Hybridization in weeds and invasive plants: Implications for management

Plant hybridization is the result of pollen-mediated gene flow between genetically differentiatedindividuals, either distinct genotypes with a taxon (intraspecific hybridization) or individuals fromdifferent species (interspecific hybridization). Now recognized as a key component of plant evolution,hybridization is an important - but often overlooked - factor in the adaptive responses of weedyand invasive plants in crop and non-crop agroecosystems. Human management imposes selection onagronomic weeds, and hybridization generates novel recombinants that may evade control strategies.The spread of herbicide resistant phenotypes via intraspecific hybridization within and among weedpopulations is an example currently attracting research attention. Hybridization has also recently beenidentified as an important driver of invasion by introduced plants in non-crop areas such as rangeland.In these cases, selection pressure from human management is often less intense than that imposed byadaptation to environmental biotic and abiotic stressors in the new habitat. However, as with agronomicweeds, selection among novel intra- and interspecific hybrid recombinants in invasive non-nativeplant populations can result in aggressive biotypes that evade control. In this presentation, I will useexamples from my research in agronomic weeds and invasive rangeland plants to explore ways inwhich novel hybrids can undermine weed management, and I will discuss the importance of controlstrategies to mitigate gene flow and hybrid spread.