Comparisons of Upper Thermal Tolerances Between the Invasive Argentine Ant (Hymenoptera: Formicidae) and Two Native Australian Ant Species

The Argentine ant, Linepithema humile (Mayr), is a signicant pest species, having become established on almost every continent, particularly in areas with a Mediterranean climate. In its introduced range, the Argentine ant has been associated with reductions in the abundance and diversity of native ant and nonant invertebrate fauna, as well as the interruption of antplant mutualisms. The distribution of Argentine ants has been correlated with particular abiotic factors, including soil moisture, relative humidity, disturbance, and particular soil and vegetation types. This study assessed the importance of temperature on the survival of Argentine ants and two native ant species (Iridomyrmex "rufoniger" and Rhytidoponera "convexa") in the laboratory. Workers were placed in incubators of varying temperatures (25, 32, 40, 45, 47, and 50C), and counts of the numbers dead and alive were recorded after 1, 2, and 3 h. The results showed that all species displayed almost 100% survival at 25, 32, 40, and 45C, but at 47C the mortality rate of all species increased, with Argentine ants experiencing 100% mortality after 3 h. At 50C, Argentine ants displayed no survival at 1 h, whereas the Iridomyrmex exhibited 50% survival after 3 h. These results may have signicant implications in Australia, where the ground surface temperatures may become very high during the summer, potentially limiting the spread of Argentine ants.