Amazonian Ants Use Own Herbicide to Poison Unwanted Plants

A species of ants in the Amazon rainforest controls its environment by selectively killing off plants it doesn't like, a new study reveals. Findings published today in the journal Nature, indicate that a formic acid herbicide produced and used by ants is responsible for single-species swatches of trees.

Sections of the rainforest made-up almost entirely of the tree species Duroia hirsuta, are called "Devil's gardens." Local legend holds that they were produced by an evil forest spirit, report Megan E. Frederickson of Stanford University and her colleagues. But the results of a four-year field study reveal that ants that make their nests in D. hirsuta are the driving force between the homogeneous plots of vegetation. The team introduced saplings of another common Amazonia tree to "Devil's gardens," using a barrier to protect some of them from the ants. Those that were unprotected, however, were quickly attacked by worker ants, which injected poisonous formic acid into the leaves. Trees began to show signs of withering within 24 hours and most of the leaves were lost after five days.