Hybridization is hypothesized to promote invasiveness, but empirical tests comparing the performance of hybrid versus parental taxa in novel regions are lacking. We experimentally compared colonization ability of populations of wild radish (Raphanus raphanistrum) versus populations of advanced-generation hybrids between wild and cultivated radish (R. sativus) in a southeast Texas pasture, well beyond the known invasive range of hybrid radish. We also manipulated the strength of interspecific competition to better generalize across variable environments. In...

In a recent study of the symbiosis between bacteria and plasmids, the available evidence suggests that experimental evolution of plasmid virulence was primarily driven by within-host competition caused by superinfection. The data do not exclude the possibility, however, that a trade-off between virulence and infectious transmission to uninfected bacteria also played a minor role.