Tropical Fire Ants Traveled The Globe

Researchers at the University of Illinois at Urbana-Champaign have found out a bit more about tropical fire ants--an invasive insect species that's native to parts of North America, South America and Central America.

A new study shows that they may have been traveling on 16th century ships, making them the first ant species to travel the globe by sea.

"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," said University of Illinois entomology professor, study author and animal biology department head Andrew Suarez, in a news release. "They were unknowingly moving huge numbers of organisms in the ballast soil."

Findings published in the journal Molecular Ecology show that 16th century Spanish galleons shuttled tropical fire ants from the Pacific to the Philippines and to other parts of the world from there.

Today, the ant species is found in virtually all tropical regions, including in Africa, the Americas, Australia, India and Southeast Asia.

"Invasive ants are a huge problem. Once they arrive, they establish really high densities in new habitats, with negative consequences for agriculture, native species and human quality of life," Helms Cahan said. "Controlling them costs millions of dollars annually."

For the study, researchers analyzed the genomes of tropical fire ants from 192 locales, looking at patterns of genetic diversity. They also analyzed trading patterns of Spanish sailing vessels going to and from the New-World during the mid-1600s.

From there, they were able to date the ants' invasion of the Old World to the 16th century. At this time, the Spanish had just established a regular trade route between Acapulco and Manila, Philippines, which is responsible for the first trade route as well as effective globalized commerce.

"Uncovering events that happened long ago, before the age of digital tracking codes and customs enforcement, is often a difficult task," Helms Cahan said. "Luckily for us, however, it turns out that invasive species keep their own records of their history, encoded in their genomes."