By Richard Black
Environment correspondent, BBC News website
The ant is capable of forming supercolonies, pushing out native species
A recently discovered ant species may soon be colonising parks and gardens across northern Europe, including the UK, scientists suggest.
The ant, Lasius neglectus, was identified only 20 years ago after establishing a colony in Budapest.
Writing in the journal PLoS One, scientists say the species probably originated in west Asia.
A garden infested with them can contain between 10 and 100 times more ants than if it bears native European varieties.
"When I saw this ant for the first time, I simply could not believe there could be so many garden ants in the same lawn," said Professor Jacobus Boomsma from the University of Copenhagen, who oversaw the research.
Although superficially similar in appearance to the common black garden ant, the invasive species is very different in its behaviour, and particularly in the social structure within colonies.
This, the researchers believe, is key to understanding why it can invade parks and gardens and exterminate varieties that previously held sway.
The ants have probably been transported across Europe in soil used to grow pot plants. Colonies now exist in France, Germany, Poland and Belgium.
Although it is thought to have west Asian origins, its "home patch" has never been found.
Into the cold
Species of ants and other social insects differ in the way mates are selected and in what happens to new queens.
In Lasius neglectus, queens mate within the existing colony rather than leaving and establishing a new one.
Over time, this probably carries an evolutionary cost as it limits the mixing of different genetic variants.
However, for an invasive species it is a highly advantageous trait.
A queen leaving a colony that had been transported to new pastures would find no mates.
But if she can mate with other males from the same colony, it can just expand, with the ever-growing number of ants burrowing through soil and building new nests connected to the old one, until the entire area is populated with one "supercolony".
"It is now becoming clear that rather many ant species share this lifestyle, so it is no surprise that a number of them have become invasive pests with giant supercolonies based on the same principles," said lead scientist Dr Sylvia Cremer, who now works at the University of Regensburg in Germany.
Other invasive ant species include the Argentine ant. Having come to Europe about 1900, by 2002 it had established what was effectively a single supercolony along thousands of kilometres of coast, from northwestern Italy round southern France and the Iberian peninsula to the northern coast of Spain.
Northern Europe has escaped its attention so far; but researchers believe the invasive garden ant is sure to establish itself further in the region, with the UK unlikely to find itself exempt.