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

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Quantifying the abundance, distribution and behaviour of a generalist marine consumer, the loggerhead turtle, in coastal foraging habitat

Date created: 
2011-04-05
Abstract: 

Conservation of large-bodied marine taxa, many of which have undergone population declines, is often hindered by difficulty in quantifying spatiotemporal patterns of abundance. This is especially true for diving species that spend little time at the surface, and is largely responsible for gaps in our understanding of the habits of highly migratory, long-lived marine turtles in coastal foraging areas. Here, I use a variety of field and analytical techniques to study these elusive ectotherms on a foraging ground, focusing on loggerhead turtles (Caretta caretta) in Shark Bay, Western Australia. First, I combine stable isotope analysis, animal-borne video and mark-recapture data to describe loggerhead foraging ecology. Low stable isotope (δ13C and δ15N) variance in slow-turnover tissue, particularly among large individuals, combined with evidence of a general diet and strong fidelity to a foraging location suggest that adult loggerheads in Shark Bay are foraging generalists and site specialists. While isotopic evidence of polymodal foraging has been found among females on nesting grounds, this may reflect isotopic characteristics of preferred migratory routes or foraging habitat as opposed to prey specialization within foraging areas. Subsequently, I focus on an important methodological problem in population ecology: detection probability during abundance surveys. During transects for long-diving taxa (e.g., marine turtles, beaked whales) a large proportion of the population will be missed because they are submerged, leading to ‘availability bias’ in count data. I collected dive data for loggerhead and green turtles (Chelonia mydas) and demonstrated that dive-surfacing patterns were highly heterogeneous and correlated with water temperature and habitat depth. Current approaches do not incorporate diving variability, without which abundance indices can be biased and spatiotemporal comparisons unreliable. For example, in seasonal environments marine turtle counts often decrease in colder months. Usually interpreted as emigration, this may also reflect reduced availability (extended dive times), leading to misinterpretation of local population dynamics. Finally, Bayesian methods of incorporating diving variability are applied to survey data, revealing that seasonality, habitat depth and regional characteristics drive variation in loggerhead distribution. Loggerhead density was stable over ten years, and the foraging population in Shark Bay may be substantially larger than believed.

Document type: 
Thesis
Senior supervisor: 
Dr. Lawrence Dill
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

Impacts of salmon on estuarine birds

Author: 
Date created: 
2011-04-06
Abstract: 

Salmon (Oncorhynchus spp.) that spawn around the Pacific Rim subsidize coastal ecosystems with marine-derived nutrients. I examined effects of (1) salmon biomass availability for scavenging birds in the fall, and (2) the stored salmon nutrients on bird assemblages in the summer, while accounting for the influences of other environmental variables. Over two years, I studied 17 estuaries in fall and 21 estuaries in summer, which varied across a range of spawning salmon biomasses. I discovered that many aspects of scavenging and breeding bird abundance and diversity were strongly related to salmon biomass and landscape features. Overall, findings suggest that nutrients from salmon are important to avian consumers through both indirect and direct pathways and point to the possibility of using birds as indicators of salmon nutrient input to watersheds.

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

Development of mutation-based breeding technology in forest tree species

Author: 
Date created: 
2011-03-15
Abstract: 

Agricultural breeding based on phenotypic selection of desired variants in self-fertilized populations has been highly successful. This approach has not been applied successfully to forest trees due to the constraints from long generation times and difficulties with controlled large-scale self-fertilization. Novel technologies allow identification of mutants based on DNA sequence deviations in heterozygous mutants, potentially circumventing the need for identification based on phenotype. To test this approach, we generated >6000 poplar trees from mutagenized calli and screened for genetic variants in targeted genes using TILLING technology. While we found genetic variants, DNA sequencing suggested that they were due to natural rather than induced genetic variation. As an alternative approach, we tested mutagenesis of willow pollen and generated a mutant population. We thereafter used novel DNA sequencing technology to screen for genetic variants in targeted loci. This approach identified potential mutants that cannot be explained by background natural variation.

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

Plant-derived compounds: acute toxicity, synergism, and effects on insect enzyme activity and flight motor responses.

Author: 
Date created: 
2011-01-21
Abstract: 

Botanical extracts may contain compounds that have insecticidal properties that may be developed as inexpensive insecticides. In this thesis, I used a series of techniques to identify the acute toxicities and modes of action of plant-derived compounds against the Yellow Fever mosquito Aedes aegypti and the blowfly Phaenicia sericata. Initially I evaluated the acute toxicity of 16 phytochemicals on aquatic and terrestrial insects alone or with the synergist piperonyl butoxide (PBO) to quantify their lethal and sublethal effects. From this study 5 compounds, thymol, eugenol, pulegone, α-terpineol and citronellal, were selected for further study. I then evaluated the biochemical mechanisms underlying the activity of these phytochemicals and the basis of their increased toxicity in the presence of PBO. These phytochemicals affected the biotransformational capacity of these insects to detoxify the compounds, and their effects were enhanced by PBO. I then developed an electrophysiological system to evaluate the physiological effects of the plant-derived compounds and several commercially available insecticides on flight muscle impulses and wing beat signals of the blowfly, P. sericata. These compounds readily penetrate the insect cuticle and interfere with flight muscle and/or central nervous system function. All 5 compounds depressed flight-associated responses, and acted similarly to compounds that block sodium channels and facilitate Ɣ-amino butyric acid (GABA) action. I compared these responses to those induced by several synthetic insecticides whose mode of action is well known to allow us to make a more precise prediction of how the 5 compounds affect the target insects. I then evaluated the effect of the 5 phytochemicals, and octopamine on the octopaminergic system of insects by comparing the production of a second messenger molecule, cAMP, after treatment. Some monoterpenoids interfere with the octopaminergic system by targeting the octopamine receptors. The acute toxicity observed in Ae. aegypti and P. sericata may be the collective result of these compounds on complex biological systems in the insect and may depend on their structure, concentration, or exposure time. The overall results indicate that plant-derived compounds directly and indirectly affect aspects of insect physiology and could possibly be developed as new insecticides.

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

Prospecting decisions and habitat selection by a nocturnal burrow-nesting seabird

Date created: 
2011-03-11
Abstract: 

Introduced predators have caused declines and extirpations of many populations of insular avifauna, especially nocturnal burrow-nesting seabirds. The successful eradication of these introduced predators has resulted in recovery of some species but not others, the reasons why are not understood. The objectives of my study were to understand the recovery of seabird populations after the removal of an introduced predator by studying the processes underlying the formation of new colonies and the expansions of colonies after establishment. Specifically I asked: 1) how nocturnal seabird colony area and population size change with time and across a metapopulation; and 2) how prospectors choose suitable breeding habitat by looking at habitat selection and use of public information. Using an information theoretic approach I found 1) regional differences in both colony area and population density over time and between island groups; 2a) Ancient Murrelets breeding in Haida Gwaii exhibit a high degree of plasticity in their use of available breeding habitats and the amount of suitable habitat at Langara Island has not changed between 1981-2007; 2b) differences in colony attendance decisions between sites, but prospectors were not conclusively more risk averse than breeders; and 2c) Ancient Murrelet prospector activity increased during playback of conspecific vocalizations, but found no preference for burrows with olfactory and/or visual cues over those left empty. Overall, I conclude that although Ancient Murrelet life-history may prolong recovery times, both recovery and recolonization of restored breeding sites are plausible and using playbacks of conspecific vocalizations is an effective method to attract prospecting individuals to those sites.

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

Brood parasitism, reproductive success, and survival in Yellow Warblers

Date created: 
2011-01-18
Abstract: 

Understanding mechanisms responsible for population declines of migratory birds requires knowledge of factors limiting population growth at all stages of the annual cycle. Interspecific brood parasites are known to have negative, short-term impacts on the reproductive success of their hosts and could have longer-term costs that reduce survival. I used an information theoretic approach to examine the age-specific costs of brood parasitism in Yellow Warblers (Dendroica petechia), a common host of Brown-headed Cowbirds (Molothrus ater) in Revelstoke, British Columbia. Age did not mitigate the costs of brood parasitism that influenced each stage of the nesting cycle and reduced annual productivity. However, there was little evidence that brood parasitism influenced the survival of yearling or older Warblers. Adult survival was influenced by climate patterns, El Niño/La Niña, that influence conditions during spring migration, demonstrating the importance of this phase of the life-cycle for population dynamics of Neotropical migrants.

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

The microtubule associated protein end binding 1 and root responses to mechanical/gravity stimuli

Author: 
Date created: 
2011-01-11
Abstract: 

Do microtubules influence growth responses to environmental stimuli in plants? Microtubules (MTs) have numerous roles in plant development and these functions are assisted by Microtubule Associated Proteins (MAPs). To further explore MT function we study a MAP called END BINDING 1 (EB1). Previous analysis of eb1 mutants indicates root defects in responses to mechanical stimulation (MS) and/or gravity. To determine whether EB1 activity contributes to root responses to MS or gravity or both, two approaches were taken. First, I analyze the effects of altering the type and amount of MS perceived by the root. Second, I analyzed double mutants between eb1b and plants carrying mutations in genes associated with responses to MS and gravity. Results from both approaches suggest that EB1 has a role in root responses to MS and an indirect role in responses to gravity.

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

Maternal allocation decisions impacted by variable ecological conditions in a solitary bee: behavioural ecology perspectives

Date created: 
2010-12-01
Abstract: 

Parents can invest in offspring through a variety of behaviours. I use a combination of theoretical and empirical studies to examine how resource and sex allocation decisions toward offspring were altered in response to changing ecological conditions. My empirical work was done using the haplodiploid alfalfa leafcutter bee (Megachile rotundata), where sex of offspring can be controlled and mothers do all offspring provisioning. My theoretical research demonstrated no single factor determining sex allocation; instead, there is some ‘optimal balance’ between factors. Empirical work results suggest a similar situation. All three experiments demonstrated different factors that impacted sex allocation decisions: flight distance to resources, resource levels, and local population density. Longer flight distances resulted in fewer offspring produced throughout the season, but a greater proportion of daughters produced in the first half of the season and a lower proportion of daughters in the second half of the season compared to mothers with short distance to resources. Lower resource-level treatments had similar effects during the first half of the season as with long flight distance; however, during the second half mothers continued to produce a greater proportion of daughters under low resource conditions compared to high. Lower local population density resulted in both a greater proportion of daughters being produced as well as a greater number of offspring per individual nest compared with high-density conditions. We also addressed two other allocation decisions. We used flight distance to address the question of what foraging currency mothers maximize when collecting resources for offspring. We found mothers increased load size with increased flight distance, suggesting that they are behaving in a manner that maximizes efficiency as opposed to net rate of energy intake. In regards to nest defence, mothers slightly increased nest defense as the nest size increased. However, unlike traditionally studied organisms, this increase in defense continued more steeply until the nest was basically completed and sealed, after which defense dropped suddenly. In combination, these studies contribute to our basic understanding of offspring allocation decisions in solitary organisms.

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

Biotransformation and modelled bioconcentration factors (BCFs) of select hydrophobic organic compounds using rainbow trout hepatocytes

Date created: 
2010-12-10
Abstract: 

Biotransformation is an important factor in determining the extent that chemicals bioaccumulate. Since most anthropogenic chemicals lack data on biotransformation, this research used rainbow trout isolated hepatocytes to determine the depletion rates of several hydrophobic chemicals (benzo(a)pyrene, chrysene, 9-methylanthracene, polychlorinatedbiphenyl-153). These results were extrapolated to the organism level and bioconcentration factors (BCFs) modelled. Since concurrent chemical exposure and temperature modify biotransformation, they were investigated for effects on modelled BCF values. Depletion rate constants were generally lower for chemical mixture than for individual incubations. At acclimation temperatures, chrysene biotransformation exhibited thermal compensation; for benzo(a)pyrene and 9-methylanthracene, lower acclimation temperature resulted in lower rate constants and increased BCFs. Acute temperature increases significantly increased depletion rate constants for benzo(a)pyrene and chrysene, and decreased BCF values. Acute temperature decreases had no effect. This research highlights the importance of considering environmental factors in evaluating the bioaccumulative potential of chemicals.

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

The Flamingo ortholog FMI-1 and the CDK8 Mediator subcomplex regulate axon navigation in Caenorhabditis elegans

Author: 
Date created: 
2010-12-07
Abstract: 

The nervous system is a highly complex organ system that controls the body’s physiology and behaviour. It is our place of thought and consciousness. Neurons are the functional units of the nervous system, which send out cellular processes, dendrites and axons, to connect to other neurons and muscle cells. The correct interconnection of neurons or neurons and muscles is of critical importance for nervous system function. Neuronal circuits are established during embryonic development, when neuronal processes navigate to their target areas and establish synapses with appropriate partner cells. Early outgrowing axons (pioneers) establish the main axon tracts. Later outgrowing axons (followers) frequently extend along these previously established axon tracts. We use the roundworm Caenorhabditis elegans to identify and characterize novel genes regulating axon pathfinding. The aim of this study was to identify and characterize two genes previously isolated in genetic screens for axonal defects. The first was identified as the ‘non-classical’ cadherin FMI-1, a member of the cadherin superfamily of cell adhesion molecules. Loss of FMI-1 caused strong axon navigation defects of pioneer and follower axons in the ventral nerve cord. Follower axons, which exclusively depend on pioneer axons for correct navigation, frequently separated from the pioneer, defining a novel role for this highly conserved molecule. We found that follower axon navigation depended on the extracellular but not on the intracellular domain, suggesting that FMI-1 primarily mediates adhesion between pioneer and follower axons. The study of FMI-1, presented in chapter two, contributes to our understanding of the molecular basis of pioneer-mediated navigation of follower axons. The second gene encoded a subunit of the Mediator of transcriptional regulation, LET-19/MDT-13. Further analysis revealed that several Mediator subunits, including the complete CDK8 subcomplex, participate in regulating axon navigation in subsets of neurons. Mutations in Mediator subunits likely change the expression of genes required for correct axon navigation. For example, during dorsal navigation of motoneuron axons, the Mediator complex is required to suppress the function of the SAX-3/ROBO guidance receptor. These results, described in chapter three, highlight the importance of transcriptional control for correct axon navigation.

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