Garden discovery reveals a link between oak trees, gall wasps and ants
WHEN HUGO DEANS POINTED OUT some seed-like objects near an ant nest, his father, Andrew, recognised them as oak galls – plant growths triggered by insects. “I was surprised that ants would collect galls,” says Hugo, now aged 10.
When certain wasps lay eggs in an oak leaf, the tree surrounds them with hardcased galls, protecting the leaf and sheltering the wasp larvae. Some flowering plants also make edible growths – through eating them, ants help to disperse their seeds.
A “mind-blowing” new link between these occurences has now been made by Andrew Deans and colleagues at Pennsylvania State University: the gall wasp stimulates an oak tree to make a gall, but with a cap that ants love to eat. The galls drop, are harvested by ants and taken to their nest, where the wasp larvae may get extra protection.