Ants of Ethiopia: Invasion from Within

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As in many developing economies, most of the forests in Ethiopia are cleared away. Much of what remains surrounds the properties of some 3,500 Orthodox churches, maintaining a sanctuary for nature.

Ironically, one native ant species has risen to dominance within these church forests, like an invasion from within. That's according to a recent study published in the journal Insectes Sociaux, lead by Dr. Magdalena Sorger, a post-doctoral researcher with the North Carolina Museum of Natural Sciences.
(See the press release here).

We went to Ethiopia on a biodiversity survey. Instead of finding a lot of different ants and recording all the different ants that were there, we found a single ant that was present all over. And as we were looking at this ant, we realized that it behaves kind of like an invasive ant. A species is invasive when it can thrive in a new location; usually outcompeting native species. Think kudzu and fire ants.

Any invasive species, like fire ants for example, that is really successful in its invasive habitat has a set of characteristics that really work for them.  

The most invasive species are generalists. They can just feed on anything they can find. They can be ecologically dominant, so they have the ability to be really aggressive.

And then another characteristic is this ability to form supercolonies. So, that's just where you essentially have the benefit of numbers. That is a huge cooperative unit that they can work together. And by that, they can take over even bigger expanses of land because their organized supercolonies are giant colonies that can, in some cases, extend over thousands of kilometers.

All members of a supercolony share a common biochemical marker, or scent. And so you can take one ant from somewhere in the supercolony, bring it a few hundreds miles away and it will accepted by the locals.

However, Dr. Sorger and her team determined that this ant species, Lepisiota Canescens, is native and not invasive. The ants show enough genetic diversity across the supercolony to suggest they were not the descendants of only a few individuals that might have arrived in a ship's cargo, for example.

So, what environmental conditions are causing the ants to behave this way?

In this case, we found this ant to be really prevalent and really common in disturbed areas, like one church forest that was actually not doing so well, that was not in great shape, by the side of the road in a more urban setting, and that's where this ant was really present. And so it's possible that while this ant is native to the area, it could have moved into this disturbed habitat and done really well there and just increased their numbers there.

These ants may offer a unique opportunity to study a potentially invasive species before it becomes invasive.

So the question is, “What exactly do the ants do in their native habitat?” So, for this particular ant that we found, and this is in the genus Lepisiota, it's native in this area, but other ants in this genus have actually been found to be invasive elsewhere. There have been invasions that have been eradicated in time. In addition, there's a team that studied another ant in this genus in South Africa that is behaving very weirdly in Kruger National Park, and it also seems to be forming supercolonies - moving in very aggressively toward native species - and we don't know whether they're native to the region as well or if they are invasive. But what this shows us is that ants in this genus seem to have a predisposition, maybe, to become invasive.

This research could have a very important outcome.  

Invasive species are a big problem, and they're mostly a big problem for the native fauna and flora because they change the species competition. We know that they drive down native species, they drive down diversity, and that's a problem. So here we have a species with the potential to become invasive. It has a lot of these characteristics we see in other invasive species. Currently it has not become invasive, but this could happen. And if it does, we want to do everything we can do to prevent that. So I think that's why this matters.

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