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

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Assessment of embryotoxicity, post-hatch development, and long-term effects on behavior and reproduction in zebra finches (Taeniopygia guttata) following in ovo methylmercury exposure

Author: 
Date created: 
2015-04-16
Abstract: 

Mercury is an environmental contaminant that can bioaccumulate in terrestrial ecosystems as organic methylmercury (MeHg); however little is known on the effects of mercury exposure on terrestrial-feeding songbirds. The objectives of the current study were to 1) assess embryotoxic effects of in ovo exposure, via egg injection, to MeHg concentrations similar to those reported in free-living songbirds; and 2) investigate long term post-hatching effects of in ovo exposure to MeHg on offspring development, mating behavior, and reproduction in a model songbird species, the zebra finch (Taeniopygia guttata). In ovo MeHg decreased hatching success in a dose-dependent manner. However, it had no long-term post hatching effects on growth, hematological traits, male courtship song quality, mating behavior in either sex, or female reproductive performance. These findings would suggest that in ovo exposure to MeHg has acute effects on embryo survival, but no long-term effects on the behavioral endpoints measured or reproductive performance.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Tony Williams
Department: 
Science:
Thesis type: 
(Project) M.E.T.

Variance and extreme events in population ecology

Date created: 
2015-03-04
Abstract: 

Assessing, managing, and communicating variance and risk is fundamental to effective ecological decision making. One promising approach is to borrow concepts from financial portfolio management. Ecological populations behave like portfolios in many ways—we can treat the abundance of populations, such as salmon in streams, as financial stock value, and groups of populations, such as salmon within a river catchment, as portfolios. If a group of populations react differently to an environmental event then the probability of sudden decline may be lowered, similar to a diversified financial portfolio. This risk reduction has been referred to as the portfolio effect. In this thesis I consider three applications of portfolio concepts to ecology. I begin by evaluating ways of estimating portfolio effects and applying these metrics to moth, reef fish, and salmon metapopulations from around the world. I show an inherent bias to a commonly used method, develop a new method based on Taylor's power law of mean--variance scaling, and outline recommendations for estimating portfolio effects. Next, I use a portfolio approach to inform conservation priorities for salmon populations under a changing climate. I show that preserving a diversity of thermal tolerances minimizes risk and ensures persistence given long-term environmental change. However, this reduction in variability can come at the expense of long-term persistence if climate change increasingly restricts available habitat, forcing ecological managers to balance society's desire for short-term stability and long-term viability. Finally, I take the concept of black swans (extreme and unexpected events) from the financial literature and ask what the evidence is for these events across hundreds of bird, mammal, insect, and fish abundance time series. I find strong evidence for the infrequent (3–5\%) occurrence of ecological black swans. Black swans are predominantly (87%) downward events and tend to be associated with extreme climate, natural enemies (predators and parasites), or the combined effects of multiple factors, with little relationship to life history. My thesis demonstrates the importance of conserving ecological properties that may contribute to portfolio effects, such as thermal-tolerance diversity and habitat heterogeneity, and developing conservation strategies that are robust to unexpected extreme events.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Nicholas K. Dulvy
Andrew B. Cooper
Department: 
Science:
Thesis type: 
(Thesis) Ph.D.

Effects of anthropogenic disturbance on sensitive wildlife and habitats

Author: 
Date created: 
2015-01-20
Abstract: 

The cumulative ecological impacts of broad-scale anthropogenic disturbances, such as forestry or energy development, are a challenge to predict and evaluate. Here, I evaluate the potential of future run-of-river (ROR) hydropower development to impact riparian ecosystems in British Columbia, Canada. I found the projected spatial footprint of ROR in the riparian zone to be 40 times smaller than the footprint of existing disturbance from forestry, roads, and powerlines, but concentrated in watersheds that currently have low levels of disturbance. Habitat degradation for small riparian vertebrates from ROR development was cumulative with substantial existing impacts. I also tested whether harvest data in Species Distribution Models can aid in evaluating species responses to logging at different scales and sensitivity levels using a simulation framework. I found that logging becomes a strong predictor of species distributions at landscape scales, or when the spatial heterogeneity of forestry exceeds that of other variables (e.g. climatic or topographical) in the model.

Document type: 
Thesis
Senior supervisor: 
Wendy Palen
Department: 
Science: Biological Sciences
Thesis type: 
(Thesis) M.Sc.

Insect-derived hybrid antimicrobial peptides: antibiotics for the next generation?

Date created: 
2014-04-04
Abstract: 

There has been recent interest in utilizing natural antimicrobial peptides (AMPs) as novel antibiotics. Hybrid antimicrobial peptides (hAMPs) are synthetic molecules containing active motifs from multiple parental AMPs. This thesis presents in vitro activity data of hAMPs designed b y combining binding and killing motifs from different invertebrate and vertebrate AMPs. The goals of hAMP design are to improve antimicrobial efficacy and reduce host cytotoxicity. Activity was further optimized by modifying basic properties of the peptide such as charge, hydrophobicity, peptide length and specific amino acid composition. Overall, hAMPs exhibited higher antimicrobial efficacy than their active motifs alone in vitro. Some hAMPs kill bacteria through membrane permeabilization while others likely attack intracellular targets. Synergistic activity was observed when different hAMPs were combined together separately or when combined in the form of a multivalent hAMP. Our results indicate that hAMPs may be suitable for use as novel antimicrobial agents.

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

Multimodal mechanisms of early mate-detection in the parasitoid wasp Pimpla disparis (Hymenoptera: Ichneumonidae)

Date created: 
2015-04-20
Abstract: 

Males of the hymenopteran parasitoid Pimpla disparis have been observed to aggregate on gypsy moth, Lymantria dispar, host pupae before the emergence of a female. This led me to test the hypothesis that males respond to chemical cues associated with parasitized pupae. Results of laboratory experiments suggest that females mark the host pupae they have parasitized and that males discern between such pupae and those not parasitized. Males continue to recognize parasitized pupae throughout the development of the parasitoid. To investigate potential acoustic and vibratory cues that males may exploit to detect the presence and track the progress of a developing parasitoid (DePa; future mate) inside a host pupa, I analyzed DePa-derived cues by airborne sound and laser Doppler vibrometer recordings. Parameters (e.g., amplitude) of sound and vibratory cues change significantly over time and thus could ‘inform’ a visiting adult male about the stage of DePa’s development. To test the hypothesis that male P. disparis memorize and revisit the location(s) of parasitized host pupae as a strategy to attain mates, we color-coded P. disparis males in a field survey and recorded their behaviour. We learned that they revisit parasitized moth pupae on consecutive days, and arrest on those pupae with a near-emergence parasitoid. These results are supported by laboratory experiments, revealing that males memorize both the macro- and micro-locations of parasitized host pupae. DePa’s quiescence a few days before emergence could be a cue for a visiting male that the emergence of a mate will soon take place but it would not help the male to precisely predict the time of emergence. In contrast, oral fluid produced by emerging adult parasitoids may be indicative of the emergence process. I tested the hypothesis that semiochemicals associated with DePa’s emergence arrest males on a parasitized host pupa. I found that these semiochemicals emanate from oral fluid secreted by parasitoids while chewing their way out of a host. Attraction of males to oral fluid semiochemicals from males and females indicates that mate-seeking males co-opt chemicals involved in the eclosion process as a mate finding cue, taking a 50% chance that the prospective mate is a female.

Document type: 
Thesis
File(s): 
Sound recording of a Pimpla disparis larva 8 days post parasitism of the host pupa
Sound recording of a Pimpla disparis pupa 14 days post parasitism of the host pupa
Sound recording of a Pimpla disparis pupa 18 days post parasitism of the host pupa
Video of spinning 14-day-old Pimpla disparis pupa inside host pupa
Video of adult Pimpla disparis chewing its way out of the host pupal case
Senior supervisor: 
Gerhard Gries
Department: 
Science:
Thesis type: 
(Thesis) Ph.D.

Baculovirus infection, host immunity and pathogen competition in the cabbage looper, Trichoplusia ni

Date created: 
2015-04-22
Abstract: 

Competition between pathogens within a host could change the short term and evolutionary outcomes of an infection. These interactions include resource-based and immune-mediated competition. We understand little about the insect immune response to virus infection and how this alters the host for future co-infecting pathogens. I characterised several immune parameters of the cabbage looper, Trichoplusia ni, in response to challenge by a baculovirus, TnSNPV, and found that all parameters reduced with increasing virus dose. To measure the effect of competing pathogens on virus success, I exposed T. ni to TnSNPV followed by either the bacterium, Bacillus thuringiensis, or the fungus, Beauvaria bassiana. The fungus reduced the infection success of the baculovirus and the bacterium negatively impacted virus replication. This outcome has consequences for microbial control agents in insect pest management and adds to our fundamental understanding of the effect of mixed infections on pathogen and host populations.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Jenny Cory
Department: 
Science:
Thesis type: 
(Thesis) M.P.M.

Pregnancy associated plasma protein-a2 (papp-a2) contributes to the regulation of skeletal growth in mice

Author: 
Date created: 
2015-03-17
Abstract: 

Pregnancy associated plasma protein-A2 (PAPP-A2) is a metalloproteinase that cleaves insulin like growth factor binding protein-5 (IGFBP-5), the most abundant IGFBP in bone. Deletion of the Pappa2 gene reduces post-natal growth and skeletal size in mice. This research aimed to further understand the role of PAPP-A2 in skeletal physiology using mice with Pappa2 disrupted constitutively, spatially (in bone), or temporally (in adulthood). I demonstrate that PAPP-A2 produced in bone AND other tissues regulates post-natal growth and skeletal size. Constitutive Pappa2 deletion increases cortical bone mineral density (BMD), whereas disruption of Pappa2 in adulthood decreases trabecular BMD in males alone. PAPP-A2, therefore, appears to play age-specific and potentially site-specific roles. Currently, there is a need for anabolic agents for the treatment of diseases like osteoporosis, making PAPP-A2 an interesting avenue of research.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Julian Christians
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Mitochondrial form and function: an investigation of the mechanism and significance of mitochondrial remodelling in rat cortical astrocytes

Author: 
Date created: 
2015-04-02
Abstract: 

Elucidations of the mechanisms that regulate mitochondrial morphology have contributed to a greater understanding of mitochondrial function in eukaryotic cells. To date, mitochondrial morphological changes have mostly been attributed to fission and fusion. Mitochondrial fission is a calcium (Ca2+)/calcineurin mediated process that activates the dynamin related mechanoenzyme DRP1 to cleave the mitochondrial membranes. This thesis explores new evidence that elevations in intracellular calcium produces some mitochondrial fission but the change in morphology is predominately caused by mitochondrial “remodelling”. Mitochondrial remodelling results from a structural change (rounding or elongating) in the membrane of a single mitochondrion without fission or fusion. Due to the nature of tools utilized to assess mitochondrial morphology, remodelling has been largely overlooked in the literature. Using real-time live cell fluorescence microscopy I show that remodelling can occur concomitantly with fission and have provided evidence that the mechanism of remodelling is distinct from fission. Throughout these studies, I used mitochondrially targeted yellow fluorescent protein (mt-eYFP), ratiometric ROS-sensitive GFPs, the mitochondrial membrane potential dye TMRM as well as Ca2+ and ATP FRET probes in rat cortical astrocytes to measure mitochondrial morphological and functional changes in real time. In the first objective chapter, I blocked mitochondrial fission using FK506 and Cyclosporine A and showed that Ca2+ induced mitochondrial remodelling was unaffected. In the second objective, I induced fission and remodelling by applying ROS generating agents such as rotenone and Ca2+ and demonstrated that remodelling was blocked using antioxidants but fission was not attenuated, indicating that remodelling is regulated by ROS. In the final objective chapter, I further investigated the mechanism of remodelling as well as the functional significance of remodelling. I provided evidence that inhibition of glycogen synthase kinase 3β (GSK3β), an enzyme previously associated with fission, induced only mitochondrial remodelling. Furthermore, I showed that remodelling protects cells against some staurosporine induced cell death and that the mechanism of protection may occur through reduced Ca2+ uptake into the mitochondrial matrix. Through exploration of the mechanism and function of mitochondrial remodelling this thesis provides a greater understanding of the role of mitochondria in cellular maintenance and survival.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Gordon Rintoul
Department: 
Science:
Thesis type: 
(Thesis) Ph.D.

Opposing forces: evaluating multiple ecological roles of Pacific salmon in coastal stream ecosystems

Date created: 
2015-03-09
Abstract: 

Resource subsidies can alter the productivity, structure and function of ecosystems. These effects can be particularly strong when the resource is in limited supply within recipient habitats. Migratory species can act as subsidy vectors, transporting vast quantities of nutrients to recipient habitats. They can also significantly disturb the physical, chemical and biological landscape of recipient habitats through their behaviour. This thesis explores how adult spawning salmon affect 1) algal and biofilm biomass, 2) benthic macroinvertebrate biomass, 3) benthic macroinvertebrate diversity and 4) food web structure in streams of the Pacific Northwest. I draw spatial comparisons across multiple streams, compare pre-spawn with post-peak spawning periods, and test for habitat characteristics that mediate these effects. In Chapters 2 and 3, I show that algal and invertebrate biomass in streams decline after salmon spawn, a likely result of substrate disturbance. Through the use of stable isotopes, I also show that algae and invertebrates readily incorporate salmon-derived material. However, only algal biomass in the spring increases with salmon density. Spring invertebrate biomass is low in streams with high salmon densities, despite being enriched in both salmon-derived nitrogen and carbon. This may be due to a slow recovery from the previous fall or in response to salmon nutrients subsidizing higher trophic levels and eliciting a trophic cascade. Chapter 4 reveals that this decline in invertebrate biomass may also be linked to life history traits. Invertebrate family composition shifted significantly across a gradient in salmon density and stream temperature, both prior to and post spawning. However, invertebrate family richness was not related to salmon density; it declined with drainage size, a composite measure of stream and terrestrial habitat measurements. Finally, Chapter 5 reveals that aquatic invertebrates and resident fish species in these coastal streams consume a variety of resources throughout the year and that salmon are an important dietary source for many of these organisms, regardless of season. This thesis demonstrates that salmon are a major structural component of coastal stream food webs, as a resource to benthic production, a major contributor to the diets of freshwater consumers, and as a source of disturbance that contributes to losses in lower trophic levels. Declines in wild Pacific salmon populations would significantly impact how coastal stream food webs function.

Document type: 
Thesis
File(s): 
Senior supervisor: 
John Reynolds
Department: 
Science:
Thesis type: 
(Thesis) Ph.D.

Migratory diversity of juvenile salmon in a threatened estuary

Date created: 
2015-01-16
Abstract: 

Understanding how migratory species such as juvenile salmon (Oncorhynchus spp.) utilize key transition habitats such as estuaries can illuminate their vulnerability to pressures such as habitat alteration or climate change. This thesis examined the diversity of migratory juvenile salmon in the estuary of the vast Skeena River, Canada. First, I compared abundances of different species of juvenile salmon in different regions, and found that sockeye (O. nerka) and Chinook (O. tshawytscha) salmon were most abundant in areas proposed for development. These estuary salmon were genetically linked to dozens of locally-adapted populations from throughout the Skeena watershed and beyond. I also found that downstream migration timing was population-specific and related to the elevation of the different rearing lakes and distance travelled. Different populations encountered different zooplankton communities in the estuary. These results suggest that the Skeena estuary integrates multiple scales of salmon diversity, which could be compromised by impending habitat degradation.

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