Abstract: Invasive species may pose significant threats to biodiversity and ecosystem structure and functioning. The number of introduced species that have become invasive is substantial and is rapidly increasing. Identifying potentially invasive species and preventing their expansion are of critical importance in invasion ecology. Phylogenetic relatedness between invasive and native species has been used in predicting invasion success. Previous studies on the phylogenetic relatedness of plants at the transition from naturalization to invasion have shown mixed results, which may be because different methods were used in different studies. Here, I use the same method to analyze two comprehensive data sets from South Africa and China, using two phylogenetic metrics reflecting deep and shallow evolutionary histories, to address the question whether the probability of becoming invasive is higher for naturalized species distantly related to the native flora. My study suggests that the probability of becoming invasive is higher for naturalized species closely related to the native flora. The finding of my study is consistent with Darwin's preadaptation hypothesis.

Key words: Angiosperms, Exotic species, Introduced species, Invasive species, Naturalized species, Phylogenetic relatedness