Environmental and Life Sciences

Understanding habitat needs of a species is critical, especially for species reintroduced to an area or expanding their range. I evaluated roost tree selection and survival probability of GPS-tagged eastern wild turkeys (Meleagris gallopavo silvestris) from 2017–2020 and 2022 in Peterborough County, Ontario, Canada. Fine-scale roost tree selection was associated with larger trees, with microclimate factors such as wind speed, temperature, and precipitation having little to no influence. Turkeys showed high annual survival probabilities relative to other northern regions of their range, but survival was not influenced by proximity of roost tree to a building. The behaviour of roosting in an elevated perch helps turkeys avoid ground-dwelling predators, but specific selection of one tree versus another has little additional benefit to survival. Turkeys appear to survive well in a landscape that is a mix of agricultural and urban, with forest patches intact for roosting habitat.

Author Keywords: Eastern wild turkey, habitat, Meleagris gallopavo silvestris, microclimate, roost sites, survival

Understanding threats to declining species at multiple stages of their annual cycle is important for determining the cause of their declines and conserving their populations. To assess potential responses to changing habitat and predators under climate change, I compared the nest site characteristics, responses to human intruders, and migratory patterns between Short-billed Dowitchers and Stilt Sandpipers breeding in Churchill, MB. I conducted behavioural observations and habitat surveys and deployed radio transmitters on birds during incubation. Short-billed Dowitcher nests had higher concealment and adults were more aggressive than Stilt Sandpipers. Short-billed Dowitchers took an eastern migratory route and stopped in the southeast US, whereas Stilt Sandpipers migrated west. Short-billed Dowitchers displayed relatively high connectivity during migration with nearly 1/3 of confirmed stopovers occurring at a single site in Georgia. These findings highlight the importance of considering varying antipredator defense and migration strategies in the face of climate change.

Author Keywords: Central Flyway, incubation, Midcontinent, migratory connectivity, Motus, nest concealment

Migration, space use, and phenology play key roles in shaping avian populations and are therefore critical for conservation. My thesis examines the migration strategies and non-breeding spatial requirements of Virginia's beach-nesting American Oystercatchers (Haematopus palliatus), as well as the nesting phenology of mid-Atlantic American Oystercatchers and Piping Plovers (Charadrius melodus). I assessed migratory decisions using field-readable bands and GPS transmitters, finding that ~90% of Virginia's beach-nesting American Oystercatchers migrate out-of-state during the non-breeding season, though tested hypotheses did not strongly predict migration patterns. I then estimated home range sizes of American Oystercatchers during the non-breeding season, revealing high individual variation (12.1-201.6 km²) and a potential trend toward larger home ranges in males. Finally, I analyzed clutch initiation timing of American Oystercatchers and Piping Plovers in response to climate change, finding that American Oystercatchers advanced timing of breeding by 10.7 days between 2005-2022, while Piping Plovers showed no significant shift.

Author Keywords: behavioural ecology, climate change, home-range, migration, movement ecology, phenology

Heart failure (HF) is a condition with several possible etiologies that influence patient symptomatology, including response to exercise. The purpose of this review was to assess how cardiopulmonary exercise testing (CPET) parameters used for risk stratification differ and are associated with mortality and adverse cardiac events in patients with different HF etiologies. We completed a systematic review of studies that assessed CPET data in adult heart failure patients and reported outcomes of mortality, left ventricular assist device implantation, heart transplantation, or hospitalization. Interestingly, the optimal threshold values derived from CPET were strikingly similar for stratifying risk in patients with different HF etiologies. Even with heterogeneity in the data, the literature suggests that optimal threshold values from CPET can be applied generally without consideration of HF etiology. However, there is a need to consider a broader spectrum of HF etiologies and CPET parameters in larger and more representative study populations.

Author Keywords: Cardiopulmonary Exercise Testing, Etiology, Heart Failure, Ischemic Cardiomyopathy, Non-Ischemic Cardiomyopathy, Prognosis

Nurses have a vital role in counselling their patients towards healthier living. However, nurses tend to have poor metabolic health that may be influenced by lifestyle. Whether this begins during their nursing education is poorly understood. Undergraduate nursing (n=42) and biology (n=15) students had their metabolic health assessed through body measurements, fasting blood glucose and lipids. Lifestyle factors of physical activity, nutrition, stress, and sleep were assessed using questionnaires, accelerometry, diet logs, and heart rate variability. At an individual level, 31.0% of nursing students are at-risk of poor metabolic health. Results suggest that nursing students are sedentary, obtaining poor sleep quality, consuming elevated amounts of saturated fat, and perceiving themselves to be under mild stress. The implementation of lifestyle interventions should be considered for this cohort. However, few differences were found between nursing and biology groups, indicating that the results are potentially generalizable to a larger group of undergraduate students.

Author Keywords: metabolic health, nursing students, nutrition, physical activity, psychological stress, sleep quality

Hybridisation is an important evolutionary mechanism with diverse outcomes, including the formation of new lineages, the exchange of alleles between species, or their extinction through genetic swamping. In some cases, hybrids exhibit higher fitness than their parental species, which can lead to hybrid invasions that threaten ecosystems. In North America, hybridisation between the native cattail Typha latifolia and the non-native T. angustifolia produces the hybrid T. × glauca, which is a highly impactful invader in wetlands across large areas of southern Canada and northern USA; contrastingly, in Europe and Asia, where its parental species also co-occur, T. × glauca is rare to non-existent. This thesis examines the evolutionary history of T. latifolia and T. angustifolia, which, in addition to being the parental species of T. × glauca, are two of the most globally widespread Typha species, a genus of plants foundational to wetlands. First, we developed genomic resources, including ~12M nuclear SNPs and plastome assemblies to facilitate genetic research on Typha; we also described a cost-effective library preparation and genotyping protocol that makes population genetic studies of freshwater plants accessible. Then, we applied those genomic resources to investigate the roles of drift, selection, and hybridisation in the divergence of T. angustifolia, T. latifolia, and their sister species, T. domingensis and T. shuttleworthii. We found that speciation in these taxa was driven by drift under allopatry, resulting from historical bottlenecks, and that natural selection has played a minimal role in the divergence of these species; additionally, we observed introgressive hybridisation from T. latifolia into T. angustifolia. Finally, we reconstructed the demographic histories of T. angustifolia and T. latifolia from North America and Europe. We observed that reproductive isolation is strong in Europe, where the two species have potentially been sympatric for ~800,000 years, and weak in North America, where they have been sympatric for only a few centuries. Our results exemplify how the divergence and demographic histories of species can correlate with their strength of reproductive isolation. We emphasise that preventing invasions by hybrids will require limiting the movement of Typha and other historically allopatric species, which likely lack reproductive barriers.

Author Keywords: biological invasions, cattails, demographic histories, evolutionary histories, population genomics, reproductive isolation

I investigated the climate vulnerability of a cold-water salmonid by observing the upper thermal tolerance of brook trout (Salvelinus fontinalis) across multiple life stages. Using hatchery- and wild-ancestry fish, I assessed variation in thermal tolerances and carryover effects within and among brook trout life stages and populations that were reared under varying winter thermal regimes as embryos. Embryonic, fry, and gravid adult upper thermal tolerance were tested via CTmax. Warm acclimation was associated with an increase in embryonic upper thermal tolerance. CTmax variability was markedly higher in embryos than juvenile or adult salmonids. Effects of thermal incubation treatments varied by life stage, with incubation temperature and life stage both influencing body size and thermal tolerance. Collectively, these results suggest that brook trout only exhibit short-term carryover effects from thermal stressors during embryo incubation, with no lasting effects on phenotype beyond the first few months (10 weeks) after hatch.

Author Keywords: acclimation response, climate change, ontogeny, salmonid, stress, thermal plasticity

Climate-driven permafrost thaw releases microorganisms and dissolved organic matter (DOM) into northern lakes, where their interactions with microbial communities and seasonal processes shape greenhouse gas emissions. In a factorial experiment mixing DOM and microbes from thermokarst ponds and lakes, we found that both DOM and microbial identity strongly influenced degradation. Lake microbes preferentially consumed thermokarst DOM, producing 3× more CO₂ due to low growth efficiency, while thermokarst microbes altered DOM with little CO₂ release. A survey of 40 lakes across a climate gradient showed CO₂ fluxes peaking in spring from under-ice buildup and CH₄ fluxes peaking in fall after summer accumulation. Dissolved gas concentrations served as early indicators of these events, with CH₄ linked to reduced DOM and CO₂ to multiple pathways. Overall, DOM quality, microbial traits, and seasonal dynamics interact to control lake carbon cycling, emphasizing the need for year-round monitoring under climate change.

Author Keywords: Dissolved Organic Matter (DOM), Fluxes, Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), Greenhouse Gases (GHGs), Lakes, Thermokarst

Although stormwater management ponds (SWMPs) are frequently used to mitigate flooding in urban areas, we still do not fully understand how these systems impact water quality in a watershed. Currently, most research focuses on the effectiveness of SWMPs to retain nutrients during high flows, even though there is potential for internal nutrient releases to occur in these systems during low flows. To investigate if SWMPs act as nutrient sources or sinks during low flow conditions, we analyzed how sewershed characteristics, pond properties, and hydrological and limnological factors influenced nutrient dynamics and stoichiometry in 10 SWMPs. Our study ponds were located in Peterborough, Whitby, and Richmond Hill, which are urbanized municipalities in southern Ontario, Canada. During October 2010 to 2011, we took monthly measurements of various carbon (C), nitrogen (N), and phosphorus (P) forms. We collected samples in the inlets, permanent pools, and outlets to determine any changes in concentrations, loads, and stoichiometric ratios into and out of the ponds. At the time of sampling, we also measured a variety of hydrological and limnological parameters. Our findings indicate that more urbanized sewersheds with higher drainage densities tend to have higher inflowing particulate and dissolved nutrient loads. In addition, we found that pond properties such as depth, length-to-width ratio, volume, and age differentially influence the retention of particulate and dissolved C, N, and P forms. Influential hydrological and limnological factors were antecedent moisture conditions, season, and thermal stratification. We found higher particulate P concentrations near the sediments when the catchments were drier and the ponds were ice-free and stratified. As well, we found higher outflowing stoichiometric ratios for DOC:TDN and DOC:TDP. This indicates an enrichment of C compared to N and P and suggests biogeochemical processes may be occurring in SWMPs. Overall, our results demonstrate that SWMPs are complex aquatic systems, and we need to consider biogeochemical processes in our design and maintenance activities, so that the effectiveness of SWMPs is not compromised during low flow conditions as a result of internal nutrient releases.

Author Keywords: Carbon, Nitrogen, Phosphorus, Urban biogeochemical cycling, Urban stormwater pond

Diversity of flowers in flowering plants is understood to facilitate mating success, and yet understanding the relationships between plant sexual diversity and mating patterns remains a challenge. In this thesis, I used Sagittaria latifolia, an aquatic plant with unique sexual systems, to investigate relationships between plant sexual diversity, mating patterns, and reproductive success and to understand their evolutionary consequences. First, I measured the magnitude of sexual selection in a dioecious and a monoecious population of S. latifolia, while accounting for size variation. I showed that sexual selection does operate in natural populations of plants. Estimates of sexual selection were similar in both populations, possibly due to the temporal separation of female and male flowering in hermaphroditic S. latifolia, enabling individuals to act temporarily as unisexuals. Second, I examined how seasonal differences in sex allocation and flowering time can affect male mating opportunities, and the effect on reproductive success in hermaphroditic S. latifolia. I found that shifting allocations to be more male-biased with earlier flowering increased male mating opportunities. However, greater mating opportunities did not equate to higher rates of siring, indicating that factors other than temporal overlap contribute to male reproductive success. Finally, I determined the factors affecting mating and reproductive success of males and male-function hermaphrodites, distinguishing between the predictable effects of plant-level traits and population-level features, and unpredictable effects of stochastic factors. Across both populations, we found that plant-level traits had a greater impact on mating and reproductive success than population-level features. Nevertheless, these effects were frequently masked by stochastic factors. Furthermore, unexplained variation in mating and reproductive success may stem from additional plant traits affecting post-pollination gametophyte-sporophyte interactions. My findings indicate that while sexual selection does operate in natural populations of S. latifolia as expected under Bateman's principles, temporal overlap in flowering, plant traits and population features did not explain patterns of male mating or reproductive success, suggesting that post-pollination factors may be influencing mating outcomes.

Author Keywords: Phenology, Plant mating, Plant reproduction, Sagittaria latifolia, Sex allocation, Sexual selection