South African Iridaceae with rapid and profuse seedling emergence are more likely to become naturalized in other regions

1 Plant invasions constitute a large biological problem and screening protocols are needed to assess the invasive potential of species considered for introduction. However, insufficient information is available on species characteristics associated with successful establishment outside their native range. 2 We tested experimentally whether seed and seedling emergence characteristics and early growth of seedlings are associated with naturalization of South African Iridaceae. In a common garden experiment, we compared these characteristics between 30 species that have become naturalized elsewhere and 30 congeneric species that have been introduced elsewhere but have failed to become naturalized. 3 The average seed mass did not differ between naturalized and non-naturalized species but seedlings of naturalized species emerged faster and more profusely than their nonnaturalized congeners. As a consequence of fast seedling emergence, naturalized species reached a larger size early in the season than did non-naturalized species. 4 The results of our study indicate that rapid and profuse seedling emergence play important roles during naturalization, at least for Iridaceae from South Africa.