August 20, 2010

Species Most Affected By Radioactive Contamination Predicted

Scientists found a way to help predict which species are likely to be most affected by radioactive contamination.

The scientists in Chernobyl said that the secret to a species' vulnerability lies in its DNA.

The research helps to reveal which species are most likely to decline or become extinct in response to other types of environmental stress.

Professor Tim Mousseau from the University of South Carolina and Dr. Anders Moller from the National Center for Scientific Research in Paris France both led the study.

The scientists worked in Chernobyl for over a decade, gathering data about the populations of insects, birds and mammals in "zone of alienation" surrounding the desolate nuclear power station.

The researchers used databases to help examine the DNA patterns of each of the species they studied in Chernobyl.

The pattern of each species' DNA changes slightly with each generation, resulting in the natural balance between mutations and the individual's ability to repair damaged DNA.  

The rate of this change is known as substitution rate.

"This information is available in large database," Mousseau explained to BBC News. "So you can get the DNA sequences [of each species] and examine the changes that have occurred among a species over time.

"What we have discovered is that when we look at the species in Chernobyl, we can predict, based on their substitution rates, which ones are most vulnerable to contaminants."

Mousseau told BBC that the Chernobyl setting offered a "unique opportunity to look at a natural experiment in progress - [to see] what happens to species when they have this kind of environmental perturbation".

The results of this study might help to bring light on which species are the most vulnerable during environmental contamination.

Some of the organisms most likely to be affected by contaminants were brightly colored birds and birds that have a long distance migration.

"One explanation may be that these species have, for whatever reason, less capable DNA repair mechanisms," Mousseau told BBC.

Lousise Johnson, an evolutionary biologist from the University of Reading, told BBC that the findings were "fascinating."

"Extreme events like Chernobyl provide opportunities to test predictions about evolution," she said.

"One of the difficulties of such research is that it isn't really an experiment- it is impossible to control for all of the confounding variables."

"But [the scientists] have been very careful to test all of the other factors that could be important - antioxidants, population size, body size, etc. of bird species and it appears... that there is a shared causal relationship between accumulating mutations over time and the ability to withstand radiation."

The findings were published in the Journal of Evolutionary Biology.


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