The invasion of alien ants across continents with special reference to Argentine Ants and Red Imported Fire Ants

Abstract

Alien ants are considered to be among the more damaging of invasive insects. Five ant species are ranked among the 100 world's worst invaders by the IUCN. Within the introduced regions, they displace or disrupt the local arthropod fauna, cause agricultural damage by protecting plant pests, and even affect human health. The Argentine Ant, Linepithema humile, has successfully spread from its native range in South America across much of the globe. This species is highly polygynous and possesses a social structure, called unicoloniality, whereby individuals mix freely among separated nests. The introduced populations of the Argentine Ant are characterized by the formation of very large supercolonies across tens or thousands of kilometers, whereas supercolonies in the native ranges are generally smaller, varying from just a few meters in diameter to many hundreds of meters long. In Japan the Argentine Ant, first noted in 1993, is now found in several regions. Early detection and rapid response systems as well as control measures are required to prevent further expansion of the species. A vital component of this prevention is the identification of pathways of introduction into new locations. The recent advances in molecular markers have allowed us to retrospectively construct the invasion history as well as that of the Red Imported Fire Ant, Solenopsis invicta. More recently, many studies on invasion biology have focussed on the ecological and economic links. We first review the previously published studies inferring historical introduction pathways of the alien ants. We then combine our genetic studies with human activity history to describe global dispersal pathways of the alien ants. Finally, we discuss the interactions between human activity and biodiversity through understanding the dispersal history of the alien ants.