution. Author Keywords: Daphnia, ecological stoichiometry, indirect predator effects, life history, phosphorus, predator-prey relationships
Habitat Preferences and Feeding Ecology of Blackfin Cisco (Coregonus nigripinnis) in Northern Algonquin Provincial Park
Blackfin Cisco (Coregonus nigripinnis), a deepwater cisco species once endemic to the Laurentian Great Lakes, was discovered in Algonquin Provincial Park in four lakes situated within a drainage outflow of glacial Lake Algonquin. Blackfin habitat preference was examined by analyzing which covariates best described their depth distribution using hurdle models in a multi-model approach. Although depth best described their distribution, the nearly isothermal hypolimnion in which Blackfin reside indicated a preference for cold-water habitat. Feeding structure differentiation separated Blackfin from other coregonines, with Blackfin possessing the most numerous (50-66) gill rakers, and, via allometric regression, the longest gill rakers and lower gill arches. Selection for feeding efficiency may be a result of Mysis diluviana affecting planktonic size structure in lakes containing Blackfin Cisco, an effect also discovered in Lake Whitefish (Coregonus clupeaformis). This thesis provides insight into the habitat preferences and feeding ecology of Blackfin and provides a basis for future study. Author Keywords: allometric regression, blackfin cisco, habitat, hurdle models, lake whitefish, mysis
Seasonal habitat use and movement of native brook trout (Salvelinus fontinalis) in urban headwater streams
Coldwater streams are becoming increasingly impacted due to urbanization. Using environmental surveys, mark-recapture and telemetry, I assessed factors influencing seasonal brook trout (Salvelinus fontinalis) habitat use and movement in urban headwater streams in central Ontario between 2017-18. Generalized additive models were used to assess which habitat variables best explained seasonal yearling and older brook trout abundance, while generalized least squares models were used to assess overall trends in radio-tagged brook trout movement. My research demonstrated dynamic patterns in habitat use and movement by urban stream-dwelling brook trout. Yearlings were primarily influenced by water quality (stream temperature, conductivity), while older brook trout were most strongly influenced by stream morphology (depth, undercut bank). Movement occurred disproportionately around the spawning season and was more limited in the smaller, more altered stream. These findings may be used to inform fisheries managers on crucial timing and location of brook trout habitat refugia within urbanized environments. Author Keywords: Brook trout, coldwater stream, groundwater, habitat use, radiotelemetry, urbanization
mechanistic analysis of density dependence in algal population dynamics
Population density regulation is a fundamental principle in ecology, however there remain several unknowns regarding the functional expression of density dependence. One prominent view is that the patterns by which density dependence is expressed are largely fixed across a species, irrespective of environmental conditions. Our study investigated the expression of density dependence in Chlamydomonas reinhartti grown under a gradient of nutrient densities, and hypothesized that the relationship between per capita growth rate (pgr) and population density would vary from concave-up to concave-down as nutrients became less limiting. Contrary to prediction, we found that the relationship between a population's pgr and density became increasingly concave-up as nutrient levels increased. Our results suggest that density dependence is strongly variable depending on exogenous and endogenous processes acting on the population, implying that expression of density regulation depends extensively on local conditions. Population growth suppression may be attributable to environments with high intraspecific competition. Additional work should reveal the mechanisms influencing how the expression of density dependence varies across populations through space and time. Author Keywords: Chlamydomonas reinhartti, density dependence, logistic model, population dynamics, single species growth, theta-logistic equation
Enhancing post-mortem interval estimates
The growth of immature insects that develop on human remains can be used to estimate a post-mortem interval (PMI). PMI estimate confidence is negatively affected by: larval killing and preservation methods altering their size, limited morphological parameters to assess larval growth and therefore age, and few available alternate species development data. I compared live specimens to preserved specimens of the same development stages to assess the effects of killing-preservation techniques on morphology, and I introduce a new method that uses digital photography to examine maggot mouthparts for stage grading of Phormia regina. Digital photographic methods enable live insects to be quantified and improve approximations of physiological age. I then use these digital methods to produce a growth-rate model for a beetle commonly found on human remains, Necrodes surinamensis, providing data for PMI estimates that was previously unavailable. Author Keywords: Forensic Entomology, Insect development, Morphometrics, Necrodes surinamensis, Phormia regina, Postmortem interval
Bank Swallow (Riparia riparia) Breeding in Aggregate Pits and Natural Habitats
I examined Bank Swallow (Riparia riparia) colony persistence and occupancy, in lakeshore, river and man-made aggregate pit habitat. Habitat persistence was highest on the lakeshore and lowest in aggregate pits, likely due to annual removal and relocation of aggregate resources. Bank Swallow colonies in aggregate pit sites were more likely to persist if a colony was larger or if burrows were located higher on the nesting face. I also compared nest productivity and health factors of Bank Swallows in lakeshore and aggregate pit habitats. While clutch size was the same in both habitat types, the number of fledglings from successfully hatched nests was significantly higher in aggregate pit sites than from lakeshore sites. Mass of fledgling Bank Swallows did not differ significantly between habitat types, however mass of adults from aggregate pits decreased significantly over the nesting season. Parasite loads on fledgling Bank Swallows were significantly lower in aggregate pits than in lakeshore sites. According to these indicators, aggregate pits appear to provide equivalent or higher quality habitat for Bank Swallows than the natural lakeshore sites, making them adequate and potentially key for this species’ recovery. Aggregate pit operators can manage for swallows by (1) creating longer, taller faces to attract birds and decrease predation, and (2) supplementing their habitat with water sources to encourage food availability. Author Keywords: Aerial insectivore, aggregate pits, Bank Swallow, colony persistence, ectoparasites, substitute habitat
Detectability and its role in understanding upland sandpiper (Bartramia longicauda) occurence in the fragmented landscape of southern Ontario
Upland Sandpipers (Bartramia longicauda), like many grassland birds, are undergoing population decline in parts of their range. Habitat fragmentation and change have been hypothesized as potential causes of decline. I used citizen-science occurrence data from Wildlife Preservation Canada’s Adopt-A-Shrike Loggerhead Shrike (Lanius ludovicianus) program in conjunction with validation surveys, using similar point-count methods, to examine detectability and determine if landscape level habitat features could predict occupancy of Upland Sandpipers in Southern Ontario. In a single season detectability study, I used Wildlife Preservation Canada’s survey protocol to determine detectability in sites that were known to be occupied. Detectability was low, with six surveys necessary to ensure detection using a duration of at least 18 minutes early in the breeding season. The proportion of open habitat did not affect detection on the landscape. Using a larger spatial and temporal scale, with five years of citizen-science data, I showed that Annual Crop Inventory data could not effectively predict Upland Sandpiper occupancy. Model uncertainty could be attributed to survey protocol and life history traits of the Upland Sandpiper, suggesting that appropriate survey methods be derived a priori for maximizing the potential of citizen-science data for robust analyses. Author Keywords: Bartramia longicauda, citizen-science, detection, landscape, occupancy, Ontario
Assessing the environmental correlates of a lethal amphibian pathogen, Batrachochytrium dendrobatidis, in Ontario wetlands
Many emerging infectious diseases are caused by pathogens that possess free-living life stages, in which they interact with the environment directly rather than through the mediation of a host. These diseases represent major impediments to wildlife conservation; however, the dynamics of their interaction with the environment are poorly studied, often due to the difficulty of detecting these microscopic pathogens in environmental samples. One of these pathogens is Batrachochytrium dendrobatidis (Bd), a fungus that has been linked to declines in many amphibian species. In this thesis I use an emerging technique, environmental DNA detection (eDNA), to detect and quantify Bd in the water of southern Ontario (Canada) wetlands and examine its correlation with a variety of aspects of water quality, surrounding habitat, and seasonal timing. My purpose was to inform not only on potential environment-pathogen dynamics for Bd in northern environments, but to provide insight into the use of eDNA as a disease surveillance tool. I found that not only was there high geographic variation in Bd detection and intensity, but also high temporal variation within the same site on time scales as low as two weeks. While Bd prevalence was not strongly correlated with any of the variables tested, intensity showed strong correlation with canopy cover, with greater canopy cover over a waterbody correlating to lower Bd intensity. My results present several promising avenues for further examination of Bd in northern ecosystems, and indicate that, while caution is warranted in its implementation, eDNA may become an important tool in amphibian pathogen surveillance. Author Keywords: amphibian disease, Batrachochytrium dendrobatidis, disease monitoring, environment-pathogen dynamics, environmental DNA, wildlife disease
Larval lake whitefish (Coregonus clupeaformis) recruitment dynamics in Lake Huron
Lake whitefish (Coregonus clupeaformis) recruitment has declined substantially in several regions of the Laurentian Great Lakes since the establishment of non-native dreissenid mussels in the early 1990’s. In Lake Huron, the reasons for the observed recruitment declines are currently unknown and there is limited knowledge about larval life stage. In our study, we determined whether larval hatching and growth rates have changed before and after dreissenid mussel invasion, and the role of several key environmental variables in influencing annual variation in larval densities. Larval fish were collected in the Fishing Islands spawning shoal during two time periods: a historical period (1976-1986) and a contemporary period (2017-2019). Larval densities and growth were lower in recent years, suggesting that recruitment is being limited at the larval life stage and that reduced food availability may be further limiting the growth during the larval stage. Annual variation of larval densities were influenced by spawning stock biomass, water levels, and dreissenid mussel presence, with higher water levels and the presence of dreissenid mussels being associated with higher larval densities. The direction of the effect of spawning stock biomass was either negative or positive depending on the model. We also found that larval density was a significant predictor of age 4 recruitment, indicating that year-class strength may be partly established at the larval life stage. Author Keywords: Coregonus clupeaformis, Great Lakes, Lake Huron, Lake whitefish, Larval, Recruitment
Aquatic Invertebrate Studies from Two Perspectives
Leaf litter decomposition represents a major pathway for nutrient cycling and carbon flow in aquatic ecosystems, and macroinvertebrates play an important role in the processing of this material. To assess the causes of variable leaf breakdown and nutrient fluxes, I measured decomposition rates and the nutrient release ratios of decomposing leaf material across a broad latitudinal gradient in Ontario boreal lakes which varied in nutrients, temperature, and pH. I examined the effects of macroinvertebrates using inclusion and exclusion bags. Generally, leaves decomposed faster in nutrient-rich, warmer lakes. Macroinvertebrates increased decomposition rates but their effects were relatively small compared to regional effects of nutrients and temperature. In addition, we found differential effects of nutrients and temperature on nutrient release ratios, which were partially determined by the release and retention of N and P. These results indicate that changes in these important environmental lake variables could alter decomposition dynamics in Ontario lakes, with implications for nutrient cycling and the storage of this important external carbon source. I studied the biogeography of predaceous diving beetles (Coleoptera: Dytiscidae) in two remote and understudied regions: the Far North of Ontario, and Akimiski Island, Nunavut. I identified 35 species from northern Ontario, including three first provincial records for Ontario, Acilius athabascae Larson (1975), Hygrotus unguicularis (Crotch 1874), and Nebrioporus depressus (Fabricius 1775). I also documented three significant range extensions and six gap-infills for this region. I collected and identified 16 species from Akimiski Island, Nunavut, which include several first time reports for these species for the Nunavut territory. My collections also extend the known ranges of five species into the Hudson Plains Ecozone. This work provides important baseline information on the distribution of diving beetles for these regions. Author Keywords: biodiversity, Boreal Shield, decomposition, Dytiscidae, ecological stoichiometry, macroinvertebrates

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2004 - 2024
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Format: 2024/03/28