(Excerpt from the article:
Not all hosts, including some domesticated ones, will necessarily be ecological incompetents
Although many types of GEOs will be ecologically incompetent, serious ecological concerns remain first because not all hosts that are and will be engineered, and not even all row-crop plants, have been as genetically manhandled as corn, wheat, and white rats.
Forage grasses, alfalfa, trees, wild rice, cranberries, sunflowers, numerous species used in landscaping, fishes, shellfish, insects, and so on are much closer to wild-types than are corn or wheat.
When novel adaptive traits are taken from a donor and added to such hosts, the transgenic forms will be much more difficult to screen for ecological safety than genetically engineered corn in Iowa or genetically engineered tropical bromeliads in Minnesota, which are quite unlikely to cause ecological problems.
This group of species, of unknown membership, seems to present the greatest challenge for risk assessment of plants or animals at the present state of the technology. Ecologically competent GEOs with new adaptive features have been compared to exotic or introduced species.
The record of natural species that were brought to one continent from another suggests that 90% have not caused significant problems. But the remaining 10% have caused significant problems, and that includes a substantial number of great disasters (Sharples 1982; Simberloff 1985; Regal 1993). [See Keeler & Turner (1991) for a review of the potential for problems of weediness in transgenic plants, also Sukopp & Sukopp (1993), Williamson (1993). Vitousek (1985) has done an excellent job of summarizing the significant ways in which exotic plants have sometimes altered soil chemistry and hydrology.]
Lateral transfer of genes to ecologically competent relatives
Even ecologically incapacitated crop plants or animal species, might in theory pass novel adaptive genes on to relatives and enhance the competitiveness of these (Regal 1986, 1990b; Doebley 1990; Ellstrand & Hoffman 1990; Wilson 1990; Keeler & Turner 1991).
Thus, even the most ecologically incapacitated crop plants may be of concern in the sense that they have wild relatives with which they might cross somewhere in the world, such as corn in the Mexican highlands or wheat in the Middle-East.
A less obvious concern is that if adaptive transgenes enter a related wild population and give the progeny of some individuals a large competitive advantage, the genotypes of these could, by 'genetic hitch-hiking', in some cases sweep the population, eliminate other genotypes, and reduce the amount of genetic variation. This could have practical implications, because plant breeders at some time in the future might have had important uses for the genes that were eliminated from these natural 'germ-plasm banks'. Study of this issue is needed.
"Genetically Engineered Food - Safety Problems"