Invasive Species Colonization Potential in New England: Distributions, Demography, and Adaptation

I investigated the invasive species colonization in New England and the driving ecological factors behind the success of some signature invasive species in the region. The first chapter chronicles the process of obtaining important invasive species distributional data through the Invasive Plant Atlas of New England (IPANE), a regional database documenting invasive alien species (IAS) presences and absences. Distribution models using IPANE data have highlighted areas of northern New England, currently lacking IAS, as places where these species may potentially thrive. In chapter three I used experimental biogeography to evaluate a suite of environmental conditions, mitigated by demography, which may facilitate the establishment of three invasive alien species compared to three native ecological analogues. For the two woody species, Berberis thunbergii and Celastrus orbiculatus , I also looked into how evolution has played a role in species' distributions by investigating local adaption and plasticity through a series of common garden experiments (chapter two). Using individual-based hierarchical Bayesian models, I investigated the response of each species' vital rates to the environment. In the fourth chapter, I built demographic Integral Projection Models for each of the herbaceous species to assimilate demographic information and make population-level predictions.;The invasives in this study tolerated a wide variety of habitats and climates. I validated previous predictive model results as all three of the invasive species were able to germinate, survive, grow, and, in some cases, reproduce outside their current known distributions. Overall the invasives were better able to exploit resources under typically less favorable conditions pointing to potential empty niches which these species were able to occupy. Demographic data revealed that survival to reproductive size and copious seed production were complimentary contributing factors to the high population growth rates for the invasive herbaceous mustard. The ability to link environmental drivers with vital rates allowed me to investigate the mechanisms behind the success of the invasive Alliaria petiolata. The observed species tolerance limits and responses to environmental variables at different demographic stages, together with species plasticity help us understand how these IAS, in comparison with their native ecological analogs, may continue their spread in New England.