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

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Preserving the opportunity to expand: conservation implications of ancient DNA

Author: 
Date created: 
2010-11-15
Abstract: 

The application ancient genetic information to management practices can provide a critical understanding of species of conservation concern. Utilizing the interpretations from two ancient DNA datasets I assess conservation implications for the locally threatened caribou (Rangifer tarandus) and the globally endangered saiga antelope (Saiga tatarica). Using Bayesian Inference to assess herd affinity of ancient caribou, I identify a dynamic history, including an unexpected lineage replacement event coincident with the deposition of the White River tephra (~1,000yrsBP). I then combine a recently published saiga aDNA dataset identifying a 65-75% population decline likely related to the glacial-interglacial transition at the Pleistocene-Holocene boundary with recent observations of frequent periods of sudden die-off to imply a life history inherently susceptible to dramatic population swings. Accordingly, conservation strategies for these two dynamic northern species must acknowledge both the likelihood of sudden declines, and the necessity for expansion and recovery.

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

Effect of larval environment on some life history parameters in anopheles gambiae s.s. (diptera:culicidae))

Date created: 
2010-08-13
Abstract: 

The effects of larval density, nutrition and cannibalism risk on some life history parameters of Anopheles gambiae larvae were evaluated in the laboratory. Adult body size was inversely correlated with larval density whereas larval mortality and mean age at pupation varied across experiments. When density increased, the secondary sex ratio shifted toward female bias. Effects of different types of nutrition on larval life were compared by providing larvae with algae Chaetophora sp., fish food or both. The fish food generated the highest mortality, longest developmental time and produced smaller adults. Mortality and developmental time was higher with algae diet. With regard to somatic body reserves, algae-fed larvae had more sugar and lipid and full diet mosquitoes had more glycogen and protein reserves. In a separate set of experiments with cannibalism pressure the mortality rate and developmental time decreased but larval activity and body size increased compared to risk-free larvae.

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

Quantitative links between Pacific salmon and freshwater ecosystem structure

Author: 
Date created: 
2010-07-22
Abstract: 

Spawning Pacific salmon affect freshwater ecosystems through substrate disturbance and the marine-derived nutrient pulse they deliver. I examined relations between a) salmon abundance and stream periphyton after spawning, and b) salmon abundance and invertebrate communities in the spring. I used 24 sockeye salmon (Oncorhynchus nerka) spawning streams in central British Columbia, Canada. After spawning, periphyton was enriched in salmon nitrogen but abundance was negatively related to salmon abundance, likely from substrate disturbance during spawning. Thus nutrient enrichment does not always translate into increased abundance. In the spring, the abundance of grazing mayflies and predatory stoneflies was positively related to salmon abundance, probably from increased algal growth caused by salmon nutrients delivered in previous years. Thus the salmon nutrient pulse can have ecological effects that extend long after spawning. The influence of spawning salmon on freshwater ecosystems differs through the year, across ecosystem components, and in relation to salmon abundance.

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

Functional ecology and evolution of sockeye salmon (Oncorhynchus nerka) life history in the dynamic environments of Aniakchak and Katmai

Date created: 
2010-07-23
Abstract: 

Sockeye salmon exhibit great ecological diversity among populations. During the last glacial period, ice covered much of what today are freshwater habitats. As the glaciers retreated, sockeye colonized new freshwater habitats from relatively few glacial refugia. Colonizing populations adapted at a very fine spatial scale among river drainages, tributaries and lakes within rivers, and even divergent habitats within lakes. All of this occurred within the past 15,000 years since the last glacial maximum. This resulted in many thousands of locally adapted populations and a grand display of the process of evolution within a species. In this dissertation, I explore genetic and phenotypic diversity in the dynamic and changing environments of Aniakchak National Monument and Preserve as well as Katmai National Park in southwest Alaska. Recent eruptions at Aniakchak include events 500 and 79 years ago and the caldera presently contains sockeye salmon populations spawning in different habitats. Using genetic tools, I find that ecological divergence occurred in egg size and body depth in less than 500 years or 100 generations. Secondly, sockeye salmon exhibit a broad life history division by rearing habitat; some populations rearing in lakes (lake-type sockeye) and others rearing in rivers (riverine sockeye). I describe differences in juvenile body shape and relate these to differences in foraging strategy and predation. Finally, I apply gene expression technology to understand the life history differences and the molecular trade-offs in sockeye salmon populations. I start with a review of recent technological advances that relate gene expression to ecology, evolution, and the formation and maintenance of new species. I then relate functional, expressed genes in muscle tissue to lake-type and riverine juvenile populations. This provides an ecological context to genes that are normally only described in artificial situations. Taken together, this work furthers the understanding of the interaction of ecology and evolution, from genes to populations to broad life history types.

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

Naturally occurring variation in virulence in Aspergillus

Date created: 
2010-05-11
Abstract: 

Naturally-occurring variation in virulence was studied in the opportunistic fungal pathogens, Aspergillus nidulans and Aspergillus fumigatus. I measured variation in growth on Neiland’s solid agar medium and virulence in an insect model host, Galleria mellonella, in 92 A. nidulans recombinant strains generated by a cross between two wild type strains. A weak positive correlation was found between rate of growth and virulence. No difference in virulence was found between strains with pigmented and unpigmented conidia, even though conidial pigments are thought to be an important defence against the innate immune system. In 20 A. fumigatus wild type strains, isolates of the MAT 1-1 mating type were significantly more virulent in G. mellonella compared to MAT 1-2 mating type isolates. Surprisingly, environmental isolates were significantly more virulent than clinical isolates. My work provides the first step towards identifying the genes underlying virulence using quantitative trait locus mapping.

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

Detection, characterization and conservation of evolutionarily isolated species

Date created: 
2010-02-10
Abstract: 

Most published phylogenetic trees are imbalanced, meaning that while many species have many close relatives a minority have few. Importantly, these few isolated species have few closely-related species with which they can share the burden of their slice of the world's biodiversity, i.e. they are non-redundant. Of the ten or so published measures of evolutionary isolation, several overlap in the information they contain and therefore need not be used concurrently in analyses. Interestingly, isolated species that score highly using many such measures are generally overdispersed in a phylogeny, and therefore might collectively represent the shared branches contained within that phylogeny. This property is important if we consider isolated species as targets for increased conservation attention under an 'agony of choice' framework. One way to target them is using the novel 'expected loss' method, which multiplies our 'value' measure (evolutionary isolation) with an 'urgency' rating (threat of extinction) to prioritise those species that are both isolated and threatened. I show that evolutionary isolation and expected loss in primates is correlated with how far from the mean a species scores for many different biological, ecological and geographical traits, suggesting perhaps some link between evolutionary isolation and ecological distinctiveness. Lastly, evolutionarily isolated species are, in general, found in the most species rich areas of the world with geographic isolation playing a limited role in explaining their distribution. Overall, evolutionarily isolated species are both phylogenetically infrequent and morphologically unusual suggesting they may well warrant greater future conservation attention

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

Molecular genetic, biochemical & anatomical characterization of monoterpenoid synthesis in western redcedar (Thuja plicata).

Author: 
Date created: 
2011-08-25
Abstract: 

Western redcedar (Thuja plicata) is an economically and culturally important tree species to British Columbia (BC). Wood from T. plicata is highly valued for being light weight, dimensionally stable and resistant to rot. However, T. plicata silviculture is not without problems. Reforestation with T. plicata is expensive due to extensive browsing of seedlings by ungulates. Also, woody stems of mature trees can be susceptible to heartwood rotting fungi. Resistance to ungulate browsing positively correlates with the overall abundance of monoterpenoids in foliage, notably the oxygenated monoterpenoid α-thujone, while heartwood rot resistance is relative to the amount of tropolones, a class of compounds derived from monoterpenes, in the wood. To better understand factors that affect monoterpenoid content in young T. plicata foliage, leaves were examined for ontogenetic changes in morphology, anatomy and monoterpenoid content during the first year of growth. The two morphologically different leaf types, needles and scales, possess different monoterpenoid storage structures and very different chemical contents, punctuated by the absence of α-thujone in needles. To determine the genetic basis for the production of foliar monoterpenoids, a transcriptome database was generated from which to draw candidate genes. Complementary DNA profiling was used to determine the differential gene expression between a natural variant lacking foliar monoterpenoids and wild type tree. This analysis yielded more than 600 genes with low or undetectable expression in foliage of the variant, and up to 10000-fold higher transcript abundance in foliage with resin glands. Amongst the candidate genes was a single monoterpene synthase gene that produced sabinene, the likely monoterpene precursor to α-thujone, as its major product in vitro. A second, more comprehensive, transcriptome was generated to identify additional monoterpene synthases from other tissues. Eleven terpene synthase gene fragments were identified, one of which was found to produce terpinolene, the likely precursor of the tropolone β-thujaplicin. The transcriptome datasets together with the characterization of monoterpene synthases represents a major first step into understanding the genetics of T. plicata terpenoid based defenses.

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

Competition between parasitoids of the cabbage seedpod weevil: effects on sex ratios and consequences for biological control

Date created: 
2011-08-05
Abstract: 

In any biological control program, it is important to have an in-depth knowledge of the ecosystem. Competition between natural enemies can have unpredictable effects, potentially disrupting biological control of the pest in question. Trichomalus perfectus and Mesopolobus morys are two parasitoids of the cabbage seedpod weevil. Both are candidates for introduction as classical biological control agents in Canada. I examined the effects of intra- and interspecific parasitoid competition in field and laboratory experiments. I found that a multiple-species introduction would not be more effective at controlling pest populations than a single-species introduction. I also found T. perfectus produced a female-biased offspring sex ratio in response to intraspecific competition. Using a theoretical approach, I explored how this shift might affect parasitoid-host population dynamics and biological control, incorporating the influence of increased virginity in the parasitoid population.

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

Expression levels and localization of pregnancy-associated plasma protein-A2 (PAPP-A2) in mouse placenta and embryo

Author: 
Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2009
Abstract: 

Pregnancy-associated plasma protein-A2 (PAPP-A2) is a metalloproteinase that specifically cleaves insulin-like growth factor binding protein-5 (IGFBP-5), a major modulator of insulin-like growth factor (IGF) bioavailability. Among several murine tissues surveyed, PAPP-A2 is most highly expressed in the placenta, and is also present in pregnancy serum and embryo. In the placenta, PAPP-A2 is localized in the junctional zone, where its degradation of IGFBP-5 may lead to the release of IGFs and so promote the development of the fetal portion of the placenta into the uterine wall. These expression patterns suggest that PAPP-A2 may play important roles during murine pregnancy. Cloning of the gene to further investigate its biochemical actions and allelic variation was also attempted. This work offers insight into the potential importance of a poorly-understood protein which may play crucial roles during pregnancy and fetal development in both mice and humans.

Document type: 
Thesis
File(s): 
Department: 
Biological Sciences
Thesis type: 
Thesis

The behavioural ecology of trophic egg-laying

Author: 
Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2004
Document type: 
Thesis
File(s): 
Senior supervisor: 
Bernard D. Roitberg
Department: 
Science: Department of Biological Sciences
Thesis type: 
Thesis (M.Sc.)