Resources limit the invasion of natural communities by Argentine ants

The ability of species to invade new habitats is often limited by various biotic and physical factors or interactions between the two. Invasive ants, frequently associated with humans, flourish in disturbed urban and agricultural environments. However, their ability to invade and establish in more natural habitats is variable. This is particularly true of the invasive Argentine ant (Linepithema humile). While biotic resistance and low soil moisture can limit their invasion of natural habitats, the effect of food availability has not been explored. Field experiments were conducted to determine if resource availability was limiting the movement of Argentine ants into remnant natural habitat in North Carolina, where abiotic issues such as soil moisture are less limiting. Replicated transects paired with and without sucrose solution feeding stations were run from invaded urban edges into forest remnants and compared over time using baits and direct counts at stations. Access to sucrose increased local Argentine ant abundances and facilitated their progression into the forest such that densities were greater at most distances relative to control transects. Following the removal of sucrose stations, Argentine ant densities appeared to decrease in conjunction with a retreat to the urban / forest boundary. Availability of sufficient carbohydrates allows Argentine ants to invade natural habitat and possibly overcome additional impeding factors such as biotic resistance. Our findings demonstrate the potential for Argentine ants to sustain an invasion of forest areas where they can opportunistically exploit existing carbohydrates such as tending Homoptera or extra-floral nectaries.