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Western University

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Full-Text Articles in Life Sciences

The Role Of Adult Hippocampal Neurogenesis In Depression-Relevant Reward-Related Behaviours, Katrina Zmavc Dec 2019

The Role Of Adult Hippocampal Neurogenesis In Depression-Relevant Reward-Related Behaviours, Katrina Zmavc

Electronic Thesis and Dissertation Repository

The variability in the symptomatology of depressive disorders and antidepressant treatment response has led to an increased interest in the molecular, cellular, and circuit mechanisms of many aspects of affect. Evidence suggests a reduction in adult hippocampal neurogenesis (AHN) is associated with an increase in depression-like behaviour, though much of this evidence has been from studies using aversive tests (e.g., forced swim test). Here, I used touchscreen operant chambers, which allow for non-aversive and translational testing, to test the hypothesis that AHN plays a contributing role in emotion regulation. A panel of three touchscreen tests were chosen to assess ...


Arthropod Diversity In Contrasting Ontario Peatlands, Grace Carscallen Dec 2019

Arthropod Diversity In Contrasting Ontario Peatlands, Grace Carscallen

Electronic Thesis and Dissertation Repository

Peatlands are important wetland systems, but dominant macroarthropod groups endemic to peatlands and the environmental factors that affect them are poorly represented in the literature. I examined the richness, abundance, and community composition of soil and surface dwelling macroarthropods using emergence traps, peat sorting, and pitfall traps in two Ontario fens differing in water table, nutrient level, and vegetation. I found 218 arthropod morphospecies, with each site having a similar richness of emergent arthropods, but patterns of community composition differed between the two sites. The Carex (sedge) dominated site had twice as many emergent individuals, and total abundances declined dramatically ...


Narratives Of Canadian Identity At The Ultimate Fighting Championship, Jared V. Walters Dec 2019

Narratives Of Canadian Identity At The Ultimate Fighting Championship, Jared V. Walters

Electronic Thesis and Dissertation Repository

The purpose of this dissertation was to examine the use of representations and symbols of Canadian identity within the event coverage produced by the Ultimate Fighting Championship Corporation, in the context of its two key events, Ultimate Fighting Championship, and Fight Night, produced in Canada. To establish the historical context in which the sport developed in Canada, a narrative historiography of the political and legal struggles that led to the legalization and increasing popularity of Mixed Martial Arts, and the UFCC’s version of the sport, in particular. This first major part of the dissertation is contained in Study 1 ...


The Difference In A1c Of Children And Adolescents With Type 1 Diabetes Mellitus Using Carbohydrate Counting Compared To Those Using A Structured Meal Plan, Alia El Kubbe Nov 2019

The Difference In A1c Of Children And Adolescents With Type 1 Diabetes Mellitus Using Carbohydrate Counting Compared To Those Using A Structured Meal Plan, Alia El Kubbe

Electronic Thesis and Dissertation Repository

Carbohydrate counting (CHO) is a nutrition education tool used by patients with type 1 diabetes mellitus (T1DM). The primary objective was to assess glycated hemoglobin (A1C) in participants with T1DM using CHO counting vs. those using a structured meal plan (SMP). The secondary objectives were to determine if BMI-for-age, parental income, parental involvement, and mothers’ educational level were associated with their children’s glycemic control. A cross sectional study was conducted, where participants aged 4-18 years, or their parents completed a survey. Total sample size was 88 participants (77 in the CHO counting group and 11 in the SMP group ...


Recovery Following Proximal Humerus Fracture, Azar Varahrami Vigeh Nov 2019

Recovery Following Proximal Humerus Fracture, Azar Varahrami Vigeh

Electronic Thesis and Dissertation Repository

There is currently a glaring gap in the existing knowledge to address individuals’ experiences while recovering from a proximal humeral fracture (PHF). The main objective of this dissertation was to understand better how recovery is perceived by individuals after PHF. This overarching objective aligned well with the broad conceptualization of the issue at hand as those provided by the International Classification of Functioning, Disability and Health (ICF). Three inter-linked studies were conducted to provide a broader picture of recovery after PHF. The first study was a systematic review of prognostic factors predicting recovery after PHF in adults. This review demonstrated ...


The Role Of Connexin And Pannexin Large-Pore Channels In Hearing, Julia Abitbol Nov 2019

The Role Of Connexin And Pannexin Large-Pore Channels In Hearing, Julia Abitbol

Electronic Thesis and Dissertation Repository

Connexin and pannexin large-pore channels allow the regulated passage of small molecules at sites of cell-cell contacts, and from the cytosol to the extracellular milieu, respectively. Since it has been known for many years that Cx26 and Cx30 gap junction proteins are crucial in hearing we propose that Cx43 might also be important in hearing. Here we used two different genetically modified mouse lines that contain systemic Cx43 gene mutations that reduces gap junctional intercellular communication (GJIC) to examine whether Cx43 is also important for proper hearing function. Furthermore, since pannexins have also been postulated to be involved in auditory ...


Executive Dysfunction Following A Sport-Related Concussion Is Independent Of Task-Based Symptom Burden, Naila Ayala Angumba Nov 2019

Executive Dysfunction Following A Sport-Related Concussion Is Independent Of Task-Based Symptom Burden, Naila Ayala Angumba

Electronic Thesis and Dissertation Repository

The present work examined whether oculomotor deficits associated with a sport-related concussion (SRC) reflect an impairment to executive-based planning mechanisms or a task-based increase in concussion symptomology (e.g., headache, vertigo). Therefore, I employed a standardized measure of SRC symptom severity (SCAT-5), antisaccade performance and pupillometry metrics in persons with a SRC during early (i.e., initial assessment: ≤12 days post-SRC) and later (i.e., follow-up assessment: 14-30 days post-SRC) stages of recovery. In the initial assessment, the SRC group yielded longer reaction times (RT) (p=0.001), increased directional errors (p=0.002) and larger task-evoked pupil dilations (TEPD ...


The Grand Experiment: Jerome Dwight Davis And The Young Men’S Christian Association’S War Prisoner Aid Sports Programing For German Pows In Canadian Camps During World War Two, Courtney Hope Van Waas Nov 2019

The Grand Experiment: Jerome Dwight Davis And The Young Men’S Christian Association’S War Prisoner Aid Sports Programing For German Pows In Canadian Camps During World War Two, Courtney Hope Van Waas

Electronic Thesis and Dissertation Repository

Jerome Davis, head of the Young Men’s Christian Association War Prisoner Aid program, was a devout Congregationalist dedicated to providing for the basic sport and recreation endeavours of German Prisoners of War interned in Canadian POW camps during the Second World War. Having worked with German Prisoners of War in Russia during the First World War, Davis firmly believed that WWII Allies the world over needed to change their generally antagonistic point of view towards German POWs, indeed, a point of view that required “moral revisionism.” Davis believed that the vilification and demeaning status of German POWs was not ...


The Role Of Xenopus Laevis Reck In Ecm Remodeling And Tissue Patterning, Jessica Willson Nov 2019

The Role Of Xenopus Laevis Reck In Ecm Remodeling And Tissue Patterning, Jessica Willson

Electronic Thesis and Dissertation Repository

Proper cell-cell and cell-extracellular matrix (ECM) interactions are vital for cell migration and patterning of the vertebrate embryo. Matrix metalloproteinases (MMPs) and their inhibitors, reversion-inducing cysteine-rich proteins with Kazal motifs (RECK) and tissue inhibitors of metalloproteinases (TIMPs), are all differentially expressed during embryogenesis to regulate such ECM remodeling events and cell interactions. While TIMPs are a family of 4 secreted proteins that share overlapping substrate specificities of MMPs, RECK is unique in that it is a membrane-anchored MMP inhibitor that is embryonic lethal in mice. I used Xenopus laevis as a model organism to investigate the role of RECK as ...


Engineering Self-Assembling Proteins To Produce A Safe And Effective Vaccine For Porcine Reproductive And Respiratory Syndrome, Ondre H. Harper Oct 2019

Engineering Self-Assembling Proteins To Produce A Safe And Effective Vaccine For Porcine Reproductive And Respiratory Syndrome, Ondre H. Harper

Electronic Thesis and Dissertation Repository

Commercially available vaccines for porcine reproductive and respiratory syndrome virus (PRRSV) provide some control over the virus but none are ideal since they either are not completely safe for use, lack efficacy in promoting long-lasting immunity or provide no protection from heterologous PRRSV strains. Innovative approaches to designing vaccines are being pursued to overcome these drawbacks. One example is the use of nanoparticles to present a dense array of antigenic epitopes to the immune system which can effectively stimulate antibody producing cells (B cells) and T cells, resulting in long-lasting immunity. Here, I genetically fused antigenic epitopes from PRRSV to ...


Tracing Nutrient Sources To Lipid Production In Birds And Insects Using Stable Isotope (Δ13c, Δ2h) Tracers: Implications For Nutritional Physiology Of Migratory Species, Libesha Anparasan Oct 2019

Tracing Nutrient Sources To Lipid Production In Birds And Insects Using Stable Isotope (Δ13c, Δ2h) Tracers: Implications For Nutritional Physiology Of Migratory Species, Libesha Anparasan

Electronic Thesis and Dissertation Repository

Using stable isotope measurements of inert tissues to determine origins and migratory patterns is well established. However, isotopically determining nutritional origins of lipids, the primary fuel of migration, has not been attempted. I explored isotopic links between diet and stored lipids in captive White-throated Sparrows (Zonotrichia albicollis) and true armyworm moths (Mythimna unipuncta) using δ13C and δ2H measurements. Isotopic discrimination between body lipids and diet was established as linear calibration functions. Isotopic uptake following a diet switch in moths was used to trace lipid accumulation over time. Isotopic correlations between breath metabolic by-products of fed and ...


Strains In Regions Of The Brain Modelled From Female Youth Soccer Players Performing Purposeful Headers In Season, Wayne Allison Oct 2019

Strains In Regions Of The Brain Modelled From Female Youth Soccer Players Performing Purposeful Headers In Season, Wayne Allison

Electronic Thesis and Dissertation Repository

Soccer is the world's most popular sport, and intentional heading of the ball is exclusive to it. Head impacts in youth players are riskier than adults as their brains are developing. Finite element models can quantify parameters, like strains within regions of the brain, that are otherwise difficult to assess. The purpose of this stay was to examine the relationship between head kinematics collected by wireless head impact sensors and brain strains in regions of interest related to concussion. As well, we assessed head impact strains in regions of interest related to concussion for headers from various game scenarios ...


The Characterization Of The Rat Bone Sialoprotein Knockout Phenotype, Benjamin Harvey Oct 2019

The Characterization Of The Rat Bone Sialoprotein Knockout Phenotype, Benjamin Harvey

Electronic Thesis and Dissertation Repository

Bone sialoprotein (BSP) is an extracellular phosphoprotein that has been associated with mineralizing tissues, such as the periodontium, the fibrocartilaginous enthesis, and long bone formation. In this study, we characterized the phenotype of BSP-deficient rats. Histomorphometric analysis discovered a thinning of the acellular cementum in both 20 and 50 week-old Bsp-/- rats with no related periodontal defects and an organized periodontal ligament. Analysis of the mature quadriceps tendon (QCT) enthesis determined that BSP and osteopontin are present in the calcified fibrocartilage of wild-type rats at 14 weeks. The developing QCT enthesis of Bsp-/- rats appears similar in mineral content, collagen ...


In Search Of Psychiatric Kinds: Natural Kinds And Natural Classification In Psychiatry, Nicholas Slothouber Oct 2019

In Search Of Psychiatric Kinds: Natural Kinds And Natural Classification In Psychiatry, Nicholas Slothouber

Electronic Thesis and Dissertation Repository

In recent years both philosophers and scientists have asked whether or not our current kinds of mental disorder—e.g., schizophrenia, depression, bipolar disorder—are natural kinds; and, moreover, whether or not the search for natural kinds of mental disorder is a realistic desideratum for psychiatry. In this dissertation I clarify the sense in which a kind can be said to be “natural” or “real” and argue that, despite a few notable exceptions, kinds of mental disorder cannot be considered natural kinds. Furthermore, I contend that psychopathological phenomena do not cluster together into kinds in the way that paradigmatic natural ...


How Do Humans Process Magnitudes? An Examination Of The Neural And Cognitive Underpinnings Of Symbols, Quantities, And Size In Adults And Children, Helen Moriah Sokolowski Oct 2019

How Do Humans Process Magnitudes? An Examination Of The Neural And Cognitive Underpinnings Of Symbols, Quantities, And Size In Adults And Children, Helen Moriah Sokolowski

Electronic Thesis and Dissertation Repository

A striking way that humans differ from other species is our unique ability to represent and manipulate symbols. This ability to process numerical magnitudes symbolically (e.g., ‘three’, ‘3’) is widely thought to be supported by an ancient system that evolved to process nonsymbolic numerical magnitudes (i.e., quantities). In this thesis, I present four empirical studies to uncover whether symbolic representations are indeed supported by the system that evolved to process quantities, or if symbolic representations are sub-served by a similar but ultimately distinct system.

In experiments 1 and 2, I investigate how the adult brain processes symbols and ...


How Does The Brain Represent Digits? Investigating The Neural Correlates Of Symbolic Number Representation Using Fmri-Adaptation, Celia Goffin Oct 2019

How Does The Brain Represent Digits? Investigating The Neural Correlates Of Symbolic Number Representation Using Fmri-Adaptation, Celia Goffin

Electronic Thesis and Dissertation Repository

How does the brain represent numerical symbols (e.g., Arabic digits)? Activity in left parietal regions correlates with symbolic number processing. Research with functional resonance imaging adaptation (fMRI-A) indicates that the intraparietal sulcus (IPS) exhibits a rebound (increase in activation) effect when a repeatedly presented number is followed by a new number. Importantly, this rebound effect is modulated by numerical ratio as well as the difference between presented numbers (distance). This ratio-dependent rebound effect could reflect a link between symbolic numerical representation and an approximate number system (ANS). In this doctoral dissertation, fMRI-A is used to investigate mechanisms underlying symbolic ...


The Stability Of Temperate Lakes Under The Changing Climate, Aleksey Paltsev Sep 2019

The Stability Of Temperate Lakes Under The Changing Climate, Aleksey Paltsev

Electronic Thesis and Dissertation Repository

There is a collective prediction among ecologists that climate change will enhance phytoplankton biomass in temperate lakes. Yet there is noteworthy variation in the structure and regulating functions of lakes to make this statement challengeable and, perhaps, inaccurate. To generate a common understanding on the trophic transition of lakes, I examined the interactive effects of climate change and landscape properties on phytoplankton biomass in 12,644 lakes located in relatively intact forested landscapes. Chlorophyll-a (Chl-a) concentration was used as a proxy for phytoplankton biomass. Chl-a concentration was obtained via analyzing Landsat satellite imagery data over a 28-year period (1984-2011) and ...


Excess No Stabilizes The Luminal Domain Of Stim2 In A Cys-Specific Manner Thereby Regulating Basal Calcium Homeostasis And Store-Operated Calcium Entry, Matthew Novello Sep 2019

Excess No Stabilizes The Luminal Domain Of Stim2 In A Cys-Specific Manner Thereby Regulating Basal Calcium Homeostasis And Store-Operated Calcium Entry, Matthew Novello

Electronic Thesis and Dissertation Repository

Stromal-interaction molecule 2 (STIM2) is an endoplasmic reticulum (ER) membrane-inserted Ca2+-sensing protein which, together with the plasma membrane Ca2+ channel Orai1, regulates basal Ca2+ homeostasis and store-operated Ca2+ entry (SOCE). Recent evidence suggests that S-nitrosylation, which is the covalent attachment of a nitric oxide (NO) moiety to a cysteine thiol, can attenuate the function of the paralog STIM1 protein. Compared to STIM1, STIM2 also functions as a basal Ca2+ homeostatic feedback regulator. Therefore, the objective of my study was to evaluate the susceptibility of STIM2 to S-nitrosylation and the effects that this ...


Rna Interference Of Worker Sterility Genes: Testing Mechanisms Of Reproductive Regulation In Apis Mellifera, Anthony J. Gallo Sep 2019

Rna Interference Of Worker Sterility Genes: Testing Mechanisms Of Reproductive Regulation In Apis Mellifera, Anthony J. Gallo

Electronic Thesis and Dissertation Repository

Social insects such as the honey bee (Apis mellifera) are well known for their reproductive division of labour and eusocial colony systems. Honey bee workers forgo reproduction in favour of being selfless in directing reproductive benefits towards their queen mother. This altruistic tendency is a result of both behavioural and physiological changes under control of the presence of the queen’s mandibular pheromone. The genetic mechanism that underlies this response is, however, not well understood. Here, this study used RNA interference to knock down the expression of single genes (fruitless and ftz-f1) that have been previously identified as influential in ...


Carbon And Nitrogen Dynamics In Plants Grown At Low Co2 Conditions Of The Past, Andre Galvao Duarte Sep 2019

Carbon And Nitrogen Dynamics In Plants Grown At Low Co2 Conditions Of The Past, Andre Galvao Duarte

Electronic Thesis and Dissertation Repository

For most of the recent evolutionary history of plants, atmospheric CO2 concentrations have been far below modern values. However, little is known about how plants grown in a low CO2 environment balance their carbon demand for growth while meeting their requirement for nitrogen acquisition, the establishment of mycorrhizal fungal associations, and the production of defense compounds. Here, I investigated how low CO2 affects Elymus canadensis and Picea mariana by comparing their growth at low and current CO2 concentrations. I found that reduced N availability exacerbated low CO2 effects on growth, and reduced stomatal index and ...


The Effects Of Exercise Training Versus Intensive Insulin Treatment On Skeletal Muscle Fibre Content In Type 1 Diabetes Mellitus Rodents, David P. Mcbey Sep 2019

The Effects Of Exercise Training Versus Intensive Insulin Treatment On Skeletal Muscle Fibre Content In Type 1 Diabetes Mellitus Rodents, David P. Mcbey

Electronic Thesis and Dissertation Repository

In patients with Type I diabetes mellitus (T1DM) undergoing intensive insulin therapy, the development of insulin resistance (IR) is linked to the improper storage of intramyocellular lipid (IMCL) species. While both IR and IMCL are improved with combined aerobic and resistance training, it is unclear how these adaptations relate to individual fibre-type transitions and metabolic function. This study aimed to compare the effects of combined exercise training versus conventional and intensive insulin therapy on skeletal muscle fibres in T1DM rodents. Seventeen Sprague-Dawley rats were divided into groups: Control-Sedentary (CS; n=4), conventionally-treated T1DM sedentary (DCT; n=4), intensively-treated T1DM sedentary ...


Cognitive, Neural, And Educational Contributions To Mathematics Performance: A Closer Look At The Roles Of Numerical And Spatial Skills, Zachary C.K. Hawes Sep 2019

Cognitive, Neural, And Educational Contributions To Mathematics Performance: A Closer Look At The Roles Of Numerical And Spatial Skills, Zachary C.K. Hawes

Electronic Thesis and Dissertation Repository

The principal aims of this thesis were to (1) provide new insights into the cognitive and neural associations between spatial and mathematical abilities, and (2) translate and apply findings from the field of numerical cognition to the teaching and learning of early mathematics.

Study 1 investigated the structure and interrelations amongst cognitive constructs related to numerical, spatial, and executive function (EF) skills and mathematics achievement in 4- to 11-year old children (N=316). Results revealed evidence of highly related, yet separable, cognitive constructs. Together, numerical, spatial, and EF skills explained 84% of the variance in mathematics achievement (controlling for chronological ...


Above- And Belowground Community Linkages In Boreal Peatlands And Climate Warming Implications, Caitlyn Lyons Sep 2019

Above- And Belowground Community Linkages In Boreal Peatlands And Climate Warming Implications, Caitlyn Lyons

Electronic Thesis and Dissertation Repository

Aboveground plants provide resources to the belowground microbial community via plant litter and, in turn, the belowground microbial community provides nutrients for plant uptake, linking the two systems. My aim was to characterize and describe differences in plant community composition, plant litter quality and microbial community composition between two boreal peatlands in northern Ontario. These peatlands have contrasting plant and microbial communities, the Sphagnum moss-dominated peatland harboring a higher fungi to bacteria ratio compared to the Carex sedge-dominated peatland. Clear open top chambers were installed at both sites to simulate warming. Higher temperatures decreased Sphagnum moss in the Sphagnum-dominated ...


Synthesis Of Crosslinkable Poly(Ester Amide)S For Cell Encapsulation And Delivery, Yu Ting (Natalie) Liang Sep 2019

Synthesis Of Crosslinkable Poly(Ester Amide)S For Cell Encapsulation And Delivery, Yu Ting (Natalie) Liang

Electronic Thesis and Dissertation Repository

Tissue engineering using adipose-derived stromal cells (ASCs) shows promise for soft tissue regeneration. Biodegradable polymers are potential biomaterials as they support the growth and delivery of cells. Specifically, poly(ester amide)s (PEAs) are a class of biodegradable polymers with tunable structures that have been shown to exhibit low cytotoxicity and support the growth of various cell types. This thesis involved the development of new water soluble amino acid-based PEAs with crosslinkable moieties to enable formation of hydrogel scaffolds for ASC encapsulation. These hydrophilic phenylalanine-based and alanine-based PEAs were synthesized by solution polycondensation and photo-crosslinked into a series of hydrogels ...


Assessing The Role Of Drosophila Melanogaster Neuroligin 3 On Social Spacing And Climbing Behaviour, J. Wesley Robinson Aug 2019

Assessing The Role Of Drosophila Melanogaster Neuroligin 3 On Social Spacing And Climbing Behaviour, J. Wesley Robinson

Electronic Thesis and Dissertation Repository

Autism spectrum disorders can be clinically defined in part by impairments of social interactions. Social interactions can be modeled in Drosophila melanogaster with behaviours such as social spacing. Here, I examined the effects of autism-related gene neuroligin 3 on fly social spacing. I hypothesized if neuroligin 3 is mutated or gene expression is targeted for knockdown, then flies will have altered social space in males and females at different ages. Using the social space assay, I found that different mutations to neuroligin 3 change the fly’s behavior, in a mutation and sex-specific manner. Using an antibody against Nlg3, I ...


The Relations Between Newcomer Integration Processes And Youth Athletes’ Perceptions Of The Group Environment In Competitive Ice Hockey, Jeffrey J. Chamberlain Aug 2019

The Relations Between Newcomer Integration Processes And Youth Athletes’ Perceptions Of The Group Environment In Competitive Ice Hockey, Jeffrey J. Chamberlain

Electronic Thesis and Dissertation Repository

Abstract

The ways in which new members are integrated into a particular group environment—also known as organizational socialization processes—have been shown to be a powerful predictor of newcomer adjustment in the workplace. Yet, there is a scarcity of research on how sport teams manage the integration of new team members, and the consequences of different tactics. The current research uses the recently developed Sport Team Socialization Tactics Questionnaire (STSTQ) to evaluate how socialization processes are systematically related to youth athletes’ perceptions of their group environment. Across two time points, 202 competitive adolescent ice hockey players (Mage = 14 ...


The Role Of Tra1 In Cellular Stress Responses In Yeast: Implications For Human Diseases, Yuwei Jiang Aug 2019

The Role Of Tra1 In Cellular Stress Responses In Yeast: Implications For Human Diseases, Yuwei Jiang

Electronic Thesis and Dissertation Repository

Regulation of gene expression under stress conditions involves chromatin remodeling through post-translational modification of histones. One of these modifications, acetylation of lysine residues, regulates transcription initiation and is linked to a variety of essential cellular processes including cell cycle control, DNA repair, and importantly, activation of cellular stress response pathways. Dysregulation of histone acetylation has been observed in many stress-related diseases such as inflammatory diseases, cancer, neurodegenerative disorders, and fungal infections. Tra1 is the only essential component of both the highly conserved SAGA and NuA4 histone acetyltransferase (HAT) complexes that are responsible for acetylation of histones and other proteins. Tra1 ...


The Relative Importance Of Larval And Adult Nutrition In The Isotopic Profile Of The Spermatophore Produced By The Male True Armyworm Moth (Mythimna Unipuncta) (Haworth)., Aida Parvizi Aug 2019

The Relative Importance Of Larval And Adult Nutrition In The Isotopic Profile Of The Spermatophore Produced By The Male True Armyworm Moth (Mythimna Unipuncta) (Haworth)., Aida Parvizi

Electronic Thesis and Dissertation Repository

The wings of true armyworm (Mythimna unipuncta) are metabolically inactive tissue and as their isotopic profiles are determined by resources obtained during larval development, they provide information on natal origin of immigrants. The majority of female immigrants are mated so could the isotopic profiles of spermatophores dissected from her reproductive tract provide information about the natal origin of her mates? However, as spermatophores are produced by metabolically active male accessory glands and could use resources obtained from larval and adult feeding I conducted experiments to determine the relative importance of these two dietary sources on the isotopic profiles of spermatophores ...


Early Warning Of Global Change Effects On Catchment Nutrient Exports, Haibin Dong Aug 2019

Early Warning Of Global Change Effects On Catchment Nutrient Exports, Haibin Dong

Electronic Thesis and Dissertation Repository

Global change scientists seek sentinels of change. On forested landscapes, first-order catchments serve as sentinels of global stressors and their effects on downstream surface waters. Here, I explored global stressors – including climate warming, hydrological intensification, and recovery from atmospheric acidic deposition – and their effects on nutrient exports in 22-year stream chemistry records from 41 forested first-order catchments in a network of North American long-term monitoring sites. First, I used multivariate autoregressive models to establish relationships between changes in global stressors and changes in catchment nutrient exports. Second, I analyzed the residuals of these relationships to determine if there was evidence ...


The Cost Of Protection: Frost Avoidance And Competition In Herbaceous Plants, Frederick Curtis Lubbe Aug 2019

The Cost Of Protection: Frost Avoidance And Competition In Herbaceous Plants, Frederick Curtis Lubbe

Electronic Thesis and Dissertation Repository

Perennial herbaceous plants in regions that experience winter freezing must survive using belowground structures that can tolerate or avoid frost stress. Soil and plant litter can insulate plant structures from frost exposure, but plants must invest into growth to penetrate through these layers to reach the surface in the spring. The overall goal of my thesis was to test the hypothesis that the protection of overwintering clonal structures by soil or plant litter (frost avoidance) comes at the expense of subsequent reduced growth and competitive ability in absence of freezing stress. I first explored this trade-off with a suite of ...