Invasive exotic species threaten the biodiversity and function of native ecosystems. Existing models, attempting to predict and control successful invaders, often emphasize isolated stages of in their life history and fail to formalize interactions between exotic species and recipient environments. In order to elucidate key mechanisms in the success of select invaders, I investigated the role of dispersal, establishment, proliferation, and persistence in their threat to natural areas. Focusing on Riding Mountain National Park, Manitoba, Canada, I integrated the native climatic range and biological traits of 251 exotic vascular plants reported inside and outside the park. Based on their climatic range in Europe, 155 among 174 exotic plant species absent from the Park were predicted to establish within its boundaries; among these, 40 clonal perennials were considered the highest threat to the Park’s biodiversity. Focusing on smooth brome (Bromus inermis Leyss.), a Eurasian perennial, threatening the structure and function of native prairies throughout the Great Plains, I extended my research to investigate the role of dispersal, establishment, proliferation, and persistence in characterizing its threat to the endemic diversity of northern fescue prairies, protected within Riding Mountain National Park. Patterns of smooth brome invasions were contingent on the type of propagules dispersed. The shallow dispersal gradient of individual florets combined with the steeper gradient of panicles and spikelets suggested that smooth brome is capable of simultaneously invading along dense fronts as well as by establishing isolated foci. While low correlations between the number of dispersed seeds and their recruitment suggested post-dispersal transport, seedling establishment remained contingent on prairie diversity. Seedling biomass increased with declining plant diversity, however, its impact depended on the availability of soil nitrogen. As a result, disturbed areas, preserving the root function of native plants, resisted smooth brome establishment. Even though low nitrogen contributed to a decline in seedling biomass, physiological integration between ramets facilitated their vegetative proliferation in low resource environments. Despite its rapid establishment and proliferation, smooth brome productivity declined at the center of invading clones. Although field and greenhouse observations failed to implicate soilborne pathogens, reasons for the observed decline remain unresolved. My research demonstrates that while Riding Mountain National Park and other natural areas in western Canada will continue to be impacted by exotic plants, integrating key stages in their life history provides an important conceptual framework in predicting their threat to natural areas and prioritizing management.

There has been a global decline of specialist species observed in recent decades due to the impacts of climate change, invasive species, and habitat loss. Habitat loss and degradation may lead to a mismatch between habitat attractiveness and actual quality, otherwise known as an ecological trap. Ecological traps occur when an organism is constrained by its evolutionary past to select for cues that no longer accurately predict habitat quality. Specialist species are more susceptible to ecological traps due to greater reliance on and fidelity to historic sites and resources. The burrowing owl (Athene cunicularia), a specialist bird species adapted to open ecosystems, has declined throughout its extent. Anthropogenic activity has drastically and rapidly altered burrowing owl native habitat, exposing their habitat to disturbances such as cheatgrass (Bromus tectorum) invasion. The presence of cheatgrass is known to impact the biota of a region and understanding those impacts is becoming increasingly important. The purpose of this study was to quantify the impact of cheatgrass on burrowing owl populations. By assessing how cheatgrass influences the resource selection, nesting success, and food habits of burrowing owls, we provided information that can be utilized to make more informed decisions on how to conserve burrowing owls and their critical nesting habitat. In addition, this information can provide insight into the risk of ecological traps occurring to all specialist species experiencing degradation of their native habitat.