500 species of ants outside habitats, should we be concerned?

Ants are one of the most abundant and hard-working insects in the world. With at least 14,000 registered species, they carry out a fundamental task in their habitats: protecting the health of animals, plants and microorganisms.

"Crucially, the research found that more than 300 species have a high ability to establish non-native populations and that around two-thirds of them are not being intercepted."

500 species of ants outside habitats

A recent study published this month in the journal Current Biology found that at least 520 ant species have been transported by humans outside their native ranges and that at least 60% of them managed to naturalize. The massification of means of transport, especially fluvial, among other factors, has led to its indiscriminate expansion throughout the world.

A team of scientists from Australia, Japan and Hong Kong analyzed more than 146,000 ant "occurrence records" to comprehensively map where the tiny stowaways had spread outside their native regions.

“Not all unfamiliar become invasive, for this, they must reproduce without human help. There are species that arrive with large populations, but are not successful in a new environment”, explains Armbrecht, who was not involved in the study. As he mentions, the main threat of invasive ants is that they are normally detected when they are already generating negative effects on native ecosystems, in addition to economic and even social damage.

Although the study could only verify that 17 species had direct impacts on native biodiversity, another 292 managed to naturalize and their effects would be less detectable. In addition, as Clara Peña, a researcher and coordinator of the Leticia branch of the Sinchi Institute, points out, science is still a long way from knowing the diversity of ants, so there could be many more invaders.

The research also found that unfamiliar species established indoors, such as residential areas, reached their maximum in the Palearctic, but those with the greatest capacity to settle in natural areas were those of the Nearctic and Oceania, with ants coming mainly from the Neotropics, where it predominates the forest ecosystem.

World's most damaging invasive species

Dr Mark Wong, a Forrest Fellow at the University of Western Australia's School of Biological Sciences and lead author of the study, said the minuscule marauders included some of the world's most damaging invasive species.

“Biological invasions of alien species are a complex global problem, and a basic understanding of where they originate, where they are headed, and their ability to establish themselves is key to strengthening biosecurity,” Dr. Wong said.

“Our study provides this information on a global scale for ants, which are extremely important organisms in their native ecosystems, but can also be among the most damaging when inadvertently transported by humans to non-native ecosystems.

"Crucially, we found that more than 300 species have a high ability to establish non-native populations, and that around two-thirds of them are not being intercepted."

Stopping ants

To stop alien ants, environmentalists and officials need to know where they originate and where they might stop along the way. Most of these invaders came from the tropics and subtropics, particularly central and northern South America and the islands of Southeast Asia, the article reports, areas with high density and diversity of ants.

"What we've shown is where species originate from and where they end up," says Wong. "But the big gap in the road is, 'How did they get there?'" For most species, we just don't know, he says.

Climate change must also be taken into account in planning. "Climate change will probably favour ant invasions overall because the most invasive ants are tropical or subtropical species, so there will be more suitable areas," says Bertelsmeier. “It is especially worrying for biodiversity hotspots,” which are often vulnerable and hospitable to ants.

It will be essential to improve the detection of ants at the borders. Research like Wong's, which reveals regions that are often "donors" for ants, could help countries learn how to fine-tune detection processes for the types of ants that tend to come from those areas. Countries can put strict controls on plants and soil, as New Zealand and Australia have done.

What are the risks of invasive ants?

To be invasive, individuals of any species must overcome barriers to dispersal, survival, and reproduction, allowing them to establish themselves and expand into a new habitat. In the case of ants, they need human help to cross those borders.

The ecological impacts of invasive ants include predation, hybridization, and competition with native species that changes ecosystem processes with loss of biodiversity and increase in pests.

The effects of invasion on native fauna in the same habitats can be catastrophic for the native community through various ecological mechanisms, for example, habitat alteration, competition for resources, limiting the feeding activity of native species, and various other indirect mechanisms of invasive species.

Invasive species can have damaging impacts on habitats and devastating effects on natural flora and fauna, and stopping the introduction of these new species is the most effective way to deter future invasions and maintain biodiversity.

Another impact is the economic losses they generate in crops. As Armrecht explains, they not only attack all types of species but also cause irreparable damage to native flora and agricultural products. The affectation can be in two ways: degrading the crop naturally or preying on organisms that had the function of protecting them.

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