Apparently whether transgenes spread from GM crops to wild species remains controversial - though there have been some reports of this happening in the past. http://www.nature.com/news/case-studies-a-hard-look-at-gm-cr... >>In 2003, Snow and her colleagues showed that when Bt sunflowers (Helianthus annuus) were bred with their wild counterparts, transgenic offspring still required the same kind of close care as its cultivated parent but were less vulnerable to insects and produced more seeds than non-transgenic plants. Few similar studies have been conducted, says Snow, because the companies that own the rights to the technology are generally unwilling to let academic researchers perform the experiments.<<