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
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
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
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
Stress Axis Function and Regulation in New World Flying Squirrels
Across vertebrate taxa, the hypothalamic-pituitary-adrenal axis (or the stress axis) is highly conserved, and is central to vertebrate survival because it allows appropriate responses to psychological stressors. Habitat shapes successful physiological and ecological strategies, and to appreciate how individual species respond to stressors in their environment, it is essential to have a thorough knowledge of the basic stress physiology of each species. In this dissertation, I studied the functioning and evolution of the stress physiology of New World flying squirrels. I showed that baseline, circulating cortisol levels in northern (Glaucomys sabrinus) and southern (G. volans) flying squirrels are some of the highest ever reported for mammals, indicating that their stress axes operate at a higher set point than most other species. I also assessed other aspects of their acute stress response, including free fatty acid and blood glucose levels, and indices of immune function, and showed that the flying squirrels’ physiological reaction to stressors may differ from that of other mammals. Using immunoblotting, I found that corticosteroid-binding globulin (CBG) expression levels in flying squirrels appeared to be higher than previously reported using alternative methods. I also concluded however, that these levels did not appear to be high enough to provide their tissues with the protective CBG-bound buffer from their high circulating cortisol concentrations experienced by the majority of vertebrates. Thus, this arm of cortisol regulation within the flying squirrel stress axes may be weak or non-existent. Following this, I focused on southern flying squirrels and showed evidence that the second arm of cortisol regulation — the negative feedback mechanism at the level of the brain — functions effectively, but that this species is glucocorticoid resistant. Their tissue receptors appear to have a reduced affinity for cortisol, and this affinity may change seasonally to allow for the onset of other biological processes required for survival and reproduction. Due to their distinctive stress physiology, northern and southern flying squirrels may provide comparative physiologists with model systems for further probing of the function and evolution of the stress axis among vertebrates. Author Keywords: corticosteroid-binding globulin, flying squirrel, Glaucomys, glucocorticoids, physiological ecology, stress physiology
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:
Temporo-spatial patterns of occupation and density by an invasive fish in streams
Since its introduction to North America in the 1990s, the Round Goby has spread throughout the Great Lakes, inland through rivers and is now moving into small tributary streams, a new environment for this species in both its native and invaded ranges. I explored density and temporal occupation of Round Gobies in four small streams in two systems in south-central Ontario, Canada in order to determine what habitat variables are the best predictors of goby density. Two streams are tributaries of Lake Ontario and two are tributaries of the Otonabee River, and all of these streams have barriers preventing upstream migration. I found that occupation and density differed between the systems. In the Otonabee River system, Round Gobies occupy the streams year round and the most important factor determining adult density is distance from a barrier to upstream movement, with the entire stream occupied but density highest next to the barriers. In the Lake Ontario system, density is highest at mid-stream and Round Gobies appear to occupy these streams mainly from spring to fall. Adult density in Lake Ontario tributaries is highest in sites with a high percentage of cobble/boulder and low percentage of gravel substrate, while substrate is less important in Otonabee River tributaries. Occupation and density patterns may differ due to contrasting environmental conditions in the source environments and distance to the first barrier preventing upstream movement. This study shows diversity in invasion strategies, and provides insight into the occurrence and movement patterns of this species in small, tributary streams. Author Keywords: biological invasion, Generalised Additive Mixed Model, habitat, Neogobius melanostomus, Round Goby, stream
Testing for Interspecific Hybridization and a Latitudinal Cline Within the Clock Gene Per1 of the Deer Mouse (Peromyscus maniculatus) and the White-Footed Mouse (Peromyscus leucopus)
The recent northward expansion of the white-footed mouse (Peromyscus leucopus) in response to climatic changes provides a natural experiment to explore potential adaptive genetic variation within the clock gene Per1 in Peromyscus undergoing latitudinal shifts, as well as, the possibility of hybridization and introgression related to novel secondary contact with its sister species the deer mouse (Peromyscus maniculatus). Because clock genes influence the timing of behaviors critical for survival, variations in genotype may reflect an organism’s ability to persist in different environments. Hybridization followed by introgression may increase the adaptive potential of a species by quickly generating adaptive variation through novel genetic recombination or by the transfer of species-specific alleles that have evolved in response to certain environments. In chapter 2, I used microsatellite and mtDNA markers to test for hybridization and introgression between P. maniculatus and P. leucopus and found that interbreeding is occurring at a low frequency (<1%). In chapter 3, I tested for a latitudinal cline in a polyglycine repeat located within the Per1 gene of Peromyscus and discovered a putative cline in the Per1-142 and Per1-157 allele of P. leucopus and P. maniculatus, respectively. Chapter 4, further expands upon these findings, limitations, and the lack of evidence supporting introgression at the Per1 locus. Despite this lack of evidence, it is possible that novel hybridization has or could lead to adaptive introgression of other genes, allowing for the exchange of adaptive alleles or traits that could be advantageous for range expansion and adaption to future environmental changes. Author Keywords: Clock genes, Hybridization, Latitudinal gradient, Per1, Peromyscus, Range Expansion
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:
Understanding Historical and Contemporary Gene Flow Patterns of Ontario Black Bears
Consequences of habitat loss and fragmentation include smaller effective population sizes and decreased genetic diversity, factors that can undermine the long-term viability of large carnivores that were historically continuously distributed. I evaluated the historical and contemporary genetic structure and diversity of American black bears (Ursus americanus) in Ontario, where bear habitat is largely contiguous, except for southern regions that experience strong anthropogenic pressures. My objectives were to understand gene flow patterns in a natural system still largely reflective of pre-European settlement to provide context for the extent of genetic diversity loss in southern populations fragmented by anthropogenic influences. Phylogeographic analyses suggested that Ontario black bears belong to a widespread "continental" genetic group that further divides into 2 subgroups, likely reflecting separate recolonization routes around the Great Lakes following the Last Glacial Maximum. Population genetic analyses based on individual genotypes showed that Ontario black bears are structured into 3 contemporary genetic clusters. Two clusters, located in the Northwest (NW) and Southeast (SE), are geographically vast and genetically diverse. The third cluster is less diverse, and spatially restricted to the Bruce Peninsula (BP). Microsatellite analyses revealed that the NW and SE clusters are weakly differentiated from each other relative to mitochondrial DNA findings, suggesting male-biased dispersal and isolation by distance across the province. I also conducted simulations to assess competing hypotheses that could explain the reduced genetic diversity on the BP, which supported a combination of low migration and recent demographic bottlenecks. I showed that management actions to increase genetic variation in BP black bears could include restoring landscape connectivity between BP and SE; however, the irreversible human footprint in the area makes regular translocations from SE individuals a more practical alternative. Overall, my work suggests that: 1) historical genetic processes in Ontario black bears were likely predominated by isolation by distance, 2) large mammalian carnivores such as black bears can become isolated and experience reduced diversity in only a few generations, and 3) maintaining connectivity in regions under increased anthropogenic pressures could prevent populations from becoming small and geographically and genetically isolated, and should be a priority for conserving healthy populations. Author Keywords: American black bear, carnivore, conservation genetics, Ontario, phylogeography, population genetics
Using automated radio-telemetry to link food availability, reproductive success, and habitat use of Barn Swallows (Hirundo rustica erythrogaster)
Drivers of North American Barn Swallow population declines are not well understood, but foraging habitat loss is thought to be a contributing factor. Determining patterns of habitat use is challenging for swallows because they move rapidly but are too small to carry GPS tags. We showed that automated radio-telemetry could be used to track the movements of swallows with enough accuracy (median error 250 m) to monitor local habitat use. We then combined information on breeding Barn Swallows habitat use, land cover, aerial insect abundance, and fledging success to test for a link between foraging habitat quality and reproductive success. Foraging activity was concentrated within 600 m of nest sites and varied with land cover; however, responses to land cover were not consistent across birds. Aerial insects were most abundant near wetlands and least abundant near open water and over cropland. Consistent with a link between foraging habitat and reproductive success, nests in barns with more wetland and less open water within 1 km, and with less field area within 2 km occupied by row crops, on average fledged more young swallows. Author Keywords: aerial insectivores, automated telemetry, habitat use, land cover, movement, nest success
Using genomic and phenotypic data to explore the evolution and ecology of the North American mountain goat
Evaluating the impact of climate change is arguably one of the main goals of conservation biology, which can be addressed in part by studying the demographic history of species in the region of interest. In North America, landscape and species composition during the most recent Pleistocene epoch was primarily influenced by glaciation cycles. Glacial advance and retreat caused species ranges to shift as well, leaving signatures of past population bottlenecks in the genetic code of most species. Genomic tools have shown to be important tools for understanding these demographic events to enhance conservation biology measures in several species. In my thesis I first reviewed the state of ungulate genomics, with a focus on how such data sets can be used in understand demography, adaptation, and inform conservation and management. Importantly, the review introduces key analyses like the pairwise sequentially Markovian coalescent and features like variation in antlers and horns and selection pressures that are used throughout subsequent chapters. Using the North American mountain goat as a model species, I then explored the genomic and phenotypic variation in this alpine specialist mammal. Starting with the generation of the first genome assembly for the mountain goat, I identified genes unique to the mountain goat and modeled demographic history going back millions of years using a pairwise sequentially Markovian coalescent approach. Species’ effective population size generally paralleled climatic trends over the past one hundred thousand years and severely declined to under a thousand individuals during the last glacial maximum. Given the biological importance of horns in mountain goats and the recent scientific interest in genetic basis of headgear, I analyzed over 23,000 horn records from goats harvested in British Columbia, Alaska and Northwest Territories from 1980 to 2017. Overall, variation in horn size over space and time was low; goats harvested further North had shorter horn lengths and smaller horn circumferences in one year old and 4 years and older age classes and 4 years and older age class, respectively. Proximity of roads, which was used as an indicator of artificial selection, had a small effect on horn size, with larger horns being harvested closer to major roads. Finally, I used two range-wide genomic data sets sequenced with a whole genome re-sequencing and reduced representation approaches to provide estimates of genetic diversity, contemporary effective population sizes and population structure. These insights can help inform management and will potentially make an impact in preserving the mountain goat. Author Keywords: genome assembly, horn size, Oreamnos americanus, population demography, reduced representation sequencing, whole genome resequencing

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