Gene flow and introgression from domesticated plants into their wild relatives

Domesticated plant taxa cannot be regarded as evolutionarily discrete from their wild relatives. Most domesticated plant taxa mate with wild relatives somewhere in the world, and gene flow from crop taxa may have a substantia l impact on the evolution of wild populations. In a literature review of th e world's 13 most important food crops, we show that 12 of these crops hybr idize with wild relatives in some part of their agricultural distribution. We use population genetic theory to predict the evolutionary consequences o f gene flow from crops to wild plants and discuss two applied consequences of crop-to-wild gene flow-the evolution of aggressive weeds and the extinct ion of rare species. We suggest ways of assessing the likelihood of hybridi zation, introgression, and the potential for undesirable gene flow from cro ps into weeds or rare species.