Alien ants invade Europe for the first time

One of the world’s most invasive species has now established colonies in Europe, scientists warn.

The red imported fire ant (Solenopsis invicta) is an aggressive species originating from South America, that has expanded beyond its native range in Brazil, Argentina and Peru to North America, Asia and across Oceania over the past century.

Warnings about the ants come a week after international assessments by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) found invasive alien species cost the global economy half a trillion US dollars each year.

Now, the Spanish Institute of Evolutionary Biology (IBE) has confirmed the arrival of the dangerous pest in Sicily, with the potential to spread as far as the UK if not controlled.

“For decades, scientists have feared that it would arrive [in Europe],” says Mattia Menchetti, an evolutionary biologist on the study. “We could not believe our eyes when we saw it.”

“There are a vast number of alien ant species currently establishing in Europe, and the absence of this species was kind of a relief… S. invicta is one of the worst invasive species [and] can spread alarmingly quickly.”

88 red imported fire ant nests in Sicily

Menchetti and his IBE colleagues travelled to Syracuse to investigate the reports after seeing photos published online that appeared to be the red fire ant.

They collected samples from 88 nests across a 4.7-hectare site (about the size of 7 football/soccer pitches) hosting thousands of worker ants.

But Menchetti and his colleagues believe the ants have likely spread beyond this local site, and were told by locals had been enduring painful ant bites since 2019.

“So the ants have probably been there for a while,” Menchetti says. He says locals could help inform researchers and authorities of the extent of the invasion through initiatives the IBE hopes to quickly establish.

“Citizens can play a very important role in this. We hope that, with their help, we will be able to cover a wider area. This will help us track and spot all the possible areas invaded in the region.”

“There needs to be more awareness about this problem because the problem is already in Europe. We need coordinated action, and we need it now.”

As the climate changes, so does the risk of outbreaks

Upon confirming the presence of red fire ants in Sicily, the IBE modelled how the species could spread.

Fire ants can cover substantial distances from ‘wind carry’ blowing them to new locations where colonies can be established. Shipping is also a major cause of this species being exported across the globe: it was behind the unintended introduction of the species to Alabama in the 1930s, Taiwan in 2003 and mainland China the following year. Ports in Brisbane, Botany Bay and Fremantle have served as Australian entry points since 2001.

The IBE extracted DNA from queen ants found at each site, which they found closely match known colonies in China and the US. Though the exact pathway for the species’ entry to Italy isn’t clear, Syracuse’s commercial port is considered a likely source and continued monitoring of the shipping hub is recommended by the research group.

Red fire ants have been controlled in other locations, but rarely eradicated. Only New Zealand has successfully contained and ended an outbreak, with other jurisdictions looking to its approach as an example for future control.

Modelling undertaken as part of the study suggests about 7% of Europe provides suitable habitat and climate for the species to thrive. As the climate warms, that could increase to potentially half of the continent with major built-up port cities providing prime real estate for the invaders.

“This is especially concerning because many of the cities, including London, Amsterdam, and Rome, have large seaports, which could allow the ants to spread rapidly to more countries and continents,” says the study’s senior author Roger Vila.