Are fire ant venom alkaloid and cuticular hydrocarbon patterns useful taxonomic characters?

Classical taxonomic efforts with fire ant species have been likened to “walking through a mine field” or one “of the more knotty problems in ant taxonomy.” The imported fire ant, Solenopsis invicta, is an economically important pest ant. Its origin is thought to be northern Argentina. Successful introduction of biocontrol agents for imported fire ants depends on accurate identification of S. invicta populations. We report on efforts to gain greater confidence that purported S. invicta populations in northern Argentina match the imported fire ant populations in the USA. We use fire ant venom alkaloids, cuticular hydrocarbons, and recruitment pheromone analyses to define S. invicta in the USA and survey the same chemical characters in an area in northern Argentina thought to be composed of S. invicta. Our results show patterns similar to those in USA fire ant populations, but 36% of 25 collection sites had atypical USA S. invicta patterns. The consequences of these findings will be discussed.