Stanford University biologist Deborah M. Gordon and her co-workers describe the findings in the Sept. 22 issue of the journal Nature. The discovery was made during a four-year field study led by Stanford graduate student Megan E. Frederickson in the Amazon jungle of western Peru. The research focused on devil's gardens, mysterious tracts of vegetation that randomly appear in the Amazonian rainforest.
"Devil's gardens are large stands of trees in the Amazonian rainforest that consist almost entirely of a single species, Duroia hirsuta, and, according to local legend, are cultivated by an evil forest spirit," write Frederickson and her colleagues in Nature. "Here we show that the ant, Myrmelachista schumanni, which nests in D. hirsuta stems, creates devil's gardens by poisoning all plants except its hosts with formic acid. By killing other plants, M. schumanni provides its colonies with abundant nest sites--a long-lasting benefit, as colonies can live for 800 years."
Most tropical rainforests are densely populated with a remarkable diversity of trees, vines, shrubs and wildflowers. But devil's gardens usually consist of a single plant, D. hirsuta, which happens to be the preferred habitat of the devil's garden ant, M. schumanni.
In addition to the evil-spirit legend, two scientific proposals have been offered to explain why devil's gardens occur. One hypothesis is that D. hirsuta trees release toxic secretions that kill competing plants--a process botanists call allelopathy. Others argue that devil's garden ants are responsible for controlling vegetation, either by extensive pruning or poisoning. "The idea is that by killing other plants, the insects create a space for young D. hirsuta saplings to grow, thereby allowing the ant colony to expand as it occupies new nesting sites in