Invader ants don’t last in New Zealand

The faltering march of an invasive ant species has been making headlines both in New Zealand and overseas.

The invasive Argentine ant (Linepithema humile), first detected in New Zealand over 20 years ago, is well known internationally for its ability to spread in new territories.

The ants are concern to authorities as the ants compete with other insect species (including pollinators) contaminate food and disrupt agriculture. In 2002 it was estimated that the ants could cost New Zealand$68 million a year if they became fully established in their potential range.

However, Victoria University scientists have now found that, in New Zealand, the invading ants do not maintain their foothold for long.

Research published this week in the prestigious journal Biology Letters, reveals that Argintine ant colonies in New Zealand are collapsing. According the study, most established colonies only last an average of 14 years, although climate change could lead to colonies lasting slightly longer due to more favourable weather in New Zealand.

The researchers were unsure what exactly was causing the colonies to collapse but suspect that it may be a pathogen such as a virus. They note that as the ants are genetically very similar, they will have increased susceptibility to diseases. Ironically, it this lack of genetic variation which has been cited as the reason for the ants invasive success around the globe; ants from different colonies seldom attack each and even switch colonies (unusual in most ant species),  leading some researchers to call the global population of Argentine ants a ‘super-colony’.

You can read more about the study in a Victoria University press release here, and find out more about Argentine ants in New Zealand on the Landcare Research resource site.

The collapsing army of invader ants has appeared in news media in New Zealand and overseas.

Examples include:

Radio New Zealand: Research shows invasive ant populations often die out

New Scientist: New Zealand’s invasive ants mysteriously vanish (and Fairfax press) : Invasive ant dying out

MSNBC: Invasive ants wave white flag in New Zealand