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Graduate Theses & Dissertations
Pages
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- Range dynamics of two closely related felids
- Species ranges are changing and the rate at which the climate is warming is faster than anything previously seen in the past, consequently species will need to adapt quickly, track the climate or perish. Cold adapted terrestrial species are the most vulnerable, because they are limited by the availability of land at the cold edge of their range. This means that many alpine, boreal and polar species essentially have nowhere to go as the climate warms. Habitat generalists are widely distributed across the globe and are highly adaptable to anthropogenic change. Our future biodiversity may only consist of several habitat generalists. The Canada lynx (Lynx canadensis) is a boreal species that has limited range expansion potential at the cold end of its range and its range has already contracted by 40%. The lynx has nowhere to go as climate warming progresses in this current century. Therefore, understanding the causes of its range contraction could enlighten us on conservation and management strategies that we might undertake as climate warms. My analyses indicated that the Canada lynx seems to have tracked the habitat that it is adapted to in more northern homogenous boreal forests and the bobcat (Lynx rufus), a habitat generalist, has simply replaced it in the south. Author Keywords: Anthropogenic Change, Competition, Connectivity, Lynx canadensis, Lynx rufus, Range change
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- Investigating Ecological Niche Differentiation Among Wild Candids Experiencing Hybridization in Eastern North America
- Currently there are large areas of the North American landscape that are occupied by Canis spp. hybrids of several varieties, leading to the logical question as to the genetic structure and ecological function of Canis populations across the continent, and to what extent hybrids reflect contemporary landscapes. This study illustrated patterns of niche differentiation between parental canid species and their hybrids using individual high quality genetic profile and species distribution models to support the intermediate phenotype hypothesis. In general, hybrids demonstrated an intermediate habitat suitability compared to its parental species, across most environmental variables used. A similar trend was observed in the niche metric analysis, where we found that hybrids exhibit intermediate niche breadth, with eastern coyotes and eastern wolves exhibiting the broader and narrower niche, respectively. Our results demonstrate that the intermediate phenotype hypothesis is supported even at a large scale and when involving highly mobile large mammal species. Author Keywords: canid, ecological niche modelling, hybridization, intermediate phenotype, microsatellite genotype, niche differentiation
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- Influence of Habitat on Woodland Caribou Site Fidelity
- Site fidelity is the behaviour of individuals to return to the same location; for female woodland caribou it may reflect reproductive success and depend on habitat quality. I investigated the influence of landscape and disturbance conditions on fidelity among three populations in Manitoba and Ontario, Canada. Habitat classifications were based on Forest Resource Inventory (FRI) and Landsat TM landcover maps. A total of 261 sites were ground-truthed to determine mapping accuracy. An amalgamated map incorporating FRI and Landsat TM data was estimated from field measurements to have an overall accuracy of 69.0%. Site fidelity was expressed as the distance between consecutive-year locations of individuals and was investigated during five week-long periods representing calving, early and late post-calving, winter, and breeding. Site fidelity was strongest during the post-calving seasons and weakest during the winter. Habitat had little influence on site fidelity in all seasons, excepting winter, even under highly disturbed conditions, suggesting maintenance of fidelity may be a maladaptive trait. Individual variation proved a strong predictor and cursory mapping indicated that caribou may return to sites visited two or more years earlier. Conservation management and policy should recognize that site fidelity may represent an ecological trap. Author Keywords: calving, disturbance, habitat, movement, Rangifer tarandus caribou, site fidelity
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- THE LIFE HISTORY STRATEGY, GROWTH, BODY CONDITION, AND DIET OF STOCKED AMERICAN EEL (Anguilla rostrata) IN THE UPPER ST. LAWRENCE RIVER AND LAKE ONTARIO
- My study was primarily focused on the comparison of life history traits between stocked American eel and their naturally recruited conspecifics in Lake Ontario and the upper St. Lawrence River (USLR/LO). I found that stocked eels experienced faster annual growth than their naturally recruited conspecifics and were comprised of a greater proportion of males. These findings indicate that the life history patterns of American eel may be genetically predisposed. Additionally, my study served to characterize the diets of stocked American eel and examine possible associations between eel and prey size. The eels consumed a number of macroinvertebrate prey orders as well as fishes and macrocrustaceans, with the latter prey items being more prevalent in the diets of larger eel specimens. A disparity in eel growth and body condition was observed between two primary stocking locations and were likely attributable to differences in available forage and habitat. Lastly, growth, body condition, and stocked eel diet were compared between lentic and lotic habitats. Eels from lotic streams experienced slower annual growth and had reduced body condition, and their diets were comprised of smaller prey items. The results of this study suggest that the current stocking methods employed in the USLR/LO are not suitable to restore the natural recruitment of individuals that will exhibit desired life history traits. Author Keywords:
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- Long-Term Population Dynamics of an Unexploited Lacustrine Brook Trout (Salvelinus fontinalis) Population
- Long-term studies of demographic processes such as survival and abundance conducted in unexploited systems provide unique insight into the natural population ecology of fish, but are rarely available. I used historical tagging records of a sanctuary population of brook trout (Salvelinus fontinalis) in Algonquin Park, Ontario to investigate long-term population dynamics in an unexploited population. Adult brook trout in Mykiss Lake (23.5ha) were surveyed and tagged biannually (May and October) between 1990 and 2004. Open-population capture-mark-recapture models were used to test the importance of time, size, sex and season on estimates of apparent survival and abundance. Seasonal population growth and recruitment were estimated and compared with large-scale climate indices. Time-dependent survival and abundance estimates fluctuated, with distinct periods of increase. Population growth and recruitment were positively correlated with summer NAO and ENSO values, whereas survival was negatively correlated. Seasonally, larger individuals experienced higher apparent survival during winter and decreased survival during summer. These findings provide valuable insights into the natural demography of unexploited brook trout populations, and should help inform sustainable management of inland fisheries. Author Keywords: capture-mark-recapture, long-term, population dynamics, Salvelinus fontinalis, seasonal variation, survival
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- Stopover Movement Patterns by Blackpoll and Canada Warblers Across Southeastern Canada During Fall Migration
- Stopover ecology is a topic that surges in relevancy as choices made by migrants during stationary periods (stopover sites) may not only have important individuals’ fitness consequences but also can affect population dynamics. I used MOTUS automated telemetry array to study fall stopover duration of Blackpoll Warbler (BLPW) and departure decisions of BLPW and Canada Warbler (CAWA) in relation to various predictors. I affixed radio-transmitters on 55 BLPWs and 32 CAWAs at two banding stations in Ontario in September-October 2014-2015. Radio-tagged individuals were tracked through the MOTUS network across southeastern Canada. I developed models relating age class, fat score, Julian date and stopover movement types to Blackpolls’ stopover duration. I also examined whether there were species-related differences of wind selectivity when resuming migration. No explanatory variable significantly influenced BLPW’s stopover duration. Both species tended to depart under increased tailwind assistance, but with no difference in the effect of wind conditions between the two species. This study provides further evidence supporting the relevance of local wind conditions as a key factor affecting the departure likelihood, especially when migrating birds face an ecological barrier. Author Keywords: Cardellina canadensis, departure decisions, minimum stopover length, MOTUS, overland fall migration, Setophaga striata
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- third wheel
- Population cycles are regular fluctuations in population densities, however, in recent years many cycles have begun to disappear. With Canada lynx this dampening has also been seen with decreasing latitude corresponding to an increase in prey diversity. My study investigates the role of alternate prey on the stability of the lynx-hare cycle by first comparing the functional responses of two sympatric but ecologically distinct predators on a primary and alternate prey. I then populated a three species predator-prey model to investigate the role of alternate prey on population stability. My results showed that alternate prey can promote stability, though they are unlikely to “stop the cycle”. Furthermore, stability offered by alternate prey is contingent on its ability to increase intraspecific competition. My study highlights that population cycles are not governed by a single factor and that future research needs to be cognizant of interactions between alternate prey and intraspecific competition. Author Keywords: alternate prey, Canis latrans, functional response, Lepus americanus, Lynx canadensis, Tamiasciurus hudsonicus
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- 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
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- Habitat use and community structure of grassland birds in southern Ontario agro-ecosystems.
- Most grassland bird populations are in decline, so it is becoming increasingly important to understand how they use agricultural field types and form their communities. I performed point counts in cultural meadow, intensive agriculture, and non-intensive agriculture areas in 2011 and 2012. Generalized linear models were used to determine the habitat relationships of six focal species. I found that non-intensive agriculture was used most often and intensive agriculture was often avoided, but there were exceptions which indicate habitat use can be species-specific. I determined in which habitats competition was likely occurring and which species pairs were competing in 2011. In 2012, I experimentally tested these relationships by introducing artificial competitors onto sites. By comparing presence-absence data from 2011 to 2012, I found evidence of habitat-mediated interspecific and conspecific attraction involving Bobolink and Grasshopper Sparrow. This research contributes to the current understanding of grassland bird community ecology and conservation. Author Keywords: agriculture, BACI, community ecology, habitat use, species at risk, species interactions
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- 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
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- Understanding Angler Dynamics in a Recreational Lake Trout (Salvelinus namaycush) Fishery in Algonquin Provincial Park Using Long-Term Access Creel Data
- In order to effectively manage recreational fisheries, it is important to understand how the resource is being used. In this thesis, long-term creel census data, collected on Lake Opeongo in Algonquin Provincial Park, Ontario, Canada was used to assess fine-scale angler dynamics within a recreational Lake Trout (Salvelinus namaycush) fishery. The spatial distribution of angler reported catch locations of Lake Trout within the lake, was assessed using an Optimized Hotspot Analysis in ArcGIS. Areas of significant clustering of catch locations were revealed during all time periods and varied in size and location both seasonally and temporally. Cormack-Jolly-Seber models were used to evaluate the probability of individual angling boats persisting in the regional fishery and being detected on Lake Opeongo through time, as well as to examine the effect of angler travel distance and gas prices on participation parameters. Time-varying models revealed that the probability of an angler persisting in the fishery varied, while detection estimates remained stable. Travel distance had a negative effect on both parameters while increased gas prices only had a slight negative effect on detection estimates. Additionally, among Lake Opeongo anglers, angling avidity varied as did lake specific fishing experience. Average CUE was found to be higher among angling parties who visited the lake more often than fishing parties who visited relatively few times. Author Keywords:
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- Islands, ungulates, and ice
- Central to wildlife conservation and management is the need for refined, spatially explicit knowledge on the diversity and distribution of species and the factors that drive those patterns. This is especially vital as anthropogenic disturbance threatens rapid large-scale change, even in the most remote areas of the planet. My dissertation examines theinfluence of land- and sea-scape heterogeneity on patterns of genetic differentiation, diversity, and broad-scale distributions of island-dwelling ungulates in the Arctic Archipelago. First, I investigated genetic differentiation among island populations of Peary caribou (Rangifer tarandus pearyi) in contrast to continental migratory caribou (Rangifer tarandus) and evaluated whether genetic exchange among Peary caribou island populations was limited by the availability of sea ice – both now and in the future. Differentiation among both groups was best explained by geodesic distance, revealing sea ice as an effective platform for Peary caribou movement and gene flow. With future climate warming, substantial reductions in sea ice extent were forecast which significantly increased resistance to caribou movement, particularly in summer and fall. Second, I assessed genetic population structure and diversity of northern caribou and deciphered how Island Biogeography Theory (IBT) and Central Marginal Hypothesis (CMH) could act in an archipelago where isolation is highly variable due to the dynamics of sea ice. Genetic differentiation among continental and island populations was low to moderate. In keeping with IBT and CMH, island-dwelling caribou displayed lower genetic diversity compared to mainland and mainland migratory herds; the size of islands (or population range) positively influenced genetic diversity, while distance-to-mainland and fall ice-free coastlines negatively influenced genetic diversity. Hierarchical structure analysis revealed multiple units of caribou diversity below the species level. Third, I shifted my focus to the terrestrial landscape and explored the elements governing species-environment relationships. Using species distribution models, I tested the response of caribou and muskoxen to abiotic versus abiotic + biotic predictors, and included distance to heterospecifics as a proxy for competitive interactions. Models that included biotic predictors outperformed models with abiotic predictors alone, and biotic predictors were most important when identifying habitat suitability for both ungulates. Further, areas of high habitat suitability for caribou and muskoxen were largely disjunct, limited in extent, and mainly outside protected areas. Finally, I modelled functional connectivity for two genetically and spatially disjunct groups of island-dwelling caribou. For High Arctic caribou, natural and anthropogenic features impeded gene flow (isolation-by-resistance); for Baffin Island caribou we found panmixia with absence of isolation-by-distance. Overall, my dissertation demonstrates the varying influences of contemporary land- and sea-scape heterogeneity on the distribution, diversity and differentiation of Arctic ungulates and it highlights the vulnerability of island-dwelling caribou to a rapidly changing Arctic environment. Author Keywords: Circuitscape, connectivity, Island Biogeography, landscape genetics, population structure, species distribution models