Global Invasion History of the Fire Ant Solenopsis invicta

"Our study indicates that fire ants have been introduced on no fewer than nine separate occasions to California, Asia, and Australia from the southern United States, where S. invicta populations previously were confined for decades. We consider this a minimum estimate, because our NIA sample collections were not geographically exhaustive, and analyses of a few individuals obtained in Trinidad and New Zealand (from intercepted colonies) suggest that these ants also originated in the United States (Science)."