Because the reproductive barriers in plants are more lenient than in animals, it is possible to transfer genes between different species. Successful cross-pollination is further made possible by the close proximity of compatible species. Remember that agriculture emerged as a result of domesticating wild, native plants. Even though cultivated varieties of plants dominate today's agricultural landscape, their wild relatives and progenitors exist in populations often growing nearby. Therefore, the opportunity for cross-pollination is very high.
Plants also migrate to new habitats through dispersal of their seeds.
The seed that flows down stream of the parent population or is carried to a neighboring field on the fur of a deer eventually grows to maturity and yields pollen to be dispersed by wind or insects. The range for potential gene transfer is thus expanded. This is how genes get around in the plant world and why ecosystems will be affected by the introduction of new genes through biotechnology. Scientists who study the relationship between crops and their wild relatives are increasingly concerned about the commercialization of genetically engineered crops. Forty-five million acres of GE crops produce a lot of pollen with the potential to contaminate wild populations of plants.