ECOSYSTEM

African ant 'supercolony' poised to invade the planet

PUBLISHED : Sunday, 27 November, 2016, 3:37pm
UPDATED : Sunday, 27 November, 2016, 8:52pm

A species of ant in the forests of Ethiopia looks poised to become a globally invasive species, capable of spreading around the world, disrupting ecosystems and becoming a pest for humans.

The speciesLepisiota canescens is showing signs it forms "supercolonies," which are colonies comprised of more than one nest. These supercolonies allow a single species of ant to spread out over a large territory, a key step to becoming an invasive species.

This concerns a group of researchers from various institutions in American and Ethiopia, who published a study on the ants in the journal Insectes Sociaux . They observed that one similar species of ant in the same genus (Lepisiota) have invaded South Africa's Kruger National Park, and another temporarily shut down Australia's Darwin Port after the ants were discovered among cargo.

"The species we found in Ethiopia may have a high potential of becoming a globally invasive species," said lead author D. Magdalena Sorger, a post-doctoral researcher with the North Carolina Museum of Natural Sciences.

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"Invasive species often travel with humans, so as tourism and global commerce to this region of Ethiopia continues to increase, so will the likelihood that the ants could hitch a ride, possibly in plant material or even in the luggage of tourists. All it takes is one pregnant queen. That's how fire ants started!"

The ant colonies are in the forests that surround Orthodox Christian churches in Ethiopia, which are some of the last natural forests in the country. Ethiopian Christians have long surrounded their churches with woodland. Some of these forests are more than a thousand years old, and are unusually rich areas of biodiversity in areas otherwise barren or deforested for agriculture.

The researchers say these ants have built the largest supercolonies ever observed among an ant species in its native habitat — the largest supercolony they found spanned 38 km. That, along with the ants' diet and nesting habits suggest they have the characteristics of an invasive species.

Ant supercolonies are rare — out of the 12,000 known species, only about 20 have ever shown supercolony behaviour. Other species of ants tend to be more territorial and less tolerant of ants from other nests.

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The Argentine ant is perhaps the most famous example of the supercolony builder. Argentine ants have spread across a roughly 4,000km of Western Europe, including parts of Spain, France, Italy, and Portugal. In the US, California is home to an Argentine ant supercolony spanning more than 800 km. That's because in their non-native habitats, they can thrive.

Once in a region, the invasive ants drive out native ant populations, and though ant wars may seem to be of little consequence to some, the invasions have impacts that can often be seen without a magnifying glass.

The Argentine ants' assault on native California ant species has also led to declines in predators that fed on those native ants, such as the coastal horned lizard.

They have also become a pain for Californians who have reported them infesting homes, crawling out of plumbing and even sneaking into handbags.

The team included scientists from several institutions in Ethiopia and the US, including North Carolina Museum of Natural Sciences, The University of Tulsa, Bahir Dar University, California Academy of Sciences, and Smithsonian Institution.

Sorger said that the research will offer a record of how the ants live in their natural habitat, which could be critical if the species becomes invasive.

"Rarely do we know anything about the biology of a species BEFORE it becomes invasive," Sorger said.