A Megalomyrmex symmetochus ant (top) confronts a Gnamptogenys hartmani raider ant (bottom)ANDERS ILLUMSocially parasitic Megalomyrmex ants establish colonies in the gardens of fungus-growing ants, where they restrict the growth and reproduction of their hosts by feeding on resident broods and clipping the wings of virgin queens. But according to a study out today (September 9) in the Proceedings of the National Academy of Sciences, the presence of these parasitic guests can be beneficial when the host colony comes under attack from another species of ant—the guests use their potent alkaloid venom to fight the raiders and defend the fungal gardens.
“This is really intriguing,” said evolutionary biologist Joan Herbers of Ohio State University, who was not involved in the study. “It’s a novel demonstration that in a certain context, when this nasty predatory ant is around, the parasite can protect the host.” In other words, the parasite-host relationship has shifted to a context-dependent mutualism in which the cost to the host is compensated for by protection against a shared enemy. “That hadn’t been appreciated before for social insects,” Herbers added.
“The findings also highlight how ‘parasitic’ or ‘mutualistic’ relationships are not so clear-cut, and [instead] belong on a continuum of interaction between the two,” Natasha Mehdiabadi, an entomologist at the Smithsonian Institution in Washington D.C., who was not involved in the study, told The Scientist ...
