Ant "Supercolony" in Europe Raises Questions About Getting Along

Updated April 23, 2002

Squabbling parties within the European Union could learn a lot about how to get along from the invasive Argentine ant population. Researchers have discovered an enormous "supercolony" of these ants that extends across 6,000 kilometers (3,728 miles) of Southern Europe.

All the ants within this supercolony, even those from different nests, seem to behave amicably toward each other. This is the largest cooperative biological unit ever discovered.

By contrast, in Argentina, ants from different nests are particularly belligerent and fight to the death, says Laurent Keller, an entomologist from the University of Lausanne, Switzerland, who led a study on their behavior.

Keller's team captured about 5,000 ants from 33 separate nests in Italy, France, Spain, and Portugal and transported the insects back to his laboratory. Once in the lab, the scientists arranged ant fights—pitting ants from one nest against ants from the other 32 nests. Over the span of a year, the scientists conducted almost 1,100 ant fights.

What they discovered was that all the ants were members of either one of two enormous supercolonies.

A supercolony is a remarkable structure because it involves hundreds of billions of individuals.

Ants from 30 of the nests belonged to the main supercolony, which stretches from northern Italy along the Mediterranean coastline past France and Spain and curves around the Iberian Peninsula past Portugal. Ants from three Spanish nests represented a smaller Catalonian supercolony.

Defying Expectations

What is extraordinary is that ants from nests separated by thousands of kilometers did not show any aggressive tendencies towards each other; ants from Portugal, Spain, Italy and France all got along, says Keller.

What has scientists befuddled is how a supercolony arises.

The whole concept of these large colonies clashes with the "kin selection theory," which basically predicts that altruistic behavior should only occur between related individuals. But within the European colony, a visiting ant from the Portuguese branch of the supercolony, for example, is just as welcome in an Italian nest as a local ant.

A possible explanation was that the entire supercolony arose from a very small number of founders, which would mean that the ants within the colony are genetically very similar—hence their surprising tolerance of ants from distant nests.

Continued on Next Page >>




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