Linepithema humile, the Argentine ant

Argentine Ants have spent the past century following commerce around the world, aggressively subsuming the territories of native ants. However, a study by Meghan Cooling et al out today in Biology Letters reports a dent in the Argentine ant empire:

Argentine ants had disappeared from 40 per cent of our sampling sites. In many other sites, Argentine ant populations had been reduced from occupying multiple nests encompassing large areas to one or two small nests in a few square metres. These results are consistent with our observations of the slow shrinkage and disappearance of large Argentine ant infestations in areas, such as Wellington. They do not appear to move and to our knowledge are not managed by humans in any way that might reduce their abundance.

This result echos anecdotes I’ve heard from several people in California. Places once thick with Argentine ants have returned, in part, to a native fauna.

Cooling et al pair their collapse data with climate models to predict whether the process will continue under global warming. I wish they hadn’t. Without knowing the cause of the collapse (pathogens?) the whole climate model exercise is silly. Can’t a straightforward ecological finding just be published on its own?

Source: Cooling, M. et al 2011. The widespread collapse of an invasive species: Argentine ants (Linepithema humile) in New Zealand. Biology Letters, Published online before print , doi:10.1098/rsbl.2011.1014