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

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Impact of temperature and relative humidity on the eye-spotted bud moth, Spilonota ocellana (Lepidoptera: Tortricidae): a climate change perspective

Author: 
Date created: 
2016-04-15
Abstract: 

Global climate change models predict an increase in the frequency, severity and duration of extreme weather events. Weather extremes are important for poikilothermic species limited by their capacity to withstand conditions beyond their optimum for survival and development. To understand insect population dynamics, and forecast outbreaks in agro-ecosystems, we need a better understanding of the biology of insect pests of concern. In this study, I explored physiological responses of Spilonota ocellana (Denis & Schiffermüller) in the context of spring frost and summer drought, by focusing on the most vulnerable life stages. I determined that S. ocellana spring larval instars are freeze-avoidant and susceptible to temperatures above their mean supercooling point (SCP) which ranged from -9.1 ± 0.2 °C (4th instar) to -7.9 ± 0.2 °C (6th instar). While supercooling point increased with instar, the median LLT of -7.3 ± 0.4 °C across all instars demonstrates that a hard spring frost would be necessary to cause larval mortality. Exposure to low humidity resulted in lower egg hatch; this effect was exacerbated at higher temperatures. Furthermore, I discovered that exposure to low humidity during the latter half of egg development resulted in reduced survival and faster development rates; these effects were also observed during a period of hot and dry conditions in an apple orchard. This study provides information on the impacts of extreme weather events on survival and development within and between life stages of S. ocellana, which could have the potential to alter population abundance, phenology, and thus management of this pest.

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

The sublethal effects of Cu exposure on the osmoregulatory and swimming performance in juvenile rainbow trout (Oncorhynchus mykiss)

Date created: 
2016-04-21
Abstract: 

Cu is a widely occurring contaminant in aquatic systems and is acutely toxic to fish. The current paradigm of copper’s toxic mechanism of action in fish is believed to be through direct effects on several important functions of the teleost gill; therefore experiments were conducted to examine Cu effects on the osmoregulatory ability and swimming performance of juvenile rainbow trout (Oncorhynchus mykiss) in water of varying hardness. Fish were exposed to three Cu concentrations (0, 20 and 60 µg/L in hard water [100 mg/L CaCO3], and 0, 6 and 16 µg/L in soft water [6 mg/L CaCO3]), for 4, 8 and 16 d and then tested for their ability to osmoregulate and burst swim. Burst swimming speed (Uburst) was not different between control and Cu-exposed fish in either soft or hard water. Osmoregulatory ability following Cu exposure was examined through several biochemical measurements related to osmoregulation and a seawater challenge. Cu exposure did not elicit a change in any osmoregulatory-related measurement or result in mortalities during the seawater challenge. These results indicate that the current paradigm of Cu toxicity may not reflect the mechanism of sublethal Cu toxicity or that compensatory mechanisms are offsetting major physiological disturbances caused by Cu, at concentrations that are near those which typically cause mortality in salmonids.

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

Contributions to the development of effective food baits and pheromone lures for capturing mice and rats

Date created: 
2016-04-21
Abstract: 

My research aimed to improve trap captures of mice and rats by incorporating food cues and pheromone signals into a bait complex. I show that a food bait consisting of cereals, fructose, soy lecithin and a semiochemical blend in safflower oil, suspended in a gelatine/water solution, mediates feeding by mice and rats in the laboratory and capture of wild mice in the field. Traps baited with bedding soiled by caged male mice attracted juvenile and adult female mice, indicating the presence of a sex pheromone in soiled bedding. Analyses of male and female bedding odorants by gas chromatography-mass spectrometry show that the known primer pheromone components 3,4-dehydro-exo-brevicomin (DEB) and 2-sec-butyl-4,5-dihydrothiazole (DHT) were present in male bedding. In a field experiment, traps baited with DEB and DHT captured four times more female mice than corresponding control traps, indicating that DEB and DHT are sex attractant pheromone components of male house mice.

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

Habitat-mediated predation and selective consumption of spawning salmon by bears

Date created: 
2016-04-15
Abstract: 

Predator–prey interactions are key elements of ecosystem functioning and can be mediated by physical characteristics of the environment. To examine this, I studied interactions between bears and spawning salmon on the Central Coast of British Columbia, Canada. I first show how size-biased predation is mediated by stream characteristics that provide refuge for prey, with implications for size-selective pressures acting on salmon in different streams. I then demonstrate that bears feed selectively on energy-rich parts of salmon, depending on characteristics of the stream, with consequences for terrestrial nutrient transfer via uneaten salmon biomass. Overall, I found that bears captured larger salmon in streams with less wood and fewer undercut banks and fed more selectively in narrower, shallower streams with less pool volume. This suggests that habitat characteristics play a role in mediating predator behaviour and, therefore, have implications for the selective pressures faced by salmon, and nutrient subsidies to surrounding habitats.

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

Population structure in Western Sandpipers (Calidris mauri): Variation in genes, morphology and vocalizations in a migratory shorebird

Author: 
Date created: 
2016-01-25
Abstract: 

Effective conservation management of migratory birds can be challenging and requires knowledge about population structure and the strength of migratory connectivity. The latter likely affects the degree to which populations are locally adapted and differentiated, and both may affect their ability to adapt to environmental changes. Western Sandpipers (Calidris mauri) are long-distance migrants that exhibit latitudinal differences in morphology and life-history strategies across their non-breeding range. The differential migration patterns in this small shorebird species could be based on population genetic differences or phenotypic plasticity. I investigated the population structure of Western Sandpipers, and its implications for differential migration and conservation, across their global range using genetic, morphometric and acoustic data. I recorded and analyzed breeding male vocalizations, conducted playback experiments and collected genetic and morphometric data across breeding and non-breeding ranges. Amplified Fragment Length Polymorphisms (AFLP) and mtDNA sequence data indicated low, but significant genetic population structure across breeding and non-breeding ranges. I found evidence for an evolutionarily recent demographic expansion (mtDNA), for latitudinal clines in genetic scores (AFLP) and for isolation by distance (AFLP). A scan of thousands of AFLP markers in a pooled lane approach revealed no fixed genetic differences among juveniles with a postulated difference in life-history strategy or migratory direction. Songs, but not alarm calls, varied geographically, decreasing in length and increasing in fundamental frequencies from southern to northern breeding sites. These geographic differences were sufficiently large to allow males to discriminate between local and non-local songs and hence are potentially biologically relevant. AFLP scores and vocalization frequencies showed correlations with body size. In conjunction, my results suggest that Western Sandpipers underwent a recent range and population expansion that has resulted in divergence patterns that are primarily isolation by distance driven. My results suggest interrelationships among genetic population structure, morphology and latitudinal segregation. While populations were not sufficiently distinct to allow for assignment tests, the latitudinal gradients found across both the breeding and non-breeding grounds are suggestive of a gradual ’chain’-like migration pattern, but do not indicate strong migratory connectivity. Consequently, conservation strategies could focus on the protection of major sites at different latitudes.

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

Assessment of endocrine disrupting chemicals in water and sediment samples from British Columbia, Canada

Author: 
Date created: 
2015-11-25
Abstract: 

Endocrine Disrupting Chemicals (EDCs) can interfere with the endogenous hormone system that leads to adverse health effects in the exposed population of wildlife and humans. Thus, the objective of the present study was to identify and quantify four different classes of EDCs, i.e. estrogens, androgens, glucocorticoids and aryl hydrocarbon receptor agonists in the water and sediment samples from 22 sites in British Columbia. All sites were bodies of water that are impacted by agricultural and/or urban activities. Samples were collected during the dry and rainy periods at each sampling location. EDC levels were higher in sediment than in water across all sites. The highest activity was found using the glucocorticoid assay compared to the other two steroid hormone assays. Chemical analysis was performed using gas chromatography-mass spectrometry on a subset of samples to identify specific compounds in the mixture. The chemicals identified were 17β-estradiol, estrone, bisphenol A and dehydroabietic acid. Findings from this study may be used as benchmark levels for future studies in the same region.

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

Acute but not chronic effects of predator presence on song sparrow (Melospiza melodia) singing behaviour

Date created: 
2015-09-15
Abstract: 

The North American Breeding Bird Survey (BBS) indicates long term declines for many songbird species. As surveys are based partially on auditory cues, a change in the song rate could affect survey numbers. Here I test the hypothesis that the danger posed by raptor presence affects songbird singing behaviour. I measured the singing behaviour of song sparrows (Melospiza melodia) in relation to both chronic (active Cooper’s hawk Accipiter cooperii nest nearby) and acute (playback of hawk calls) predator exposure. I found no evidence for a chronic effect, but song sparrows reduced their singing rate by 37.5% in the minutes after acute exposure. There was no reduction in response to control playbacks. My results suggest that the BBS census declines of songbirds could potentially be partially accounted for by a reduction in song as raptor populations recovered after the 1973 ban on DDT.

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

Beauty in the Eyes of the Beholders: Colour Vision and Mate Choice in the Family Poeciliidae

Date created: 
2015-09-21
Abstract: 

Sexual selection plays a major role in numerous aspects of evolution. Many models have attempted to explain how mate preferences evolve both across populations within a species and across species. ‘Sensory bias’ predicts that the traits involved in mate choice will co-evolve with the tuning of the sensory systems responsible for detecting such traits. The family Poeciliidae is a classic system for studies of mate choice and provides an excellent opportunity to examine the co-evolution of preference for colour traits and the sensory system detecting such traits: colour vision. In this dissertation, I present a body of work investigating how colour vision differs across species and populations, thus exploring the potential role sensory systems have in shaping mate preferences. To do this, I focus on the opsin genes, which play a predominant role in tuning the wavelength sensitivity of cone cells – the detectors for colour vision. I found the Long Wavelength Sensitive opsins (detecting red/orange colours) experience high rates of gene conversion due to their genomic architecture. The effects of conversion may be influenced by the importance of red/orange in mate choice decisions. While traditional models of duplication and divergence suggest sensory repertoire expansion occurs slowly, I found hybridization can expand sensory repertoires in one generation. I have termed this process: Hybrid Sensory Expansion. I then focus on one species to show that differences in visual tuning (gene expression and allele frequency) co-vary with mate preferences across populations in a manner that is consistent with the Sensory Exploitation (SE) model for the evolution of female mate preferences. However, I go on to find that closely related, highly sympatric species differ in colour vision more across populations than across species within populations on mainland South America. This suggests that while SE could explain differences in mate preference across populations, it may not scale up to explain species level differences as generally assumed. Taken together, these results show that the evolution of visual tuning may not always evolve through traditional mutation-selection models and that visual systems are far more variable across populations within species than generally assumed.

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

PLR-1, a putative E3 ubiquitin ligase and AEX-3, the GDP/GTP exchange factor homologue for RAB-3, respectively regulate cell polarity and axon navigation of the ventral nerve cord pioneer AVG in Caenorhabditis elegans

Author: 
Date created: 
2015-10-27
Abstract: 

Accurate and precise neuronal circuit formation is the hallmark of a functional nervous system. During development neurons extend axons and dendrites that have to reach their appropriate targets. This process is highly regulated and is achieved by using a set of conserved guidance cues and receptors. ‘Pioneer’ neurons extend axons first and are closely followed by the late outgrowing axons called ‘followers’ to extend upon. In Caenorhabditis elegans, the AVG axon pioneers the right axon tract of the ventral nerve cord (VNC). The molecular basis for the navigation of the AVG axon is largely unknown. The aim of this study was to identify novel regulators of AVG axon navigation. In genetic screens for AVG axon outgrowth and guidance defects we identified alleles of plr-1 that reversed the polarity of AVG neuron and also caused outgrowth and navigation defects in the AVG axon and several other neuronal and non-neuronal cells. plr-1 is predicted to encode a putative transmembrane E3 ligase, widely expressed during the development including in the AVG neuron. plr-1 and its vertebrate homologues control Wnt signalling by removing the frizzled receptors from the cell surface. We have shown that mutations in a gene reducing Wnt-signalling as well as mutations in unc-53 and unc-73 suppress the AVG polarity reversal defects, but not the other defects seen in plr-1 mutants. This suggests that plr-1 has Wnt dependent and Wnt independent functions.Simple genetic screens have not yielded mutants with penetrant AVG axon navigation defects except plr-1. In enhancer screens for AVG axon navigation defects in a nid-1 mutant background we isolated several candidate mutants including an allele of aex-3. aex-3 mutant animals show penetrant AVG axon navigation defects as well as follower axon navigation defects in the VNC, which are nid-1 dependent. AEX-3 is a GDP/GTP exchange factor for RAB-3 and RAB-27 GTPases. Our genetic interaction data suggests that AEX-3 regulates RAB-3 and not RAB-27. We also show that aex-3 acts along with unc-31/CAPS, ida-1/IA-2 and unc-64/Syntaxin in the same genetic pathway for AVG navigation. Moreover, our genetic interaction data suggests that AEX-3 might regulate the transport of the Netrin receptor UNC-5 in the growth cone.

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

Foraging and Communication Ecology of the Common Green Bottle Fly, Lucilia sericata (Meigen) (Diptera: Calliphoridae)

Author: 
Date created: 
2015-09-28
Abstract: 

In accordance with their physiological state, adults of Lucilia sericata must locate mates, food and oviposition resources. I investigated the cues they exploit to obtain these resources. As females require a protein-rich diet and frequently visit pollen/protein-rich flowers, I studied the effects of generic floral scent and colour cues, and of Oxeye daisy-specific cues, on foraging decisions by flies. I show that (1) flies in the presence of generic floral scent respond more strongly to a uniformly yellow cue than to most other uniform colour cues (green, white, black, blue, red); (2) daisy scent enhances the attractiveness of a yellow cue; and (3) pollen with adequate moisture content facilitates oocyte maturation of flies. Males respond to long-range mate recognition cues. I show that (1) wing movement of females is a visual mate recognition cue, (2) wings are thin-film reflectors that produce light flashes during movement, and (3) light flashes are absent under diffuse light. Wings also produce stable structural colours, UV- and polarized-light reflections, but these optic effects per se are insufficiently gender-specific and thus do not appear to serve as mate recognition cues. Instead, the frequency of light flashes reflected off moving female wings may allow males to recognize prospective mates.Foraging decisions by females change in accordance with their physiological state. Protein-hungry females respond to feces and carrion, whereas protein-fed gravid females with mature oocytes respond only to fresh carrion. Gravid females discriminate against aging carrion (which is detrimental to their offspring) as soon as it produces appreciable amounts of indole, which is an abundant feces semiochemical and apparently serves as an indicator of a food rather than an oviposition resource. Gravid females locate recently deceased vertebrates as oviposition sites in response to dimethyl trisulfide and carrion-type colour cues (dark red, black), indicating that a bimodal cue complex signifies suitable oviposition sites.Oviposition site-seeking females do not respond to an oviposition pheromone. Instead, they coopt semiochemicals associated with feeding flies as resource indicators. This conclusion is based on data that gravid or non-gravid females ovipositing and/or feeding on oviposition resources enhance their attractiveness to gravid and non-gravid females.

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