Fire Ants Sailed the World on 16th Century Spanish Galleons

Posted on February 18, 2015

Range of tropical fire ants

Scientists say fire ants (Solenopsis geminata) sailed the world on 16th century Spanish galleons. These ships helped the ant spread to new tropical locations. Today, the fire ant can be found in Africa, the Americas, Australia, India and Southeast Asia. The above image shows how the fire ant is found in most tropical regions of the world after once only being found in the Americas.

Researchers from the University of Illinos, University of Vermont and U.S. Department of Agriculture conducted the study that followed the spread of the invasive first ant. The researchers found the empty ships would fill their ballast with soil before heading to a new port to collect cargo. This soil would sometimes contain large numbers of fire ants.

University of Illinois entomology professor Andrew Suarez says in a statement, "A lot of these ships, particularly if they were going somewhere to pick up commerce, would fill their ballast with soil and then they would dump the soil out in a new port and replace it with cargo. They were unknowingly moving huge numbers of organisms in the ballast soil."

The researchers analyzed the genomes of tropical fire ants from 192 locales and examined patterns of genetic diversity. They also analyzed the trading patterns of Spanish sailing vessels going to and from the New World in the mid-1600s. The researchers were able to date the ants' invasion of the Old World to the 16th century. The Spanish established a regular trade route between Acapulco and Manila, Philippines around this time period. They also set up up the first trade route across the Pacific Ocean which globalized commerce and fire ant populations.

Suarez also says, "If you look at the records, you look at the history, you look at the old trading routes and you look at the genetics, it all paints this picture that this was one of the first global invasions, and it coincided with what could be the first global trade pattern of the Spanish. The ants from the introduced areas in the Old World are genetically most similar to ants from southwestern Mexico, suggesting that their source population came from this region."

A research paper on the study was published here in the journal, Molecular Ecology.

Image: Julie McMahon