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

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The allometry of oxygen supply and demand in the California Horn Shark, Heterodontus francisci

Author: 
Date created: 
2021-01-21
Abstract: 

The scaling relationship between metabolic rate and body mass is one of the most notable functional relationships in comparative physiology and macroecology. In aquatic ectotherms, the surface area of the gills is thought to be a major contributor to the allometric scaling patterns we see for metabolic rate, both within and across species. Here, I first examined the allometric relationship between oxygen supply (gill area) and consumption (metabolic rate) and found that the allometry of gill area was isometric and very similar to that of metabolic rate. Second, I tested the effects of three statistical analysis techniques for estimating maximum metabolic rate and found that a rolling regression model was the best candidate model across four fish species. Together, these results support the hypothesis that oxygen supply and demand are closely matched and suggest that a two-dimensional gill can overcome geometric constraints to increase at the same rate as the three-dimensional mass of an inactive organism. Additionally, they highlight the importance of statistical choices in producing comparable and reproducible estimates of metabolic rate across species.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Nicholas Dulvy
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

The respiratory basis of metabolic rate and life histories

Author: 
Date created: 
2021-06-04
Abstract: 

Oxygen fuels aerobic metabolism and as such, plays an important role in the physiology, ecology, and evolution of organisms. Traits related to oxygen acquisition (respiratory surface area) and use (metabolic rate) or the balance of oxygen supply and demand (or its mismatch, termed ‘oxygen limitation’) have been proposed to underlie broad patterns such as the temperature-size rule and the geographic distributions of marine species. Moreover, traits related to oxygen acquisition and use form the central focus of seemingly disparate macroecological theories that aim to explain and predict the structure and dynamics of ecological systems and how these systems and their constituents will respond to a changing climate. While these existing theories and oxygen-related explanations offer a compelling story, the role of oxygen in shaping biological observations, responses, and patterns is hotly debated. Further, much work in this area is experimental in nature and typically focuses on a single species in laboratory settings. Broader scale, macroecological research stemming from meta-analysis and modeling is needed to understand the generality of patterns. To that end, this thesis takes a macroecological approach and examines the generality of the relationships among traits related to oxygen acquisition and use, ecology, and life histories. First, I reveal that respiratory surface area explains patterns of metabolic rate across the vertebrate tree of life. Second, I uncover that larger-bodied, active, pelagic sharks have greater gill surface areas (respiratory surface area in fishes) for a given size compared to their smaller-bodied, less active, benthic counterparts. Conversely, the rate at which gill surface area increases with body mass is the same for all species, regardless of activity level, habitat type, or maximum size. Third, I test a central prediction of the Gill Oxygen Limitation Theory and find that across fishes, growth and maximum size more strongly relate to activity level than gill surface area. Collectively, my thesis highlights the complexities of integrating data across scales and illustrates that oxygen acquisition and use is tightly correlated with activity level, but the relationships with life histories are less straightforward. This body of work builds on existing theory while empirically testing relationships among oxygen acquisition and use, ecological lifestyle, and the life histories among fishes and other vertebrates.

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

Characterizing and engineering a dengue refractory phenotype in Aedes aegypti

Date created: 
2019-06-25
Abstract: 

Dengue viruses infect ~400 million people annually and are transmitted principally by Aedes aegypti. Severe dengue (dengue hemorrhagic fever and dengue shock syndrome) can be fatal, and there are no efficient drugs or vaccines to prevent the disease. Not all Ae. aegypti transmit dengue viruses; in Cali, Colombia, approximately 30% of feral populations are naturally refractory to all four viral serotypes through midgut mechanisms (Cali-MIB), while the remaining 70% are susceptible (Cali-S) and transmit the viruses. We used a combination of molecular biology and bioinformatic methods to identify differences between the refractory and susceptible strains. RNA sequencing, 16S rRNA bacterial profiling, and a genome wide association study (GWAS) were used to identify a subset of genes thought to contribute to the Cali-MIB and Cali-S phenotypes. Genes from this subset that were able to ‘flip’ the phenotype from susceptible to refractory through RNAi based knockdowns were further tested with gene-editing technology to knock-out these genes using clustered regularly interspaced palindromic repeats (CRISPR) – CRISPR-associated protein 9 (Cas9) guide RNA complexes. This research identified multiple genes we believe contribute to vector competence, created a DNA based assay for identifying Cali-MIB and Cali-S mosquitoes, and edited the germ-line of Ae. aegypti. This information could allow us to create lines of permanently refractory mosquitoes to dampen dengue transmission.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Carl Lowenberger
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

Effects of climate change on two species of foundational brown algae, Nereocystis luetkeana and Fucus gardneri, within the Salish Sea

Date created: 
2021-01-22
Abstract: 

Ocean acidification and warming have large-scale impacts on marine organisms and ecosystems. To evaluate effects of these stressors, two foundational algal species in the Salish Sea were chosen, Fucus gardneri and Nereocystis luetkeana. Using Fucus, we evaluated how a wide range of pH levels (8.0-6.0) impacts embryonic development. During exposure to acidic conditions, embryos were capable of germination and forming a rhizoid on time. However, rhizoid elongation was significantly reduced. In a second study, we found that Nereocystis zoospores developed normally when incubated at 10 or 15°C. However, significant reductions in germination were observed when zoospores were exposed to 17.5°C while many lysed at 20°C. In addition, more of the N. luetkeana sampled from a population growing in the warmer region (Stanley Park) were able to maintain low levels of reactive oxygen species (ROS) when exposed to 17.5°C than N. luetkeana collected from a population living at a cooler site (French Beach).

Document type: 
Thesis
File(s): 
Supervisor(s): 
Sherryl Bisgrove
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

Evolution of gonad transcriptomes and gamete-recognition genes in sea stars

Author: 
Date created: 
2020-12-22
Abstract: 

Evolved differences in life history traits, including fertilization ecology and mating systems, are expected to affect the strength of sexual selection acting on gamete-recognition genes (GRGs) responsible for gamete compatibility and fertilization success. The evolution of life history traits such as internal fertilization of eggs and mating system traits such as self-fertilization is expected to weaken the effects of sexual selection (due to the resolution of sperm competition among males and sexual conflicts between males and females). To assess these expectations, I compared the responses to selection of GRGs and other genes expressed in the gonads from multiple species of sea stars with different life histories. I first developed a bioinformatic protocol to reconstruct the transcriptomes of gonads from RNA-seq libraries using the data from the crown-of-thorns sea star Acanthaster cf. solaris and used that protocol to characterize GRGs and gene expression. I then compared GRGs in two recently diverged species with contrasting mating systems. I found little evidence of positive selection in the GRGs of the outcrossing species (Cryptasterina pentagona). Instead, I found evidence of relaxed selection in the self-fertilizing and hermaphroditic species (Cryptasterina hystera). I also found evidence of selection in non-GRG-genes linked to abiotic stressors, DNA regulation, polyspermy, and egg retention. In the last chapter, I compared the selection on female GRGs and other ovary genes using a phylogenetically broad sample of sea star species with two modes of reproduction. I found evidence of rapid evolution acting on female GRGs and of a stronger response to selection on female GRGs from sea stars with expected stronger sexual selection (gonochoric, broadcast spawning, planktonic fertilization) compared to species with derived life history traits associated with weaker sexual selection (hermaphroditic, benthic fertilization, brood protection). In summary, these results support the expectation of rapid evolution and strong selection on GRGs compared to other parts of animal genomes. GRG evolution likely contributes to the speciation process as a mechanism of reproductive incompatibility. And when selection targets GRG, life history traits can affect the response to selection.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Michael Hart
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

The lethal and sublethal effects of anti-sea lice chemotherapeutants in marine benthic and pelagic invertebrates

Author: 
Date created: 
2021-01-14
Abstract: 

The salmon aquaculture industry has become a major contributor to the Canadian economy, however, many practices including sea lice pest management strategies have resulted in the contamination of the environment near these operations. Compounds used in sea lice control include Salmosan® (active ingredient [AI] azamethiphos), Paramove®50 (AI hydrogen peroxide), ivermectin (IVM) and SLICE® (AI emamectin benzoate [EMB]). Salmosan® and Paramove®50 are water-soluble formulations applied as bath treatments, whereas IVM and SLICE® are in-feed additives that are hydrophobic and partition to sediment with persistent physicochemical properties. This research assessed both the lethal and sub-lethal effects of these compounds on non-target benthic and pelagic invertebrates at environmentally relevant concentrations. A short-term fertilization success bioassay using the sea urchin Strongylocentrotus purpuratus was performed using pest management application-level concentrations of Salmosan® and Paramove®50 in seawater. Paramove®50 significantly inhibited fertilization success with a calculated IC50 value of 7.27 mg/L; Salmosan® only marginally inhibited fertilization at the highest concentration (IC50 > 100 µg/L). Avoidance behaviour and oxygen consumption were assessed in the benthic amphipod, Eohaustorius estuarius, and the polychaete Nereis virens, following sub-chronic exposure to environmentally relevant sediment concentrations (< 5 µg/kg) of EMB, IVM and a combination of both (EMB/IVM). E. estuarius avoided sediment containing IVM and EMB/IVM ratio concentrations containing 25 and 50 µg/kg IVM, while N. virens avoided sediment with 50 and 200 µg/kg IVM and 0.5, 5, 50 and 200 µg/kg EMB/IVM ratio. Impaired burrowing and locomotory behaviour in N. virens was also observed with both treatments. Oxygen consumption was significantly decreased in E. estuarius and increased in N. virens when exposed to EMB, IVM and EMB/IVM at concentrations < 5 µg/kg over a 28-d exposure period. This research provides evidence of impacts to S. purpuratus, E. estuarius and N. virens from anti-sea lice chemotherapeutant exposure at environmentally relevant concentrations and will supplement regulatory decisions and management policies associated with chemicals used in aquaculture in Canada.

Document type: 
Graduating extended essay / Research project
File(s): 
Supervisor(s): 
Christopher Kennedy
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.

Polarized light - host location and selection cue in phytophagous insects?

Author: 
Date created: 
2020-12-16
Abstract: 

Insect herbivores exploit plant cues to discern host and non-host plants. Studies of visual plant cues have focused on color despite the inherent polarization sensitivity of insect photoreceptors and the information carried by polarization of foliar reflectance, most notably the degree of linear polarization (DoLP; 0-100%). The DoLP of foliar reflection was hypothesized to be a host plant cue for insects but was never experimentally tested. I investigated the use of these polarization cues by the cabbage white butterfly, Pieris rapae (Pieridae). This butterfly has a complex visual system with several different polarization-sensitive photoreceptors, as characterized with electrophysiology and histology. I applied photo polarimetry revealing large differences in the DoLP of leaf-reflected light among plant species generally and between host and non-host plants of P. rapae specifically. As polarized light cues are directionally dependent, I also tested, and modelled, the effect of approach trajectory on the polarization of plant-reflected light and the resulting attractiveness to P. rapae, showing that certain approach trajectories are optimal for discriminating among plants based on these cues. I then demonstrated that P. rapae exploit the DoLP of foliar reflections to discriminate among plants. In experiments with paired digital plant images that allowed for independent control of polarization, color and intensity, P. rapae females preferred images of the host plant cabbage with a low DoLP (31%) to images of the non-host plant potato with a high DoLP (50%). These results indicated that the DoLP had a greater effect on foraging decisions than the differential color, intensity or shape of the two plant images. To investigate potential neurological mechanisms, I designed behavioral bioassays presenting choices between images that differed in color, intensity and/or DoLP. The combined results of these bioassays suggest that several photoreceptor classes are involved and that P. rapae females process and interpret polarization reflections in a way different from that described for other polarization-sensitive taxa. My work has focused on P. rapae and its host plants but there is every reason to believe that the DoLP of foliar reflection is an essential plant cue that may commonly be exploited by foraging insect herbivores

Document type: 
Thesis
File(s): 
Supervisor(s): 
Gerhard Gries
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

Regimes of river temperature and flow in an interior watershed, and their implications for Chinook salmon

Author: 
Date created: 
2020-12-07
Abstract: 

Climate change and human activities are altering river flows and temperatures, with potentially large consequences for aquatic life. I investigated how changing river flows affect salmon productivity, and how climate sensitivity varies across a watershed. First, I tested the effects of shifting river conditions on Chinook salmon productivity in a river where average August river discharge decreased by 26% in the last century. Summer low flows had the greatest negative impact on productivity: cohorts that experienced 50% below average flow in the August of spawning and rearing had 40% lower productivity. Second, I examined whether watershed characteristics could predict which streams were warmest and most sensitive to regional climate. Streams with more riparian forest cover were cooler overall and less sensitive to warmer air temperatures. Overall, this research shows that restoring river flows and watershed-scale forest management are essential parts of salmon conservation.

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

Temporal patterns and behavioural states of mountain goat (Oreamnos americanus) movements to hotspots in the Rocky Mountains

Author: 
Date created: 
2020-12-01
Abstract: 

Concentrated resources, or hotspots, can influence movement behaviour of many species. I studied the movement ecology of two groups of mountain goats (Oreamnos americanus) and their relationship with hotspots in the Canadian Rocky Mountains. First, I investigated fidelity to two roadside mineral licks. Movement patterns to mineral licks were documented over several temporal scales and I found that mountain goats have strong trans-generational, seasonal and daily movements to these mineral licks. Second, I investigated movements to foraging, travelling, and bedding areas in summer ranges, using hidden Markov models (HMMs) and predicted behavioural states. These behavioural states were ground validated and the results showed that HMMs can be used as a proxy for habitat hotspots. Understanding how animals adjust their movement behaviour to hotspots can provide valuable information for the management of these critical habitat features and the wider conservation of mountain goats.

Document type: 
Thesis
File(s): 
Supervisor(s): 
David Hik
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

The continuing persistence and biomagnification of DDT and metabolites in American robin (Turdus migratorius) fruit orchard food chains

Author: 
Date created: 
2020-12-14
Abstract: 

DDT is an organochlorine insecticide that was widely used in fruit orchards in the South Okanagan Valley from the late 1940s and in the 1990s, this was documented to have caused extensive contamination of American robin (Turdus migratorius) food chains. Due to the environmental persistence of DDT and its metabolite, p,p’-DDE, the objective of this study was to re-sample previous orchards, as well as several new agricultural areas with the prediction that DDT and metabolite concentrations would significantly decline twenty-six years after a similar sample collection was conducted in 1993-1995. This was done by: 1) collecting soil, earthworms and American robin eggs from orchard and non-orchard areas in the South Okanagan Valley, 2) comparing previous and current contaminant burdens for DDE, DDT and DDD metabolites, and 3) calculating biomagnification factors for earthworms and robins on a lipid normalized basis. All robin eggs contained DDE, DDT and DDD, with the highest concentration being p,p’-DDE at 107 ug/g (wet weight), confirming that contamination is still present at similar and high levels relative to the 1990s. DDE and DDT levels in robins were significantly higher than Aporrectodea and Lumbricidae earthworms, and earthworm-robin regressions for DDE showed a significant positive relationship. Biomagnification factors were generally > 1 and were higher for DDE than DDT and DDD. Concentrations of p,p’-DDE in American robins in this study were comparable to and/or exceeded published levels in other migratory birds nesting in fruit orchards, including the eastern bluebird (Sialia sialis), where reproductive and immunostimulation effects were observed. The relatively high concentrations of DDE in the South Okanagan Valley may pose a health risk to local predators and birds of prey, such as Accipiter hawks and falcons, who often feed at higher trophic levels where DDE and other contaminants are biomagnified.

Document type: 
Graduating extended essay / Research project
File(s): 
Supervisor(s): 
John Elliott
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.