Graduate Theses & Dissertations

Pages

Influence of Habitat on Woodland Caribou Site Fidelity
Site fidelity is the behaviour of individuals to return to the same location; for female woodland caribou it may reflect reproductive success and depend on habitat quality. I investigated the influence of landscape and disturbance conditions on fidelity among three populations in Manitoba and Ontario, Canada. Habitat classifications were based on Forest Resource Inventory (FRI) and Landsat TM landcover maps. A total of 261 sites were ground-truthed to determine mapping accuracy. An amalgamated map incorporating FRI and Landsat TM data was estimated from field measurements to have an overall accuracy of 69.0%. Site fidelity was expressed as the distance between consecutive-year locations of individuals and was investigated during five week-long periods representing calving, early and late post-calving, winter, and breeding. Site fidelity was strongest during the post-calving seasons and weakest during the winter. Habitat had little influence on site fidelity in all seasons, excepting winter, even under highly disturbed conditions, suggesting maintenance of fidelity may be a maladaptive trait. Individual variation proved a strong predictor and cursory mapping indicated that caribou may return to sites visited two or more years earlier. Conservation management and policy should recognize that site fidelity may represent an ecological trap. Author Keywords: calving, disturbance, habitat, movement, Rangifer tarandus caribou, site fidelity
Conservation genetics of Redside Dace (Clinostomus elongatus)
Recent range reductions of endangered species have been linked to urban development, increased agricultural activities, and introduction of non-native species. I used Redside Dace (Clinostomus elongatus) as a focal species to examine the utility of novel monitoring approaches, and to understand historical and contemporary processes that have influenced their present distribution. I tested the efficacy of environmental DNA (eDNA) to detect Redside Dace, and showed that eDNA was more sensitive for detecting species presence than traditional electrofishing. Parameters such as season, number of replicates, and spatial versus temporal sampling need to be accounted for when designing an eDNA monitoring program, as they influence detection effectiveness and power. I also assessed the species’ phylogeographic structure using both mitochondrial and microsatellite DNA analysis. The data from the microsatellite markers indicate that Redside Dace populations are genetically structured, with the exception of several populations from the Allegheny River basin. Combined sequence data from three mitochondrial genes (cytochrome b, ATPase 6 and ATPase 8) indicated that Redside Dace persisted within three Mississippian refugia during the last glaciation. Secondary contact between two lineages was indicated by both mitochondrial and microsatellite data. The combined results from the eDNA and conservation genetics studies can be used to inform Redside Dace recovery efforts, and provide a template for similar efforts for other aquatic endangered species. Author Keywords: eDNA, endangered, genetics, phylogeography
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
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
Enduring Attack
Numerous prey taxa employ defensive postures for protection against attack by predators. Defensive postures mitigate predation risk at various stages of the predator-prey sequence, including through crypsis, mimicry, thanatosis, aposematism, and deflection. In terrestrial salamanders, defensive postures may be aposematic, or deflect attacks away from vital body parts and towards the tail, however the extent to which these strategies act exclusively or synergistically remains poorly understood. Herein I demonstrate a novel approach to study the function of salamander defensive postures through experimental manipulation of predator response to antipredator behaviour in a natural field setting. I deployed 1600 clay salamander prey on Pelee Island, Ontario, manipulating prey size (small, large) and posture (resting, defensive) and documented attack rates across three predator types to further assess the effect of prey body size and predator type on antipredator efficacy. My research suggests that irrespective of prey body size, defensive posture does not function through aposematism, but rather acts to deflect predator attacks to the tail, which is commonly noxious and expendable in terrestrial salamanders. An intriguing possibility is that this behaviour facilitates taste-rejection by predators. Overall, my research should further contribute to our understanding of the importance and potential evolutionary significance of defensive posturing in Ambystoma salamanders, and more broadly, on the determinants of prey vulnerability to predation. I also briefly discuss the implications of my results to the conservation of Ambystoma populations on Pelee Island. Author Keywords: Anti-predator behaviour, Aposematism, Attack deflection, Predator avoidance, Small-mouthed salamander, Taste-rejection
Habitat Characteristics, Density Patterns and Environmental Niches of Indo-Pacific Humpback Dolphins (Sousa chinensis) of the Pearl River Estuary and Eastern Taiwan Strait
The purpose of this thesis is to quantify the habitat characteristics, density patterns and environmental niches of two groups of Indo-Pacific humpback dolphins: Chinese white dolphins (CWD) of the Pearl River estuary (PRE), and Taiwanese white dolphins (TWD, =Taiwanese humpback dolphin, THD) found in the eastern Taiwan Strait (ETS). Much work has already been done on the habitat use of CWDs in parts of the PRE, so the purpose of my first two chapters was to advance knowledge of the TWD to a comparable level. Chapter 2 contains the first published description of the relatively shallow, inshore, estuarine habitat of the TWD. General environmental characteristics and observed group sizes were consistent with other populations of humpback dolphins, and group sizes were not correlated with the environmental variables measured during surveys. Chapter 3 investigated density patterns of TWDs, finding spatiotemporal heterogeneity across the study area. Humpback dolphin densities fluctuated from year to year, but some parts of the study area were consistently used more than others. Environmental characteristics again did not influence dolphin densities, though more dolphins than expected were sighted in waters adjacent to major land reclamations, which may be related to the location of these areas close to major rivers. In Chapter 4, niches of the TWD and CWDs found in the PRE were compared using species distribution models, which indicated significant niche overlap. This may be due to niche conservatism maintaining similar fundamental niches between the two groups since their historical split >10,000 years ago, or a result of the intrinsic biotic factors that influence occurrence data affecting the hypervolume dimensions of each realized niche in similar ways. Geographic predictions indicate that most of the TWD’s range has likely been surveyed, and that there may be connectivity between PRE humpback dolphins and at least one neighbouring putative population due to continuous predicted suitable habitat in waters that remain poorly surveyed. Overall, my thesis demonstrates that density patterns may vary over time, but on a broad temporal scale, these two allopatric groups of Indo-Pacific humpback dolphins have similar habitat requirements in geographically isolated, but environmentally similar locations. Author Keywords: density, habitat, Indo-Pacific humpback dolphin, niche overlap, Sousa chinensis, species distribution model
Assessing Connectivity of Protected Area Networks and the Role of Private Lands in the United States
Forestalling biodiversity loss through the establishment of protected areas is a universally accepted conservation strategy, yet despite established guidelines for protected area coverage and placement, much of the world is currently failing to meet its commitments to conservation planning and landscape protection. Calls for the United States to protect more land usually focus on the need for strategic selection of land parcels to bolster protected area coverage and network functionality, but to date there lacks focused research on either the role of private protected areas in conservation planning or the factors affecting individual protected area selection and importance. We determined gaps in conservation planning in the contiguous United States by analyzing the connectivity of protected area networks by state, and assessing the importance of private protected areas in improving linkages in protected area connectivity. We found that all states had low coverage from protected areas (average <8.4% of total land mass), and especially private protected areas (average <1.1% of total land mass), and that the overall contribution of such areas to protected area network connectivity also was low. Terrain ruggedness was identified as the main factor affecting the current location of protected areas, and that protected area spatial layout is a primary influence on landscape connectivity. We conclude that establishment of private protected areas could offer a viable conservation tool for increasing protected area coverage and connectivity, but that current efforts are inadequate to either adequately link existing protected areas or to meet established land protection guidelines. Author Keywords: Aichi Target 11, conservation planning, graph theory, network theory, private conservation, protected areas
Risk of Mortality for the Semipalmated Plover (Charadrius semipalmatus) Throughout Its Life Cycle
Three long-term mark and recapture/resight data sets of individually marked Semipalmated Plovers (Charadrius semipalmatus) were analyzed using Cormack-Jolly- Seber models. Data came from two breeding populations (Churchill, Manitoba, Canada, n=982, and Egg Island, Alaska, USA, n=84) and one overwintering population (Cumberland Island, Georgia, USA, n=62). For Alaska and Georgia, time-invariant models were best-supported, giving annual survival estimates of 0.67 (95%C.I.: 0.58- 0.76) and 0.59 (95%C.I.: 0.49-0.67) respectively. Data from Manitoba supported a timedependent model: survival estimates varied from 1.00 to 0.36, with lowest estimates from recent years, supporting observations of local population decline. Seasonal survival analysis of the Georgia population indicated lower mortality during winter (monthly Φoverwinter: 0.959, 95%CI: 0.871-0.988; for 6 month period Φoverwinter: 0.780 (0.440-0.929)) than during combined breeding and migratory periods (monthly ΦBreeding+Migration: 0.879 (0.825-0.918); for 8 month ΦBreeding+Migration: 0356 (0.215-0.504)). I recommend, based on high resight rates, continued monitoring of survival of wintering populations, to determine potential range-wide population declines. Keywords: survival, longevity, mortality, shorebird, overwinter, breeding, migration, life cycle Author Keywords: life cycle, longevity, mortality, non-breeding, shorebird, survival
Tests of the Invasional Meltdown Hypothesis in invasive herbaceous plant species in southern Ontario
According to the Invasional Meltdown Hypothesis (IMH), invasive species may interact in their introduced range and facilitate future invasions. This study investigated the possibility that Alliaria petiolata, an invasive allelopathic herbaceous plant in Ontario, is facilitating invasions by additional alien species. Two allelopathic focal species were chosen for this study: the native Solidago canadensis and the invasive A. petiolata. Field surveys in southern Ontario that quantified plant biodiversity in plots that included one or both focal species revealed no support for the IMH, although fewer species co-existed with A. petiolata than with S. canadensis. A year-long recruitment experiment in Peterborough, Ontario, also produced results inconsistent with the IMH, although did provide some evidence that A. petiolata limited recruitment of other species. These results collectively show negative impacts on regional biodiversity by A. petiolata, even in the absence of an invasional meltdown. Author Keywords: allelopathy, Alliaria petiolata, co-occurrence surveys, invasional meltdown hypothesis, invasive species, Solidago canadensis
Assessing the population genetic structure of the endangered Cucumber tree (Magnolia acuminata) in southwestern Ontario using nuclear and chloroplast genetic markers.
Magnolia acuminata (Cucumber tree) is the only native Magnolia in Canada, where it is both federally and provincially listed as endangered.Magnolia acuminata in Canada can be found inhabiting pockets of Carolinian forest within Norfolk and Niagara regions of southwestern Ontario. Using a combination of nuclear and chloroplast markers, this study assessed the genetic diversity and differentiation of M. acuminata in Canada, compared to samples from the core distribution of this species across the United States. Analyses revealed evidence of barriers to dispersal and gene flow among Ontario populations, although genetic diversity remains high and is in fact comparable to levels of diversity estimated across the much broader range of M. acuminata in the USA. When examining temporal differences in genetic diversity, our study found that seedlings were far fewer than mature trees in Ontario, and in one site in particular, diversity was lower in seedlings than that of the adult trees. This study raises concern regarding the future viability of M. acuminata in Ontario, and conservation managers should factor in the need to maintain genetic diversity in young trees for the long-term sustainability of M. acuminata in Ontario. Author Keywords: conservation genetics, cpDNA, forest fragmentation, Magnolia acuminata, microsatellites, population genetic structure
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
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

Pages

Description

Graduate student theses produced at Trent University. You may also browse theses and dissertations by year, program, or author.

In collections

Search Our Digital Collections

Query

Enabled Filters

  • (-) ≠ Bowman
  • (-) ≠ Williams
  • (-) = Conservation biology

Filter Results

Date

2004 - 2024
(decades)
Specify date range: Show
Format: 2024/04/16

Collection

Author Name

Show more

Name (Any)

Show more

Degree

Degree Discipline

Subject (Topic)

Show more