Effects of abiotic factors on the distribution and activity of the invasive Argentine ant (Hymenoptera: Formicidae)

The Argentine ant, Linepithema humile (Mayr), has spread worldwide, often decimating native ant populations and other arthropod species in invaded areas. It is not known what abiotic and biotic conditions limit its distribution. We investigated the distribution of the Argentine ant in the Jasper Ridge Biological Preserve in northern California, a nature preserve that has been partially invaded by these ants. Canonical correlation analysis showed that the Argentine ant is most likely to occur near the edges of the preserve, which are next to disturbed areas and in low-elevation areas. Native ant species are associated with higher-elevation areas farther from the preserve edge. Distance to surface water and insolation were less important in predicting Argentine ant distribution. This suggests that dispersal from disturbed areas strongly determines the spread of the invasion. We examined how the daily activity patterns of Argentine ants and several native and species depend on soil temperature, air temperature, and relative humidity. There was considerable overlap in activity times, and there were no values of any of the abiotic factors measured in which native ant species were more likely to be active than Argentine ants. Because the Argentine ant is usually active at the same times as any native species, most native species in invaded areas are likely to encounter the invaders frequently. Diet overlap was high with most native ant species except for seed-eating species. Overlap in activity times may intensify both exploitative and interference competition between the Argentine and native ant species.