Genetically Modified Organisms as Invasive Species?

The release of genetically modified organisms (GMOs) is a controversial subject. Some perceive it to be the single most important development in biology since the discovery of natural selection. Others are concerned that the movement of genes with no reference to natural species boundaries could pose new ecological risks. One conjectural risk is that transgenes will either cause the host species to become invasive or they will escape from the original host species and cause other species to become invasive. Gene flow between species occurs naturally, although the frequency varies within and across kingdoms. Such gene flow is responsible for creating new combinations of genes, with the potential for introgression or speciation. Hybridisation has been proposed as a stimulus for the evolution of invasiveness in plants (Ellstrand and Schierenbeck 2000), suggesting that new combinations can create genotypes with different, and perhaps surprising ecological behaviours. Do transgenes pose particular risks in this respect? Is it possible to predict the probability that transgenes will cause invasiveness in recipient organisms?