Graduate Theses & Dissertations

Pages

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
Assessment of an adult lake sturgeon translocation (Acipenser fulvescens) reintroduction effort in a fragmented river system
North American freshwater fishes are declining rapidly due to habitat fragmentation, degradation, and loss. In some cases, translocations can be used to reverse local extirpations by releasing species in suitable habitats that are no longer naturally accessible. Lake sturgeon (Acipenser fulvescens) experienced historical overharvest across their distribution, leading to endangered species listings and subsequent protection and recovery efforts. Despite harvest and habitat protections, many populations do not appear to be recovering, which has been attributed to habitat alteration and fragmentation by dams. In 2002, 51 adult lake sturgeon from the Mattagami River, Ontario, Canada were translocated 340 km upstream to a fragmented 35 km stretch of the river between two hydroelectric generating stations, where sturgeon were considered extirpated. This study assessed the translocation effort using telemetry (movement), demographics and genetic data. Within the first year, a portion of the radio-tagged translocated individuals dispersed out of the release area, and released radio-tagged individuals used different areas than individuals radio-tagged ten years later. Catches of juvenile lake sturgeon have increased over time, with 150 juveniles caught within the duration of this study. The reintroduced population had similar genetic diversity as the source population, with a marked reduction in effective population size (Ne). The results indicate that the reintroduction effort was successful, with evidence of successful spawning and the presence of juvenile lake sturgeon within the reintroduction site. Overall, the results suggest adult translocations may be a useful tool for re-establishing other extirpated lake sturgeon populations. Author Keywords: conservation, endangered species, lake sturgeon, reintroduction, telemetry, translocation
Intra-seasonal Variation in Black Tern Nest-site Selection and Survival
Resources and risk are in constant flux and an organism’s ability to manage change may improve their likelihood of persistence. I examined intra-seasonal variation in nest-site selection and survival of a declining wetland bird, the Black Tern (Chlidonias niger surinamensis). I modelled nest site occupancy and survival of early and late-nesting birds as a function of static and dynamic factors. Early-nesting birds selected nest sites based on the degree and direction of habitat change that occurred over the nesting cycle, while late-nesting birds selected sites based on static conditions near the time of nest-site selection. Nest age had the strongest influence on daily survival rate for both early and late-nesting birds, but the shape of this relationship showed intra-seasonal differences. Additionally, early-season survival improved slightly with increasing vegetation coverage and distance between conspecific nests, while late-season survival increased with clutch size. My results suggest that intra-seasonal variation in nest-site selection and survival is driven by changing habitat conditions and predator behavior. Author Keywords: Black Tern, Chlidonias niger surinamensis, daily survival rate, intra-seasonal variation, nest-site selection
Habitat use within and among roosts of chimney swifts (Chaetura pelagica)
Chimney swifts are listed as Threatened nationally and in many provinces within Canada due to rapid population declines. I examined large-scale spatial variation in the maximum size of chimney swift roosts at the northern edge of their range to identify where larger roosts occur. I used multi-sourced data collected across Ontario and Quebec between 1998 and 2013. I found that larger roosts were found at more northerly latitudes, and that very large roosts (>1000 birds) only occurred north of 45°. I also investigated fine-scale patterns of chimney swift positioning inside one of the largest roosts in Ontario. Using digitally recorded images, I calculated the angular position of swifts inside the roost relative to ambient and roost temperature. I found that swifts showed a strong preference for clinging to the south facing wall and clustered more when ambient air temperature was warmer. Thus, huddling in swifts provides additional or alternate benefits, other than serving purely to reduce costs of thermoregulation at low ambient temperatures. This research contributes to the understanding of chimney swift roosting ecology and identifies large roosting sites that should be retained for conservation. Author Keywords: chimney swift, communal roosting, conservation, group size, social thermoregulation, species-at-risk
Ground-truthing effective population size estimators using long-term population data from inland salmonid populations
Effective population size (Ne) is a foundational concept in conservation biology, in part due to its relationship to the adaptive potential of populations. Although Ne is often estimated for wild populations, it is rarely calibrated against actual population estimates (Nc) other than to produce Ne/Nc ratios. This project used demographic and genetic data for from two intensively-studied populations of lake trout (Salvelinus namaycush) in Ontario’s Experimental Lake Area (ELA) as baseline data for evaluating the performance of multiple Ne estimators. Several temporal and single-time (point) genetic methods of estimating Ne were compared against demographic Ne estimates and known population data, as well as variation and consistency within and among Ne estimators. Changes in genetic Ne estimates over time were also compared to changes in demographic structure and fluctuating census estimates, including the effect of an experimentally manipulated population bottleneck on demographic and genetic Ne estimates during population reduction and recovery. Sampling years that included the most pre-, during and post-bottleneck data revealed the lowest estimates using temporal estimators (Ne = 16 to 18) despite pre- and post-bottleneck census estimates of 591 and 565. Estimation of Ne had increasingly tighter confidence intervals as sample sizes approached the actual number of breeding individuals in each population. Performance differences among the tested estimators highlight their potential biases and reliance on different assumptions, illustrating their potential value and caveats for assessing adaptive potential of wild populations. Author Keywords: Effective Population Size, Experimental Lakes Area, Fish Population Assessment, Lake Trout, Population Demographics, Population Genetics
Temperature effects on the routine metabolic rates of brook trout (Salvelinus fontinalis) eggs, alevin and fry
Early developmental stages of cold-adapted ectotherms such as brook trout (Salvelinus fontinalis) are at risk of mortality with increasing water temperatures because of their sensitivity to changes in their environment. I studied the mass and routine metabolic rate (RMR) of wild-origin brook trout eggs, alevin and young fry reared at normal (5°C) and elevated (9°C) temperatures for the duration of the study or at mismatched temperatures. This setup determined if preconditioning acclimation for one temperature benefits or hinders the organism later in life. Three levels of biological organization (ancestry, population, family) were studied using Akaike’s Information Criterion (AIC) to identify models that best accounted for variation in the data. Family, mass and temperature were most important in predicting body mass and mass-adjusted RMR, although population and ancestral-level differences were also detected at some life stages. Strong variation in body mass and mass-adjusted RMR among families may indicate adaptive potential within brook trout populations to respond to increases in water temperature with climate change. Author Keywords: Acclimation, AIC, Brook trout (Salvelinus fontinalis), Environmental matching, Routine metabolic rate, Temperature
Conservation Genetics of Woodland Caribou in the Central Boreal Forest of Canada
Maintaining functional connectivity among wildlife populations is important to ensure genetic diversity and evolutionary potential of declining populations, particularly when managing species at risk. The Boreal Designatable Unit (DU) of woodland caribou (Rangifer tarandus caribou) in Ontario, Manitoba, and Saskatchewan has declined in southern portions of the range because of increased human activities and has been identified as 'threatened' by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). In this dissertation, I used ten microsatellite DNA markers primarily from winter-collected fecal samples to delineate genetic structure of boreal caribou in declining portions of the range and increase understanding of the potential influence of the non-threatened Eastern Migratory DU of woodland caribou on genetic differentiation. Eastern migratory caribou are characterized by large home ranges compared to boreal caribou and migrate seasonally into portions of the Boreal DU range. A regional- and local-scale analysis using the spatial Bayesian clustering algorithm in program TESS delineated four regional clusters and 11 local clusters, with the majority of local clusters occurring along the southern periphery of the range. One of those clusters in Ontario corresponded spatially with the seasonal overlap of boreal and eastern migratory caribou and was characterized by substantial admixture, suggesting that the two DUs could be interbreeding. Next, I decoupled the impacts of historical and contemporary processes on genetic structure and found that historical processes were an important factor contributing to genetic differentiation, which may be a result of historical patterns of isolation by distance or different ancestry. Moreover, I found evidence of introgression from a currently unsampled population in northern Ontario, presumably barren-ground caribou (R. t. groenlandicus). Finally, because our analysis suggested recent processes were also responsible for genetic structure, I used a landscape genetics analysis to identify factors affecting contemporary genetic structure. Water bodies, anthropogenic disturbance, and mobility differences between the two DUs were important factors describing caribou genetic differentiation. This study provides insights on where conservation and management of caribou herds should be prioritized in threatened portions of the boreal caribou range and may have implications for future delineation of evolutionarily significant units. Author Keywords: boreal forest, genetic structure, landscape genetics, microsatellite DNA, Rangifer tarandus, woodland caribou
Development of genetic profiles for paternity analysis and individual identification of the North Atlantic right whale (Eubalaena glacialis)
The endangered North Atlantic right whale (Eubalaena glacialis) has been internationally protected from whaling since 1935 but recovery has been slow compared to the southern right whale (Eubalaena australis) due to anthropogenic mortalities and poor reproduction. Prey availability, genetic variability, and alleles of genes associated with reproductive dysfunction have been hypothesized to contribute to low calf production. The North Atlantic Right Whale DNA Bank and Database contains 1168 samples from 603 individuals. I added 115 new genetic profiles to the database which now contains profiles for 81% of individuals alive since 1980. Paternity assignments using these profiles resulted in 62% of sampled calves being assigned a father and only 38% of candidate males being assigned a paternity. This may suggest false exclusion due to genotyping errors or the existence of an unknown group of males. The use of the DNA database allowed for the identification of 10 deceased individuals which has implications for identifying cause of death and reducing mortalities. However, genetic identification is dependent on the time of post-mortem sample collection which influences DNA quantity and quality. An assessment for variations in methylenetetrahydrofolate reductase, a candidate gene associated with reproductive dysfunction, revealed six females heterozygous for a synonymous A/T variant in exon four which may influence reproductive success through changes in enzyme production, conformation or activity. Author Keywords: Eubalaena glacialis, Forensic Identification, Genetic Profiling, North Atlantic Right Whale, Paternity, Reproductive Dysfunction
Assessment of the impacts of noise and vessel traffic on the distribution, abundance and density of Chinese humpback dolphins (Sousa chinensis chinensis) in the waters of Hong Kong
Marine mammals with near-shore distributions are susceptible to human-related recreational and commercial disturbances, particularly near densely populated and industrialized coastal areas. A population of over 2,500 Chinese humpback dolphins (Sousa chinensis chinensis) occupies the Pearl River Estuary in southern China. A part of this population uses Hong Kong’s waters off of Lantau Island, where they are subjected to a number of anthropogenic threats, including vessel disturbance, fisheries interactions, and boat-based tourism. Previous research has shown that the abundance of this subspecies in Hong Kong’s waters has declined about 60% since 2003. Using a combination of acoustic recordings, dolphin distribution and abundance data, and vessel traffic information I found that: 1) Four types of vessels common to the waters on Hong Kong generate noise that is audible to Sousa chinensis chinensis; 2) The spatial distribution of underwater noise in Hong Kong’s waters does not significantly vary among the six sites sampled; 3) High-speed ferry traffic and passenger volume has increased dramatically during the study period; 4) There has been a significant decline in dolphin density in areas within and near vessel traffic; and 5) Dolphins are most at risk of vessel collisions and being exposed to vessel noise near Fan Lau and within the Urmston Road waterway just northeast of the Sha Chau and Lung Kwu Chau Marine Park . These results can inform future acoustic studies on this species and guide conservation and management efforts in Hong Kong. Author Keywords: Human impacts, Humpback dolphin, Management, Noise, Sousa chinensis chinensis, Vessel traffic
Effects of Hydroelectric Corridors on the Distribution of Female Caribou (Rangifer tarandus) on the Island of Newfoundland
A species of concern is caribou (Rangifer tarandus), a species in decline across most of the circumpolar North, including the island of Newfoundland. Resource exploitation across caribou ranges is projected to accelerate in the coming decades as oil extraction, roads, forest harvesting, and mining encroach upon their habitat. Hydroelectric corridors, in particular, are anticipated to expand significantly. The effects of these linear developments on caribou habitat remain unclear. I capitalized on an existing dataset of nearly 700 radio‐tracked female caribou, 1980‐2011, to determine the long‐term effects of hydroelectric corridors on their seasonal distributions. Using an island-wide landcover map, I tested for preference or avoidance hydroelectric corridors in each of 4 seasons using the Euclidean Distance habitat selection technique at the extent of the population ranges (broad scale) for each decade (1980s, 1990s, 2000s). I also examined the distribution of caribou ≤10 km and ≤20 km from corridors (narrow scale) for five herds. At the broad scale, the response was highly variable. Female caribou were most likely to avoid corridors during the 1980s, but they often exhibited little aversion, even preference for corridors, particularly in the 1990s and 2000s. Hydroelectric corridors, therefore, did not appear to be limiting at this scale. I surmise that these long-term shifts reflect the heightened density-dependent food limitation for Newfoundland caribou. At the narrow scale, avoidance of corridors was common – typically, a 50% reduction in use within 2-5 km of the corridor. Consistent with the broad scale, caribou exhibited the strongest tendency for avoidance in the 1980s compared to subsequent decades. Understanding space-use remains central to the study of caribou ecology. Hydroelectric lines in Newfoundland tended to coincide with other anthropogenic features. Cumulative effects must be considered to understand the full range of effects by human developments on caribou. Author Keywords: Caribou, distribution, habitat, hydroelectric, Newfoundland, Rangifer tarandus
Sex-Specific Graphs
Sex-specific genetic structure is a commonly observed pattern among vertebrate species. Facing differential selective pressures, individuals may adopt sex-specific life historical traits that ultimately shape genetic variation among populations. Although differential dispersal dynamics are commonly detected in the literature, few studies have investigated the potential effect of sex-specific functional connectivity on genetic structure. The recent uses of Graph Theory in landscape genetics have demonstrated network capacities to describe complex system behaviors where network topology intuitively represents genetic interaction among sub-units. By implementing a sex-specific network approach, our results suggest that Sex-Specific Graphs (SSG) are sensitive to differential male and female dispersal dynamics of a fisher (Martes pennanti) metapopulation in southern Ontario. Our analyses based on SSG topologies supported the hypothesis of male-biased dispersal. Furthermore, we demonstrated that the effect of the landscape, identified at the population-level, could be partitioned among sex-specific strata. We found that female connectivity was negatively affected by snow depth, while being neutral for males. Our findings underlined the potential of conducting sex-specific analysis by identifying landscape elements that promotes or impedes functional connectivity of wildlife populations, which sometimes remains cryptic when studied at the population level. We propose that SSG approach would be applicable to other vagile species where differential sex-specific processes are expected to occur. Author Keywords: genetic structure, Landscape Genetics, Martes pennanti, Population Graph, sex-biased dispersal, Sex-Specific Graphs
Adaptive Genetic Markers Reveal the Biological Significance and Evolutionary History of Woodland Caribou (Rangifer tarandus caribou) Ecotypes
Migratory and sedentary ecotypes are phenotypic distinctions of woodland caribou. I explored whether I could distinguish between these ecotypes in Manitoba and Ontario using genetic signatures of adaptive differentiation. I anticipated that signatures of selection would indicate genetic structure and permit ecotype assignment of individuals. Cytochrome-b, a functional portion of the mitochondrial genome, was tested for evidence of adaptation using Tajima’s D and by comparing variations in protein physiology. Woodland caribou ecotypes were compared for evidence of contemporary adaptive differentiation in relation to mitochondrial lineages. Trinucleotide repeats were also tested for differential selection between ecotypes and used to assign individuals to genetic clusters. Evidence of adaptive variation in the mitochondrial genome suggests woodland caribou ecotypes of Manitoba and Ontario corresponded with an abundance of functional variation. Woodland caribou ecotypes coincide with genetic clusters, and there is evidence of adaptive differentiation between migratory caribou and certain sedentary populations. Previous studies have not described adaptive variation in caribou using the methods applied in this study. Adaptive differences between caribou ecotypes suggest selection may contribute to the persistence of ecotypes and provides new genetic tools for population assessment. Author Keywords: Adaptation, Cytochrome-B, Ecotype, RANGIFER TARANDUS CARIBOU, Selection, TRINUCLEOTIDE REPEAT

Pages

Search Our Digital Collections

Query

Enabled Filters

  • (-) ≠ Morrison
  • (-) ≠ Kallikragas
  • (-) = Conservation biology

Filter Results

Date

2011 - 2031
(decades)
Specify date range: Show
Format: 2021/10/16

Degree Discipline