Mutualisms have the potential to aid in the success and spread of invasive species.  Several species of invasive ants engage in food-for-protection mutualisms with honeydew-producing hemipterans and plants with extrafloral nectaries.  For example, the red imported fire ant, Solenopsis invicta, frequently associates with aphids and mealybugs in the southern US.  However, the relative extent to which S. invicta recruit to carbohydrate resources (e.g. honeydew-producing hemipterans and extrafloral nectaries) in their native and introduced ranges is not known.  We compared the propensity of S. invicta to recruit to carbohydrate resources on the ground and in vegetation in their native range in Argentina and their introduced range in the southern US. 

Results/Conclusions

In Argentina, S. invicta recruited to vials with sugar water on the ground but were not observed climbing vegetation and did not recruit to sugar water vials at 1 or 2 m height.  However, in the US, S. invicta were frequently observed climbing vegetation and recruited to carbohydrate resources above the ground.  In addition, during surveys of vegetation S. invicta were not found above ground on vegetation in Argentina but were frequently collected on vegetation in the US.  These data suggest that opportunities to monopolize arboreal sources of carbohydrates might be much greater in introduced populations.  Future studies will test the mechanisms responsible for greater use of carbohydrate resources by S. invicta and Linepithema humile (the Argentine ant) in the US and whether or not this may have aided in their ability to invade and spread.