Understanding Macroscale Patterns and Processes of Invasion

The increasing rate of biological invasions and their impacts are one of the major threats in the Anthropocene. However, certain knowledge gaps remain in our understanding of patterns and processes of invasion, despite an extensive body of research dedicated to this phenomenon. Highly-debated topics in invasion ecology could benefit from a macrosystems perspective. Studies performed at the macroscale are able to capture the effect of global-level processes that drive invasions, detect patterns that transcend taxonomic and geographic boundaries, and minimize biases stemming from the specificity of studies performed at more localized scales. Here, I aim to provide novel insights into highly-debated invasion questions by approaching these questions with a macrosystems perspective. Specifically, I explored two topics in invasion ecology: 1) the prediction of invasiveness of exotic species through traits, and 2) the role of native beta diversity in biotic resistance. In the first study, I provide an overview of biotic resistance in forest ecosystems. Here, I summarize current research on mechanisms and inconsistencies of biotic resistance, as well as remaining gaps in research. In the second study, I sought to identify key traits of invasiveness through a comparative analysis on 45 traits of 63 invasive and 824 non-invasive exotic woody species found across the contiguous United States. Through this comprehensive comparative analysis, I was able to identify key determinants of invasiveness and create a statistical model able to accurately predict the invasiveness of exotic woody species. In the third study, I performed a multi-scaled assessment of the influence of native beta diversity on NERR slope and exotic fraction in freshwater systems across the contiguous United States. The purpose of this study was to describe the role of native beta diversity in biotic resistance across scales. My findings show that native beta diversity increases biotic resistance, albeit only at the largest spatial scales. The contributions of these studies have the potential to be of great utility for resource management. The knowledge generated by the invasive traits study can be used to improve existing screening tools and current classifications of invasive status. In addition, my findings suggest that native beta diversity could potentially be used to identify areas vulnerable to invasion or as a tool to increase biotic resistance