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

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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.

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.