Ruderals naturalize, competitors invade : Varying roles of plant adaptive strategies along the invasion continuum

1. It is increasingly recognized that the factors facilitating plant invasions depend on the stage along the introduction–naturalization–invasion continuum. Adaptative strategies, that is, combinations of functional traits that represent overall fitness in the face of one or more selection pressures, have shown promise in explaining plant invasions. However, whether adaptive strategy patterns change with stages of plant invasion is not yet known. 2. Using the Pladias Database of the Czech Flora and Vegetation, we explored how Grime's adaptive strategies (competitors, stress-tolerators, ruderals; CSR) and introduction pathways (deliberate vs. accidental) relate to plant invasion along the introduction–naturalization–invasion continuum. 3. Phylogenetically corrected ANOVAs showed that naturalized species (referring to non-invasive naturalized species in this study) were mostly R-selected, whereas invasive species tended to be C-selected. The results of phylogenetic regression analysis further confirmed that across the deliberately and accidentally introduced species, R-and C-selection were positively related to naturalization and invasion success respectively. We also found that deliberate introduction was negatively related to naturalization success and grid-cell occupancy of naturalized species, likely due to the different CSR strategies of deliberately and accidentally introduced aliens. 4. Our study provides empirical evidence that different adaptive strategies are associated with species that have reached different invasion stages and confirms the usefulness of the CSR strategy framework for understanding plant invasion. This has implications for predicting and preventing potential high-impact invaders. For example, our results show that naturalized C-selected species have a higher probability of becoming invasive than naturalized R-selected species. Therefore, management actions are essential to prevent further introductions and spread of competitors.