Graduate Theses & Dissertations

Genomic architecture of artificially and sexually selected traits in white-tailed deer (Odocoileus virginianus)
Understanding the complex genomic architecture underlying quantitative traits can provide valuable insight for the conservation and management of wildlife. Despite improvements in sequencing technologies, few empirical studies have identified quantitative trait loci (QTL) via whole genome sequencing in free-ranging mammal populations outside a few well-studied systems. This thesis uses high-depth whole genome pooled re-sequencing to characterize the molecular basis of the natural variation observed in two sexually selected, heritable traits in white-tailed deer (Odocoileus virginianus, WTD). Specifically, sampled individuals representing the phenotypic extremes from an island population of WTD for antler and body size traits. Our results showed a largely homogenous genome between extreme phenotypes for each trait, with many highly differentiated regions throughout the genome, indicative of a quantitative model for polygenic traits. We identified and validated several potential QTL of putatively small-to-moderate effect for each trait, and discuss the potential for real-world application to conservation and management. Author Keywords: evolution, extreme phenotypes, genetics, genomics, quantitative traits, sexual selection
Effects of Silver Nanoparticles on Lower Trophic Levels in Aquatic Ecosystems
Due to their effective antibacterial and antifungal properties, silver nanoparticles (AgNPs) have quickly become the most commonly used nanomaterial, with applications in industry, medicine and consumer products. This increased use of AgNPs over the past decade will inevitably result in an elevated release of nanoparticles into the environment, highlighting the importance of assessing the environmental impacts of these nanomaterials on aquatic ecosystems. Although numerous laboratory studies have already reported on the negative effects of AgNPs to freshwater organisms, only a handful of studies have investigated the impacts of environmentally relevant levels of AgNPs on whole communities under natural conditions. This thesis examines the effects of chronic AgNP exposure on natural freshwater littoral microcrustacean, benthic macroinvertebrate and pelagic zooplankton communities. To assess the responses of these communities to AgNPs, I focused on a solely field-based approach, combining a six-week mesocosm study with a three-year whole lake experiment at the IISD – Experimental Lakes Area (Ontario, Canada). Our mesocosm study tested the effects of AgNP concentration (low, medium and high dose), surface coating (citrate- and polyvinylpyrrolidone [PVP]-coated AgNPs), and type of exposure (chronic and pulsed addition) on benthic macroinvertebrates in fine and stony sediments. Relative abundances of metal-tolerant Chironomidae in fine sediments were highest in high dose PVP-AgNP treatments; however, no negative effects of AgNP exposure were seen on biodiversity metrics or overall community structure throughout the study. I observed similar results within the whole lake study that incorporated a long-term addition of low levels of AgNPs to an experimental lake. Mixed-effects models and multivariate methods revealed a decline in all species of the littoral microcrustacean family Chydoridae in the final year of the study within our experimental lake, suggesting that this taxon may be sensitive to AgNP exposure; however, these effects were fairly subtle and were not reflected in the overall composition of littoral communities. No other negative effects of AgNPs were observed on the pelagic zooplankton or benthic macroinvertebrate communities. My results demonstrate that environmentally relevant levels of AgNPs have little impact on natural freshwater microcrustacean and benthic macroinvertebrate communities. Instead, biodiversity metrics and community structure are primarily influenced by seasonal dynamics and nutrient concentrations across both lakes. This thesis highlights the importance of incorporating environmental conditions and the natural variability of communities when examining the potential risks posed by the release of AgNPs into the environment, as simplistic laboratory bioassays may not provide an adequate assessment of the long-term impacts of AgNPs on freshwater systems. Author Keywords: Benthic macroinvertebrates, IISD - Experimental Lakes Area, Littoral microcrustaceans, Silver nanoparticles, Whole lake experiment, Zooplankton

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