The only organisms affected in an asexually reproducing species would be the direct descendants of those that you treat. In a sexually reproducing species, the

The only organisms affected in an asexually reproducing species would be the direct descendants of those that you treat. In a sexually reproducing species, the goal is to engineer the gene to spread throughout the entire population, even if it reduces the individual fitness. Edit: though I guess I'm stating this poorly, since it would still only affect the direct descendants of those that you treat in a sexually reproducing species, however there's the possibility of that becoming 100% of the species without having to kill off all the untreated specimens.