How the Argentine ant is taking over the world
In moist areas, under trash, concrete, buildings and sidewalks, a network of nests lie hidden. The inhabitants are 1/16 of an inch long and travel in long lines that practically go unnoticed by people walking by. These brown creatures can crawl into virtually any space seeking sweets to eat. They are everywhere and they are nearly unstoppable. These tiny, seemingly harmless, creatures are Argentine ants and they are cleverly on their way to world domination.
According to the National Center for Biotechnology Information, the mega Argentine ant colony consists of hundreds of thousands of ants spanning six continents and various oceanic islands. This supercolony is the largest insect community of its kind and may be rivaling humans in scale. Soon, with the unwitting help of humans and the ants’ ability to outcompete other species, they may further expand their range and fully live up to their title as the number one household pest.
Andrew Suarez, an associate professor of entomology and animal biology at the University of Illinois and an expert in Argentine ants, said these little pests originated from northern Argentina before being unintentionally introduced by humans to the southeastern United States and other countries in the late 1800s.
Humans unwittingly caused the spread of the Argentine ant by allowing the species of ant to stow away in ships that were traveling between countries. Suarez said the ants became hitchhikers on ships because they were trapped in human cargo.
“They were first detected in a few islands and places like New Orleans and from there they were very successful and they spread rapidly throughout parts of the Southeastern United States and hitchhiked over to California,” Suarez said.
What makes these ants unique is their colony did not remain small like other ant colonies. Suarez said the Argentine ants’ ability to rapidly increase their population is due to high reproduction rates, and their success in expanding their range is what enabled the colony to get so large.
“They basically were forming these colonies over very expansive areas and, unlike a typical ant colony, which is in one little place at a time, they formed expansive supercolonies,” Suarez said.
Another reason Argentine ants have become so established is that even though ants are a highly territorial species, the Argentine ant supercolony does not fight each other, even if the ants are from vastly different places. Jan Nyrop, an entomology professor at Cornell University, said this could be because the Argentine ant supercolony has less genetic diversity.
Typically, greater genetic diversity enables the invader to become successful in their new environment because they have the genetic background to adapt to and exploit their new environment. However, Nyrop said this is not the case for ants.
“With ants, it turns out to be the reverse and the reason for that is because with low genetic diversity, they don’t recognize other colonies as competitors,” Nyrop said.
Nyrop said supercolonies can form because the ants are not competing with other ants of the same species. In the case of the Argentine ant supercolony, the ants are not very genetically diverse and the separate Argentine ant colonies are able to come together to outcompete all other native ant species.
Nyrop said different ants colonies, like fire ant colonies, do not come too close to each other because they can sense the differences between the colonies. Nyrop said these ants have the ability to recognize friend or foe due to an odor cue.
However, he said this is not seen with the Argentine ant. Because they do not have much genetic diversity, they lack the odor cue that signals a new colony.
“With the Argentine ant, there was not a genetic diversity in there. So … they all say, ‘Oh, we are all the same. We all come from the same colony,’” Nyrop said.
The vastness of the Argentine ant supercolony is making the invasive ant a powerful oppressor of native life and is impacting the ecosystems they invade. According to the NCBI, Argentine ants can outcompete native ant species because of their large populations and can essentially push out the native species by using native ants’ resources and fighting for territory.
Invasive species are detrimental to native environments because they are able to prey on and outcompete native species for food, according to the National Wildlife Federation. Invasive ants, like the Argentine ant, are no exception. Once they establish in a foreign environment, they can replace native species. After replacing the native species, there is a reduction in biodiversity — allowing the Argentine ant to spread rapidly across its new environment.
Suarez and Nyrop are both concerned with the ecological impacts the Argentine ant species is having on its non-native environment.
“Native ants often serve very diverse roles in the ecosystems they live in and replacing the diverse ant community with a single introduced ant, we fear that we are not only losing diversity but also those ecosystem services,” Suarez said.
However, Ana Jesovnik — a PhD candidate in entomology at the University of Maryland — said there is little hope for humans to control the invasive Argentine ant population.
“We can try to lessen the impact by controlling shipping and things like that but, because ants have colonized for many years before us, we are minor players in this story,” Jesovnik said.
Sydney O’Shaughnessy is a junior journalism and environmental science major who wishes Argentine ants were more like the ants in the movie “A Bug’s Life.” You can email her at firstname.lastname@example.org.