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

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Mapping the movement of marine fishes: methods, mechanisms, and implications for invasion management

Date created: 
2015-09-21
Abstract: 

Movement represents a key ecological trait of individuals that has important implications for the spatial structuring of population, community, and ecosystem processes. However, the spatial ecology of terrestrial organisms is much better understood than that of their comparatively understudied aquatic counterparts. My thesis focuses on the methods and mechanisms underpinning the study of movement ecology in fishes, with special attention on the movement of invasive Indo-Pacific lionfish (Pterois volitans and P. miles) on Caribbean coral reefs and its implications for invasion management. I begin by comparing broad-scale patterns of space use across all vertebrates, including fishes, to draw general conclusions about the factors driving their space requirements. My models reveal that body mass, locomotion strategy, foraging dimension, and trophic level predict ~80% of the variation in vertebrate home range size. I then describe a versatile method for GPS-based underwater mapping that will enable more routine collection of a wide variety of spatial data, including movement patterns, habitat characteristics, and bathymetry. This method is ideal for studies operating on smaller scales and budgets and will help advance the study of spatial ecology in aquatic environments. Next, I apply this mapping method to characterize the movements of tagged lionfish on Bahamian coral reefs, and find that lionfish movement is density dependent, declines at larger body sizes, and varies with seascape structure. Using these movement data, I model the metapopulation dynamics of lionfish in a patch reef network to show how removing lionfish from single patches influences metapopulation dynamics at the network scale, and show how landscape features that facilitate recolonization of cleared patches can negatively influence management outcomes. My thesis helps to fill critical gaps in our understanding of movement and space use of animals in general, and of marine fishes in particular. This work also demonstrates how a better understanding of movement ecology can help to optimize the distribution of limited resources for the management of marine invasive species, which represent a significant and growing threat to marine ecosystem biodiversity and function.

Document type: 
Thesis
Senior supervisor: 
Isabelle Côté
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

From earth and ocean: Investigating the importance of cross-ecosystem resource linkages in estuaries of the Pacific Northwest

Date created: 
2015-09-22
Abstract: 

Similar to how political boundaries do not reflect the cultural ties and ancestral lineages of human history, classical ecological perspectives often do not account for the complex relationships amongst ecosystems at local, regional or global scales. Cross-ecosystem resource linkages provide crucial subsidies to many ecosystems on Earth. Resource subsidies can contribute to the productivity, form, and function of recipient ecological communities. However, a subsidy’s importance can vary widely among landscapes as a result of resource availability, ecosystem characteristics and consumer traits. Estuaries are composed of highly connected habitats that reside at the interface between terrestrial, freshwater and marine environments. Consequently, they are ideal systems to explore the importance of resource subsidies and how their role can vary spatially. This thesis examines the assimilation of, and response to resource subsidies in estuaries of the Northeastern Pacific. I focus on two spatial subsidies: terrestrial resources delivered to estuaries via the movement of freshwater, and salmon resources that enter coastal watersheds during fall spawning seasons. First, I show that species-specific distributions of live spawning salmon, their associations with terrestrial predators, and physical characteristics of individual systems drive salmon subsidies to riparian forests and estuaries. I then focus on subsidy responses in two estuarine consumers; soft-shell clam (Mya arenaria) and Dungeness crab (Metacarcinus magister). Through the use of stable isotopes, I demonstrate that landscape-level traits such as watershed size and salmon density drive the assimilation of subsidies in both species and that location within an estuary can mediate responses in sedentary consumers. However, terrestrial-derived subsidies also influence the size of individuals, suggesting this resource may have farther-reaching effects. Finally, I compare the dietary composition of three consumers and find that subsidy contributions increase with availability while accounting for other estuarine resources. Mobile consumers may benefit most, by being better able to exploit heterogeneous resource pools. This thesis demonstrates that terrestrial- and salmon-derived resource subsidies contribute to the resource base in estuarine ecosystems and that terrestrial subsidies may have the most pronounced effects. Ecosystems are connected, but the strength of these connections varies. It is therefore crucial to place resource dynamics within the context of specific landscapes and species to properly evaluate subsidy importance.

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

Using a panel of in vitro yeast screening bioassays to assess endocrine disrupting chemical contents in water and sediment samples from Surrey and Langley, British Columbia

Author: 
Date created: 
2015-06-03
Abstract: 

Exposure to endocrine disrupting chemicals (EDCs) potentially leads to adverse health effects in wildlife and humans. In this study, a panel of genetically modified yeast bioassays containing human estrogen, androgen, or progesterone receptors along with the appropriate steroid responsive elements of the β-galactosidase reporter gene were used to screen for EDCs in samples collected from various river and stream sites close to cattle farms and agricultural operations in Surrey and Langley. Water and sediment samples were collected on three different occasions either before or after a rainy period. The yeast screening bioassays were reproducible, accurate, and precise. They also showed calibration linearity and low detection limits for the EDC marker chemicals. Results of the studies showed high levels of androgen-, estrogen-, glucocorticoid- and aromatic hydrocarbon-like chemicals in the water and sediment samples from Surrey and Langley. As expected, the samples collected near dairy farms and agricultural operations contained much higher levels of EDCs compare to sites far away from farming and agricultural activities. The EDCs in the water samples were generally lower in concentrations than the sediments. Selected water samples were further analyzed for estrogens and androgens chemically using a gas chromatography-mass spectrometer. The water samples were found to contain estradiol, estrone, nonylphenol, bisphenol A, and androstendion with mean concentrations ranging from 0.041 to 30.10 ng/ml. Our studies demonstrate that animal farms and agriculture activities account for significant amounts of EDCs released into the aquatic environment at Surrey and Langley.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Francis Law
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Two Faces of Drosophila suzukii Invasion: Effects on Invaders and Communities

Date created: 
2015-09-14
Abstract: 

The spotted wing drosophila (SWD, Drosophila suzukii) has quickly spread since its introduction in 2008 to North America and Europe. Most Drosophila oviposit in rotting fruit, but SWD puncture the skin of fresh fruit to lay eggs inside, leading to premature fruit rot. I used SWD to study how new selective pressures shape invasive populations, and how invaders impact communities in their invaded ranges. I hypothesized that flies that were unable survive the winter conditions in Agassiz, BC would have quickly died out, but flies living in California would have experienced less intense selection for overwintering adaptations. I found that SWD reared at short photoperiods showed phenotypic plasticity that indirectly improved cold tolerance, and that the response was different between populations, but not in the manner predicted. To explore the impact SWD may have on communities in their invaded ranges, I conducted a sensitivity analysis of 3 parameters in an individual based model that simulated the change in fruit resources from ripe to rotten. I found that the greatest amounts of rot occurred when fruit was slow developing, many adult SWD were present, and females were adept at finding oviposition sites. Lastly, batches of cherries collected from orchard tree branches and floors both produced SWD and other species of Drosophila, suggesting that the species are not spatially separated and congener competition could be occurring on or in fruit in the field. The three data chapters presented here tested one way in which new environments could be shaping this introduced species, explored the conditions that could lead to the greatest impact of SWD on their new communities, and confirmed that the communities SWD are hypothesized to affect, do overlap. This represents a small amount of what could be learned from the SWD invasion, especially in ecology and evolution.

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

Integrative Studies of Southern Ocean Food-Webs and Pygoscelis Penguin Demography: Mechanisms of Population Response to Environmental Change

Date created: 
2015-01-08
Abstract: 

Unraveling the proximate physiological, ecological and evolutionary mechanisms that underlie population responses to environmental variability is an increasingly important challenge facing conservation biologists and is the primary motivation of this thesis. I studied Pygoscelis penguins that breed west of the Antarctica Peninsula (AP). Here, breeding populations of Adélie (P. adeliae), chinstrap (P. antarctica) and gentoo (P. papua) penguins are undergoing pole-ward range shifts that correlate with long-term warming trends of the region. However, mechanistic relationships that link marine ecosystem variability with demographic parameters that drive population change are rarely quantified. My data support the following conclusions. At Anvers Island, where reductions in sea ice have been notable, Pygoscelis penguins became more similar isotopically throughout the breeding season, due to a depletion in δ13C and δ15N of blood tissue. Here, crèched chicks of all species occupied similar trophic levels and isotopic mixing models indicated that the proportions of prey provisioned to crèched chicks were generally similar across species within years. Crèched Adélie chicks were isotopically enriched at Avian and Charcot Islands, southern rookeries where sea ice is more prominent, and their trophic level increased with latitude. Penguin food-webs are isotopically wider in regions with greater sea ice coverage. Molecular primers (P2/P8) amplified DNA of all species to discern sex. At Anvers Island, I detected little evidence of trophic foraging influencing body and egg mass of adult penguins and chick body mass. However, regional analyses suggested that a provisioning diet enriched in δ15N, such as that found at southern rookeries, resulted in heavier five-week-old Adélie penguin chicks. Corticosterone hormone did not mediate individual variation in Pygoscelis breeding performance. I found no overall genetic structure among Adélie penguins based on microsatellite and mitochondrial DNA markers, however, pairwise comparisons including Charcot Island were significant. Gene flow was asymmetrical from the species’ regional core to its northern range. In conclusion, variability in sea ice-associated food-webs of the western AP is an important determinant of Pygoscelis penguin reproductive performance, but not at the physiological level. A lack of genetic structure implicates dispersal as an important demographic factor that may structure population responses to future ecosystem change.

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

Contributions to the ecology of North American vespines: Rearing yellowjackets in nest boxes and unraveling pheromone-mediated nest defense in bald-faced hornets

Date created: 
2015-08-18
Abstract: 

To obtain an ample supply of study insects, we attempted to rear yellowjackets from spring-collected queens, achieving a high nest initiation rate for German yellowjackets, Vespula germanica. To study nest defense, we placed paired boxes near the nest entrance of bald-faced hornets, Dolichovespula maculata, and audio recorded sound impulses caused by nest mates striking the boxes. The number of strikes increased 27-fold when – compared to two control boxes – one of the two boxes was treated with venom sac extract (VSE), providing evidence for an alarm response. The VSE-treated box also induced a greater proportion of strikes than the corresponding control box, providing evidence for a target-oriented response. Analyzing VSEs by gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometry, we identified seven candidate pheromone components which – based on molecular structure – triggered primarily alarm or target-oriented responses. VSE was more effective than synthetic pheromone in triggering alarm, indicating a missing alarm pheromone component.

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

Life History and Chemical Ecology of Xenos peckii (Strepsitera, Xenidae)

Author: 
Date created: 
2015-07-27
Abstract: 

I investigated life history traits and pheromonal communication of Xenos peckii, a parasitoid of the paper wasp Polistes fuscatus. To emerge, males cut the puparium with their mandibles, and then push aside the pupal cap with their head. The endoparasitic females engage in active calling (pheromone release) behaviour assuming a particular body posture. Seasonal and diel emergence periods of males coincide with seasonal and diel calling periods of females. Mate-seeking males land on the anterior portion of the host wasp’s abdomen, and then step backward until their mesothoracic legs contact the female’s cephalothorax, upon which the male initiates copulation. Analyzing pheromone gland extracts by gas chromatographic-electroantennographic detection revealed a candidate pheromone component (CPC) that consistently elicited responses from male antennae. CPC was identified as (7E,11E)-3,5,9,11-tetramethyltridecadienal based on mass and NMR spectra, and the synthesis of an authentic standard. In field experiments, traps baited with synthetic CPC captured X. peckii males.

Document type: 
Thesis
File(s): 
Female Xenos peckii assuming her mate-calling posture (16x speed).
Emerging male using his mandibles to cut along the ecdysial suture line.
Male Xenos peckii emerging from his puparium.
Mating sequence of Xenos peckii (filmed at 1000 fps).
Mating sequence of Xenos peckii (30 fps, real-time).
Senior supervisor: 
Gerhard Gries
Carl Lowenberger
Department: 
Science: Biological Sciences
Thesis type: 
(Thesis) M.Sc.

The effects of six organophosphate flame retardants on endocrine receptor targets in mammalian cancer cell lines

Date created: 
2015-05-20
Abstract: 

The effects of six selected organophosphate flame retardants (OPFRs) tris(2-butoxyethyl) phosphate (TBOEP), tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCIPP), tris(methylphenyl) phosphate (TMPP), tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and triethyl phosphate (TEP) on the activities of the androgen-, estrogen- and aryl hydrocarbon receptors were assessed in human prostate cancer cells (LNCaP) and endometrial cancer cells (ECC-1 cells). Binding affinity for the estrogen receptor (ER) of the selected OPFRs appeared limited in ECC-1 cells, as no profound changes in ER inducible target gene expression were observed. Furthermore, the six selected OPFRs exerted few effects on the aryl hydrocarbon receptor-inducible CYP1A1 expression, although at high concentrations TMPP mildly induced gene expression. Messenger RNA and protein accumulation of androgen receptor (AR) target genes were examined for TDCIPP. Additionally, secretory PSA detection, chromatin immunoprecipitation and a ligand binding assay were performed using TDCIPP and the synthetic androgen methyltrienolone. AR inducible target gene and protein expression were significantly altered by TDCIPP exposure, as well as excreted prostate specific antigen. For the first time it was demonstrated that TDCIPP does not have binding affinity for the AR-ligand binding domain and appears to exert its anti-androgenic effects in LNCaP cells in a non-competitive fashion. Furthermore, TDCIPP exposure could adversely influence clinical outcomes for prostate cancer screenings, resulting in false negatives. Prolonged TDCIPP exposure could also carry the risk of exacerbating the progression of prostate cancer into a metastatic androgen-independent sub-type by simulating androgen deprivation.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Dr. Timothy Beischlag
Department: 
Science: Biological Sciences
Thesis type: 
(Project) M.E.T.

The pappalysins and their substrates in early pregnancy

Author: 
Date created: 
2014-05-14
Abstract: 

Abnormal levels of pregnancy-associated plasma proteins -A and -A2 (PAPP-A and PAPP-A2) have been associated with adverse pregnancy outcomes, including preeclampsia and intrauterine-growth-restriction, two leading causes of maternal and perinatal mortality. The goal of this thesis was to assess the roles of PAPP-A, PAPP-A2, and their substrates, insulin-like growth factor-binding proteins -4 and -5 (IGFBP-4 and IGFBP-5), in early pregnancy. In contrast to previous findings with PAPP-A, first trimester maternal serum levels of PAPP-A2 were elevated in pregnancies that subsequently developed preeclampsia. In a model of early placental development, IGFBP-4 and IGFBP-5 inhibited the migration-stimulating effects of insulin-like growth factors -I and -II, although to different extents. Investigation of the location of IGFBP-4 and IGFBP-5 in the placenta revealed sites of protein localization that suggest previously unknown functions. Taken together, these findings suggest different roles of PAPP-A and PAPP-A2 in the first trimester placenta.

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

The identification and characterization of bacterial and host epithelial factors involved in the pathogenesis of invasive Francisella tularensis and extracellular enteropathogenic E. coli (EPEC)

Author: 
Date created: 
2015-04-22
Abstract: 

Enteropathogenic Escherichia coli (EPEC) and Francisella tularensis possess a toolkit of virulence factors that allow them to adapt to the host environment and prevail over the body’s natural defenses in different ways. For diarrheagenic EPEC, a type III secretion system is used to inject virulence factors directly into the host cell allowing the extracellular microbe to co-opt key host processes and generate motile ‘pedestal’-shaped structures at the site of intimate bacterial-host contact. Because many of the same principles that drive the biogenesis and movement of EPEC pedestals are paralleled at the leading edge of migrating cells, I used EPEC pedestals as a model of the leading edge and developed a strategy to identify pedestal proteins and tease out their biological functions. Using mass spectrometry-based proteomics of concentrated pedestal preparations, I identified 17 highly abundant novel proteins as well as 11 previously known pedestal proteins. One of the identified molecules, nexilin, was characterized in depth. Using EPEC and Listeria monocytogenes as bacterial models for actin-based dynamics, I revealed that nexilin is concentrated towards the rear of pedestals and Listeria comet tails when these actin-rich structures become motile. The use of siRNA-mediated knockdowns further suggested that depletion of nexilin results in unusually thin and short filamentous comet tails. Another pathogen that can colonize non-phagocytic cells is F. tularensis—the etiological agent of Tularemia. Here, I examined the internalization process and intracellular fate of Francisella in hepatocytes. To study the strategy that F. tularensis uses to invade epithelial cells I developed in vitro infection models and used those models to uncover clathrin, its associated endocytic components and cholesterol as key molecules needed for F. tularensis internalization. Finally, I elucidated the role of two Francisella virulence factors (IglC, PdpA) and showed that both PdpA and IglC are needed for the efficient invasion and intracellular growth of F. tularensis. Taken together, I have identified multiple novel targets co-opted by the extracellular EPEC and the intracellular pathogens L. monocytogenes and F. tularensis that play a central role in their pathogenesis such as the actin associated protein nexilin and clathrin endocytic components clathrin, epsin1, and Eps15.

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