‘Ant mega-colony takes over world’ – headlines mostly hype, says expert

Research reported online last week on BBC Earth News asserts that the vast numbers of invasive Argentine ants living in the US, Europe and Japan belong to a single, massive mega-colony. The researchers analysed ants from each region, and evaluated their behaviour to see how aggressive they would be when confronting each other.

Read the full article here.

The Science Media Centre asked Phil Lester, a New Zealand expert on invasive ants, to comment on the research.

Dr Phil Lester, entomologist, School of Biological Sciences, Victoria University of Wellington comments:

“This study is novel in that the authors move populations of an invasive ant between countries to examine behavioural interactions. The authors then observed low levels of aggression between widely separated populations. That’s really what we would expect from our knowledge of their genetics as spearheaded by groups in the US and Europe. This ant species has very little genetic diversity in many of the invaded populations. For example, there are likely to have been only a few invasion events into Europe, which have then spread to several countries and possibly Asia. Given that the ants are all quite closely related, we wouldn’t expect them to fight amongst each other. In an evolutionary framework, it’s generally advantageous to be nice to those who have your genes.

“My laboratory group has undertaken similar work on Argentine ants in New Zealand. We sampled populations from throughout their range here-Kaitaia to Christchurch. The closest related population is on the east coast of Australia, where we are pretty confident the NZ population originated. There is very low genetic diversity in NZ and our estimate is that one nest entered the country with between 16- 24 reproductive queens. Populations of these have then spread throughout the country. Perhaps because of this low genetic diversity, Argentine ants now found in Wellington and Auckland (or anywhere else in the country) don’t fight and instead cooperate to defend resources or help forage. As long as you put them together… clearly populations from Auckland and Wellington would not interact normally without human assistance.

“And that these ants wouldn’t normally interact is an important point. There is occasionally quite a bit of hype around these studies when terms like “massive intercontinental supercolonies” or “ant mega-colony takes over world” are bandied about. These sorts of terms conjure up images of landscapes coated in ants scuttling everywhere and over everything. That type of scenario will never happen. The large European supercolony, for example, has populations that are widely separated with large gaps in the landscape of no Argentine ants. Similarly in New Zealand we could be said to have one large “supercolony”, but Argentine ants here are primarily found in urban settings often separated by hundreds of kilometers.”