Graduate Theses & Dissertations

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Ice age fish in a warming world
In the face of climate change, the persistence of cold-adapted species and populations will depend on their capacity for evolutionary adaptation of physiological traits. As a cold-adapted Ice Age relict species, lake trout (Salvelinus namaycush) are ideal for studying potential effects of climate change on coldwater fishes. I studied the thermal acclimation capacity and aerobic metabolism of age 2+ lake trout from four populations across four acclimation temperatures (8ºC, 11ºC, 15ºC, and 19ºC). One population had marginally significant higher active metabolic rate (AMR) and metabolic scope across all temperatures. There was no interpopulation variation for critical thermal maximum (CTM), standard metabolic rate (SMR), or thermal acclimation capacity. Acclimation resulted in a 3ºC increase in thermal tolerance and 3-fold increase in SMR for all populations. At 19ºC, SMR increased and AMR declined, resulting in sharply reduced metabolic scope for all populations. The limited intraspecific variation in thermal physiology suggests that climate change may threaten lake trout at the species rather than population level. Author Keywords: Climate Change, Lake Trout, Metabolic Rate, Salvelinus namaycush, Temperature, Thermal Acclimation
Selection on functional genes across a flying squirrel (genus Glaucomys) hybrid zone
While hybridization between distinct taxa can have undesirable implications, it can also result in increased genetic variability and potentially, the exchange of adaptive genes or traits. Adaptive variation acquired through introgressive hybridization may be particularly advantageous for species facing rapid environmental change. I investigated a novel, climate change-induced hybrid zone between two flying squirrel species: the southern (Glaucomys volans) and northern (G. sabrinus) flying squirrel. I was interested in the occurrence of hybridization and introgression, the type of selective pressures maintaining the hybrid zone and the potential for adaptive introgression. I found relatively low hybridization and introgression frequencies (1.7% and 2.9% of the population, respectively) and no evidence of selection on hybrids or backcrosses in particular environments. I conclude that the data are more consistent with a hybrid zone maintained by endogenous (environment-independent) selection. I tested for adaptive introgression using two functional genes: IGF-1 and CLOCK. I documented intermediate functional allele frequencies in backcrosses compared to parental populations, suggesting the alleles do not confer fitness advantages in backcrosses. Despite lack of evidence for current adaptive introgression, genetic admixture between G. volans and G. sabrinus may provide adaptive potential should these species face more rapid or drastic environmental change in the future. Author Keywords: adaptive introgression, flying squirrel, Glaucomys sabrinus, Glaucomys volans, hybridization, introgression
Longitudinal trends of benthic invertebrates in regulated rivers
The Serial Discontinuity Concept describes the downstream recovery of key biophysical variables below an impoundment. With the proliferation of hydropower dams to meet increasing societal demands, further refinement and understanding of the Serial Discontinuity Concept is needed to accurately predict downstream impacts and ensure the proper management of rivers. In this study, I examine SDC predictions on physical, chemical and biological recovery in regulated rivers providing evidence from 1) a comprehensive literature review and 2) a formal test using two regulated rivers in Northern Ontario. I specifically address how these changes are reflected in benthic invertebrate abundance, diversity, and community composition. The literature review and case studies support the predicted recovery of temperature, periphyton, substrate, and drift. In addition, the study suggests that two recovery gradients exist in regulated rivers: 1) a longer, thermal gradient taking up to hundreds of kilometres downstream; and 2) a shorter, resource subsidy gradient recovering within 1-4 km downstream of an impoundment. Total benthic invertebrate abundance varies considerably and depends on the degree of flow alteration and resource subsidies from the upstream reservoir. In contrast, benthic diversity is reduced below dams irrespective of dam location and operation with little recovery observed downstream. Contrary to SDC predictions, the longitudinal gradient in regulated rivers is not a compaction of functional changes seen over several stream orders in natural rivers but a response to dam design and reservoir conditions. Stoneflies and dragonflies are particularly sensitive to regulation while filter feeding invertebrates are enhanced. Ward and Stanford's (1983) Serial Discontinuity Concept is still a useful framework for testing hypotheses. Future studies should further expand the SDC through empirical estimation within the context of the landscape to gain a better scientific understanding of regulated river ecology. Author Keywords: benthic invertebrates, dams, longitudinal, recovery, River Continuum Concept, Serial Discontinuity Concept
Spatial dynamics of pollination in dioecious Shepherdia canadensis in Yukon, Canada
Sexual reproduction in flowering plants depends on investment in reproduction, the mode of pollen transfer, the availabilities of nutrient resources and potential mates, and the spatial scales over which these processes take place. In this thesis, I studied the general reproductive biology of Shepherdia canadensis (L.) Nutt. (Elaeagnaceae) and the suite of pollinators that visit the plants in Ivvavik National Park, Yukon, Canada. Across ten sites, I found that S. canadensis females were larger than males, but males produced more flowers than females at most sites. Males typically occurred at higher frequencies than females with the average male to female sex ratio being 1.19 ± 0.08 (mean ± SE, n = 10 sites). Both shrub size and flower production were significantly influenced by interactions between soil nitrogen and sex. Insect visitors to S. canadensis flowers were primarily ants and flower flies (Syrphidae), but exclusion experiments indicated that visitation by flying insects yielded greater fruit production than visitation by crawling insects. I found that fruit set was limited by the density of males within populations, but only over small distances (4-6 m). This is the first study to demonstrate that female reproductive success of a generalist-pollinated dioecious plant is limited by the density of males over small spatial scales. Author Keywords: dioecy, pollinators, sex ratio, sexual dimorphism, Shepherdia canadensis
THE EFFECTS OF ROTATIONAL GRAZING AND HAY MANAGEMENT ON THE REPRODUCTIVE SUCCESS OF BOBOLINK AND EASTERN MEADOWLARK IN EASTERN ONTARIO
I investigated the impact of beef-cattle farm management on the reproductive success of Bobolink (Dolichonyx oryzivorus) and Eastern Meadowlark (Sturnella magna) within Eastern Ontario. I monitored rotational grazing management regimes and hay cut dates while assessing breeding phenology and reproductive success of Bobolinks and Eastern Meadowlarks. In pasture paddocks the major factor determining Bobolink reproductive success was the date that cattle entered a paddock to graze, with earlier entries resulting in lower reproductive success. On a landscape scale, within a series of paddocks grazed by a single herd, as the number of paddocks grazed during the nesting season increased, the number of Bobolinks that reproduced successfully decreased. Experimental quantification of trampling showed that cattle exposure to clay pigeon targets, regardless of stocking rates, resulted in the majority of targets being trampled. In hayfields associated with beef- cattle operations, grassland birds had a higher likelihood of success when cutting occurred after 4 July. The best method to improve the reproductive success of Bobolinks and Eastern Meadowlarks is to leave some hayfields and pasture paddocks undisturbed until nesting is complete. Author Keywords: Bobolink, Dolichonyx oryzivorus, farm management, hayfield, pasture, rotational grazing
USE OF SALIVARY CORTISOL TO EVALUATE THE INFLUENCE OF RIDES ON THE STRESS PHYSIOLOGY OF DROMEDARY CAMELS (CAMELUS DROMEDARIUS)
Many facilities attempt to alleviate the risk of chronic stress in captivity by providing environmental enrichment shown to minimize behavioural disorders and stress in several species. One potential form of enrichment used in zoos is training animals to perform rides for guests, however, the effect of this activity on the welfare of individual animals has never been examined. I validated the use of saliva for assessing stress in dromedary camels (Camelus dromedarius) an animal commonly used for rides. I then measured variation in salivary cortisol in four male camels during animal rides for guests at the Toronto Zoo. The camels were sampled during the ride season (from June to August) using four treatments: 1) in their pasture, 2) at the ride area not performing rides, 3) performing a low number of rides (n=50/day) and 4) performing a high number of rides (n=150/day). Furthermore, samples were taken before and after the ride season for comparison. There was a significant difference between the post-ride season treatment and the three treatments involving guest presence during the ride season (ride area, low rides, high rides. This indicates that performing rides is not a stressful experience based on the stress metrics I used, and suggests that rides may be a form of enrichment for dromedary camels. Author Keywords: ACTH challenge, animal welfare, camels, environmental enrichment, salivary cortisol, stress
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
Effect of Water Surface Simulated Rain Drop Impacts on Water to Air Chemical Transfers of Perfluorinated Carboxylic Acids (PFCAs)
Perfluorinated carboxylic acids (PFCAs) are anthropogenic environmentally ubiquitous surfactants that tend to concentrate on water surfaces. This investigation looked at the effect of simulated rain on the atmospheric concentration of a suite of PFCAs (C2 - C12) above the bulk water system. Increased air concentrations of all PFCAs were detected during simulated rain events. Long chain PFCAs (>C8) were found to be much more concentrated in the air above the bulk water system than their short chain counter parts (
Early Responses of Understory Vegetation to Above Canopy Nitrogen Additions in a Jack Pine Stand in Northern Alberta
Abstract Early Responses of Understory Vegetation After One Year of Above Canopy Nitrogen Additions in a Jack Pine Stand in Northern Alberta Nicole Melong Nitrogen (N) emissions are expected to increase in western Canada due to oil and gas extraction operations. An increase in N exposure could potentially impact the surrounding boreal forest, which has adapted and thrived under traditionally low N deposition. The majority of N addition studies on forest ecosystems apply N to the forest floor and often exclude the important interaction of the tree canopy. This research consisted of aerial NH4NO3 spray applications (5, 10, 15, 20, 25 kg N ha-1yr-1) by helicopter to a jack pine (Pinus banksiana Lamb.) stand in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada. The main objective was to assess the impacts of elevated N after one year of treatment on the chemistry of understory vegetation, which included vascular plants, terricolous lichens, epiphytic lichens and a terricolous moss species. Changes in vegetation chemistry are expected to be early signs of stress and possible N saturation. Increased N availability is also thought to decrease plant secondary compound production because of a tradeoff that exists between growth and plant defense compounds when resources become available. Approximately 60% of applied N reached the ground vegetation in throughfall (TF) and stemflow (SF). Nitrate was the dominant form of N in TF in all treated plots and organic N (ON) was the dominant form of N in SF in all plots. The terricolous non-vascular species were the only understory vegetation that responded to the N treatments as N concentration increased with increased treatment. Foliar chemistry of the measured epiphytic lichens, vascular species, and jack pine was unaffected by the N treatments. Based on biomass measurements and N concentration increases, the non-vascular terricolous species appear to be assimilating the majority of TF N after one year. Vegetation from the high treatment plot (25 kg N ha-1yr-1) was compared to a jack pine forest receiving ambient high levels of N (21 kg N ha-1yr-1) due to its proximity to Syncrude mining activities. Nitrogen concentrations in plant tissues did not differ between the two sites; however, other elements and compounds differed significantly (Ca, Mg, Al, Fe). After one year of experimental N application, there were no environmental impacts consistent with the original N saturation hypothesis. Author Keywords: Athabasca Oil Sands Region, Canopy Interactions, Jack Pine, Nitrogen, Secondary Chemistry, Understory Vegetation
MOVEMENT PARAMETERS AND SPACE USE FOR THE SOUTHERN HUDSON BAY POLAR BEAR SUBPOPULATION IN THE FACE OF A CHANGING CLIMATE
Changes to the Arctic and sub-Arctic climate are becoming increasingly evident as it warms faster than other areas of the globe, supporting evidence that predictions of future warming will be amplified due to positive feedback mechanisms. The Southern Hudson Bay polar bear (Ursus maritimus) subpopulation is one of the most southerly subpopulations in the world, putting it at increased risk due to effects of climate change. Whereas many other subpopulations have been the subject of intense research and monitoring, little research has been completed detailing the movement behaviour and space use of bears within Southern Hudson Bay. I used detailed movement data collected on female polar bears to establish a baseline of movement information for this subpopulation to which future work can be compared and effects of climate change can be assessed I evaluated the use of core areas during critical periods of the year (breeding and ice breakup) and evaluated common space use as a means of assessing site fidelity during the breeding season. Movement rates and home range sizes were comparable to those of the neighbouring Western Hudson Bay subpopulation. I also found evidence of increased occurrences of long distance, late fall movements along the coast to the northwest, presumably to gain earlier access to first ice. Though space use analysis did not reveal evidence of site fidelity to specific breeding areas in Hudson Bay, I found that core use areas are at risk of substantially shortened ice duration (x¯ =76 days shorter) using projected ice data based on the high emissions A2 climate change scenario. Author Keywords: climate change, Hudson Bay, movement, polar bear, sea ice, utilization distribution
Nutritional stoichiometry and growth of filamentous green algae (Family Zygnemataceae) in response to variable nutrient supply
In this study, I investigate the effects of nitrogen (N) and phosphorus (P) on the nutritional stoichiometry and growth of filamentous green algae of the family Zygnemataceae in situ and ex situ. I found a mean of Carbon (C):N:P ratio of 1308:66:1 for populations growing in the Kawartha Lakes of southern Ontario during the summer of 2012. FGA stoichiometry was variable, with much of the variation in algal P related to sediment P (p < 0.005, R2 = 0.58). Despite large variability in their cellular nutrient stoichiometry, laboratory analysis revealed that Mougeotia growth rates remained relatively consistent around 0.28 day-1. In addition, Mougeotia was found to be weakly homeostatic with respect to TDN:TDP supply (1/HNP = 0.32). These results suggest that FGA stoichiometry and growth rates are affected by sediment and water N and P. However, they will likely continue to grow slowly throughout the summer despite variable nutrient supply. Author Keywords: Chlorophyll concentration, Filamentous algae, Growth rate, Homeostatic regulation, Nutritional stoichiometry
Human Activity and Habitat Characteristics Influence Shorebird Habitat Use and Behaviour at a Vancouver Island Migratory Stopover Site
Pacific Rim National Park Reserve's 16 km of coastal beaches attract many thousands of people and shorebirds every year. To identify locations where shorebirds concentrate and determine the impact of human activity and habitat characteristics on shorebirds, I conducted shorebird and visitor surveys at 20 beach sectors during fall migration in 2011 to 2013 and spring migration in 2012 and 2013. The probability of shorebird presence decreased with increasing number of people at a beach sector. The time that shorebirds spent at a sector increased with increasing sector width. Close proximity to people increased the proportion of time shorebirds spent moving while shorebirds spent more time moving and less time foraging on wider beaches than on narrower ones. My findings suggest that placing restrictions on beach access and fast moving activities (e.g., running) may be necessary to reduce shorebird disturbance at Pacific Rim and similar stopover areas. Author Keywords: habitat use, human disturbance, predation risk, prey availability, shorebird, stopover

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Graduate student theses produced at Trent University. You may also browse theses and dissertations by year, program, or author.

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