Genetic differences in growth of an invasive tree species

Evan Siemann and William E. Rogers Department of Ecology and Evolutionary Biology, Rice University, Houston, TX 77005, U.S.A. Correspondence: Evan Siemann. E-mail: [email protected] Abstract Invasive plants are often more vigorous in their introduced ranges than in their native ranges. This may re ̄ect an innate superiority of plants from some habitats or an escape from their enemies. Another hypothesis proposes that invasive plants evolve increased competitive ability in their introduced range. We present the results of a 14-year common garden experiment with the Chinese Tallow Tree (Sapium sebiferum) from its native range (Asia), place of introduction to North America (Georgia) and areas colonized a century later (Louisiana and Texas). Invasive genotypes, especially those from recently colonized areas, were larger than native genotypes and more likely to produce seeds but had lower quality, poorly defended leaves. Our results demonstrate signi®cant post-invasion genetic differences in an invasive plant species. Postintroduction adaptation by introduced plants may contribute to their invasive success and make it dif®cult to predict problem species.