Dec. 3 - Research showing how fungus-farming ants allow parasites to pillage their crop and eat their offspring, in exchange for offering protection against an even more brutal enemy, is offering clues into co-evolution between species. Jim Drury reports.
The parasitic Megalomyrmex ant prepares to kill an invader. She's taken over a farming host's colony to exploit its brood and its fungus garden, and won't stand for a competing parasite looking for its own slice of the action. The host ants accept the arrangement as the lesser of two evils. They know the Megalomyrmex guest ants will defend the colony at all costs against the raiders. University of Copenhagen evolutionary biologist Rachelle Adams spent two years examining the phenomenon. SOUNDBITE (English) RACHELLE ADAMS, EVOLUTIONARY BIOLOGIST AT UNIVERSITY OF COPENHAGEN, SAYING: "The guest ants have a much better strategy of defending the colony because they have a toxic venom that they apply to the raiding ants and effectively kills them almost instantaneously." Such killings are part of life for colonies across Panama and Adams has recreated the three-way ant warfare in her Danish laboratory. Colleague David Nash calls the Megalomyrmex a 'benign parasite'. He says the mutualism it demonstrates to protect the colony may be a common feature in nature, but is one rarely witnessed by humans. SOUNDBITE (English) DAVID NASH, LECTURER IN EVOLUTIONARY ECOLOGY AT UNIVERSITY OF COPENHAGEN, SAYING: "It goes into the nest, it lives long term with the host ants. It gets food from the fungus garden, it eats the brood of the host, it eats the host's brood, but it stays there throughout the life of the colony, so it also relies on the colony itself being alive to collect the food to feed to the fungus garden." The host colony's rate of reproduction is reduced when Megalomyrmex guest ants are present. But, without its benign protector, the colony would be wiped out by agile raiders whose scouts are constantly looking for nests to destroy. And while the host ants are relatively weak and flee the battle, the Megalomyrmex recruits additional workers to fight. The Megalomyrmex's powerful alkaloid poison also turns raiders against each other. SOUNDBITE (English) RACHELLE ADAMS, EVOLUTIONARY BIOLOGIST AT UNIVERSITY OF COPENHAGEN, SAYING: "One thing that I was quite surprised (at) is that not only is the Megalomyrmex guest ant venom toxic to the raiding ants and repels the raiding ants but it actually confuses them. So after they're stung by a Megalomyrmex ant they are attacked by their own nest mates." Adams says the study illustrates the sophistication of co-evolutionary processes driven by natural selection. And for the Panamanian fungus farming ant, it's clear that cultivating the right kind of enemies is a sound survival instinct.