Biology Reference
In-Depth Information
characteristics that can be engineered is increasing. Combining multiple
genetically engineered traits in individual crop varieties is also becoming
increasingly common. Efforts are being made to modify insecticidal trans-
genes, such as the gene for the Bt endotoxin, so they are effective against
a wider range of insect types.
Genetic engineering is being extended to many new groups of organ-
isms, and it is already being employed in biological control programs for
pests such as the pink bollworm (
Pectinophora gossypiella
), in which a gene
for a fluorescent protein is being introduced to the bollworm as a genetic
marker (Thibault et al. 1999). Genetic engineering is spreading to domes-
ticated and semidomesticated animals, forestry and horticultural plants,
and aquacultural animals. Genetically engineered fish of several species
that grow faster and reach larger sizes in aquaculture have been developed
(Muir and Howard 2002). Genes for tolerance by plants and other organ-
isms to insecticides, fungicides, and other pesticides are being sought to
permit the increased use of increased dosages of these agents in a manner
comparable to the present use of herbicides with herbicide-tolerant crops.
Developments such as these would considerably broaden the impacts of
pesticide chemicals on all living organisms.
Thus, genetic engineering is setting the stage for future evolutionary
change by many organisms. Intensified selection for counter-responses by
weeds and animal pests within the crop environment will certainly occur.
Because of the potential for transgenes to escape to wild and weedy plants
in grasslands, forests, and other environments, however, these evolutionary
effects will extend much farther.
How natural ecosystems will be affected by the spread of alien species
carrying transgenes is difficult to predict. Questions of what factors make
natural ecosystems vulnerable to invasion by alien organisms and what
factors enable alien species to invade such ecosystems are themselves of
great evolutionary interest.We shall consider these in the next chapter.
