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

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Effects of nutrient addition and sheep grazing on tundra rangelands in the Icelandic highlands

Author: 
Date created: 
2020-04-15
Abstract: 

Overgrazing and soil erosion are widespread and chronic environmental problems in the Icelandic highlands. Restoration efforts have included the application of fertilisers and grazing exclusion to increase plant biomass and reduce bare ground, but the effects of fertilisers on plant community composition across ecological conditions remain unresolved. I measured the combined effects of grazing exclusion and fertilisation, including factorial applications of nitrogen (N), phosphorus (P) and potassium (K), in both vegetated and degraded areas at sites with contrasting soil conditions. After four years I found 1) above-ground biomass induced by fertiliser was counteracted by sheep grazing, and 2) joint application of fertiliser and grazing exclusion had contrasting effects on species diversity in vegetated habitats where NPK applications and grazing exclusion reduced species diversity, than in degraded habitats where NPK applications increased species diversity irrespective of grazing. These results contribute to improving restoration efforts in high latitude tundra rangelands.

Document type: 
Thesis
Senior supervisor: 
David Hik
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

Studying the foraging and communication ecology of European fire ants

Author: 
Date created: 
2020-04-16
Abstract: 

The European fire ant (EFA), or ruby ant, Myrmica rubra L., is an invasive pest in Greater Vancouver, British Columbia, Canada. EFAs are a nuisance to humans, swarming and stinging aggressively when nests are disturbed. They also cause ecological damage by altering invertebrate communities. The overarching goal of this thesis was to create a control method for EFAs. My specific research objectives were to: (1) develop an effective and affordable food bait; (2) determine trail following of EFAs in response to synthetic trail pheromone; and (3) determine trail following of ants in response to synthetic trail pheromone blends of multiple ant species. Food baits comprising diverse macronutrients such as carbohydrates (apples), proteins and lipids (dead insects) elicited the strongest foraging responses by EFAs. Re-hydrated freeze-dried baits proved as appealing as fresh baits and superior to rehydrated heat-dried baits. Isomerically pure and impure synthetic trail pheromone (3-ethyl-2,5-dimethylpyrazine) prompted similar recruitment responses of ants. The presence of pheromone, irrespective of dose tested, enhanced the recruitment of ants to food baits, with the dose of 200 ant equivalents eliciting the strongest recruitment responses. Trail pheromone applied in a line leading toward the food bait, but not in a circle surrounding it, was effective in recruiting ants, suggesting that 3-ethyl-2,5-dimethylpyrazine has a guiding but not an attractive function to EFAs. The presence of con- and hetero-specific pheromones had additive or indifferent effects on trail-following responses of garden ants, Lasius niger, and carpenter ants, Camponotus modoc, respectively. These data provide key information for the development of a highly functional insecticidal food bait for EFAs and other nuisance ant species.

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

Identification and management of wasabi pathogens in British Columbia

Author: 
Date created: 
2020-03-27
Abstract: 

Wasabi (Wasabia japonica) plants in British Columbia are grown in moist conditions ideal for pathogens, and therefore, are prone to various diseases. Over 3 years, seven wasabi greenhouses were surveyed for pathogens. Prevalence and severity of diseases were documented. Pathogenic species including Phoma wasabiae (Leptosphaeria biglobosa), Botrytis cinerea, and Erysiphe cruciferarum were found in multiple greenhouses. A new disease of wasabi with symptoms of vascular blackening and wilt was discovered. Using morphological and molecular techniques, the causal organism was identified as Verticillium isaacii. Powdery mildew of wasabi caused by E. cruciferarum was prevalent in half the greenhouses surveyed. In order to evaluate management options for powdery mildew, 4 commercially available products, Actinovate®, Cueva®, Rhapsody®, and Regalia® were applied biweekly onto greenhouse plants. Both Cueva® and Regalia® significantly reduced the progression of powdery mildew on wasabi plants.

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

Ecological consequences of flow regulation by Run-of-River hydropower on salmonids

Author: 
Date created: 
2020-04-02
Abstract: 

Streams are dynamic, disturbance-driven ecosystems, where flow plays a dominant role structuring biological communities. Anthropogenic activities on streams change natural patterns of flow and disturbance, which in turn alters the conditions to which resident fishes are adapted, and their survival and fitness. Run-of-river (RoR) hydropower projects are an example of an anthropogenic activity that may alter stream ecosystems by temporarily diverting a proportion of stream flow to produce electricity. RoR hydropower projects have increased considerably in number and importance in the last three decades in both British Columbia and worldwide. Although there is a perception that RoR hydropower has minimal effects on stream ecosystems due to the small physical footprint of projects, we know surprisingly little about the impacts of RoR hydropower on fish populations. In this thesis, I use a combination of published research, empirical data, and models to evaluate a range of hypotheses regarding how RoR hydropower may affect fish populations, concentrating on salmonid species whose freshwater habitats often overlap with RoR projects. In Chapter 2, I synthesize the impact pathways by which RoR hydropower may influence salmonid populations, inferred from studies of reservoir-storage hydropower and salmonid ecology. In Chapter 3, I use empirical data to quantify increases in water temperature due to RoR flow diversion and explore the possible consequences for resident fish growth with bioenergetics models. In Chapter 4, I evaluate how stranding from anthropogenic flow fluctuations affects the long-term population dynamics of coho salmon (Oncorhynchus kisutch) in RoR-regulated rivers using a matrix model integrating both the strength and timing of freshwater density dependence. Finally, in Chapter 5, I quantify the high level of uncertainty in how much compensation habitat is required to offset chronic mortality incurred by multiple life-stages of coho salmon. The global emergence of RoR hydropower projects emphasizes the importance of understanding their effects on aquatic ecosystems. Overall, our capacity to protect and restore threatened salmonid populations rests upon our ability to not only better understand the pathways of impacts, but also the effectiveness of both natural (density dependence) and human (habitat compensation) interventions that can be used to offset anthropogenic mortality.

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

Survivorship and life history strategies in relation to migration distance in western and semipalmated sandpipers in Perú

Date created: 
2020-03-31
Abstract: 

This thesis explored the relationships between life history, migration distance, survivorship components of fitness, and molt strategies of Western and Semipalmated Sandpipers in one of the most austral non-breeding sites for both species, at Paracas, Perú. I asked how migration distance relates to pre-migratory preparation, survivorship and migratory decisions for different age classes and ecological circumstances between species and within populations. I focused particularly on how timing of first breeding relates to survivorship and thus future overall fitness. I found that adults from both species prepare for northward migration, but no juvenile Western Sandpipers did so, confirming a non-migratory over-summering ‘slow’ life history strategy for more southerly non-breeding populations. Juvenile Semipalmated Sandpipers showed bimodality in migration strategy. Most showed no migratory preparation, but ~30% fattened, molted into breeding plumage, and performed partial post-juvenal wing molt (PPW) during the pre-migratory period. The frequency of PPW is positively related to culmen length (as a proxy for eastern breeding birds with a shorter migration distance). To decompose survivorship between migrant and oversummering (resident) Semipalmated Sandpipers, I used a multi-state model with 5 years of data and found survivorship 8 percentage point higher for oversummering juveniles and 21 percentage points higher for oversummering adults compared to same aged migrant birds, as expected as compensation for the loss of a breeding opportunity. I estimated annual survivorship with an open robust multi state model using 7 years of mark-resighting data from several thousand shorebirds marked at Paracas. As predicted by some migration theories, both species had higher annual survival estimates than those obtained previously at non-breeding sites further north. Western Sandpiper juveniles also had substantially higher annual survival estimates than adults, in line with the predicted survivorship benefits needed to offset their delayed reproduction. I found that the size of the survival advantage in juvenile Semipalmated Sandpipers is migration distance dependent. Western, but not Semipalmated Sandpipers showed a negative relationship in survival with the ENSO warm phase, probably due to the former’s closer association with the Pacific migratory flyway. Finally, I corroborated that the size of the survival advantage is distance dependent. My results provide novel information on non-breeding shorebird survivorship and perspective on the interrelationships that drive avian life history strategies. I confirm that Paracas is also a site with high demographic value.

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

Morphological and functional characterization of host proteins during infections by actin-hijacking bacterial pathogens

Author: 
Date created: 
2020-04-14
Abstract: 

Cells, much like mammals, possess an internal skeleton. This cellular skeleton (called the cytoskeleton) provides structure to cells, enables their movement within the environment and promotes the internalization of extracellular cargo (endocytosis). Many pathogens have devised strategies to hijack the cytoskeleton and other crucial sub-cellular processes for their disease processes. The bacterium Listeria monocytogenes (L. monocytogenes) utilizes the clathrin endocytic machinery to invade cells, and later, the actin polymerization machinery to generate actin-rich comet/rocket tails to move within and amongst host cells. Salmonella enterica serovar Typhimurium (S. Typhimurium) and Shigella flexneri (S. flexneri) generate actin-rich membrane ruffles at the cell surface to enter cells. Once inside, S. Typhimurium occupies a long-lived vacuole, whereas S. flexneri generates comet/rocket tails. Enteropathogenic Escherichia coli (EPEC) on the other hand remain extracellular and co-opt clathrin and actin to form motile pedestals directly beneath the site of bacterial adherence. In this thesis, I explored the involvement of several host actin- and/or endocytic-associated proteins during bacterial infections and simultaneously used these infections to gain insight into novel roles of the proteins studied. In chapter 2, I discovered that L. monocytogenes co-opts the actin-associated protein palladin during its entry and intracellular motility. Importantly, I revealed that palladin can functionally replace the Arp2/3 complex during bacterial actin-based motility. In chapter 3, I uncovered that the internalization strategy used by L. monocytogenes to transfer between host cells exploits caveolin-mediated endocytosis. In chapter 4, I investigated the host enzyme cyclophilin A (CypA) and found that it is crucial for maintaining the structural integrity of L. monocytogenes membrane protrusions generated during bacterial dissemination events. In chapter 5, I determined that CypA restricts S. Typhimurium invasion but is dispensable for EPEC pedestal formation. Finally, in chapters 6 and 7, I examined the receptor of CypA, CD147, and found that this membrane protein, like CypA, is crucial for the proper formation and function of L. monocytogenes membrane protrusions. In conclusion, my research has 2 major implications: 1) I have uncovered new insight into the mechanisms behind how actin-hijacking pathogens cause disease and 2) I have demonstrated novel cellular functions for host actin-associated proteins.

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

Microplastics in the Beaufort Sea Beluga Food Web

Author: 
Date created: 
2020-02-06
Abstract: 

Microplastics (MPs, particles <5 mm) represent an emerging global environmental concern and has been detected in multiple aquatic species. Very little is known, however, about the presence of MPs in higher trophic level species, including cetaceans. Working in collaboration with Inuvialuit hunters from Tuktoyaktuk (Northwest Territories, Canada) and researchers from the Department of Fisheries and Oceans, entire stomachs and intestinal sub-sections were collected from seven beluga whales (Delphinapterus leucas) in 2017 (n=4) and 2018 (n=3) for examination. Microplastics were detected in the gastrointestinal tracts in every whale. Each whale contained an estimated 18 to 147 MPs in their GI tract with an average of 97 ± 42 per individual. FTIR-spectroscopy revealed over eight plastic polymer types, with nearly half being polyester. Dominant MP types were equally present, with fragments making up 51% and fibres 49%. The potential source of MPs to beluga via prey items was also determined by examining the GI tracts from five Arctic fish species belonging to the beluga food web (n=116). Species investigated included (Arctic cod (Boreogadus saida), saffron cod (Eleginus gracilis), Arctic cisco (Coregonus autumnalis) four-horn sculpin (Myoxocephalus quadricornis) and capelin (Mallotus villosus). Microplastics were found in 21% of prey. The fish that contained microplastics had a mean abundance of 1.42 ± 0.44 particles per individual and 85% of particles observed were fibres. Particle size and polymer types found in prey were similar to those found in beluga, suggesting that trophic transfer of MPs from prey to beluga may be occurring. The diversity of MP shapes and polymeric identities in all species investigated points to a complex source scenario, and ultimately raises questions regarding the significance and long-term exposure of this pollutant in these ecologically and culturally valuable species.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Leah Bendell
Peter Ross
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

Reproductive and thyroid endocrine axis cross-talk in rainbow trout (Oncorhynchus mykiss) alevins

Author: 
Date created: 
2020-04-27
Abstract: 

Although numerous studies on various aspects of endocrine axes and the physiology of both juvenile and adult life stages of several teleosts exists, studies characterizing the basic functions and cross-talk of endocrine axes during early developmental stages (i.e. embryonic to early feeding fry), in particular, are limited. The goal of this study was to characterize morphological and molecular effects in rainbow trout alevins after waterborne exposures to 17β-estradiol (E2 0.0008 to 0.5 μg/L), triiodothyronine (T3; 0.52 to 65 μg/L), and various co-treatments for 21 to 23 days. Interestingly, there was no consistent evidence that E2 alone influenced growth, development or deformity rates, nor the co-treatments of 0.02 and 0.1 μg/L of E2 with up to 65 μg/L of T3. However, 13 and 65 μg/L T3 alone expedited development and caused a unique opercular deformity not previously reported. Gene expression changes were observed, but these were mainly at the highest concentrations tested. These data suggest low-level E2 does not negate abnormal growth and development caused by hyperthyroidism and examining more time points is likely required to demonstrate a stronger response profile for individual hormones and endocrine axes cross-talk.

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

Fish community dynamics and nursery habitats in an undeveloped estuary

Author: 
Date created: 
2020-01-31
Abstract: 

Estuaries are potentially critically-important fish habitats. However, their temporal and spatial dynamics challenge understanding of the nursery functions of estuaries. Working in the Koeye River estuary in British Columbia, I used size-spectra analysis to infer production and predation risk across the estuary habitat mosaic and track their changes through the season. The brackish mudflat habitat exhibited the highest fish production and lowest inferred predation risk, suggesting that this area had particularly high nursery value. Spectra coefficients were seasonally dynamic, indicating that temporal shifts in the spatial patterns of risks and reward. I also investigated the potential effects of climate change on the distributions of different estuarine fish assemblages by comparing two climatically-divergent sampling seasons. Marine-oriented species expanded their range up-estuary during the dry, more saline year, but freshwater species did not shift. Collectively, this research advances understanding of the spatio-temporal dynamics of estuary nursery functions.

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

Habitat use and the impacts of agricultural land use for wintering Neotropical migrants

Author: 
Date created: 
2020-01-10
Abstract: 

For six months of each year, Neotropical forests host the highest known diversity and density of wintering migrants. Habitat loss and conversion of more than 3.5 million ha of Neotropical forests a year is frequently linked to declines in Neotropical migrants, however, data on habitat use in the wintering grounds is very limited. In this thesis, I examine habitat use, across three land cover types for wintering Yellow Warblers (Setophaga petechia) and show that in the lowlands of Jalisco, Mexico, seasonal agriculture with hedgerows, provides high quality winter sites. Yellow Warbler originating from Western Canada, were found in the highest densities in agricultural habitats, intermediate in riparian forests and lowest in coastal scrub-mangrove. Birds wintering in agriculture and riparian forest had higher apparent monthly survival compared to birds in scrub-mangrove and were able to regrow higher quality replacement tail feathers. However, I found no evidence that traits linked to competitive ability (age, sex, or size) influenced the distribution of birds across different land covers. Together, these results demonstrate that current agricultural practices in western Mexico are unlikely to have contributed to the decline of Yellow Warbler populations in Canada. Overwintering in agriculture did not appear to negatively impact the Neotropical migrant community in western Mexico. Neotropical migrants were more abundant in agriculture, and had similar species diversity and beta-diversity to riparian forests. In contrast, although a few resident species were frequently found in agriculture, resident species had lower species diversity in agriculture compared to riparian forest community. Collectively these results demonstrate that individual species, and particularly the Neotropical bird community can utilize human altered landscapes on the wintering grounds in Mexico. However, native habitats are key to retaining the full resident bird community. Identifying the features and spatial configuration of the working land that supports bird populations will be critical for the management and conservation of resident and overwintering birds.

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