Understanding the mechanisms that control the rate and trajectory of primary succession can lead to insights for ecosystem rehabilitation. Proposed mechanisms include life history traits and nutrient limitation. To explore how these mechanisms can drive successional dynamics, I devised a stoichiometric ecosystem-level model that considered the role of nitrogen and phosphorus limitation in plant primary succession in conjunction with life history traits. This model was applied to the plant community on Mount St. Helens to check the validity of the mechanisms. The results show the competitive hierarchy of plants at the local scale can be explained by nutrient limitation and plant stoichiometry. At regional scales, life history traits interact with local processes to shape community structure and successional dynamics. At all scales, the presence of Lupinus lepidus, a nitrogen-fixer, significantly altered community dynamics and succession. This study suggests that primary succession can be examined within the framework of ecological stoichiometry. / Ecology

Developing effective conservation strategies requires an empirical understanding of species' responses to human-mediated disturbances. Observable responses are typically limited to dramatic changes such as wildlife population declines or range shifts. However, preceding these obvious responses, more subtle responses may signal larger-scale future change, including changes in species' behaviours and interspecific interactions. Disturbance-induced shifts to species' diel activity patterns may disrupt mechanisms of niche partitioning along the 24-hour time axis, altering community structure via altered competitive interactions. I investigate the main questions and methods of analysis applicable to camera-trap data for furthering our understanding of temporal dynamics in animal communities. I apply these methods to evaluate the impacts of human-mediated disturbance on species' activity patterns and temporal niche partitioning in two separate studies, focusing on responses in the mammalian carnivore community. In the Canadian Rocky Mountain carnivore guild, species alter diel activities in relation to anthropogenic landscape development, although these shifts may be manifesting through indirect biotic effects instead of direct responses to human disturbance. Mesocarnivore species on a mixed-use landscape featuring anthropogenic land-use and introduced free-ranging dogs (Canis familiaris) shift activities in relation to spatiotemporal dog activity. Native carnivores partition diel activities differently on open landscapes of enhanced predation risk but abundant prey resources. Detecting shifts in species' temporal behaviours and competitive interactions may enable identification of potential precursors of population declines and shifting community assemblages, providing us with opportunities to pre-emptively manage against such biodiversity losses on human-modified landscapes. / Graduate

Tallgrass prairie in North America has been highly reduced and degraded by human activity (e.g. agriculture) and now human facilitated restoration is necessary to preserve and reestablish the biodiversity, structure and function of this system. In historical tallgrass prairie large ungulates (e.g. Bison bison) were keystone species that regulated many ecosystem properties and functions. Today, restored prairie often lacks these historical ungulates and white-tailed deer (Odocoileus virginianus) have largely assumed the role of dominant ungulates in small, tallgrass prairie restorations. Little is known about how white-tailed deer affect the development of plant communities and ecosystem function during the onset of prairie restoration. In June 2012 an agricultural field was restored to native prairie species in Konza Prairie Biological Station (KPBS) near Manhattan, KS. Immediately following seeding, experimental plots were established and fences were constructed in half of the plots to excluded white-tailed deer. From 2012 to 2013 deer browse of forbs, aboveground biomass (total, sown forbs, sown grasses, volunteer forbs and volunteer grasses), light availability at the soil surface, soil nutrients, and plant community composition were measure inside and outside of exclosures. The first year of this study occurred during a severe drought which diminished in year two, presenting the opportunity to examine the interaction of climate and deer browse on restoration. In plots where deer had access, the percentage of forbs browsed ranged from 1.3 to 10.5%. The effect of deer browsing on aboveground biomass varied across years for each category of biomass. Total biomass appeared to be regulated more strongly by deer than climate, as unbrowsed plots produced similar biomass in each year despite major climatic variation, while browsed plots did not follow this trend. Across all sampling periods, deer browsing increased light availability by 20%. In year two inorganic N was 19% lower in browsed plots, though potential net N mineralization did not vary between treatments. Plant communities were significantly different between years and, between browsed and unbrowsed plots as time and browsing affected community composition, diversity and richness. Deer browsing increased diversity and richness by 24% and 22% respectively. Community composition was most greatly affected by browsing in year one corresponding to the highest rates of browsing and greatest differences in aboveground biomass. These results indicate that deer can have substantial effects on the initial establishment of prairie communities as well as resource availability from the onset of restoration.

Mammals in freshwater aquatic systems play important roles as ecosystem engineers, trophic transfer agents, and apex predators, thus acting as indicators of freshwater ecosystem function. Watersheds inhabited by semi-aquatic mammals have increased links between adjacent terrestrial and aquatic ecosystems compared to watersheds where they are not present. Semi-aquatic mammals not only exert top-down influences on streams, but are affected by bottom-up forces from the riparian system itself. The goal of this study was to identify variables that correlate with the presence of beaver (Castor canadensis), muskrat (Ondatra zibethicus), mink (Neovison vison), and river otter (Lontra canadensis), including their interactions, resulting in a better understanding of the areas where these semi-aquatic mammals occur and their effects on the riparian system. The objectives of this study were (1) to identify variables related to the probability of detection, initial occupancy, colonization, and extinction of the 4 semi-aquatic mammals in southern Illinois; and (2) to test if the reintroduction of river otter has changed stream food webs. To address my first objective, I sampled 120 bridge sites in 2 periods (winter: Jan-Feb; and spring: Mar-Apr) during 2012–2014 in 11 major watersheds in the southern third of Illinois (44,526 km2) to estimate multi-season occupancy. Each survey unit was a 400-m stream segment visited twice by 2 observers for a total of 4 observations per site per period. Observers recorded all mammal signs found, including sign species and type. Sites were Intensive Basin Survey Sites sampled by Illinois Department of Natural Resources (IDNR) and Illinois Environmental Protection Agency (IEPA), allowing data collected by the state to be available for explanatory variables for mammal occupancy. Data collected by the Illinois Natural History Survey (INHS) also were available for a subset of sites. I collected local- and landscape-scale habitat and weather variables for each site. I developed hypotheses regarding occupancy of sites based on land-cover, human disturbance, and stream attributes for each species. I developed additional hypotheses regarding prey availability and water quality for river otter and mink. Sites used in each analysis were dependent on data available to address the hypotheses of interest. Beaver and muskrat were present at ≥100 of 103 sites for ≥1 observation. Naïve occupancy was high (≥82%) every year for both species. Detection probabilities for beaver and muskrat were best predicted by survey period. Beaver detection remained fairly constant across survey periods except for a decrease in winter 2014, whereas muskrat detection was generally lower during winter and higher during spring. Beaver were more likely to occupy larger streams than smaller streams during the initial survey period. Sites that lacked a dominant land-cover had a lower probability of beaver colonization than sites dominated by agriculture or woody vegetation at the landscape scale. In addition, the probability that a site would be colonized by beaver during the study increased with availability of water within 1 km of the surveyed segment, increased stream density, sites at larger streams, and river otter presence during the previous period. The probability of site extinction decreased as stream size, stream density within 1 km, and water availability within 500 m of the survey segment increased. Occupancy of muskrat during the initial survey period was negatively predicted by % forest in the 1-km riparian area, channel incision, and amount mercury in the sediment. Colonization by muskrats was lower during the long spring to winter intervals than the short winter to spring intervals, and was positively related to the amount of organic carbon in the sediment. The probability of site extinction by muskrat increased with increasing % forest within the riparian area around the stream segment, decreasing 1-km stream density, and when land-cover within 1 km of sites was dominated by agriculture or woody vegetation. Multi-season occupancy of river otter and mink were assessed in 2 separate analyses that used either land-cover and management variables or prey availability and riparian community composition, respectively. In the first analysis, river otter and mink were present at ≥84 of 103 sites. Naïve occupancy was higher every year for mink (≥88.3%) than for river otter (≥55.3%). Detection of river otter and mink in the first analysis increased as substrate availability increased. Occupancy of river otter during the initial survey period was predicted by large stream size, low % developed area within 250 m of the surveyed segment, and proximity to nearest river otter reintroduction point. Probability of colonization by river otter varied by survey period and was higher at sites with larger streams, higher stream density, lower % developed area, and within a known river otter population area. Site extinction by river otter in the first analysis varied by survey period and was linked to increased organic carbon in the sediment, and decreased road density within 1 km of the surveyed segment. River otter harvest was not found to affect site colonization or extinction. Mink occupancy during the initial period was negatively associated with water availability within 100 m of the survey segment. Site colonization by mink varied by month and increased with increasing developed area within 100 m of the surveyed segment, increasing channel incision, and decreasing rainfall. Probability of site extinction for mink increased as stream size and developed area within 500 m of the surveyed segment increased, and when woody vegetation was the dominant land-cover type within 1 km of the surveyed segment. The second analysis of multi-season occupancy of river otter and mink used 77 sites, 81.8% of which had ≥1 river otter detection in the study and 98.7% of which had ≥1 mink detection. Naïve occupancy differed between years but gradually increased for river otter and remained high (≥93.5%) for mink. Increasing substrate availability increased the probability of river otter detection, whereas mink detection varied by survey period. Occupancy during the initial survey period was higher in sites closer to the reintroduction points for river otter. Probability of colonization of river otter was positively associated with macroinvertebrate IBI and fish species richness, sites with high fish species richness of fish families preferred by river otter also had reduced otter extinction probability. No tested variables predicted initial occupancy for mink, but mink were more likely to colonize sites with increased fish richness and when muskrat were present during the previous period. Mink had decreased probability of extinction in sites with increasing mussel community index. My results indicate that semi-aquatic mammals in Illinois were affected by a riparian habitat, water availability, and stream community variables at both the landscape and local scale. I found high occupancy of mink, beaver, and muskrat across the entire landscape of southern Illinois, and my results suggest that the geographic range of river otter continues to expand. Relationships of occupancy of these semi-aquatic mammals to measurements of urban areas and human disturbance were not consistent across all species. Mink and river otter occupancy were both predicted by aspects of prey availability, indicating the importance of predator-prey relationships in occupancy dynamics of riparian predators. Hypotheses regarding predator pressure and changes in environmental variables were used to test the effects of river otter reintroduction on stream communities. For this objective, I used structural equation models. I compared fish and macroinvertebrate communities from before (1982-1995) and after (2005-2013) reintroduction of river otter, which occurred in 1994–1996. Fish and macroinvertebrate community data for 35 sites located throughout 6 major watersheds in southern Illinois (25,550 km2) were obtained from state agencies. Changes in stream communities were evaluated using 4 metrics (species richness, species dominance, skewness in size distribution of prey, and proportion of individuals in the size class preferred by river otter). Neither the inclusion of river otter site use nor change in stream quality, measured by change in % forest, improved models over the simple model which only included fish and macroinvertebrate communities. Overall, I found no evidence that river otter presence or change in forest cover affected stream fish and macroinvertebrate communities.

Orientador: Denise de Cerqueira Rossa-Feres / Coorientador: Vitor Hugo Mendonça do Prado / Banca: Fausto Nomura / Banca: Cinthia Aguirre Brasileiro Professor / Resumo: A diversidade local de espécies pode ser regulada por fatores locais (como competição, perturbação, condições abióticas, dispersão) e regionais (como a história climática, evolução e migração). O objetivo deste estudo foi entender quais fatores locais e da paisagem melhor explicam os padrões de distribuição de espécies de anuros. O estudo foi desenvolvido na região noroeste do Estado de São Paulo, entre julho de 2007 e fevereiro de 2009, empregando duas metodologias de amostragem: 1) armadilhas de interceptação e queda, instaladas no interior de 18 fragmentos florestais, e 2) procura auditiva e visual em 64 corpos d'água da região. Das 37 espécies conhecidas para esta região, 30 foram registradas neste estudo, sendo 13 no interior dos fragmentos florestais e 29 nos corpos d'água. A eficiência de amostragem foi avaliada por rarefação da curva do coletor. A curva do coletor atingiu a assíntota, indicando que para encontrarmos mais uma espécie o efeito amostral deveria ser muito intensificado. Modelos lineares generalizados (GLM) e análise de ordenação foram aplicados aos dados dos fragmentos florestais, incluindo uma variável espacial (coordenadas geográficas) como preditor de riqueza e composição além das variáveis ambientais que descrevem os fragmentos florestais. Para verificar qual variável ou conjunto de variáveis explicam a riqueza e composição de espécies observadas nos corpos d'água, foram aplicadas análises de regressão linear e correlação de matrizes. Se um efeito significativo fosse detectado, isso indicaria que a riqueza e composição de espécies dos fragmentos florestais e/ou corpos d'água seriam formadas por processos de seleção de habitat. Os resultados indicam que nem as características nem a sua localização geográfica dos fragmentos tem efeito significativo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Species local diversity can be regulated by local (such as competition, disturbance, abiotic conditions) and regional factors (climate history, evolution and migration). The aim of this study was understand which local and landscape factors best explain the distribution patterns of anuran species. The study was developed in the northwestern São Paulo State between july 2007 and february 2009, using two sampling methods: 1) pitfall traps, installed in the interior of 18 forest fragments, and 2) hearing and visual search in 64 ponds located around the forest fragments. We registered 30 of the 37 known species to the study region: 13 in the interior of forest fragments and 29 in ponds. A rarefaction curve was used in the assessment of the sampling efficiency and results indicate that sampling effort should be highly intensified in order to find one more species. We characterize forest fragments and ponds by measuring five and ten environmental variables, respectively. These environmental variables were used as predictors of richness and composition of these habitats. General Linear Models (GLM) and ordination analysis were applied to the forest fragments data, which includes a spatial variable (geographic coordinates) as a predictor of richness and composition besides environmental variables that describe the forest fragments. In order to verify which variable or set of variables would explain the observed species richness and composition in ponds, it was applied linear regression and matrices correlation to the data. If a significant effect was detected, this would indicate that species richness and composition of the forest fragments and/or ponds are shaped by habitat selection processes. Results indicate that neither the fragments characteristics nor their location have significant effect over the species... (Complete abstract click electronic access below) / Mestre

As an ecological disturbance agent, wildfire is highly responsive to spatial and temporal variables. At the landscape scale, the spatiotemporal characteristics of fire are influenced by climate, which is non-stable and subject to oscillations, and by weather, which affects the intensity of burning and the severity of fire effects over short time periods. Like wildfire, vegetation communities and fuels are similarly influenced and modified by climate and weather, which configure not only the type of burning possible at any given time, but also the fire effects produced by burning. Furthermore, ignition sources, both natural and anthropogenic, vary over space and time, whether they are from natural ignitions in response to weather and climate factors, and anthropogenic ignitions, which are much less constrained. Within a given physiographic setting, the spatiotemporal conditions of wildfire can be understood as fire regimes, which can be expressed in terms of typical fire frequency, season of burning, ignition source, duration, fire size, patch size, fire rotation, and return interval. As a dynamic assemblage, vegetation communities, combustible fuels, ignition sources, and fire regimes are arrayed over topographic features at landscape scales. Humans are able to affect various and multiple components of this dynamic assemblage. Humans have the most direct control over ignitions, both in terms of adding ignitions to the weather and climate-modulated background of natural ignitions, or by suppressing anthropogenic ignitions and suppressing fires that do start. Humans can also manipulate vegetation communities and fuel complexes, either promoting or diminishing the chance for fires to burn and spread. Humans have far less control over weather and climate, although the enhanced greenhouse effect is beginning to be expressed in terms of climate change and unusually extreme weather, including weather variables that drive fire growth and spread, including low humidity, high temperatures, and increased winds. The objectives of this dissertation were to: (1) investigate the influences of several waves of human occupation on temporal fire regime characteristics in the Chiricahua Mountains across major topographic settings and forest types, and to detect cessation of widespread, low-intensity wildfire in specific locations; (2) account for the mechanisms by which the U.S. state has managed fires by managing anthropogenic ignitions, which has contributed to long-term deviation in formerly frequent fire regimes; (3) examine the effects from the return of large and severe wildfire following decades of fire prevention and suppression by categorizing the ecological trajectories of montane forests following mixed-severity reburning; and (4) understand how the post-disturbance recovery of burned areas is influenced by the response of shrub species to variations in fire severity, with the post-fire regeneration strategies of shrub species driving differences in patch structure and total cover. Major findings and contributions of this research include identifying distinct anthropogenic influences on temporal fire regime characteristics in several forest types in an Arizona Sky Island, including shortened fire frequencies during times of conflict between Apaches and colonizing forces. We found that periods of conflict with Spanish and later American militaries exerted an influence on fire frequencies, with higher-elevation forests burning more frequently than pre-Apache periods or during episodes of peacetime. We also find that single-tree fires, which are likeliest to express anthropogenic ignitions, do not significantly correspond to multi-year patterns in climate (Appendix A). We found that the U.S. state used Smokey Bear and other wildfire prevention media as a pyropolitical instrument aimed at simultaneously managing people, landscapes, and flammable forests, in the process binding proper fire behavior to notions of citizenship, territory, and ecology. The wildfire prevention campaign, with Smokey Bear as its avatar, was successful because it remained flexible in the face of social, economic, and environmental change within the United States, but the ultimate result of this success is an environmental feedback loop by which fire prevention and suppression produce the need for ever-greater state response (Appendix B). We found that mixed-severity reburning has differential effects on various structural and demographic components of vegetation communities, with trees, shrubs, and regeneration responding differently according to plant functional traits. Although the effects of recent disturbance tend to overwrite prior disturbance, mixed severity fire produces different response in plant communities than single events. Repeated high and moderate severity fire suppress tree regeneration and shift the community to shrub dominance, with recovery in pine-oak vegetation types dominated by resprouting species and by resprouting species in mixed conifer. Unburned areas contain different vegetation communities, with pine-oak forests increasing the proportions of fire-intolerant species typical of mixed conifer, as well as oaks and other potentially shrubby species growing as trees (Appendix C). Finally, we found that the proportion of the landscape dominated by shrub cover and the structure of shrub patches is influenced strongly by fire severity, with high severity burns producing the largest shrub patches as well greater area:stem ratios. Unburned areas have the lowest amount of shrub cover, and shrub patches tend to be single-stemmed, indicating that sufficiently long fire-free periods can produce monopodial trees that would otherwise grow in shrub form. The effects of antecedent disturbance can be seen in shrub patch structure, suggesting that the organizing effects of fire can persist for decades (Appendix D). Together, this body of work underscores the means by which human activities interact with the natural world to produce historic fire regimes, and the ecological communities that arise following long periods of fire regime disruption.

Islands have typically been considered isolated entities, patches of habitat surrounded by an entirely inhospitable marine or aquatic environment. However, there is increasing evidence that islands can be linked to the surrounding environment through the influx of subsidies, which may alter the relationship between species richness and island area. Little empirical work has been done to test these hypotheses in productive ecosystems, however. To better understand the effects of the influx of marine subsidies on island ecosystems, I assessed plant community responses to wrack biomass in an observational study on 74 small islands on the Central Coast of British Columbia. In Chapter 2, I focused on 1) how seaweed wrack subsidies affect the diversity of understory plant communities, 2) whether wrack subsidies affect the species-area relationship, and 3) whether the effect of wrack subsidies is mediated by landscape-scale habitat characteristics such as island area and shoreline slope. To assess the support for these hypotheses, I used selected from models that combined plant community data, remotely-sensed habitat characteristics, and shoreline wrack biomass. I used hierarchical models to provide further insight into the cross-scale influence of these factors on plot-scale responses. I found that wrack subsidies were associated with increased island-scale plant species richness. Although wrack subsidies did not alter the relationship between species richness and area on these islands, I found that smaller islands had higher levels of marine-derived nitrogen, indicating a greater influence of marine subsidies on the nitrogen pool of smaller islands. My results add to the weight of evidence that marine subsidies are drivers of large-scale patterns of species richness, and that the linkage between islands and the surrounding environment has implications for island communities. / Graduate

Anthropogenic development is altering watersheds and threatening freshwater ecosystems and the resources therein. Direct impacts of industry including conversion of land cover and increased water withdrawals from rivers, compounded with indirect influences such as climate change, collectively affect the health and sustainability of freshwater ecosystems. Many studies have indicated a suite of ecological impacts that large-scale anthropogenic land use and development impose on the structure and function of riverine systems. The overarching goal of this thesis was to examine the potential impacts associated with land use disturbance and Oil Sands (OS) mining operations on fish community composition patterns in three rivers located in the Athabasca Oil Sands Region (AOSR). Using historical data sets, this thesis attempted to evaluate disturbance-related patterns in fish community composition. Fish community-environmental relationships were investigated on a temporal scale, across which community composition could be constrained or altered by development. Structural and trait-based changes in fish community composition were analyzed to determine whether significant variation between levels of development (pre versus post) in the AOSR could be attributed to observed changes in fish community metrics. No significant difference in community composition patterns was observed between levels of development; however, there was a significant decline in fish species richness on a regional scale. The lack of significant results could be attributed to the limitations of the collected data, including temporal gaps, inconsistent sampling methods, and seasonal sampling inconsistencies. Furthermore, the scale of interpretation between individual tributaries and the regional datasets, demonstrates that studies of fish communities on a regional scale can elucidate different states of community change, implying that local controls can play a role in species presence/absence. An assessment of the features and patterns of the hydrograph that could explain variation in fish communities was constrained due to dataset and subsequent methodological limitations. Currently, there is an inability to link changes (historical) to hydrologic regimes, land use or development within these systems, and how they have impacted fish communities therein due to inconsistencies in the methods and sampling during most of the pre-development and for a portion of post- development time span (until 2009). Long-term, standardized community monitoring will be critical to gain a greater understanding of how land management practices affect fish communities and what kind of ecosystem management can mitigate impacts to streams, rivers and the biota therein. Further recommendations were made from synthesizing these findings in conjunction with relevant literature and are intended to provide an improved understanding of the long-term cumulative changes within these systems and to help guide and improve future monitoring plans in the AOSR. / Graduate

The Infectious Diseases of East African Livestock (IDEAL) project followed 548 East African Shorthorn Zebu (EASZ) calves in Western Kenya for the first year of life and monitored the sequelae of infections by multiple parasites. More than 50 different parasites were identified during this time. The IDEAL project also gathered environmental information about the farm and collected phenotypic data on the calf and its dam. Calves were also genotyped for 55,777 single nucleotide polymorphisms (SNPs). Recent research has looked at coinfection in rodents and humans but not in indigenous cattle. Here I investigate the evidence for coinfection in EASZ and study the associations occurring between coinfecting parasites. In addition, I examine the genetic and phenotypic factors which predispose an individual to infection with multiple parasites. Using information gathered by the IDEAL project, my thesis consists of the following chapters. An investigation of the nature of concurrent associations and of lagged effects between different parasites. Using the parasites Theileria spp., Coccidia spp., Strongyloides spp., strongyles and Calicophoron spp. I show that the patterns of association between different parasites are complex: there is evidence for both positive and negative associations. For example, infection with Strongyloides spp. increased the risk of strongyle infection. Conversely, in other cases, being infected with one parasite decreased the calf’s risk of infection with another parasite: for example, infection with Strongyloides spp. decreased the risk of infection with Calicophoron spp. A study of the relationship between different respiratory viruses and their effect upon the host. I confirm that positive associations exist between Infectious Bovine Rhinotracheitis (IBR), Bovine Viral Diarrhoea Virus (BVDV) and Bovine Parainfluenza Virus Type 3 (PIV3) in a previously unstudied setting; being seropositive for any one of these three viruses means that an individual is more likely to be seropositive for the other two viruses than expected by chance. Being seropositive for IBR, BVDV or PIV3 did not affect the average daily weight gain of the calf, nor did PIV3 and BVDV serostatus have an effect on the calf ever experiencing a clinical episode. However, IBR seropositive calves were less likely to experience a clinical episode of some form, suggestive of some protective aspect of IBR. An examination of the sources of variation in faecal strongyle egg counts (EPG), and their association with body weight, host genetics and a suite of haematological measures. Using estimates of relatedness derived from the SNP data, I established that strongyle EPG has a genetic basis in EASZ, with a heritability of 23.9% (S.E. = 11.8%) and showed a consistently strong negative association between strongyle infection and the haematological parameters white blood cell count, red blood cell count, total serum protein and absolute eosinophil count. Furthermore, calf body weight at 1 week old was a significant predictor of strongyle EPG at 16-51 weeks, with smaller calves being predisposed to a higher strongyle EPG later in life. A genome-wide association study (GWAS) to investigate if there is a genetic predisposition to East Coast Fever (ECF) death and a genetic basis to the packed cell volume at the time of seroconversion to Theileria parva (PCVTP). I found no robust evidence for a relationship between genotyped single nucleotide polymorphisms (SNPs) and ECF death or PCVTP. The effect of sample size upon GWAS and significance thresholds was investigated further through simulations. I conclude that the small number of cases influences the probability of association between a SNP and the phenotypic trait. Smaller case numbers produce more artifactual associations with SNPs, an effect not fully compensated for by the standard Bonferroni correction, suggesting that an empirical significance threshold should be used to directly account for sample size. The results of this thesis provide an understanding of the associations occurring between different parasites, and of their causes and consequences. I discuss the results in the context of their implications for disease control strategies, suggesting the benefits of an integrated approach to control worm and T. parva alongside the possible genetic selection for parasite resistance and supplementary feeding of lightweight individuals to improve the health of EASZ.

It is an unresolved paradox that non-native species are successful in novel environments whereas native species, presumably adapted to that environment, decline. This knowledge gap has persisted because third party processes in invasion ecology have been overlooked. Ungulate densities are increasing due to the eradication of predators and landscape change and I asked how herbivory and invasion might interact to cause declines of native species. In Garry oak meadows, Canada’s most endangered ecosystem, native forbs have declined relative to non-native grasses and I tested the facilitatory role of herbivory in that degradation. My investigations, novel to the field, were conducted on islands spanning the Canada-US border. Islands served as natural experimental units in a mensurative study of abundance patterns in seven plant groups and 15 focal species along gradients of herbivory, biogeography, soil depth, and human activities. Increasing ungulate densities were related to declines in abundances of native forbs, and increasing abundances of non-native annual grasses. These regional patterns were upheld by two plot-based, 2x2 factorial experiments that contrasted the fitness of native species under manipulations of herbivory and competition for light. Specifically, I showed that ungulates limited the establishment, growth, survival and reproduction of seedlings and transplanted native forbs and shrubs and that competition from non-native species had little effect. I also calculated forage selectivity indices and tested the efficacy of fencing and cutting to reduce competition, for the restoration of native community biomass. Non-native annual grasses were rarely browsed and increased with increasing ungulate density. Non-native perennial grasses declined with herbivory, however, their regional abundances were unaffected by ungulate density despite being preferentially foraged. That non-native annual and perennial grasses differed in their responses to herbivory has consequences for restoration and illustrates the challenge of developing a comprehensive theory of invasion. Reducing ungulates, necessary for the recovery of native forbs, also benefits non-native perennial grasses and therefore their removal speed recovery of Garry oak meadows. Despite advances in invasion ecology, scientists and managers are disconnected and research is rarely implemented. I conclude by proposing seven solutions to facilitate the integration of science into management. / Forestry, Faculty of / Graduate