Understanding the process of community assembly and species coexistence is a key question in evolutionary biology, and Darwin was among the first to realize the value of introduced species in eco-evolutionary studies. Later defined as “Darwin’s Naturalization Hypothesis”, he hypothesized that more distantly related species would be more dissimilar in their functional traits, and thus, compete less for community resources. Therefore, under this hypothesis, introduced species that are more distantly related to the native community would be more likely to possess novel traits that would allow them to successfully establish. In this talk I will provide a brief history of modern tests of Darwin’s Naturalization Hypothesis, with a focus on the use of phylogenies to investigate evolutionary patterns of the naturalization process, and then discuss an example from our own work in the San Juan Islands in the Pacific Northwest. This archipelago has been recently and dramatically invaded–on the 80 uninhabited islands that were measured, 30% of the flora now consists of introduced species. Using a combination of floristic data, a robust time-scaled community phylogeny, and data for five ecologically relevant functional traits (specific leaf area, seed mass, maximum height, leaf size, and leaf nitrogen content), I will deconstruct Darwin’s Naturalization Hypothesis in an attempt to better understand the subtleties of community assembly in the context of the naturalization process.