Evolutionary-genetic consequences of biological invasion in a clonal aquatic plant, Butomus umbellatus (Butomaceae)

Long-distance colonization and rapid range expansion associated with biological invasion may have major evolutionary and genetic consequences involving both stochastic processes and selection. In this study, we examined the genetic consequences of long-distance colonization of North America by a clonal aquatic plant, Butomus umbellatus. Specifically, we compared the species' reproductive system and the genetic variation at RAPD loci between 108 broadly distributed native European populations and 129 introduced North American populations to assess the relative importance of stochastic effects, selection and interactions between the two during colonization. Previous work has shown that N. American diploids and triploids strongly differ in capacity for clonal propagation. Diploids, in addition to making seed, produce hundreds of small clonal bulbils, whereas triploids only propagate through rhizome fragmentation, and have little capacity for dispersl. We argue that founder effect has yielded diploid and triploid lineages that differ stroangly in colonizing ability, and hence in relative abundance. (Abstract shortened by UMI.)...