Invasive? Or just disturbed

Invasive species often succeed in new environments because they can outcompete native species within an area for some resource, such as food, mates or habitat. What’s less clear is exactly what gives them this edge over local species that should be experts at living in their home territory.

A study by Joshua King and Walter Tschinkel published online in the Proceedings of the National Academy of Sciences investigates just what gives a common southern pest, the invasive fire ant, the ability to muscle out local ants seemingly everywhere there’s a human disturbance. Notorious for their huge nests (as many as 100,000 ants per colony on average), aggressive swarming behavior and painful stings, these red ants have become a major menace in the U.S., Australia, the Philippines, China and Taiwan.

Because the ants are usually found in highly disturbed areas, such as roadsides, parking lots, strip malls and subdivisions, the authors wondered if the ants’ success depends on their environment.  The authors compared the success of native ant populations in areas that were recently disturbed by humans to natural areas where fire ants were introduced.

Somewhat surprisingly, the fire ants by themselves had less of a negative effect on native ant populations than simple plowing.  The ecologists suggest that fire ants may not be so much an invasive species but a “disturbance specialist,” with the ability to capitalize on an open niche when they see one – a description that might fit other invasive species as well.