April 12, 2019
Peatlands are wetlands with over 40cm of organic soil dominated by anaerobic microbes, including sulphate-reducing bacteria (SRB). The SRB are the principal methylators of inorganic mercury (Hg) in the natural environment. The resultant methylmercury (MeHg) is bioaccumulative and neurotoxic. It is established that increasing the availabilityof sulphate increases bacterial methylation of Hg, and I hypothesized that peatlands that have had more atmospheric sulphate deposition historically would be ‘primed’ to better utilize added sulphate, resulting in increased methylmercury production and risk to downstream ecosystems. I investigated this effect by sampling peatlands in southern Ontario, in the boreal forest, and in the sub-arctic that fall along a latitudinal gradient of sulphate deposition. I conducted sulphate-addition experiments in the lab to test this hypothesis and my findings to date are consistent with the hypothesis, but are complicated by the interactions of multiple biogeochemical cycles which I am further investigating.
Billions of birds migrate every year between North America and the Neotropics, however many populations are declining, especially those migrating the farthest. The importance of breeding and wintering grounds is well established but the ecological needs and limitations of these birds while migrating are poorly understood. Migratory birds can make several short-stops along their routes to rest or refuel or may stay for extended periods in a few specific sites. My PhD research will use occupancy models to make spatial predictions about the distribution of migratory landbirds during their spring and fall migrations. Then, combining the results of all species, I will identify key stopover sites for the migratory community. I will test predicted distributions and assess stopover habitat quality using indicators such as fuel deposition rates. This information will allow the development of more effective conservation strategies to preserve migratory birds and habitats threatened by widespread anthropogenic change.
April 5, 2019
Bank Swallows (Riparia riparia), a threatened species in Ontario, breed primarily in either banks at lakeshores or at exposed surfaces in inland man-made aggregate pits. Pits may be ecological traps for this species but the relative trade-offs in nesting at pits vs. natural sites are unknown. Availability of aquatic emergent insects is expected to be highest at lakeshore colonies with associated nutritional benefits including Omega-3 fatty acids. However, Bank Swallows may experience differential mercury exposure depending on habitat use, with higher expected levels at lakeshores and among adult birds. Potential differences in dietary quality among sites may directly influence juvenile body condition, with higher Omega-3 fatty acids being beneficial. This study seeks to compare these breeding habitats to evaluate dietary differences as revealed by fatty acid of blood plasma, stable isotope analyses in juvenile feathers, DNA barcoding of fecal matter, and mercury levels in feathers and blood. This information will be important for management decisions related to the use of inland aggregate pits by this species and conservation of suitable nesting habitats.
Miconazole and clotrimazole are antifungal drugs that are commonly detected in municipal wastewater samples due to their use in prescription and over-the-counter antifungal creams. These drugs, however, are not significantly degraded in traditional wastewater treatment processes and persist in soils following fertilization of agricultural fields with treated municipal sewage sludge. Thus, since 2010, four 2 m2 experimental microplots at AAFC-London have been annually amended with the environmentally-relevant concentration of 0.1 mg of each drug per kg of soil and four plots have been annually amended with 10 mg of each drug per kg of soil. Amid growing concern of antifungal resistance, especially among clinical isolates to azole drugs, we aim to culture a diverse repertoire of fungi from these microplots and compare the extent of their azole resistance to fungi isolated from control plots not receiving any miconazole or clotrimazole.
March 29, 2019
Research into neuro-behavioural mechanisms influencing social behaviour suggests a potential regulatory role for brain nonapeptides across vertebrate taxa. As a general pattern it seems that arginine–vasopressin (AVP)/arginine–vasotocin (AVT) increases ‘anti‐social’ behaviour whereas oxytocin (OT)/isotocin (IT) increases ‘pro‐social’ behaviour. Many fishes form social groups, referred to as shoals, but few studies have specifically addressed the effects of nonapeptides on differences in shoal formation. Trinidadian guppy (Poecilia reticulata) is considered as a model species for understanding social behaviour because of evolved differences in shoaling propensity across populations, mainly in response to differences in predation regimes. My research: (1) characterizes differences in shoaling behaviour across populations and sexes; (2) quantifies brain AVT and IT neuron immunoreactivity; (3) examines the distribution of brain AVT and IT receptor immunoreactivity; and (4) determines whether administration of a nonapeptide and its antagonist influences shoaling behaviour in guppies.
Eusocial insects are characterized by sub-fertile castes that evolve via indirect selection, yet little is known about how this type of selection operates at the molecular level. On the one hand, genes indirectly selected for subfertility may experience relaxed adaptive molecular evolution, relative to genes directly selected for reproduction. On the other hand, genes associated with sub-fertile castes may be less constrained and thus, free to evolve rapidly. These putative yet contrasting 'signatures of kin selection' remain unresolved. In my study, I test for differences in the rate of molecular evolution across sets of caste-biased and un-biased genes from a subterranean termite. Through comparative analyses of the nucleotide substitution patterns captured in the reads of a newly-assembled RNA transcriptome, I found that genes uniquely expressed in the sterile soldier caste differ in their average age, function and level of polymorphism from non differentially expressed genes that are presumably under direct selection.
March 22, 2019
Conservation of soil health is crucial for the reduction of environmental contaminants associated with agricultural systems. Cover crops can potentially improve the sustainability of agroecosystems by reducing nutrient losses from soil erosion, increasing plant biodiversity and increasing soil organic matter. The success of cover crops in reducing nitrogen (N) losses and benefiting the yield of the subsequent main crop is contingent on the N release from the decomposition of cover crop residues being well-synchronized with the N demand of the main crop. Not only is this transfer of cover crop N to the main crop poorly documented, but because they alter the timing and form of N losses from agricultural systems, there is the potential for cover crops to be a liability from an environmental and economic standpoint. The objective of my research is to quantify and characterize the transfer of N to the main crop for a range of cover crops and cover crop mixtures. I will be utilizing state of the art field lysimeters (used for measuring soil water and nutrient fluxes) as well as a long-term cropping system experiment, both located at the Elora Research Station in Guelph, ON. For both study systems, I am applying stable 15N-labelled fertilizer tracer to cover crops and main crop mixtures in the spring. 15N recovery will be assessed in the harvested crops and soil solutions in the fall. Thereafter, I will track the fate of the 15N in this residual material over-winter and subsequently assess the balance of the transfer of the cover crop 15N to the main crop vs. losses to the surrounding environment over multiple crop rotations. This study will confirm the extent to which increased N retention and fertility by cover crops can reduce N losses to the surrounding environment and benefit crop yield.
Boreal peatlands are important global carbon sequesters due to the accumulation of peat (partially decomposed plant material). Therefore, the aboveground plants are important determinants for carbon storage potential. Boreal peatlands are mainly dominated by three different plant functional groups: Sphagnum mosses, Carex sedges, and shrubs. Sphagnum mosses comprise a vast majority of peat, meaning Sphagnum spp. contribute the most to carbon storage potential of Boreal peatlands. I have characterized two Boreal peatlands, a Sphagnum dominated and Carex dominated peatland, in terms of aboveground plant community, litter composition and belowground microbial community. I have also performed a field experiment at theses sites, looking at the effects of passive warming on the aboveground plant communities. Under climate warming, a shift from Sphagnum mosses to Carex sedges in peatlands is expected. I have two field seasons of plant community composition data collected using the point intercept method under passive warming and control treatments. I have also measured leaf area index (LAI) as an indicator of aboveground biomass. After only one growing season there were detectable changes in LAI under passive warming where the Carex dominated peatland demonstrated larger LAI in the warming treatments. In the Carex dominated peatland there was also a significant shift in plant communities under passive warming, demonstrating an increase in shrub dominance. In the Sphagnum dominated peatland there are trends depicting seasonal shifts in plant communities. Climate warming has the potential to impact the plant community composition at these two Boreal peatland sites and this could shift these sites from carbon sinks to carbon sources, exacerbating climate warming effects.
March 15, 2019
Zooplankton are a key link in the transfer of energy within marine food webs. Mortality, caused by consumptive and non-consumptive factors, is an important component of their population dynamics. Non-consumptive mortality is death caused by natural causes excluding predation. This includes starvation, toxicity, and parasitism. The prevalence of parasitism in zooplankton populations and the life cycles of these symbionts is relatively unknown. My proposed research aims to assess the protist symbionts present in zooplankton from the Strait of Georgia through DNA sequencing and identify known parasites and commensals that may influence host populations. I will investigate host species and life stage specificity as well as the seasonal variation of symbiont diversity. This research will contribute to understanding how parasitism is distributed and prevalent within zooplankton populations and further elucidate connections of the lower marine food web.
Eusocial insects such as ants, bees, wasps and termites are characterized by a differentiation of reproductively selfish (e.g., queens) and altruistic (e.g., workers) castes. Reproductive altruism is intriguing to evolutionary theorists because this trait can only evolve via indirect selection such that alleles causing the behavior are transmitted, but are not expressed, by reproducing relatives. The evolution of reproductive altruism therefore depends on a caste-specific expression pattern whereby alleles for altruism are conditionally expressed based on social circumstance. Despite this basic understanding, little is known of how variability in this conditionality or 'genetic responsiveness' to social circumstance affects the likelihood of the evolution of altruism. The goal of my research is to explore this range of genetic responsiveness. In my study I will use Price’s Theorem to model how responsive hypothetical alleles for altruism must be in order to evolve and maintain their fitness within populations of non-social organisms.
March 8, 2019
In northern temperate regions, the effects of freezing stress from late Fall into early Spring can vary substantially among herbaceous (i.e. non-woody) plant species. Anecdotal evidence and previous research suggest herbaceous legumes (family: Fabaceae) are more freeze-sensitive than other herbaceous species. This could have important implications for ecosystem nitrogen cycling in a changing climate. Though previous investigations have studied the effects of freezing on specific legume species, comparative studies on leguminous vs. non-leguminous species have been lacking. I will use a suite of controlled environment (using plant-soil mesocosms) and field experiments (increased freezing via snow removal) to investigate the impacts of freezing stress on herbaceous legumes relative to other herbaceous species. I predict legume abundance, growth, and nitrogen content will decline with increased incidence of freezing in comparison with other herbaceous species.
Social group structure can be highly organized yet vary with context. In my research, I vary the social demographic and genetic context of small populations of Drosophila melanogaster to test for changes to the number and nature of social interactions. Using a combination of video-captured behavioural trials and in silico network analysis, I have found that at high density, flies interact more often, with more individuals, and tend to cluster into well-connected neighbourhoods. Further, I found that females cluster more than males, and do so with familiar neighbours, rather than interacting with previously unencountered individuals. I am currently performing additional network analysis to test for differences in social structure as a function of sex ratio, age and genotype. My work therefore provides new insights into the hidden social life of an otherwise well-studied insect and, in the end, may have implications for the study of other, non-model taxa.
March 1, 2019
Many insect species migrate, but we typically have little understanding of their geographic origin. A recent study showed that deuterium (𝛿2H) levels in the wings of adults can be used to assign the probability of origin of the true armyworm, Mythimna unipuncta, a migratory agricultural pest. Through a series of controlled laboratory experiments I have demonstrated that the 𝛿2H values of spermatophores could provide information on the natal origin of male armyworm moths. However, when field collected immigrant males were mated with laboratory reared females there were some instances where marked differences were observed between the isotope profiles of male’s wing and the spermatophore he produced. A similar pattern was seen when comparing the wing profile of immigrant females and the spermatophores that she contained. Future research is required to better understand the effects of migratory flight and production of successive spermatophores on the turnover rate of spermatophore isotope composition.
Most natural populations inhabit complex and heterogeneous landscapes. The field of landscape genetics investigates how landscape features affect processes such as an individual’s movement and survival, and how those processes can result in genetic differences between populations. In my PhD, I use next-generation sequencing protocols to obtain genetic data from populations of the alpine butterfly Parnassius smintheus. I explore how the messy nature of NGS datasets affects different genetic analyses, and I test the claims that using NGS datasets allows the sampling of very few individuals per population. I then apply these datasets to more complex landscape genetics analyses and demonstrate how landscape features and structure (e.g. barriers to movement such as forest cover) may affect gene flow and genetic differentiation in P. smintheus. My work contributes to the growing body of work that is landscape genetics, and informs best-use practices for the use of NGS data.
February 8, 2019
It is estimated that billions of birds worldwide die each year from window collisions. Birds appear to behave as if windows are invisible, suggesting they cannot distinguish between glass and open space. The objective of my MSc research is to determine if some bird species are more vulnerable to dying from window collisions than others. I am using a combination of citizen science and bird monitoring data from the Fatal Light Awareness Program (FLAP) and regional bird banding stations, to determine if the mortality seen in downtown Toronto is simply a function of species abundance or if it is unequal among species. In addition to among species differences in mortality, I compared individuals within species to address if age is a factor in collision mortality vulnerability. Based on a comparison of the 2017 age ratios, age does not appear to be a factor.
February 1, 2019
The ‘ecology of fear’ aims at quantifying the total impact predators have on prey demography, by considering not only direct killing, but also the indirect costs of fear. Scared prey adopt anti-predator behaviours to avoid being killed that may carry physiological costs which translate into reduced survival and reproduction. Elegant experiments have demonstrated the importance of fear effects in small-scale invertebrate systems, but it remains hotly debated whether such fear effects apply equally in large mammals. My goal is to test if the fear of lions, leopards, and hyenas affects the demography of their ungulate prey. I intend to conduct large-scale playback experiments to manipulate perceived predation risk (fear) in impala and quantify the effects on pregnancy and weaning success. This research is urgently needed for conservation purposes, to determine if focusing solely on direct killing by predators, as has traditionally been done, underestimates the crucial role of large carnivores.
Forests are a net sink for atmospheric mercury largely because of leaf uptake processes. Mercury accumulates in leaves over the growing season in both deciduous and coniferous species. After litterfall, leaves are subject to decomposition which is controlled mainly by moisture, temperature, the microbial community, and litter quality. Through decomposition processes, mercury is stored in soil or released from forest soils downstream where it can methylate and pose health risks to humans and wildlife. My MSc research will focus on determining how decomposition governs the input, storage, and release of mercury into boreal forest soils. Specifically, comparing deciduous and coniferous litters, I will investigate how mercury accumulates in leaves over the growing season at different heights in the canopy and examine controls on rates of mercury release from litter into the soil. Understanding what factors control mercury release will contribute to better predictions of recovery timing of mercury contaminated ecosystems.
January 25, 2019
The competitive exclusion principle states that different species cannot occupy the same ecological niche due to interspecific competition and natural selection. Barn Swallows (Hirundo rustica), Cliff Swallows (Petrochelidon pyrrhonota) and Tree Swallows (Tachycineta bicolor) are three similar species of aerial insectivores that breed sympatrically in Southern Ontario. It is not clear how these species differ ecologically, and their coexistence implies some sort of niche segregation. For my M.Sc. thesis, I am focusing on potential differences in nestling diet and post-fledging movements of these swallow species. Using DNA barcoding and feather stable isotope (δ13C, δ15N) analysis to examine diet as well as the Motus Wildlife Tracking System to examine post-fledging movements, I am exploring evidence of potential niche segregation.
January 18, 2019
Many plants avoid freezing stress by placing buds at or below ground level where they are insulated by snow, litter, or soil. Although it can protect, increased bud depth may have a cost when frost stress is absent. Shallow bud placement may facilitate early season growth and provide a competitive advantage over neighbouring plants. Four bulbous and three tuberous plant species were subjected to different burial and frost exposure treatments to disentangle the relationship between frost avoidance and the cost of depth. Species response varied with a general trend toward greater growth with depth under frost conditions but greater growth under shallow conditions when frost stress was removed. Controlled freezing temperature exposure has yielded a trend toward increased mortality and decreased growth with greater freezing severity. This study has identified a trade-off in plant growth that may become more important as soil frost exposure increases under climate change.
Understanding the linkages between site quality, refuelling performance, and movement behaviour is vital for assessing the overall value of stopover habitat to migratory birds, and a thorough understanding of how birds interact with the stopover environment will allow for better informed land management and conservation decisions. Using physiological profiling and modern tracking technologies, my PhD research will explore how the stopover environment shapes refuelling performance and movement of migratory songbirds. At multiple stopover sites across the province of New Brunswick, site resource availability, migrant density, and the refuelling rate of individual migrants will be measured to examine the relationship between refuelling performance and per-capita resource availability. Birds will be radio tagged before release to examine how refuelling performance, competitor density, and site quality influence movement during stopover, and post departure migratory movements.
January 11, 2019
Our current understanding of mitochondrial genomes is biased toward metazoans, which represent the majority of sequenced mitochondrial DNAs. Yeast mitochondrial genomes are an appealing alternative to those of metazoans for studying genomic evolution and diversity due to their high diversity in size, shape and gene synteny. The genus Metschnikowia is known for producing two unique ascospores. Recent publication of 61 genomes belong to this genus lacks complete mitochondrial genomes of these interesting species. Therefore, mitochondrial genomes of 61 strains of large spored Metschnikowia species will be constructed and analyzed in detail, focusing on diversity in size, shape, and gene synteny to further our understanding of mitochondrial genome evolution. Also, intron rich genes cob and cox1 will be analyzed to provide new insights into evolution of introns.
Migratory species can be important disease vectors, capable of spreading pathogens between habitats. As climate change alters pathogen boundaries we need to understand the role that migratory birds play as vectors. To better understand how avian malaria effects migration, I will experimentally infect Yellow-rumped warblers with avian malaria. Birds will be held during the acute phase of infection before being released with radio-tags, and the Motus Wildlife Tracking System will record their journey south. Feathers will also be collected to isotopically determine breeding origin. I expect that avian malaria infection will negatively affect migratory preparation, migratory timing, and will increase the frequency and duration of stopovers during migration. I also expect that severity of malaria infection will correlate with distance traveled from the breeding site to the capture location.
|DATE||FIRST SPEAKER||SECOND SPEAKER|
|Apr.12||Jennifer Blythe (MSc exit)||Pilar Caicedo (MSc entry)|