Chuck Bednar for redOrbit.com – @BednarChuck
The tropical fire ant became the first insect of its kind to travel the globe by stowing away on Spanish galleons in the 1500s – boarding in Mexico and making the voyage across the Pacific to the Philippines, then continuing on to other parts of the world, according to a new study.
The discovery, which is reported in a recent edition of the journal Molecular Ecology, involved what Live Science refers to as “a bit of genetic sleuthing” by University of Illinois professor of entomology, Andrew Suarez.
[STORY: How fire ants form living balls when faced with water]
“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,” Suarez, who is also head of the university’s animal biology department, said in a statement. “They were unknowingly moving huge numbers of organisms in the ballast soil.”
Credit: Julie McMahon
The researchers traced the history of the tropical fire ants (Solenopsis geminata), which originated in the Americas, by analyzing the genomes of modern members of the species. They found that the ants found in other parts of the world were most genetically similar to those from southwestern Mexico, suggesting that country was their primary source of origin.
What is this?! A cruise ship for ants?
From there, the ants hitched a ride as the galleons continued on their trade routes, becoming one of the world’s first invasive species as the accompanied the crew from one port to another. They travelled along a trade route from Acapulco, Mexico, and Manila, Philippines, then from Manila to China along another trade route. Their travels were tracked through their genetic diversity.
“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,” said Suarez. “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.”
They were able to date the ants’ activity to the 16th century, based on the established trade routes of that era. Furthermore, they hypothesized that the original population of the ants would tend to be the most genetically diverse, and that any of the insects taken from the original population to a new environment would possess a subset of that original variability. They were right.
“There was this very clear pattern where there was the most genetic diversity in the New World, where it’s native, and then you see these stepping stones of nested subsets of diversity as you move away from the New World into the Old World,” Suarez said. He added that, “the pattern of genetic changes over time always overlaps the timing of when the Spanish trade was going on.”
“Our research highlights the importance of historical trade routes in setting up current distributions of pest species,” added Dietrich Gotzek, a formed UI postdoctoral researcher who conducted the genetic analyses for the study. “It also establishes the utility of using genetic data to reveal such patterns.”
[VIDEO: Fire ants smashed for science]
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