Graduate Theses & Dissertations


Assessing habitat suitability and connectivity for an endangered salamander complex
Habitat loss and fragmentation have significantly contributed to amphibian population declines, globally. Evaluating the state of remaining habitat patches can prove to be beneficial in identifying areas to prioritize in conservation efforts. Pelee Island, Ontario is home to a complex of salamanders including small-mouthed salamanders (Ambystoma texanum), blue-spotted salamanders (A. laterale) and unisexual Ambystoma (small-mouthed salamander dependent population). These populations have declined from intense landscape changes since the late 1800s, particularly from the historical drainage of wetlands. In this thesis, I evaluated the suitability and connectivity of habitat patches occupied by these salamanders to assess the size of, and dispersal capabilities between, remaining habitat patches. I found that there was a low amount of suitable terrestrial habitat available for this complex of salamanders, and existing habitat patches were small and isolated. Forested areas and non-breeding wetlands were considered to be suitable habitat when adjacent to existing breeding locations, suggesting that these habitats should be a focus for conservation efforts. Notably, intervention may be necessary to maintain this amphibian complex as many assemblages are isolated from one another and potential corridors currently consist of primarily unsuitable habitat. Given that much of the salamander complex is reliant on one species for reproduction, the long-term viability of this population of Ambystoma salamanders may rely on the enhancement of suitable habitat near current breeding sites by conservation organizations and local stakeholders. Ultimately, the approach used in this thesis emphasizes the value of evaluating habitat within a fragmented landscape to focus conservation efforts on imperilled species. Author Keywords: amphibians, connectivity, habitat suitability, landscape fragmentation, landscape resistance, unisexual
Linking large scale monitoring and spatially explicit capture–recapture models to identify factors shaping large carnivore densities
Understanding the spatial ecology of large carnivores in increasingly complex, multi-use landscapes is critical for effective conservation and management. Complementary to this need are robust monitoring and statistical techniques to understand the effect of bottom-up and top-down processes on wildlife population densities. However, for wide-ranging species, such knowledge is often hindered by difficulties in conducting studies over large spatial extents to fully capture the range of processes influencing populations. This thesis addresses research gaps in the above themes in the context of the American black bear (Ursus americanus) in the multi-use landscape of Ontario, Canada. First, I assess the performance of a widely adopted statistical modelling technique – spatially explicit capture-recapture (SECR) – for estimating densities of large carnivores (Chapter 2). Using simulations, I demonstrate that while SECR models are generally robust to unmodeled spatial and sex-based variation in populations, ignoring high levels of this variation can lead to bias with consequences for management and conservation. In Chapter 3, I investigate fine-scale drivers of black bear population density within study areas and forest regions by applying SECR models to a large-scale, multi-year black bear spatial capture-recapture dataset. To identify more generalizable patterns, in Chapter 4 I then assess patterns of black bear density across the province and within forest regions as a function of coarse landscape-level factors using the same datasets and assess the trade-offs between three different modeling techniques. Environmental variables were important drivers of black bear density across the province, while anthropogenic variables were more important in structuring finer-scale space use within study areas. Within forest regions these variables acted as both bottom-up and top-down processes that were consistent with ecological influences on black bear foods and intensity of human influences on the species’ avoidance of developed habitats. Collectively, this thesis highlights the opportunities and challenges of working across multiple scales and over expansive landscapes within a SECR framework. Specifically, the multi-scale approach of this thesis allows for robust inference of the mechanisms structuring fine and broad scale patterns in black bear densities and offers insight to the relative influence of top-down and bottom-up forces in driving these patterns. Taken together, this thesis provides an approach for monitoring large carnivore population dynamics that can be leveraged for the species conservation and management in increasingly human-modified landscapes. Author Keywords: animal abundance, black bear, capture-recapture, density estimation, statistical ecology, wildlife management
Islands, ungulates, and ice
Central to wildlife conservation and management is the need for refined, spatially explicit knowledge on the diversity and distribution of species and the factors that drive those patterns. This is especially vital as anthropogenic disturbance threatens rapid large-scale change, even in the most remote areas of the planet. My dissertation examines theinfluence of land- and sea-scape heterogeneity on patterns of genetic differentiation, diversity, and broad-scale distributions of island-dwelling ungulates in the Arctic Archipelago. First, I investigated genetic differentiation among island populations of Peary caribou (Rangifer tarandus pearyi) in contrast to continental migratory caribou (Rangifer tarandus) and evaluated whether genetic exchange among Peary caribou island populations was limited by the availability of sea ice – both now and in the future. Differentiation among both groups was best explained by geodesic distance, revealing sea ice as an effective platform for Peary caribou movement and gene flow. With future climate warming, substantial reductions in sea ice extent were forecast which significantly increased resistance to caribou movement, particularly in summer and fall. Second, I assessed genetic population structure and diversity of northern caribou and deciphered how Island Biogeography Theory (IBT) and Central Marginal Hypothesis (CMH) could act in an archipelago where isolation is highly variable due to the dynamics of sea ice. Genetic differentiation among continental and island populations was low to moderate. In keeping with IBT and CMH, island-dwelling caribou displayed lower genetic diversity compared to mainland and mainland migratory herds; the size of islands (or population range) positively influenced genetic diversity, while distance-to-mainland and fall ice-free coastlines negatively influenced genetic diversity. Hierarchical structure analysis revealed multiple units of caribou diversity below the species level. Third, I shifted my focus to the terrestrial landscape and explored the elements governing species-environment relationships. Using species distribution models, I tested the response of caribou and muskoxen to abiotic versus abiotic + biotic predictors, and included distance to heterospecifics as a proxy for competitive interactions. Models that included biotic predictors outperformed models with abiotic predictors alone, and biotic predictors were most important when identifying habitat suitability for both ungulates. Further, areas of high habitat suitability for caribou and muskoxen were largely disjunct, limited in extent, and mainly outside protected areas. Finally, I modelled functional connectivity for two genetically and spatially disjunct groups of island-dwelling caribou. For High Arctic caribou, natural and anthropogenic features impeded gene flow (isolation-by-resistance); for Baffin Island caribou we found panmixia with absence of isolation-by-distance. Overall, my dissertation demonstrates the varying influences of contemporary land- and sea-scape heterogeneity on the distribution, diversity and differentiation of Arctic ungulates and it highlights the vulnerability of island-dwelling caribou to a rapidly changing Arctic environment. Author Keywords: Circuitscape, connectivity, Island Biogeography, landscape genetics, population structure, species distribution models
Determinants of Breeding Bird Diversity in Ontario's Far North
190 species of birds are known to breed in Ontario’s far north making the region an important nursery for boreal birds. Digital point count data were collected using two different autonomous recording units (ARUs): one model with two standard microphones to detect birds and anurans, and one model with one standard microphone and one ultrasonic microphone for detecting bats. ARUs were deployed either in short or long-term plots, which were four to six days or approximately 10 weeks, respectively. I assessed differences in breeding bird richness detections between ARU and plot types. I also tested the relative impact of the habitat heterogeneity and species-energy hypotheses in relation to breeding birds and created predictive maps of breeding bird diversity for Ontario’s far north. I found no difference in species richness estimates between the two ARU models but found that long-term plots detected about 7 more bird species and 1.5 more anuran species than short-term plots. I found support for both the species-energy and habitat heterogeneity hypotheses, but support for each hypothesis varied with the resolution of the analysis. Species-energy models were better predictors of breeding bird diversity at coarser resolutions and habitat heterogeneity models were better predictors at finer resolutions. Breeding bird diversity was highest in the Ontario Shield Ecozone compared with the Hudson Bay Lowlands Ecozone, but concentrated areas of higher diversity found in the Lowlands were associated with large rivers and the associated coastlines. Author Keywords: boreal birds, breeding birds, habitat heterogeneity, Hill diversity, Ontario, species-energy hypothesis
Genetic Networks to Investigate Structure and Connectivity of Caribou at Multiple Spatial and Temporal Scales
Understanding genetic structure, connectivity, and movement of a species iscritical to management and conservation. Genetic network approaches allow the analysis of genetic information with flexibility and few prior assumptions. In chapter one, I tested the ability of individual-based genetic networks to detect fine-scale structure and connectivity in relation to sampling efforts. My findings revealed individual-based genetic networks can detect fine-scale genetic structure of caribou when using 15 highly variable microsatellite loci. Sampling levels less than 50% of the estimated population size resulted in highly disconnected networks which did not allow for accurate structure analysis; however community detection algorithms were robust in grouping closely related individuals despite low sampling. In chapter two, I used individual-based and population-based genetic networks to investigate structure, connectivity, and movement of caribou across a large study area in Western Canada. A community detection algorithm partitioned the population-based genetic network at multiple spatial scales which uncovered patterns of hierarchical genetic structure and highlighted patterns of gene flow. The hierarchical population structure results aligned with the known distribution of different caribou Designatable Units (DUs) and additional structure was found within each DU. Furthermore, individual-based networks that were constructed with a subset of samples from the Mackenzie Mountains region of the Northwest Territories revealed patterns of long-distance movement and high connectivity across the region. Author Keywords: Biological Conservation, Caribou, Community Detection, Connectivity, Genetic Networks, Structure
Fall Migratory Behaviour and Cross-seasonal Interactions in Semipalmated Plovers (Charadrius semipalmatus) Breeding in the Hudson Bay Lowlands, Canada
I used the Motus Wildlife Tracking System to monitor the fall migration behaviour and assess the underlying drivers of migration strategy in a small shorebird, the Semipalmated Plover (Charadrius semipalmatus), breeding at two subarctic sites: Churchill, Manitoba and Burntpoint Creek, Ontario, Canada. Semipalmated Plovers from both sites departed breeding areas between mid-July and early August, with females preceding males and failed breeders preceding successful breeders. Migrants showed between and within-population variation in migration behaviour, though birds from both sites tended to follow interior or coastal routes and congregated in three major stopover regions along the mid-Atlantic coast of North America. I found that later-departing birds had initial flight tracks oriented more toward the south, faster overall ground speeds, were less likely to stopover in North America, and stopped at lower latitudes, suggesting that later-departing individuals use aspects of a time-minimizing strategy on fall migration. My findings emphasize the importance of the mid-Atlantic coast for Semipalmated Plovers and establish connectivity between sites used during breeding and migration. Author Keywords: Breeding, Migration, Motus, Semipalmated Plover, Shorebird, Stopover
Prey abundance and habitat during the breeding season for Piping Plovers in the Ontario Great Lakes region
Similar to other shorebird trends around the world, the Piping Plover population (Charadrius melodus circumcinctus) is projected to decline if concerted conservation efforts are relaxed. To date, there is insufficient understanding of the connection between habitat type, prey abundance, and chick behaviour of the Piping Plover breeding population in Ontario. The aim of my thesis was to gain knowledge about prey abundance at recent and historic breeding locations, understanding how habitat influences prey abundance and chick behaviour across the Piping Plover breeding range in Ontario’s Great Lakes. The objective of my first study was to understand prey abundance across the breeding region Great Lakes of Ontario from 2018-2019, including occupied and unoccupied sites, and to quantify variation among habitats and periods of reproduction. To evaluate resources, I sampled 17 locations to compare prey abundance using invertebrate traps (n= 3,507). Sampling took place over the reproductive periods of nest initiation, post-hatch, and fledging and in four habitat types of shoreline, wrack, berm, and back dune. Occupied breeding sites had higher prey abundances, and different assemblages of invertebrate prey than unoccupied sites. Additionally, breeding sites had higher prey abundance during nest initiation and supported higher amounts of prey in shoreline and wrack habitat. The objective of my second study was to understand how habitat types influence chick behaviour. To evaluate behaviour-habitat trends, instantaneous chick observations were recorded at the four nest sites from the post-hatch to fledging stages. In total there were 23 fledged chicks that we observed across the two years. Chicks in this study spent 60.9% of their time foraging, 11.9% of the time displaying alert behaviour, 21.4% of their time resting or being brooded, and 5.9% of their time preening. Chicks spent a large proportion of time foraging in the shoreline, resting in the back dune, and alert in berm habitat. The frequency of these alert, defensive behaviours differed among sites, with Sauble Beach chicks spending more time in defensive behaviours compared to other sites. I concluded that in both nesting and brood-rearing periods, habitat is selected non-randomly by adult and young Piping Plovers to maximize access to invertebrate prey for growth and survival. Access by chicks to the most productive habitats should be considered in local management decisions. Author Keywords: chick behaviour, endangered, Great Lakes Region, habitat, Piping Plovers, prey abundance
Population Genetics and Gut Microbiome Composition Reveal Subdivisions and Space Use in a Generalist and Specialist Ungulate
Natural populations are often difficult and costly to study, due to the plethora of confounding processes and variables present. This is of particular importance when dealing with managed species. Ungulates, for example, act as both consumers and prey sources; they also provide economic benefit through harvest, and as such, are of high ecological and economic value. I addressed conservation and management concerns by quantifying subdivision in wild populations and combined movement with non-invasive sampling to provide novel insight on the physiological drivers of space use in multiple species. This thesis explored biological patterns in ungulates using two distinct approaches: the first used molecular genetics to quantify gene flow, while the second examined the relationship between movement and the gut microbiome using high-throughput sequencing and GPS tracking. The goal of the first chapter was to quantify gene flow and assess the population structure of mountain goats (Oreamnos americanus) in northern British Columbia (BC) to inform management. I used microsatellites to generate genotype data and used a landscape genetics framework to evaluate the possible drivers behind genetic differentiation. The same analyses were performed at both a broad and fine scale, assessing genetic differentiation between populations in all of northern BC and in a case management study area northeast of Smithers BC. The results indicated panmixia among mountain goats regardless of scale, suggesting distance and landscape resistance were minimally inhibiting gene flow. Therefore, management at local scales can continue with little need for genetically informed boundaries, but regulations should be tailored to specific regions incorporating data on local access and harvest pressure. My second chapter aimed to determine the extent to which the gut microbiome drives space-use patterns in a specialist (mountain goat) and generalist (white-tailed deer, Odocoileus virginianus) ungulate. Using fecal samples, we generated genomic data using 16S rRNA high-throughput sequencing to evaluate gut diversity and gut microbiome characteristics. Additionally, individuals were fitted with GPS collars so that we could gain insight into movement patterns. Gut microbiome metrics were stronger predictors of space use and movement patterns with respect to home range size, whereas they were weaker predictors of habitat use. Notably, factors of both the gut microbiome and age of a given species were correlated with changes in space use and habitat use. Ultimately, this research linked high-throughput sequencing and GPS data to better understand ecological processes in wild ungulates. Author Keywords: gene flow, genomics, gut microbiome, home range, population genetic structure, ungulates
Diversity, Biogeography, and Functional Traits of Native Bees from Ontario’s Far North and Akimiski Island, Nunavut
Bees (clade Anthophila), are poorly studied in northern Canada, as these regions can be difficult to access and have a short growing season. This study examined bees from two such regions: Ontario’s Far North, and Akimiski Island, Nunavut. I present this study as the largest biogeographical study of bees performed in these remote areas to enhance knowledge of northern native bees. I found 10 geographically unexpected species in Ontario and on Akimiski Island. Rarefaction and the Chao 1 Diversity Index showed that Akimiski is nearly as diverse as the Far North of Ontario, a significantly larger area. I also found, based on log femur length versus latitude, Bombus worker size was consistent with Bergmann’s rule, and there were no apparent statistical differences in the community weighted means of functional traits between the Far North’s Boreal Shield and Hudson Bay Lowlands ecozones. This work provides invaluable knowledge of the native bee species from these regions, which has implications for their future conservation. Author Keywords: Akimiski Island, Bergmann's rule, Chao 1, Community-weighted means, native bees, rarefaction
Assessment of Potential Threats to Eastern Flowering Dogwood (Cornus florida) in Southern Ontario
In Canada, eastern flowering dogwood (Cornus florida L.) is an endangered tree that occurs only in the Carolinian forest of southern Ontario. Threats to this species include habitat fragmentation and the fungal pathogen dogwood anthracnose (Discula destructiva). I conducted a population genetic analysis using seven nuclear microsatellite markers to determine if fragmented populations are genetically isolated from one another and have low levels of genetic diversity. Genetic comparisons suggest on-going dispersal among sites and relatively high genetic diversity within most sites; however, smaller populations and younger trees were less genetically diverse. I also used linear mixed effects models to assess potential relationships between several ecological variables and the prevalence of dogwood anthracnose. Disease severity was higher in trees on shallow slopes and in larger trees; the latter also had higher likelihood of infection. Insights from this study will be important to incorporate into future management strategies. Author Keywords: Cornus florida, Discula destructiva, dogwood anthracnose, Eastern flowering dogwood, endangered, population genetics
Environmental structure, morphology and spatial ecology of the five-lined skink (Plestiodon fasciatus) at high latitude range limits
Detecting relevant and meaningful patterns from the complex, interconnected network of relationships between organisms and their environment is a primary objective of ecology. Ecological patterns occur across multiple scales of space and time. In this dissertation, I examine aspects of environmental structure that influence a species’ distribution and are expressed in that species’ population dynamics. I compare the morphology of the five-lined skink (Plestiodon fasciatus) near its high latitude range limits with a lower latitude population and evaluate the economics of their behaviour in the context of its reproductive strategy. I tested the conformity of this species to biogeographical rules postulated by MacArthur, Bergmann, and Rensch. Spatial ecology was investigated in the context of the environmental potential for polygamy proposed by Emlen and Oring (1977) The five-lined skink, Plestiodon fasciatus, conformed to these biogeographic rules. Specifically, abiotic factors were the primary limiting factors affecting distribution at the high latitude range limits of the species; body size was larger in high latitude populations; and the degree of sexual size dimorphism was greater at high latitude than at low latitude. Spatial ecology at the individual scale was influenced by sites with suitable thermal conditions which facilitate the polygynandrous mating system documented in P. fasciatus in high latitude populations. My results confirm the importance of microsites with suitable thermal profiles as key habitat for ectothermic vertebrates at high latitudes. The influence of temperature as a limiting abiotic factor is expressed in population density, body size, spatial ecology, and reproductive strategy of P. fasciatus. Conservation and restoration of high latitude populations of ectothermic vertebrates should focus on ensuring thermal requirements of the species of concern are met before other factors are addressed, as temperature is likely the single most important limiting factor at high latitude range limits. Author Keywords: biogeography, lizard, Plestiodon fasciatus, range limits, sexual size dimorphism, spatial ecology
multi-faceted approach to evaluating the detection probability of an elusive snake (Sistrurus catenatus)
Many rare and elusive species have low detection probabilities, thereby imposing unique challenges to monitoring and conservation. Here, we assess the detection probability of the Eastern Massasauga (Sistrurus catenatus) in contrast to a more common and conspicuous species, the Eastern Gartersnake (Thamnophis sirtalis). We found that patterns of detection probability differed between species, wherein S. catenatus was detected less often and under a more specific set of sampling conditions. Correspondingly, detection trials with S. catenatus found a high non-detection rate, while detection trials with artificial models suggest that regional differences in detection probability are driven by variation in population density and habitat use. Our results suggest that current monitoring efforts are not sufficient, and that S. catenatus is frequently undetected. Accordingly, we highlight the importance of species-specific monitoring protocols when monitoring rare and elusive species, and recommend a multi-faceted approach that estimates detection probability and identifies species-specific challenges to monitoring. Author Keywords: detection probability, elusive species, monitoring programs, non-detection, S. catenatus, snakes


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