Hybridization between genetically modified Atlantic salmon and wild brown trout reveals novel ecological interactions

The development of genetically modified (GM) organisms has lead to much debate over the potential risks that could occur if these organisms were to escape into wild ecosystems. The majority of research on the risks of escaped GM organisms has focused on interactions with wild members of their own species, but hybridization with closely related species represents a potential route for modified or engineered genes to enter wild populations. The potential risks and ecological effects of hybridization with GM animals remains poorly understood. Through experimental crosses, we demonstrate successful hybridization between GM Atlantic salmon (Salmo salar); a candidate for commercial aquaculture production developed for fast growth, and closely related wild brown trout (Salmo trutta). Hybrid offspring inherited the modified gene at the expected rates, and demonstrated enhanced growth rates in hatchery-like conditions. Indeed, GM hybrids grew faster than non-GM and GM salmon in these conditions. When reared in conditions designed to more closely mimic nature, GM hybrids suppressed the growth rates of GM and non-GM salmon by 82 and 54 per cent, respectively. Although many factors would make hybridization between GM salmon and brown trout unlikely in the wild, these results provide empirical evidence of the first steps towards the entry of modified genes from a GM species into a different species. Our results also contribute to the growing evidence that GM animals have complex and context-specific interactions with wild populations. We propose that interspecies hybridization be considered when assessing the environmental consequences should transgenic animals escape to nature.