Ecology

Climate change affects birds' reproductive ecology by altering breeding timing, distribution, and habitat suitability. Snowmelt patterns complicate these changes affecting habitat availability and suitability for birds and their arthropod prey. Snow varies as a function of both large-scale climate patterns and local-scale topography. I used elevational gradients as a proxy for local- scale snow impacts, investigating how elevation affects arthropod abundance, and nest placement, initiation, fate, and habitat for Lapland Longspur (Calcarius lapponicus) and Semipalmated Sandpiper (Calidris pusilla) north of Baker Lake, Nunavut. I found and monitored nests over multiple breeding seasons and used pitfall traps and conducted vegetation surveys. Results show that elevation significantly affects arthropod biomass and nest placement, but not nest initiation or success. Both species preferentially nested at lower elevations with higher arthropod biomass. Thus, birds in the central Arctic choose nesting sites at lower elevations with better food availability rather than higher elevations with earlier snowmelt.

Author Keywords: Arctic, arthropod biomass, Lapland Longspur, nest site selection, nest success, Semipalmated Sandpiper

Animal migrations are ubiquitous and one of the most threatened ecological processes globally. Because of the multifaceted nature of migration – seasonal movements between home ranges – it can be difficult to tease apart the underlying mechanisms influencing this behaviour. It is necessary to understand these mechanisms, not only to deepen our fundamental understanding of migration in animals, but also because migrations in many species are vulnerable to environmental change. In Chapter 2, I first systematically identify the broad proximate drivers of migration and offer generalities across vertebrate taxa. I quantitatively reviewed 45 studies and extracted 132 observations of effect sizes for internal and external proximate drivers that influenced migration propensity. Through this meta-analysis, I found that internal and external drivers had a medium and large effect, respectively, on migration propensity. Predator abundance and predation risk had a large effect on migration propensity, as did individual behaviour. Of the studies that examined genetic divergence between migrant and resident populations, 64% found some genetic divergence between groups. In Chapter 3, I explore the genetic basis for migration and identified genes associated with migration direction from pooled genome-wide scans on a population of 233 migrating female mule deer (Odocoileus hemionus) where I identified genomic regions including FITM1, a gene linked to the formation of lipids, and DPPA3, a gene linked to epigenetic modifications of the maternal line. These results are consistent with the underlying genetic basis for a migratory trait which contributes to the additive genetic variance influencing migratory behaviours and can affect the adaptive potential of a species. Finally, in Chapter 4 I used a pedigree-free quantitative genetic approach to estimate heritability and sources of environmental variation in migration distance, timing, and movement rate of the same population of mule deer. I found low heritability for broad patterns of migration timing, and greater variation in heritability for behaviours during migration, with low heritability for distance and duration and high heritability for movement rate along the route. Insights into the genetic and environmental sources of variation for migration are critical both for the eco-evolutionary dynamics of migration behaviour, and for the conservation of species whose migrations may be vulnerable to environmental change. My thesis reveals that broad patterns of migration are driven largely by environmental effects while within these broad patterns, migration behaviour is driven to a measurable degree by genetic variation.

Author Keywords: heritability, migration, Odocoileus hemionus, reduced representation sequencing, whole genome sequencing

Many species of shorebirds depend on stopover sites to rest and refuel during their long-distance migrations. To determine how shorebirds use migratory stopover sites, we tracked three species of shorebirds at two stopover sites in British Columbia, Canada from 2018-2021 during northward and southward migration using automated telemetry. Western Sandpipers (Calidris mauri) stayed longer at the Fraser River Estuary (4-8 days) compared to Tofino (2-6 days). We assessed habitat use of Sanderlings (Calidris alba), Semipalmated Plovers (Charadrius semipalmatus), and Western Sandpipers between beaches and mudflat at the Tofino stopover site. Time spent at the beach and mudflat habitats varied by species, tidal period, time of day, migration period, and human disturbance. This study shows that different stopover sites, and habitats within stopover sites, offer a unique set of characteristics used by birds exhibiting varying migration strategies, highlighting the importance of conserving a diversity of migration stopover locations and habitats.

Author Keywords: habitat use, human disturbance, length of stay, migration, shorebird, stopover site

Measuring biodiversity has become increasingly complex as biologists and ecologists have gradually learned more about how biotic systems are structured and interact. Given the wide range of tools, techniques and approaches now in use to quantify biological diversity, it is useful to consider different "dimensions of diversity" to classify these measurements and provide context for their interpretation. Even within the genetic dimension of diversity alone, recent improvements in theory, technology, and statistics has generated several approaches which can provide distinct insights into natural systems. In this thesis, I use multiple "axes of diversity" to subdivide the dimension of genetic diversity to better understand a complex ecological system - the unisexual Ambystoma complex on Pelee Island, Ontario. By focusing on the genomotype axis, I found that the composition of local unisexual Ambystoma assemblages generally reflects the current relative abundance of the local sexual host populations. This suggests that sexual hosts can be thought of as a keystone species for the complex not only because they are required for unisexual Ambystoma to reproduce, but also because their relative abundance governs the composition of entire unisexual Ambystoma assemblages. Comparatively, when assessing the lineage axis of genetic diversity, unisexual Ambystoma assemblage diversity patterns primarily reflected historic landscape structure, and spatial patterns of increased lineage richness were linked to areas where both potential hosts were locally available (currently or historically). Thus, while both of the investigated axes of diversity are forms of genetic diversity, each revealed distinct factors that have shaped contemporary diversity patterns across the landscape operating at different spatial and temporal scales. Critically, our understanding of complex ecological systems is likely to be broadened by including additional axes of diversity (e.g., allelic, loci, or chromosomal structure axes), and such investigations are not limited to clonal hybrid systems. Overall, this work illustrates the importance of combining insights from distinct conceptual and analytical toolkits to generate a comprehensive understanding of the factors which have shaped the patterns of diversity we observe today.

Author Keywords: Biological diversity, Dimensions of diversity, Ecological genetics, Metacommunity ecology, Unisexual Ambystoma

Wildlife translocation programs are widely employed as a strategy to reintroduce extirpated species into regions they once inhabited but no longer do. Reintroduction programs can be successful at re-establishing extirpated populations and also provide unique opportunities to study post-reintroduction population dynamics and behavioural ecology. The wild turkey (Meleagris gallopavo) is a forest generalist species that, prior to European colonization, inhabited much of the Carolinian zone in Ontario. This species was hunted to extirpation in the early 1900's and reintroduced in the mid-1980's through a series of wildlife trade agreements and coordinated trap and transfer efforts. Ontario's contemporary populations are seemingly thriving, with wild turkey harvest permitted in many regions of the province. However, given this species history of extirpation, understanding the size, distribution, and behavioural ecology of Ontario's reintroduced population of wild turkeys is essential to their long-term persistence in the province. We captured and radio-tagged 77 wild turkeys over four years in Peterborough, Ontario and studied their movement, sociality, and habitat preferences. My findings indicate that Ontario may contain relatively high densities of this species when compared with other parts of their range. My analyses also elucidated interesting aspects of this species habitat selection patterns within an anthropogenic landscape, in addition to novel findings surrounding wild turkey sociality and genetic structure.

Author Keywords: behaviour, genetics, Ontario, reintroduction, wild turkey, wildlife management

In situ chlorophyll sensors are beneficial for monitoring of long-term impacts of algal blooms and accessing water quality issues in bodies of water. However, more research is needed to validate their efficacy and understand how environmental conditions can influence sensor measurements. I assessed the performance of an in situ chlorophyll sensor under controlled environmental conditions and used the same sensor to collect vertical phytoplankton patterns in south-central Ontario boreal lakes. The performance of the sensor was assessed by examining the precision of chlorophyll measurements and determining the suitable timing length that would produce precise results. In general, the sensor was relatively insensitive to conditions under lower algal concentrations and the decent of the sensor should be slowed for vertical lake profiling in lakes with higher algal biomass. Most variation resulted from the movement of particle bound algal cells. We described chlorophyll profile characteristics including surface chlorophyll levels and chlorophyll peak depth and width and investigated the relationships of these features with environmental controls. The lakes showed a typical chlorophyll profile of low phytoplankton biomass lakes. Our results showed that dissolved organic carbon was a strong predictor of epilimnetic biomass while light attenuation and dissolved organic carbon were both strong predictors of peak depth. Light attenuation and surface area were small but significant predictors of peak width. We acknowledged that any uncertainties in sensor chlorophyll readings were not an issue in our lakes due to the overall low chlorophyll biomass.

Author Keywords: chlorophyll, chlorophyll fluorescence, in situ profiling, lakes, phytoplankton biomass, water quality 

Migratory fish can influence the rivers where they spawn by depositing nutrients and organic matter which increase primary and secondary production. Past research in the Laurentian Great Lakes has focused on individual tributaries, accordingly, the spatial extent of subsidies and how environmental factors influence subsidies are not clear. To determine which tributaries received subsidies, I compared stable carbon isotope values (δ13C) of resident stream fishes above and below 54 barriers in 37 tributaries. Subsidies were found in found across 43 of the barriers. The subsidy magnitude varied among the lakes, with Lake Superior having significantly larger subsidies. Correspondence analysis of environmental factors showed that large differences in δ13C were associated with steeper river channels on the Canadian Shield with little agricultural land-use. Migratory fish supply resource subsidies to rivers across the Great Lakes basin, though their magnitude is contextually dependent.

Author Keywords: barriers, Great Lakes, migratory fish, resident stream fish, resource subsidies, stable isotopes

Ecological restoration of grassland ecosystems is increasing in scope in Ontario, as a result the demand for genetically appropriate, high-quality seeds of native plants is also increasing. This mixed methods study characterized fitness and seed quality traits using genetic, demographic and growth trial data for a keystone tallgrass prairie species Big bluestem (Andropogon gerardii). To estimate the ploidy levels in Big bluestem, our flow cytometric results indicated an average of 6.32 picograms of nuclear DNA within sixteen populations surveyed showing that hexaploid (6x) cytotypes are dominant in Southern and Central Ontario populations, aside from one 9x occurrence in Norfolk county, ON. Seed quality, measured through germination and viability testing did not change based on whether a population was remnant or restored. Concerningly, our study shows that remnant populations of Big bluestem are at risk of being lost as high quality seed sources likely because of the absence of stewardship and the resulting loss in population fitness. Workshops with prairie restoration practitioners suggest that there is significant vision behind the future of this work in the province, and that an ecosystem wide seed strategy for keystone tallgrass prairie species is a necessary next step to increase the sustainability of seed-based restoration strategies and preserve remnant site genetics.

Author Keywords: Big bluestem (Andropogon gerardii), Ecological Restoration, fitness, polyploidy, practitioner, seed quality