Tapinoma nigerrimum (Hymenoptera: Formicidae): last shield against the spread of the Argentine ant?

Conservation of biodiversity is one of the most important subjects for sustainable human development and resource use. With the expansion of international trade, invasive alien species have become a major cause of biodiversity loss on the global scale. Invasive ants are among the most harmful groups, causing serious problems to ecosystems, agriculture and human life. The Argentine ant Linepithema humile (Mayr) native to South America is one the most important invasive species as it is currently found in many parts of the world; it attains high population densities and is able to out-compete many native ant species. Like other invasive species, its eradication or effective management with existing strategies has proved difficult. For example, containing these invasions with pesticide application and toxic baits can cause serious damage to the local biodiversity. In Corsica, native ant Tapinoma nigerrimum seemed to limit the spread of Argentine ant. Moreover, we chose T. nigerrimum as an interspecific competitor because its biology, behavior and colony attributes are remarkably similar to those of L. humile. Both species exist in Provence-Côte d’Azur Region. Bioassay between L. humile and T. nigerrimum testing competition for food and space has been made to test the hypothesis of a local resistance. In the laboratory Tapinoma nigerrimum showed ability to resist or even, in some case, to exterminate the Argentine ant. This occurred irrespective of the order of introductions and until a relative excess of Linepithema humile