ngin - Norfolk Genetic Information Network

25 June 2002


1. Invasion of transgenes from salmon or other GMOs
2. GMOs Could Wipe Out Natural Species


1. Invasion of transgenes from salmon or other GMOs

Can. J. Fish. Aquat. Sci./J. Can. Sci. Halieutiques Aquat. 58(5): 841-844 (2001) Invasion of transgenes from salmon or other genetically modified organisms into natural populations Philip W. Hedrick


In recent years, there has been widespread concern about the ecological and genetic effects of genetically modified organisms. In salmon and other fishes, transgenic growth hormone genes have been shown to have large effects on size and various traits related to fitness. In this paper, I have shown by using a deterministic model that if such a transgene has a male-mating advantage and a general viability disadvantage, then the conditions for its invasion in a natural population are very broad. More specifically, for 66.7% of the possible combinations of the possible mating and viability parameters, the transgene increases in frequency, and for 50% of the combinations, it goes to fixation. In addition, by this increase in the frequency of the transgene, the viability of the natural population is reduced, increasing the probability of extinction of the natural population. These findings provide independent confirmation of previous concerns about the inherent risks of transgenic organisms, especially for native salmon populations potentially affected by commercial salmon production using transgenic stocks.


2. GMOs Could Wipe Out Natural Species

WEST LAFAYETTE, Indiana, June 21,  2002  (ENS)  -  Genetically modified  organisms  introduced into wild populations could drive the natural species toward extinction, warn two Purdue University scientists.  William Muir, professor of  animal  sciences,  and Richard Howard, professor of biology, used computer modeling and statistical  analyses  to  examine  the  hypothetical  risks   of introducing genetically modified organisms 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 genetically modified organisms (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 as few as 40 generations.   Muir and Howard labeled this the "Trojan gene hypothesis."

Further investigation  has found other scenarios that could also lead to extinction.

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 generations.

"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 genetically modified organism 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 genetically modified organism  the  time  course  to population  extinction  was  faster  rather  than slower when the genetically modified young have better survival than wild type individuals,"  Howard  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  research  appears  in  the  current  issue  of  the  journal "Transgene Research."

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