Non-linear effects of phylogenetic distance on early-stage establishment of experimentally introduced plants in grassland communities

1. The phylogenetic distance of an introduced plant species to a resident native community may play a role in determining its establishment success. While Darwin’s naturalization hypothesis predicts a positive relationship, the preadaptation hypothesis predicts a negative relationship. Rigorous tests of this now so-called Darwin’s naturalization conundrum require not only information on establishment successes but also of failures, which is frequently not available. Such essential information, however, can be provided by experimental introductions. 2. Here, we analysed three datasets from two field experiments in Germany and Switzerland. In the Swiss experiment, alien and native grassland species were introduced as seeds only with and without disturbance (tilling). In the German experiment, alien and native grassland species were introduced both as seeds and as seedlings with and without disturbance (tilling), and with and without fungicide application. For the seedling introduction exp...