Biological Sciences - Theses, Dissertations, and other Required Graduate Degree Essays

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Individual variation in foraging effort of breeding birds

Date created: 
2017-05-01
Abstract: 

Parental care (e.g. provisioning nestlings) is widely assumed to be costly, and life-history theory predicts a trade-off between reproduction and future fecundity and/or survival. However, experimental studies manipulating workload during parental care and demonstrating fitness effects are either rare or have mixed results. Here, we took a two-step approach to this problem in European starlings (Sturnus vulgaris): 1) using a 4-year dataset to ask if changes in parental investment in handicapped (wing-clipped) parents, and the fitness consequences of these decisions, vary among years (i.e. with ecological context), and 2) using an automated radio telemetry system to determine if females alter their activity to compensate for an increase in workload. We found marked individual and annual variation in response to the handicapping treatment. In addition, clipped individuals dramatically reduced their activity, while sustaining current breeding productivity, suggesting that clipped individuals reduce self-maintenance to favour their current reproductive bout.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Tony Williams
Department: 
Science: Department of Biological Sciences
Thesis type: 
(Thesis) M.Sc.

Genetic and endocrine correlates of variation in human sociality

Author: 
Date created: 
2017-06-06
Abstract: 

Hormones play evolutionarily ancient roles in social behaviour; yet the degree to which hormone systems influence human socio-emotional behaviour remains unclear. It is hypothesized that (i) hormone-associated genes linked to psychiatric conditions contribute to variation in social traits among non-clinical populations, and (ii) changes in endogenous hormone levels coordinate adaptive social behaviour with stimuli in the environment. Consistent with the first hypothesis, a vasopressin receptor polymorphism linked to autism was significantly associated with autistic-like traits in healthy individuals. Consistent with the second hypothesis, an empathy-inducing stimulus was found to mediate a trade-off in hormone levels, with oxytocin increasing and testosterone decreasing. Furthermore, a common polymorphism in the general transcription factor II-I gene, which is linked to Williams syndrome, was associated with oxytocin response to the empathy-inducing stimulus and social anxiety among healthy individuals. Together, these findings highlight the diverse ways through which hormone systems contribute to variation in human sociality.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Bernard Crespi
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

The role of AfKDNase in the growth and development of Aspergillus fumigatus

Author: 
Date created: 
2017-04-18
Abstract: 

Aspergillus fumigatus is a filamentous fungus that is the most common cause of life-threatening invasive mould infections in immunosuppressed individuals. A. fumigatus produces a sialidase enzyme that shows a preference for 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid, (KDN). Sialidases break the glycosidic bond between terminal sialic acids and an underlying glycan chain. The purpose of my research was to create and characterize the KDNase knockout and complemented strains in A. fumigatus. Both strains were successfully generated. Growth in the presence of cell wall stressors (hyperosmolarity, antifungal agents, Congo Red dye) showed that the KDNase gene deletion affected morphology and cell wall integrity. Treatment of A. fumigatus conidia with endogenous AfKDNase enzyme resulted in conidial clumping and damage, an effect not observed when conidia were treated with a bacterial sialidase. The Δkdnase strain remained virulent in an immunosuppressed murine model of invasive aspergillosis.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Margo Moore
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

Life histories and brain evolution of sharks, rays, and chimaeras

Author: 
Date created: 
2017-03-03
Abstract: 

The brain is perhaps one of the most fundamental organs in all vertebrates. It determines not only an individual’s ability to sense and process stimuli from the environment, but is also crucial in maintaining internal homeostatic processes as well as determining an individual’s cognitive abilities. Brains come at a steep energetic cost however, with neural tissue requiring ~20 times the energy of muscle tissue. With such an important role to play, the ‘expensive brain hypothesis’ was been established to understand the evolutionary correlates of brain size. Maternal investment, defined as energetic investment during development, is a strong underlying factor in brain size evolution where higher energy investment from mothers is associated with increased brain size. However, much of what we know about brains comes from studying birds and mammals, while generally overlooking other vertebrate classes. Despite their diversity, all jawed vertebrate brains are comprised of similar components, a pattern that first appeared in sharks, rays, and chimaeras (Chondrichthyans). Chondrichthyans are often disregarded as unremarkable from a comparative perspective, which overlooks their true diversity of life histories and ecological niches. This thesis seeks to understand the evolution of brain size and organization in relation to life history and maternal investment using chondrichthyans as a model system. First, I reveal the sequence of reproductive evolution, finding that egg-laying is ancestral and that live-bearing and additional maternal investment (matrotrophy) have evolved independently several times, and are correlated with increasing body size. Second, I find that the evolution of reproductive mode and ecological lifestyle underlie the evolution of both brain size and brain organization, such that shallowwater matrotrophic species have large brains that are predominantly composed of regions related to enhanced cognitive abilities, the telencephalon and cerebellum. Conversely, deepwater lecithotrophic species have small brains composed predominantly of medulla oblongata. Lastly, I find that similar patterns of regional scaling in mammals, birds and chondrichthyans differ from those of teleosts, agnathans, and amphibians, and I propose that differing reproductive strategies may underlie this variation.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Nicholas Dulvy
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

The speed of life in sharks and rays: methods, patterns, and data-poor applications

Date created: 
2017-04-11
Abstract: 

Since the theory of evolution by natural selection was first postulated, biologists have noted that life histories evolve following broad patterns across all organisms. Understanding the mechanisms causing these relationships is the central focus of life history theory; these insights can also be used to better estimate the biology and extinction risk of data-poor species. Sharks, rays, and chimaeras (class Chondrichthyes) are an ideal taxon to explore these relationships as they have evolved a broad range of life history strategies. In this thesis, I focus on two key time-related life history parameters that are often used as a measure of productivity: growth coefficient k, which is estimated from the von Bertalanffy growth function (VBGF), and maximum intrinsic rate of population increase rmax, estimated by simplifying the Euler-Lotka equation. I begin by clarifying two methodological problems regarding the estimation of growth and productivity. I first show that fixing the y-intercept in the VBGF, a common approach in chondrichthyan age and growth studies, often causes considerable bias in growth coefficient estimates, and recommend using the three-parameter VBGF instead. I then point out an important omission in a method commonly used for estimating r max in chondrichthyans and clarify the correct way to estimate it. Next I explore the effect of uncertainty on the estimation of r max and show that species with low annual reproductive outputs are bound to have very low productivities, thus focus should be placed into accurately estimating litter sizes, breeding intervals, and the variability of these traits. As an example of how these insights can be applied, I better estimate growth and productivity for a data sparse species of conservation concern, the Spinetail Devil Ray (Mobula japanica), and show it has a much lower somatic growth rate than previously thought and one of the lowest productivities among chondrichthyans. Finally, I show that productivity in chondrichthyans varies with temperature as well as depth, and that the scaling of this relationship changes with temperature according to the expectation from Bergman’s rule. My thesis demonstrates that simple insights from life history theory can further our knowledge on the broad patterns that shape the evolution of life histories we see today, which can be used to inform management of data-poor species.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Nicholas Dulvy
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

Predictive cues and fitness consequences of breeding phenology

Author: 
Date created: 
2017-04-10
Abstract: 

Individual variation in the timing of breeding in birds has been strongly linked to the fecundity, and by extension fitness of the individual. Despite this important relationship, our understanding of the determinants of timing of breeding is unclear. Photoperiod determines a window of opportunity for breeding, but small-scale variation within this window still has major fitness consequences. This thesis explores potential cues that might account for variation in individual timing decisions, and possible consequences of timing on offspring and future broods. First we assess how pre-breeding male social cues and the development of tipulid larva (prey) might determine the female’s timing of egg-laying. While many lab studies have demonstrated that the presence of a male partner is necessary for female gonadal development, our 3-year field studies found no effect of male behaviour on female breeding phenology or performance. This suggests that male song may not be an important supplemental timing cue. Next we explore potential consequences of timing on chick quality and multiple brooding behaviour. We demonstrate that somatic and physiological traits are more developed in chicks from earlier nests (first broods). We also document that physiological maturity, in the form of hemoglobin concentration, is related to fledgling flight ability. Although we show that second brood chicks maintain the same trajectory of development just prior to fledging, they may pay a higher cost in the form of oxidative stress. Finally we document that multiple brooding behaviour is unrelated to timing in our highly synchronous population, and instead relates to individual quality. Comprehensively, this thesis suggests that male social cues may not be important cues determining timing of breeding, and that the consequences of timing on offspring include maturity at fledging and oxidative stress, but not multiple brooding in our system.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Tony D. Williams
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

Sexual Communication in Yellowjackets (Hymenoptera: Vespidae)

Author: 
Date created: 
2017-04-11
Abstract: 

To determine if and how pheromones mediate sexual communication of yellowjackets [Dolichovespula arenaria, D. maculata, Vespula alascensis, V. pensylvanica, V. squamosa], I took three approaches: (1) In field trapping experiments, I baited traps with a virgin queen (gyne) or a male and tested for their ability to attract prospective mates. I found that only gynes of D. arenaria attracted males. (2) In laboratory Y-tube olfactometer experiments with D. arenaria, D. maculata and V. pensylvanica, I used sibling or non-sibling gynes as a test stimulus, and found that only D. maculata gynes attracted conspecific males, provided they were non-siblings. These results imply an olfactory-based mechanism of nestmate recognition and inbreeding avoidance. (3) I tested the hypothesis that cuticular hydrocarbons (CHCs) differentiate sex, caste, and nest membership. I found that each caste had specific CHC profiles. My data demonstrate the diversity and complexity of sexual communication in yellowjacket wasps, and inspire follow-up studies to identify the sex pheromones.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Gerhard Gries
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

From forecasting vulnerabilities to assessing recovery: the utility of demographic models in addressing population declines

Date created: 
2017-04-13
Abstract: 

Curbing species’ decline driven by anthropogenic modifications to natural systems requires a deep understanding of how specific changes to biotic and abiotic processes affect populations. Individual life history stages may differ in their response to such changes, consequently buffering or accelerating population declines. I explore the concept of demographic compensation among life stages using stage-structured demographic models to improve predictions for two conservation challenges; 1) forecasting climate change impacts to amphibian populations in montane ecosystems, and 2) identifying the most effective life history targets for recovering declining amphibian populations. In Chapters 2 and 3, I use demographic data for the Cascades frog (Rana cascadae) at northern and southern range boundaries to parameterize stochastic matrix population models under current and future environmental conditions to evaluate how climate change affects population stability. I demonstrate that R. cascadae populations at the northern range boundary are stable, but that compounding negative effects of climate on early and late life history stages creates a demographic tipping point by the 2080’s. I find that counter to range shift predictions, the population growth rate for the southern population will change little in the face of climate change, and differences in population stability between northern and southern range limits are driven by contrasting responses to climate. Equally important to forecasting population vulnerability, is preventing extinction of declining populations. In Chapter 4, I use demographic models to elucidate recovery potential for declining populations of Oregon spotted frogs (Rana pretiosa) by evaluating the effectiveness of population supplementation at multiple life stages. I compare two supplementation strategies, head-starting early life stages and captive breeding, and find captive breeding up to two orders of magnitude more effective at reducing extinction probabilities than head-starting. In Chapter 5, I extend the utility of such models using formal decision analysis to evaluate tradeoffs between the effectiveness of conservation actions and their economic costs. I reveal that the supplementation of wild populations with captive bred larvae results in the largest reduction in extinction risk per dollar invested. In this thesis, I use demographic models to improve our predictions of species’ responses to climate change before declines occur, and conversely, advance the quantitative framework for recovering declining populations.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Wendy Palen
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

A role for insect availability in limiting populations of a threatened nightjar Antrostomus vociferous

Date created: 
2017-04-13
Abstract: 

Aerial insectivore birds, those that capture prey while in flight themselves, are the avian guild experiencing the steepest population declines in Canada. Although we lack long-term data on insect abundances, one potential cause of these declines could be a change in prey availability. Furthermore, some nocturnal insectivores, like nightjars, face the additional challenge of only foraging during twilight periods, or when adequate moonlight is available. In this thesis, I take a variety of approaches to test and inform predictions associated with possible drivers of population decline in a threatened nightjar, Eastern Whip-poor-will (Antrostomus vociferous). Whip-poor-will prefer open-canopy, or fragmented, forests that allow moonlight to penetrate the canopy, so I first tested whether an increase in forest area appeared to explain their population decline. In contrast to expectation, whip-poor-will presence was positively associated with forest area at a regional scale, and only a delayed effect of urban area explained disappearances. At a more local scale, however, whip-poor-will abundance was positively related to both presence of open-canopy forests, and insect abundance. At this local scale, insect abundance also influenced daily survival rates of chicks, and productivity was higher when hatching coincided with peaks in insect abundance. Next, I tracked migration using light-logging geolocation tags to identify the wintering range of individuals from across the northern portion of the breeding range. I found evidence of migratory stopover in the southeastern United States and wintering locations in Mexico and Central America, suggesting that both regions are potentially important for this population. Finally, I tested for diet change over the past century using nitrogen isotope ratios of museum specimen tissues. Whip-poor-will isotope profiles were consistent with a gradual shift to feeding on lower trophic-level prey for both breeding season grown feathers and winter grown claws. All of these results are consistent with the hypothesis that whip-poor-will populations are declining due to changes in prey abundance, but I caution that habitat and climatic conditions at locations used throughout the annual cycle could also be contributing to these population declines.

Document type: 
Thesis
File(s): 
Senior supervisor: 
David Green
Joseph Nocera
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

Identification and characterization of Francisella tularensis proteins required for invasion and escape into non-phagocytic epithelial cells

Date created: 
2017-03-31
Abstract: 

The potential bioterror agent Francisella tularensis subspecies tularensis (F. tularensis) is an intracellular human pathogen and the causative agent of tularemia. As an invasive pathogen, Francisella invades host cells; occupies and escapes membrane bound vacuoles; replicates in the host cytosol; then initiates their release to infect other cells. Tularemia begins when bacteria invade the phagocytic and non-phagocytic cells of the host. While non-phagocytic cell colonization contributes significantly to disease, the process is poorly understood. In this thesis, I identify and characterize key proteins in the invasion and vacuole escape stages of the non-phagocytic cell infection process. In chapter 2, I evaluated Francisella in vitro cell culture infection models present in the literature side-by-side with the model our lab developed using the murine surrogate of F. tularensis, F. tularensis subspecies novicida (F. novicida) and murine cultured hepatocytes. I found compared to other models, our model most accurately reflected colonization levels seen in vivo. In chapter 3 and chapter 4, I investigated bacterial proteins involved in invasion and vacuole escape. I screened a F. novicida transposon mutant library using our infection model for microbes deficient in bacterial replication. Using bioinformatics, I searched for invasion-deficient transposon mutants inactivated in Francisella surface proteins to screen for proteins that could interact with the host cell surface. I then tested their ability to cause tularemia-induced mortality in mice. I showed that bacteria inactivated in two genes caused no disease in mice and protected mice as live-vaccines against a wild-type F. novicida challenge. One gene I identified as Francisella infectivity potentiator A (FipA). I presented evidence that FipA enables bacteria to escape the vacuole using both florescence and electron microscopy. The next gene I identified, characterized, and named Francisella virulence factor A (FvfA). I demonstrated that FvfA is a bacterial surface-exposed ligand that exploits host clathrin-mediated endocytosis for entry using functional assays and dot blots. Lastly, I crystallized FvfA and compared FvfA to its structural homolog, E. coli RcsF. Taken together, I described two virulence factors, FipA and FvfA, that are critical for the initial stages of the Francisella non-phagocytic cell infection process and consequently, tularemia-effected death.

Document type: 
Thesis
Senior supervisor: 
Julian Guttman
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.