Evolutionary Potential for Increased Invasiveness: Genetic Variation for Competitive Ability in the Invasive Plant

<p>Investigating evolution of introduced species in their new ranges offers insight into why some introduced taxa establish and become invasive while others do not. Neutral genetic variation present within introduced-range populations of non-native species can facilitate evolution, but sometimes these populations adapt to novel environments regardless of a lack of diversity as estimated by neutral genetic markers. Variation among genotypes in the form of norms of reaction for traits likely to contribute to successful establishment and spread through novel environments may be more indicative of potential to evolve increased invasiveness. Evolution of greater competitive ability is expected to enable introduced taxa to invade native communities, but attention to quantitative genetic variation for competitive response and effect in studies of ongoing biological invasions has been sparse. Here I examine the response to competition and effect on neighboring individuals of a sample of genotypes from the northeastern North American range of the invasive annual plant <em>Polygonum cespitosum</em>. The performance of a suite of previously-identified highperformance genotypes under competitive conditions was compared to a random sample of control genotypes in a greenhouse experiment. High-performance genotypes displayed greater ability to respond to competition from neighbors and to suppress neighbor performance than their control counterparts, especially in open, full-sun conditions similar to the habitats into which the species is currently spreading. I conclude that New England populations of <em>P. cespitosum</em> possess evolutionary potential to evolve increased competitive ability in open environments.</p>