Invasive species are organisms whose introduction and spread in exotic ranges result in a multitude of ecological impacts. Understanding the factors that constrain the exotic distributions of invasive species is of considerable interest. Biotic associations formed with taxa in the invaded community may be particularly important in shaping invader distributions. These associations emerge from interactions between the traits of the invasive species and some subset of the traits present in the invaded community. Focusing on how organism traits influence the outcomes of biotic interactions may inform predictions of invader distributions. This kind of trait-based approach may be most easily applied to systems where invaders specialize on particular hosts because such associations imply a close correspondence between the traits of the invader and hosts. This dissertation focuses on the South American cactus moth (Cactoblastis cactorum, Lepidoptera: Pyralidae), an invasive consumer in North America whose larvae infest prickly-pear cacti (Opuntia spp.). Chapter One is a brief introduction providing background and context to the presented research. In Chapter Two, I quantify Opuntia morphological and tissue macronutrient traits hypothesized to correlate with patterns of C. cactorum host use. Tissue macronutrient traits appear important in predicting C. cactorum infestation whereas a model containing Opuntia morphological traits had poor predictive ability. Chapter Three describes a method that uses host Opuntia identity and availability to estimate habitat suitability in order to predict the North American distribution of C. cactorum. I then simulate C. cactorum dispersal relative to scenarios of habitat suitability and Opuntia availability. Chapter Four alters the model in Chapter Three so that habitat suitability for C. cactorum is determined by the availability of trait-based groupings of Opuntia hosts. I then simulate C. cactorum dispersal via a different method from that described in Chapter Three. In Chapters Three and Four, I evaluate the degree of similarity among model predictions and the relative contribution of modeling constraints in generating variation in this similarity. Chapters Three and Four predictions were most affected by estimates of abiotic suitability and dispersal constraints, respectively. Chapter Five is a short summary of my results and a discussion of their more general applicability.

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Invasive species have become an increasing threat to many habitats worldwide. This research addressed the questions of whether several invasive woody plants can germinate, survive and grow in light levels typical of an undisturbed forest understory, and also whether alteration of the nitrogen cycle by one invader is likely to increase the rate of invasion by others.

The social, economic, and ecological costs of plant invasions are vast, through their ability to alter ecosystem structure and function. Invasive annual grasses are a nuisance in the American Southwest through promotion of the grass-fire cycle. Annual grasses such as Bromus rubens, Bromus tectorum, Schismus barbatus, and Schismus arabicus have invaded the Mojave Desert and increased fire occurrence, thus it is important to identify and characterize the areas where persistent invasion has occurred and subsequently fire risk is increased by understanding the distribution of these invasive grasses. Previous plot and landscape-scale research has revealed anthropogenic and biophysical correlates with the establishment and dominance of invasive annual grasses in the Mojave Desert. However, these previous studies have been limited in spatial and temporal scales. Here we use a remote sensing framework to map persistent and productive populations of invasive annual grass, called hot spots, in the entire Mojave Desert ecoregion over 12 years, identify important variables for predicting hot spot distribution, and identify the most invaded subregions. Hot spots were identified in over 5% of the Mojave Desert, and invasive grasses were detected in over 90% of the desert at least once. Our results indicate that soil texture, aspect, winter precipitation, and elevation are the most important predictive variables of invasive grass hot spots, while anthropogenic variables were the least useful. The most invaded subregions of the Mojave Desert were western Mojave basins, eastern Mojave mountain woodland and shrubland, western Mojave low ranges and arid footslopes, eastern Mojave basins, and eastern Mojave low ranges and footslopes.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Yes / This data article is related to the research article entitled Proteomics of Tissue Factor silencing in cardiomyocytic cells reveals a new role for this coagulation factor in splicing machinery control by Lento et al [1]. Tissue Factor (TF) is the key player in the coagulation cascade, but it has additional functions ranging from angiogenesis, tumor invasion and, in the heart, the maintenance of the integrity of cardiac cells. This article reports the nano-LC-MSE analysis of the cardiomyocytic HL-1 cell line proteome and describes the results obtained from a Gene Ontology analysis of those proteins affected by TF-gene silencing.

No / Burkholderia cepacia is known to invade and survive within respiratory epithelial cells. Previous studies have employed transformed cell lines and it is not known whether the bacterium is capable of manifesting the same phenomena in primary cell culture. Two strains of B. cepacia of environmental (NCTC 10661) and clinical origin (C1359) were examined for their ability to invade and survive (over a 24 h period) within type II pneumocytes in primary culture using a gentamicin¿ceftazidime antibiotic protection assay. Both strains of B. cepacia were capable of invasion of type II pneumocytes in primary culture. Strain C1359 was capable of multiplying intracellularly as indicated by a seven-fold increase in the numbers of bacteria from 4¿24 h, whereas strain 10661, although unable to replicate intracellularly, was found to survive in the pneumocytes for at least 24 h. Future studies on the invasiveness of B. cepacia can employ A549 cells as a valid surrogate for primary cell culture assays which are time-consuming, labour-intensive and expensive to perform.

Laboratory experiments and field studies have shown that declining populations can avoid extinction by undergoing adaptation. This process, evolutionary rescue, entails a population approaching extinction until an adaptive mutation appears and subsequently establishes by escaping stochastic loss. While most models of evolutionary rescue emphasize mutations that allow organisms to persist in hostile environments, a less explored possibility---known as positive niche construction (hereafter niche construction)---involves mutants improving their fitness by modifying their environment. In Chapter 1 of this dissertation, I analyze a model of evolutionary rescue via a niche-constructing mutation. I show that the probability of rescue is highest under low-to-moderate rates of construction: some construction is needed to ensure that mutants proliferate quickly enough to avoid stochastic extinction; but because construction is costly, requiring time and energy to perform and develop, too much of it can lead to over-exploitation of the constructed habitats by the mutants' non-niche-constructing ancestors (hereafter residents). In Chapter 2, I then model a niche-constructing population that must undergo evolutionary rescue to withstand habitat exploitation by an invading species. I find that the same fecundity costs rendering constructors vulnerable to exploitation can help facilitate rescue from such exploitation by reducing the rate of construction and thus lowering the density of habitats available to invaders. The lower habitat density leads to slower invasion, which in turn buys constructors more time to mutate. Finally, in Chapter 3, I consider the possibility that invaders directly interact with the resident population instead of exploiting resident-constructed habitats. I show that a lower resident birth rate---whether it stems from a smaller resident density independent birth rate or stronger birth-limiting competition---can promote rescue by reducing variance in mutant fitness. Together, these findings suggest that lower reproductive success among members of a population can, under a range of conditions, improve the population's chances of evolutionary rescue. / Doctor of Philosophy / Understanding when a population is most likely to avoid extinction through adaptation, a process known as evolutionary rescue, can help address critical challenges such as eliminating antibiotic-resistant pathogens and preserving endangered species. Evolutionary rescue occurs when a population is on the verge of collapse but survives after a beneficial genetic change (hereafter mutation) spreads through the population. While studies of evolutionary rescue often focus on mutations allowing organisms to survive and reproduce in harmful habitats, an alternative possibility is that the mutations permit organisms to make their habitats more hospitable through what is known as niche construction. If a population adopts this strategy, however, it risks habitat exploitation by organisms that benefit from the constructed habitats but do not expend the time and energy needed to perform construction. In this dissertation, I first model evolutionary rescue via a niche-constructing mutation. Then I consider a niche-constructing population that must evolve to withstand habitat exploitation by an invading species. Finally, I consider the possibility that the invading species interacts directly with its victims instead of exploiting their habitats. Counterintuitively, my results suggest that lower reproductive success among members of a declining population can aid in the evolutionary rescue of that population.