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

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Theoretical and experimental studies on behavioral syndromes in aphids

Date created: 
2014-07-24
Abstract: 

Individuals’ behaviors can be correlated across time and contexts, in a phenomenon now known as behavioral syndromes. Using an experimental approach, I demonstrate that genetically identical pea aphids are highly repeatable in multiple behavioral traits, however these behaviors are uncorrelated. Then using a state variable model I show that asymmetries in size can maintain a hierarchy between least and most bold individuals in foraging intensity across development. However, individuals that complete compensatory growth show an inversion in the rank-order of foraging activity between early and late development (ie individuals that are the boldest early in life are less bold than their “timid” counterparts late in life). In conclusion, I demonstrate both theoretically and empirically that non-genetic differences are capable of explaining repeatability in the expression of a single behavior; however I found no evidence that non-genetic mechanisms can correlations between multiple behaviors.

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

The impact of nutrition on within and trans-generational disease resistance in the cabbage looper, Trichoplusia ni

Author: 
Date created: 
2014-07-30
Abstract: 

Parasites and pathogens are ubiquitous, and pose a threat to all living organisms. Investment in resistance mechanisms to fight parasite challenge can be costly, often resulting in trade-offs with other life-history traits. Host nutrition can alter the availability of resources to invest in resistance mechanisms and influence host-parasite interactions and their outcomes. I investigated the impact of nutrition on disease resistance in the cabbage looper, Trichoplusia ni. I assessed the role of dietary macronutrients on the expression of fitness costs exhibited by a T. ni strain that has evolved resistance to the bacterial pathogen, Bacillus thuringiensis (Bt). Reduced pupal weight and growth rate, which are fitness costs associated with Bt-resistance, resulted from reduced food intake rather than impaired macronutrient utilization. When given a choice, Bt-resistant T. ni self-composed a higher ratio of protein to carbohydrate (P:C ratio) than Bt-susceptible T. ni, allowing males to eliminate a fitness cost (reduced pupal weight), but not females. Next, I investigated the interaction between host nutrition and another key environmental factor, temperature, on the interaction between T. ni and two species of baculoviruses differing in host range (TnSNPV, narrow range; AcMNPV, broad range). Optimal performance of T. ni shifted to higher P:C ratios when challenged by either virus as survival increased with dietary protein content. This effect was strongly affected by temperature when challenged by AcMNPV but not TnSNPV. Virus performance was also differentially affected by the host’s environmental condition, such that AcMNPV had a broader peak of optimal performance (combined measure of host mortality and virus production) across environmental conditions than TnSNPV. Lastly, I examined the impact of nutritional stress on the ability of Bt-challenged T. ni to prime the immune system of their offspring. If parental T. ni experienced only nutritional stress or Bt-challenge, they transferred nutritional stress tolerance or immune priming to their offspring respectively. However, as surviving each stressor is costly, when experienced simultaneously a trade-off was observed where only immune priming was transferred. This study highlights the important influence of host nutrition on host resistance to pathogens, costs associated with resistance, and pathogen virulence and growth.

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

Transgenerational effects of food quantity and quality on disease resistance in the western tent caterpillar, Malacosoma californicum pluviale

Author: 
Date created: 
2014-07-25
Abstract: 

Increasing population density may alter food quantity or quality. Dietary stressors can interact simultaneously and produce emergent fitness effects both intragenerationally and potentially transgenerationally, including changes in pathogen resistance. Western tent caterpillar (WTC) Malacosoma californicum pluviale populations undergo regular 6-11 year cycles; epizootics of nucleopolyhedrovirus (NPV) characterize population declines and may be triggered by density-related dietary changes. I tested the transgenerational interaction of three factors likely to be influenced in rising WTC populations. I manipulated foliage quantity, quality, and the presence of phylloplane bacteria provided to the parental generation and assessed NPV resistance and immunity in their offspring. Food limitation had strong impacts on life history traits of tent caterpillars. Somewhat unexpectedly, changes in foliage quality and ingestion of phylloplane bacteria had transgenerational effects on offspring, enhancing their NPV resistance and affecting expression of background pathogens. There was no evidence for increased disease susceptibility in offspring from combined parental stressors.

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

Investigating the vector competence of the house fly (Musca domestica) for Campylobacter jejuni

Author: 
Date created: 
2014-07-11
Abstract: 

Campylobacteriosis is a severe gastroenteric disease in humans caused by the bacterium, Campylobacter jejuni, typically obtained through the ingestion of contaminated poultry products. Poultry facilities become contaminated through the introduction of pathogens, including C. jejuni, by the house fly, Musca domestica. This thesis investigates the vector competence of M. domestica for C. jejuni to determine if the bacteria survive house fly metamorphosis from larva to adult, and can multiply within adult flies to enhance transmission, and whether innate immune factors of the house fly can clear C. jejuni infections. We demonstrate that M. domestica mounts an effective innate immune response that prevents transmission of C. jejuni from larva to adult, and eliminates C. jejuni from adult house fly gastrointestinal tracts within hours. We propose that M. domestica serves as a mechanical vector, rather than as a true, amplifying, biological vector. These findings will help elucidate the elusive epidemiology of campylobacteriosis.

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

Feeding in troubled waters: a comparative diet analysis of pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon during their first months at sea in the Broughton Archipelago, British Columbia

Date created: 
2014-06-10
Abstract: 

Closely related species divide shared resources to reduce interspecific competition and to allow for coexistence when resources are limiting. Upon ocean entry, juvenile pink and chum salmon coexist in mixed schools and feed on similar prey. The diet of juvenile pink and chum salmon during their first two months at sea in the coastal waters of the Broughton Archipelago, British Columbia, was described for 2003 and 2006. Full stomach rankings suggested a lack of prey limitation in both years. Stomach content analysis revealed a greater diet separation among pink and chum in 2003 than in 2006. Species specific prey preferences were observed. Electivity comparisons of prey consumed with prey available in the plankton indicated selective feeding in both species. Considering the importance of diet in the survival of juvenile salmon and ultimately in adult recruitment, an understanding of prey conditions provides insight into salmon population trends in the region.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Inigo Novales Flamarique
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

Building a better ark: theoretical and analytical approaches for managing species at the population level

Date created: 
2014-06-09
Abstract: 

Biodiversity losses and limited resources may soon call for the preservation of key populations rather than entire species. However, successful population-level management requires both an understanding of where evolutionarily distinct taxa occur on the landscape and an efficient method for prioritizing taxa based on survey data. The present study addresses these needs. I begin by investigating the genetic identity and origins of red foxes (Vulpes vulpes) in North America’s Intermountain West. I then demonstrate a new approach for prioritizing populations that extends the metrics for evolutionary isolation from phylogenetic trees to phylogenetic networks, using two example species. Patterns of genetic differentiation for red foxes are consistent with endemism or natural range expansion in the Intermountain West, making this population a potential conservation target. Heuristic networks generated for spotted owls (Strix occidentalis) and mountain pygmy-possums (Burramys parvus) show how the approach can highlight peripheral populations that may merit increased conservation attention.

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

The Influence of Intensive Land Use Types on the Foraging Distribution of Ducks Wintering in the Fraser River Delta, British Columbia

Date created: 
2014-03-21
Abstract: 

Current ecological theory states that food and danger considerations underlie patch selection. Foraging sites for the ~ 100,000 ducks wintering on the Fraser River delta, British Columbia, Canada, are embedded in a matrix of suburban and rural land use types. I investigated foraging by American wigeon (Anas Americana), mallard ( A. platyrhynchos), northern pintail (A. acuta) and green-winged teal (A. carolinensis) to test the hypothesis that features adjacent to foraging sites such as buildings or roads cast a 'shadow of danger' that reduces patch use and thus habitat carrying capacity. I measured patch use with winter-long dropping counts on transects across fields adjacent to residential areas, greenhouses, roads and berry fields. Usage was highest adjacent to greenhouses, lowest adjacent to residential areas, and intermediate adjacent to berry fields and roads. Seasonal usage of a field was steady once begun, began soonest adjacent to greenhouses, and latest adjacent to residential areas. The distribution pattern of droppings across fields showed that ducks avoided residential areas, and foraged close to greenhouses. They showed no strong distribution pattern at berry fields and roads. The measured level of activity (wildlife, people, traffic, noises, lights, etc.) was highest at residential areas and roads, and lowest at greenhouses. Patch use and seasonal usage was lower in fields bordering land uses with higher activity levels. Previous studies on wintering ducks on the Fraser River delta widely report that upland foraging is largely nocturnal, that diurnal use is restricted to roosting on flooded fields, and that crop type strongly influences field usage. In contrast, I found that nocturnal and diurnal foraging were similar, though fields were visited more often at night. Landscape-scale selection of fields was best explained (AIC) by models including field-level measures of danger and greenhouse proximity: neither available energy nor standing water were included in the most informative models. These findings are consistent with the hypothesis that danger from various land use types strongly influences the foraging distribution of wintering ducks.

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

Early marine distribution of out-migrating juvenile sockeye salmon (Oncorhynchus nerka)

Author: 
Date created: 
2013-11-20
Abstract: 

The early marine phase is a critical period for out-migrating juvenile sockeye salmon (Oncorhynchus nerka). They undergo physiological changes while entering into a new environment, and this is thought to be a period of high mortality. This study examined factors affecting swimming depth as juveniles migrated through Rivers Inlet, and compared swimming depth at the point of ocean entry and life history strategies in sockeye salmon from Rivers Inlet and nearby populations on the Central Coast of British Columbia. Most juvenile sockeye salmon swam within two meters of the ocean’s surface during their out-migration through Rivers Inlet, and were slightly deeper later in the out-migration. In addition, in a mesocosm experiment, Rivers Inlet juvenile sockeye salmon did not alter their swimming depth in response to increasing salinity at their preferred swimming depth, despite experiencing negative physiological effects when swimming in highly saline waters. Similar data on other nearby sockeye salmon populations were collected. Juvenile sockeye salmon from populations that out-migrate through brackish waters tended to be smaller than individuals from populations that leave fresh water and enter directly into highly saline marine environments, and they too tended swim within the top two to four meters of the surface. This shows that conditions in the top 4 m of the water’s surface represent actual conditions experienced by out-migrating juvenile sockeye salmon in the early marine environment and is a critically important observation in terms of understanding such issues as prey availability, the potential role of brackish surface layers in coastal fjords, lagoons and estuaries, and susceptibility to predators. These findings will inform future sampling efforts on these populations, and also suggest that these populations maintain varying life history characteristics which enable them to survive early marine conditions within the top 4 m of the ocean.

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

Current-use pesticides affect development of early life stages and timing of alevin emergence in Sockeye salmon (Oncorhynchus nerka)

Date created: 
2014-04-15
Abstract: 

The effects of two pesticides on Pacific sockeye salmon (Oncorhynchus nerka) exposed from fertilization to emergence were evaluated in a gravel-bed flume incubator, designed to simulate a natural streambed environment. Eggs were exposed to a commercial formulation of atrazine at 25 or 250 μg/L, and chlorothalonil at 0.5 or 5 μg/L, to examine effects on developmental success and timing, physical growth parameters, and biochemical indicators of growth. High chlorothalonil exposure reduced survival to hatch and increased finfold deformity incidence. All treatments resulted in reduced alevin condition factors at the time of emergence. Atrazine exposure resulted in premature hatch, while chlorothalonil exposure resulted in delayed hatch compared to controls. All treatment groups experienced premature emergence, highlighting the importance of using a gravel-bed incubator to examine this subtle but critical endpoint. These alterations in developmental success, timing and growth may alter survival of early life stages of sockeye salmon in the wild.

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

The evolutionary ecology of reproductive traits in the red-necked phalarope (Phalaropus lobatus)

Date created: 
2014-03-25
Abstract: 

Species with unusual mating systems and sex role reversal are valuable for testing theories about sexual selection and the evolution of reproductive traits that have been developed using more typical species. We used the polyandrous red-necked phalarope to test predictions about biases in primary sex ratio, factors influencing uniparental incubation and the evolution of small egg size in multi-clutching shorebird species. Egg density differed with embryo sex, and despite females being larger as adults, egg size increased with male-biased clutch sex ratio. Males had higher incubation attentiveness with greater body mass and in warmer, drier weather, while early nest initiation and increased incubation load decreased attentiveness. We detected no direct effect of experimentally manipulated incubation load on behaviour, however a greater incubation load increased the probability of nest abandonment. Our results highlight the effect of environmental conditions on reproduction in this species, and the need to reevalute our predictions about the effect of polyandrous breeding systems on reproductive traits.

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