GE Fish Could Cause Extinction
of Wild Species

Ecological risks of GMOs come in unexpected ways, Purdue model shows
18 Jun 2002

Introducing genetically modified organisms (GMOs) into wild populations
holds a greater theoretical risk of extinction of natural species than
previously believed, according to two scientists from West Lafayette-based
Purdue University.

William Muir, professor of animal sciences, and Richard Howard, professor
of biology, used computer modelling and statistical analyses to examine the
hypothetical risks of introducing GMOs into wild populations.

"We examined these hypothetical situations because the range of new
transgenic organisms is almost unlimited," Muir said. "It is constructive
for those developing such organisms to be able to anticipate how they could
pose a hazard."

The new computer models have shown that the risk of extinction is greater
than believed before, identifying three new scenarios in which GMOs could
result in the extinction of a natural population. "In the broadest sense,
this research tells one how to do risk assessment and what GMOs need
further containment," Muir said.

In 2000, Muir and Howard found that a release of fish that were larger,
and therefore had higher mating success, but also had shorter life
expectancy, could drive a wild population extinct in 40 generations. Muir
and Howard labelled this the "Trojan gene hypothesis."

But further investigation has found other scenarios that could lead to

In one scenario, a genetic modification increases the size of the male,
which results in the male finding more mates and also living longer. But if
the modification also has a third effect of making the male less fertile,
the predicted result is that the wild population will be extinct in just 20

"We consider this an extreme risk," Howard said. "That's the most severe
time frame we've encountered so far."

Howard said this risk could arise if fertility was restricted in a GMO as
a way to limit the spread of the gene in the natural population. "This was
the biggest surprise for me, that if you lowered fertility of GMO the time
course to population extinction was faster rather than slower when the GM
young have better survival than wild-type individuals," he said. "I still
look at the graph of those data and find it amazing."

The researchers also found scenarios in which the introduced gene could
spread through the population but not reduce the overall population size.
The researchers termed this an invasion risk: "The invasion risk is an
unknown in assessing the overall risk," Howard said. "Given the biology,
all we can say is that the gene would increase in the population. We don't
know if that would cause a problem or not. In this case you wouldn't really
know until you actually released the gene into the population."

The results of the research were published in the most recent issue of
the scientific journal Transgene Research. The research was funded by the
USDA's Biotechnology Risk Assessment Programme. The Purdue research is part
of an ongoing effort by Purdue and the USDA to determine the risks of
biotechnology, particularly transferring genetic material from one species
to another, known as transgenic technology.

"Consumer confidence in the use of transgenic technology will only happen
if there is a thorough, unbiased examination of the risks," Muir said.

The most recent study found that some of the most significant risks
occurred when the introduced gene increased the viability of the adult
organism, such as through improved immune response or resistance to a
disease or pathogen.

"It's somewhat counterintuitive that increasing the health of the adult
could hurt the overall population, but that is what we found if they had
reduced fertility," Howard said.

The scientists say the increased risk from transgenics comes about
because such transfers involve one gene from a different species. "This
gene has a mega effect that may confer new functionality on the organism,"
Howard said.

Traditional breeding, on the other hand, can only affect genes of that
species and involves an exchange of many genes, which the scientists call
polygenic inheritance.

"Selective breeding is based upon polygenic inheritance where the result
is the cumulative effect of many of genes each with a small effect. In
contrast, most genetic modification involves one gene with a major effect,"
Howard said. "The two methods are not substantially equivalent, although
they may be legally regulated as if they are."

Muir and Howard said the genetic background of the modified organism may
be a key to potential risk. A 2001 report by the Royal Canadian Society
found that highly domesticated crops, such as corn and soybeans, rarely
become weeds in natural settings because "the cultivated species have been
genetically crippled through intense artificial selection."

"What this means is that the more wild an animal is, the greater the
environmental risk when using that animal to make a transgenic organism,"
Muir said. "In other words, a transgenic salmon is going to be more of a
risk to the environment than a transgenic cow."

Muir acknowledges that hypothetical experiments may not reflect what
happens in the real world, but he said the experiments err on the side of
caution: "If we show that these plants or animals may be a risk in a
laboratory experiment, it could be that they wouldn't be a risk in nature
because nature is less hospitable. It may be that things we find to be a
risk in the lab aren't a risk at all in nature. We feel that this is a
conservative approach to determining the risk."

To get a more accurate assessment of the risk of a GMO, a facility would
need to be constructed that would replicate the natural environment. Muir
said some companies are already considering constructing such testing

"It's going to cost millions of dollars to build elaborate testing
facilities that are as close to a natural setting as possible," he said.
"But nobody said this is going to be easy. What's at stake is important
enough to spend that kind of money."

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