Les introductions d'individus domestiques au sein de populations naturelles sont des pratiques courantes partout dans le monde. Cependant, de telles pratiques peuvent modifier l'intégrité génétique des populations naturelles selon l'étendue des différences génétiques entre individus sauvages et domestiques, ainsi que l'intensité des ensemencements.Les ensemencements peuvent ainsi générer de l'hybridation entre les populations sauvages et domestiques. Cependant, les ensemencements, seuls, n'expliquent pas toujours les patrons d'hybridation observés, suggérant que d'autres facteurs environnementaux les facilitent aussi. L'objectif principal de cette thèse est d'évaluer les impacts génétiques causés par les ensemencements au sein de populations d'ombles de fontaine ( Salvelinus fontinalis ), l'espèce la plus utilisée pour supporter l'offre de pêche sportive au Québec, Canada. Environ 2000 individus, issus de 24 lacs localisés au sein de 2 réserves fauniques du Québec, ont été génotypés à l'aide de 9 marqueurs microsatellites. À travers le premier chapitre portant sur l'effet de l'intensité des ensemencements sur la diversité et la structure génétique des populations, une augmentation du niveau de variabilité génétique a été observée avec l'augmentation de l'intensité des ensemencements, en raison de l'apport de nouveaux allèles par les poissons domestiques. Et, en conséquence, une homogénéisation de la structure génétique des populations est observée avec l'intensité des ensemencements. Le second chapitre traite de l'évaluation quantitative de l'efficacité globale de deux des principaux logiciels utilisés, STRUCTURE et NEWHYBRIDS, pour déterminer les niveaux d'hybridation au sein de populations d'ombles de fontaine soumises à diverses intensités d'ensemencements. Il apparaît que les deux logiciels doivent être conjointement utilisés pour déterminer les niveaux d'hybridation. L'emploi de STRUCTURE est préférable pour détecter la présence d'hybrides au sein des populations sauvages, tandis que celui de NEWHYBRIDS l'est pour détecter précisément le nombre d'individus hybrides présent dans une population déjà connue pour son hybridation. Ainsi, l'emploi de STRUCTURE aux populations d'ombles de fontaine naturelles montre que le niveau d'hybridation augmente avec l'intensité des ensemencements. Le troisième chapitre fournit une évaluation de l'effet des facteurs environnementaux et de l'intensité des ensemencements sur le niveau d'hybridation observé dans les populations ensemencées d'ombles de fontaine.Les résultats confirment que le niveau d'hybridation augmente avec l'intensité des ensemencements. De plus, une réduction de la disponibilité d'habitats et de sa qualité favorise également l'augmentation du niveau d'hybridation. L'ensemble de ce projet a donc permis de mettre en évidence différents impacts génétiques des pratiques d'ensemencements au sein de populations en milieu naturel. De plus, pour la première fois, l'effet des ensemencements sur l'intégrité génétique des populations naturelles a été prédit à partir de connaissances sur les facteurs environnementaux et des ensemencements. Ces résultats devraient ainsi contribuer à améliorer les directives sur les pratiques des ensemencements au Québec et, de fait, renforcer la protection de l'intégrité génétique des populations naturelles.

This thesis examines the social and economic impacts of the 2014 FIFA World Cup in Fortaleza, Brazil. The study used a budget analysis, and in depth interviews to ascertain the economic impact of the world cup games and the distribution of revenue across different sectors and socio-economic divisions within the local economy. A historical and vulnerability analysis was conducted through the examination of secondary sources (historical documents, census data, previous research on vulnerable populations) to identify groups and spaces of high social vulnerability. Qualitative data was then collected through in depth interviews with sources from all facets of society during the World Cup games and the following summer to identify the social impacts on these vulnerable groups and spaces. The thesis found that the final economic costs for infrastructure and stadium refurbishments associated with the World Cup in Fortaleza far exceeded the projected costs and the final economic impact on the local economy was half of projected estimates. While the city saw social benefits in the celebratory atmosphere and public security provided during the World Cup, there were also negative impacts on socially vulnerable groups and spaces including forced community relocations, increases in cases of commercial sexual exploitation, and rises in violent crime.

Environmental justice communities, those disproportionately affected by pollutants, are simultaneously exposed to multiple environmental stressors and also experience social and cultural factors that may heighten their health risks in comparison to other communities. In addition to being more susceptible to toxic exposures and being exposed to more toxins, such communities may have weakened abilities to combat or rebound from such exposures. Many communities that are overburdened by environmental exposures reject traditional risk assessment approaches that solely consider the effects of single chemicals or mixtures of like chemicals and instead have advocated for the use of place-based approaches and collaborative problem solving models that consider cumulative exposures and impacts. Cumulative risks are the combined risks from aggregate exposures to multiple agents or stressors, including chemical, biological or physical agents and psychosocial stressors. This dissertation adapts three research approaches that each use either publicly available data (“expert” data) or community-generated data about environmental and social factors in Northwest Atlanta’s Proctor Creek Watershed. Through this work, we were able to define cumulative environmental and social impacts experienced by watershed residents and to prioritize geographic areas and environmental challenges for investments in environmental monitoring and further research, community capacity-building, and policy change. A principal finding of the study is that local community knowledge is helpful to fill critical gaps about local conditions and pollution sources than a reliance on expert data alone.

Aquatic ecosystems are especially vulnerable to human impacts associated with agricultural land-use, which provide multiple stressors altering community composition, important ecosystem functions and human valued properties of freshwaters. However, the increased occurrence of excessive levels of nitrate-nitrogen has raised major concerns about toxicity and stress on aquatic life, especially in regions such as the Canterbury Plains, New Zealand. The aims of this thesis were to identify nitrate-nitrogen effects on stream communities, and additionally provide field data to inform proposed national bottom lines for nutrients in New Zealand streams. A field survey was conducted on 41 small streams on the Canterbury Plains spanning a nitrate-nitrogen gradient (mean 0.4 – 11.3 mg/L). Spot nitrate-nitrogen was collected during and after the field survey to measure temporal variation in stream nitrate-nitrogen concentration for six months. This showed nitrate-nitrogen concentration varied between season and sub-region, where concentrations increased in winter and Ashburton had higher nitrate-nitrogen than Rangiora and Lincoln, respectively. These regimes of nitrate-nitrogen showed similar patterns in mean, median and maximum concentrations. To be confident my spot nitrate-nitrogen provided a true representation of long-term water chemistry, I compared Environment Canterbury 12 monthly data with my six monthly data in a sub-set of 15 sites. This comparison showed similar nitrate-nitrogen patterns and range of values between the two datasets. I then compared 12 common benthic invertebrate biotic metrics with my nitrate-nitrogen data and found none were correlated with this contaminant. For example, the Macroinvertebrate Community Index and quantitative variant (QMCI) derived to measure the response to organic pollution provided inconsistent results when applied to my streams. Nevertheless, gut content stoichiometry of the common mayfly grazer Deleatidium spp. indicated improvement in food quality (lower C:N ratio) with higher nitrate-nitrogen concentrations. These results indicated either nitrate-nitrogen does not alter invertebrate structural metrics across this nitrate-nitrogen gradient, or that these biotic metrics measure community structure aspects not affected by nitrate-nitrogen. I then investigated possible community composition patterns across the nitrate-nitrogen gradient. Unconstrained ordination (on presence/absence data) showed invertebrate communities at my sites were influenced primarily by discharge and shade, with the next most important driver being nitrate-nitrogen. A constrained ordination (on the same data) testing the singular effect of nitrate-nitrogen showed a marginally non-significant change in composition, with higher variability in community composition at higher nitrate-nitrogen concentrations. A further aim of my study was to test the draft nitrate-nitrogen bands proposed by Hickey (2013). These nitrate-nitrogen bands may advise guidelines to protect aquatic organisms as required by the National Policy Statement on Freshwater. Analysis of my invertebrate communities showed differences in composition, particularly at < 1 and > 6.9 mg/L bands. Several predatory caddisfly taxa: Triplectides, Neurochorema and Oeconesus were identified as potential indicator species of communities associated with low nitrate-nitrogen. These findings show that nitrate-nitrogen effects are difficult to detect, and that it is not the main driver of community composition in Canterbury streams. However, nitrate-nitrogen may be an important stressor for sensitive benthic invertebrate communities, as effects were observed on pollution tolerant organisms in this study. Therefore, this research has implications for freshwater ecologists and environmental managers striving to improve the health of streams on the Canterbury Plains.

Invasive species, a top threat affecting global biodiversity, become invasive through a process including four stages: transport, establishment, spread, impact and integration. Species currently in this process provide opportunities to empirically derive the mechanisms driving each of these stages, make predictions based on these mechanisms and then to test these predictions. This research examines the current invaded distribution, potential invasion and community-level impacts of a popular aquarium trade fish (Hemichromis guttatus Günther, 1862) in an endemic hotspot, Cuatro Ciénegas, in Coahuila, México and discusses the policy and conservation management implications of these findings. In Chapter 1, the problem of invasive species, the study site and the focal species of this work are introduced. In Chapter 2, the critical thermal minimum and maximum temperature limits and temperature preference of H. guttatus are identified because temperature is hypothesized to be an important factor controlling this fish’s distribution. The results indicate that H. guttatus has a wide temperature tolerance range (a characteristic of a ‘good’ invader), that preference is a more informative metric for predicting invasion than absolute tolerances, and that resource-poor environments may promote searching behaviors that cause an invasive fish to increase its range. In Chapter 3, the results of a field survey are analyzed and temperature, pH, depth and the presence of vegetation are all found to be related to H. guttatus presence. Invasion risk of several as-of-yet uninvaded sites in Cuatro Ciénegas is assessed. In Chapter 4, competitive and predatory interactions of H. guttatus on an endemic, threatened cichlid (Herichthys minckleyi) and a macroinvertebrate community respectively are investigated. The results suggest that while H. guttatus does not directly impact H. minckleyi through competition in these conditions, it may inhibit reproduction and alter H. minckleyi’s behavior through aggressive interactions. In Chapter 5, all results are synthesized and a determination of the invasive status of H. guttatus in Cuatro Ciénegas is made. The results presented here will be useful in identifying areas with a high risk of invasion by this popular ornamental fish, thus allowing the implementation of policy and management actions to prevent or at least ameliorate the impacts of an invasion and will add to the growing knowledge of how invasive species affect native systems. / text

4 pp. / Climate Change and Variability in Southwest Ecosystems Series / Several environmental factors are changing, including the global rise in atmospheric CO2 concentrations and global warming. These environmental changes portend needed changes in the future management of forests in the Southwestern U.S. Therefore, University of Arizona Extension Agents organized a Workshop in Sedona, AZ, in February, 2005, targeted at Southwest forest managers. This paper presents facts from one of the presentations at that workshop and summarizes what the direct effects of the increased CO2 concentrations are likely to be on future tree growth. It is expected that the growth of most trees will be stimulated by the higher CO2 concentrations but variations in response among species will alter competition among species. The fact sheet also speculates about what the implications may be for future forest management. This research benefits the forest industry, as well as the many consumers of forest products.

4 pp. / Southwest forests are complex systems that are influenced by climate variability. Wildfires naturally occur in these forests and woodlands, but with an increasing population, land management decisions are becoming more difficult. This publication is a result of discussions from the "Workshop on Climate Variability and Ecosystem Impacts" that was sponsored by UA Cooperative Extension in February 2005. It provides a summary of the current situation, a summary of climate change science for land management, and a brief description of suggested future research in climate science as it relates to forests and woodlands.

The Rodeo-Chediski Wildfire the largest in Arizona's history at the time of burning damaged and disrupted ecosystems resources and functioning in a largely mosaic pattern throughout the ponderosa pine (Pinus Ponderosa) forests exposed to the burn. Impacts of this wildfire on ecosystems resources and functioning were studied from shortly after the cessation of the wildfire in late summer of 2002 through the spring of 2007 on two previously instrumented watersheds located on sandstone derived soils within the burn. One watershed was burned by a high severity (stand-replacing fire), while the other watershed burned in a low severity (stand-modifying) fire. This dissertation focuses on the effects fire severity had on watersheds resources and functioning in terms of the tree overstories, herbaceous understories, large and small mammals, avifauna, hydrologic functioning, soil water repellency, hillslope soil movement, and fuel loadings. The results of these studies indicated the cumulative impacts incurred to ecosystem resources, hydrologic functioning, and flammable fuels were much greater on the watershed exposed to the high severity (stand-replacing) fire. It is anticipated that the overall ecological and hydrologic function on the watershed burned by a high severity will not approach pre-fire conditions for many years. The watershed burned at a low severity, however, was approaching pre-fire conditions nearly five years after fire and is expected to be recovered within the next few years.

Sedimentary deposits have been broadly used to constrain past climate change and tectonic histories within mountain belts. This dissertation summarizes three studies that evaluate the effects of climate change and tectonics on sedimentary basin development. (1) The paleoslope estimation method, a method for calculating the threshold slope of a fluvial deposit, does not account for the stochastic variations in water depth in alluvial channels caused by climatic and autogenic processes. Therefore, we test the robustness of applying the paleoslope estimation method in a tectonic context. Based on our numerical modeling results, we conclude that if given sufficient time gravel can prograde long distances at regional slopes less than the minimum transport slope calculated with the paleoslope estimation method if water depth varies stochastically in time, and thus, caution should be exercised when evaluating regional slopes measured from the rock record in a tectonic context. (2) The role of crustal thickening, lithospheric removal, and climate change in driving surface uplift in the central Andes in southern Bolivia and changes in the creation of accommodation space and depositional facies in the adjacent foreland basin has been a topic of debate over the last decade. Our numerical modeling results show that gradual rise of the Eastern Cordillera above 2-3 km prior to 22 Ma leads to sufficient sediment accommodation for the Oligocene-Miocene foreland basin stratigraphy, and thus, the Eastern Cordillera gained the majority of its modern elevation prior to 10 Ma. Also, we conclude that major changes in grain size and depositional rates are primarily controlled by mountain-belt migration (i.e., climate change and lithospheric removal are secondary mechanisms). (3) Existing equations for predicting the long-term bedload sediment flux in alluvial channels include mean discharge as a controlling variable but do not explicitly include variations in discharge through time. We develop an analytic equation for the long-term bedload sediment flux that incorporates both the mean and coefficient of variation of discharge. Our results show that although increasing aridity leads to an increase in large discharges with respect to small discharges, long-term bedload sediment transport rates decrease for both gravel and sand-bed rivers with increasing aridity.

Revised; Originally Published: 2006 / 4 pp.