Battle of the parasites: Love vine sucks the life from gall wasps

Aug. 20 (UPI) — Scientists have discovered a never-before-seen interaction between parasites. Researchers at Rice University discovered a parasitic vine preying on a parasitic wasp.

The two parasites, love vine and gall wasps, share the same host, oak trees. But the new research suggests it’s not the tree the vine is interested in, but wasp larva hiding inside the pea-sized growths found on the underside of oak leaves.

Rice University evolutionary biologist Scott Egan has spent nearly two decades studying gall-forming parasites. But until he and his students noticed love vine twisting around galls in the lab, Egan had never seen the novel interaction before.

“I had never seen this,” Egan said in a news release. “But the fact that no one, as far as we know, had ever documented this was incredible because biologists have studied each of these — the vines and the insects — for more than a century.”

Egan thinks the trophic interaction is unprecedented.

“Basically, you have a parasitic plant attacking a parasitic insect inside of another host, a host they share,” he said.

After first noting the novel interaction, Egan and his students dissected a gall strangled by the vine. Inside they found a lifeless wasp. The vine had sucked the life from the Belonocnema treatae specimen.

“Right in the center was a fully mature but mummified adult wasp,” Egan said.

A broader survey turned up additional evidence of the unique interaction. Researchers found examples of love vine preying on other species of gall wasps. They described their work this week in the journal Current Biology.

Thousands of gall-forming species use biochemistry to trick trees into growing tumors inside which a clutch of insect eggs incubate.

“The attacks are also associated with different gall sizes,” Egan said. “We found the vines attached to galls that were slightly larger than average. That means the vine is either only attacking larger galls, or the vine is inducing the galls that it attacks to grow bigger, perhaps to draw more energy from them.”

Scientists aren’t sure how the vine tracks down the galls, but if they can find it, the knowledge could help scientists sense cancer growth inside the human body.