Ant Species Weeds Out Room for Host Trees

A species of Amazonian ant has adopted a unique method of providing Lebensraum for its expanding colonies: It kills off all other species of vegetation in an area of forest to give its host trees the “living space” to expand.

The ant’s housing tracts, called “devil’s gardens” by the region’s human inhabitants, are curiosities amid the normal diversity of trees, vines, shrubs and wildflowers in the jungle.

Biologist Deborah M. Gordon of Stanford University and her colleagues reported this week in the journal Nature that the ants, Myrmelachista schumanni, injected toxic formic acid into the leaves of plants surrounding their host Duroia hirsuta trees, thereby creating space where new saplings could grow.

The discovery marks the first time ants have been shown to use an herbicide to control their environment.

The activity allows the ants to create new nests as the mother colony grows into the millions over its estimated 800-year life span.

Researchers were previously unsure whether the ants were responsible for creating the devil’s garden or whether the trees were secreting a substance that killed surrounding plant life, a phenomenon called allelopathy.

They tested the theories by planting cedar saplings inside the areas, some unprotected and others coated with a sticky insect barrier.

The ants immediately attacked the unprotected trees, but those with the barriers thrived.