In May 2000, biologist Neil D. Tsutsui and his colleagues from the University of California-San Diego (UCSD) came up with an apparent solution (for California, at least). Their results, published in the May 2000 Proceedings of the National Academy of Sciences (PNAS), were based on genetic and behavioral experiments on worker ants in California and Argentina.

In field studies conducted in Argentina, the Tsutsui team observed that ants taken from different nests often fought when placed side by side in an experimental vial. But in California, the scientists found that ants rarely engaged in combat, even if they were collected from nests hundreds of miles apart.

Why would workers in Argentina exhibit intercolony aggression but their California cousins behave so downright friendly? The Tsutsui team turned to genetics for an answer. Previous studies of other ant species have shown that insects from the same colony don't fight among themselves, because each one carries a common scent identifying it as a nestmate.

Could it be that laid-back California ants are all members of the same family, while aggressive workers in Argentina engage in territorial battles because they belong to different colonies that are genetically distinct?

To find out, the UCSD scientists compared the DNA of workers in California and Argentina by focusing their attention on microsatellites - short sequences of DNA that occur in unique patterns that are passed down from generation to generation. Unlike genes, microsatellites are nonfunctional and carry no genetic information that would affect the ant's development or behavior. But because microsatellite patterns are inherited, scientists use them as genetic markers to determine if individuals from differen
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Contact: Dawn Levy
dawnlevy@stanford.edu
650-725-1944
Stanford University
7-Apr-2004