What makes invasive ants tick?

London, Jan 22 (IANS) Certain invasive ant species that successfully invade large swathes of land do so by cooperating to form a super-colony.

While common ant colonies compete with neighbouring colonies for resources and territory, invasive ants abandon all aggressiveness among colonies and work together to form enormous super-colonies consisting of thousands of interconnected nests.

These invasive ants eradicate most native ants and other insect populations, damage trees, and in many cases cause economic and social problems by invading people's homes.

They are similar in appearance to the common black garden ant, but are smaller and lighter in colour and can work up to nine times faster than their common garden counterparts.

The species proliferates in mild climates of Europe and Asia, but it is also the first type of ant that can invade colder areas which had not been affected by more exotic plagues.

However, the origin of these species' characteristic traits which provide them with their extraordinary invasiveness is still a mystery for scientists, given that they only reveal their destructive potential following a long, inconspicuous lag phase.

As a result, many fundamental questions about the origin of their invasive behavioural patterns are still unanswered: Are they originally present in the colonies, before they begin an invasion?

Researchers at Universitat Autònoma de Barcelona (UAB) participated in the first large-scale interdisciplinary study of the invasive Lasius neglectus and its non-invasive sister species Lasius turcicus.

This study has been able to answer some of the questions on the biology of this invasive behaviour. One of the key behavioural elements of these ants consists in forming interconnected nests, with many queens mating within existing colonies instead of starting a new one.

Scientists have been able to demonstrate that the conditions needed to develop this invasiveness are already found in original populations. The study also reveals that the invasiveness is only fully expressed once the ants have escaped their natural enemies, such as parasites and pathogens, said an UAB release.

This happens when they travel to remote areas where local enemies have not had time to adapt and respond to these newcomers. In addition, researchers detected the same biological traits of invasiveness in the sister species Lasius turcicus, but which until now have not manifested themselves.

This data implies that many of the more than 12,500 ant species known to man can become a serious problem if adequate measures are not taken. The study warns that invasive ant populations such as the Lasius neglectus can become a problem of global dimensions.

The study was published in PLoS ONE.