Ants Practice Nepotism, Study Finds

John Roach
for National Geographic News
February 26, 2003

The highly social and complex world of ants is not void of selfish acts. Worker ants of the species Formica fusca apparently can distinguish who their closest relatives are and kill their more distant relations.

"That workers capitalize on this ability simply means that the workers use the information they have to enhance their genetic contribution to future generations," said Liselotte Sundström, an entomologist at the University of Helsinki in Finland.

Science has long held that ants who share the same genetic make up have a vested interest in favoring their closest kin at the expense of the social cohesion of the entire ant colony. But evidence for ant nepotism has been difficult to find.

Sundström and colleague Minttumaaria Hannonen took advantage of advances in genetic analysis to prove the theory correct. They report the results of their study in the February 27 issue of Nature.

Kenneth Ross, an entomologist at the University of Georgia in Athens, said that researchers have looked for nepotism in social insects for the last 10 to 15 years and not found it. Given that fact, Ross said he was surprised at the success of Sundström and Hannonen's study, which he described as nicely done.

"The theory tells us it should be there," he said. "But the implication from data from the last 10 to 15 years tells us it shouldn't be there. In light of these negative results, I am somewhat surprised."

Ant Study

Unlike bee colonies, ant colonies are often ruled by more than one queen. Among some species, such as fire ants, a single ant colony can have as many as 500 queens. On the surface, the ants in such colonies seem to work cooperatively for the interest of the entire group.

Scientists have often wondered if evidence for nepotism is present in such a complex social environment. But each time they have looked for it their results come up negative. Sundström said that perhaps their studies were hindered by logistical constraints.

"For instance, there has not been any way to very accurately distinguish the brood produced by different queens, especially in the field where the actual number of queens is not known," she said.

In addition, Sundström said scientists have not had a way to accurately determine how closely individuals within a colony are related to each other. As a result, they could not predict which ants should favor others if nepotism were indeed taking place.

But advances in genetic analysis enabled Sundström and Hannonen to test for nepotism. The pair were able to distinguish one ant's DNA from another's and use certain genetic markers to determine what queen was the mother of various ant offspring.

Continued on Next Page >>




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