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oddball army overruns half of europe
A vast colony of ants, spanning 5000 kilometres, has been discovered in Europe.
The colony, which stretches along the coastline from Portugal to Italy, has developed because the ants act strangely - they are nice to one another. Members from different nests co-operate and share instead of fighting one another to the death as other ants do. Scientists are having a difficult time explaining just why these "tramp ants" are so agreeable.
Their amiable behaviour contradicts a basic idea of evolutionary biology, kin selection theory - the notion that gallant behaviour should persist only among related individuals because helping your kin helps perpetuate the genes you share.
In Argentina, typical ant behaviour - defending boundaries, ripping off the legs and heads of enemies and spurting out toxic chemicals - leaves piles of wartime casualties and limits the size of colonies.
By contrast, the European transplants, and some in the massive colony of Argentinian ants that stretches across California, share what amounts to a peace dividend.
Instead of using resources for war, they spend time looking for food and nurturing the young. And this allows the colonies to develop at much higher densities than normal, eliminating 90 per cent of other types of ants living nearby, said Laurent Keller, of the University of Lausanne, Switzerland.
Professor Keller's research suggests a lack of genetic diversity is not enough to explain the ants' communal behaviour - the European ants still have a fair amount of genetic diversity. Instead, the unusual amount of co-operation among them appears to come about by a process of natural selection which favoured those with less belligerent tendencies.
Over a period, he suggests in Proceedings of the National Academy of Sciences, this resulted in a kind of "cleansing" of the recognition cues ants use to identify friend from foe. The normally peaceful ants will still fight if confronted with ants from different colonies.
That, researchers say, shows that genetic changes have not hampered their natural aggression or fighting ability. Instead, evolution has altered their ability to recognise enemies.
Copyright 2006 Los Angeles Times
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