Weeds and invasive plant species impair agriculture worldwide. They coexist with crops in agricultural habitats and often are close relatives of crops. However, crops and weeds are subject to different selection pressures, and therefore, weeds evolve into different, undesired directions (Ellstrand et al., 2010). Through competition with crop plants, weeds reduce crop yields substantially and are therefore considered highly problematic. Two concurrent models have been proposed for weed evolution, and both are supported by experimental evidence. One scenario assumes that invasion by a crop wild relative is followed by hybridization with the respective crop, resulting in feral forms that spread over the agricultural area. This process is referred to as exoferality.
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