Physiological limitations of the Argentine ant help explain its inability to invade arid environments

SCHILMAN, P.E.; LIGHTON, J.R.B. & HOLWAY, D.A.

Washington DC, USA

Congreso; XV International Union for the Study of Social Insects (IUSSI); 2006

International Union for the Study of Social Insects (IUSSI)

In seasonally dry environments the rate of invasion and local abundance of the worldwide, abundant and ecologically damaging invasive ant species, Linepithema humile (Argentine ant) is strongly limited by soil moisture. In this study we investigate how physiological limitations may contribute to the Argentine ant’s inability to invade dry environments. We measured and compared total and critical water contents (i.e., the amount of water that can be lost before the ant becomes moribund), rates of water loss (i.e., respiratory water loss and cuticular permeability) and survival times of the invasive Argentine ant and five common ant species native to southern California. To discern between respiratory and cuticular water loss in ants with continues gas exchange, we developed a novel, non-invasive technique that uses changes in gas composition to modulate spiracular conductance. For the six species combined results indicate that worker body size strongly affects water balance, explaining between 99% and 90% of total and critical water content respectively. The respiratory and cuticular water loss were higher and the survival times were shorter for L. humile than for the other five native ant species. Compared to native ants, the Argentine ant is highly prone to desiccation due to a higher area independent water loss and critical water content. We conclude that the inability of Argentine ants to invade arid environments is due in large part to its physiological limitations.