Print PageHybridization 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.
Results/Conclusions
Through the first growing season, and in both competitive environments, hybrid populations produced at least three times more seeds than wild radish populations, a distinction that was driven by greater hybrid seedling emergence, earlier hybrid emergence and more hybrid seedlings surviving to flower, rather than by greater individual fecundity. Early emergence was associated with subsequent high seed output in both taxa. Performance of both taxa was reduced by interspecific competition, although flowering duration in hybrids was less negatively affected than in wild radishes. These populations will be followed through their second growing season, permitting an assessment of population growth rates in hybrid versus wild radish. Currently, our data clearly show that hybridization can enhance colonization success in a novel region, and that the life-history traits enhancing hybrid success can differ across regions.
