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If only all ecological pests were so easily dispatched. The Argentine ant (), one of the world’s worst invasive species, is disappearing from New Zealand – without any human intervention.

The alien ant arrived in New Zealand in 1990 and has since marched across the nation’s two main islands. Dealing with the pest was projected to cost NZ$68 million (£33 million) per year.

Perhaps no longer. and colleagues at the Victoria University of Wellington say that alien ant colonies in 60 locations are collapsing on their own. Lester thinks low genetic diversity, which is associated with reduced disease resistance, is the most likely reason for the ant’s demise.

at the University of Western Australia, Perth, warns that other alien species won’t be so easily dealt with. “For thousands of other invasive species around the world we’ve seen no such collapse,” she says.

Journal reference: , DOI: 10.1098/ rsbl20111014