The study challenges the perspective that it is the lack of natural enemies that promotes invasive species success, partly because the viburnum beetle's natural predator, a parasitoid wasp, is not a major threat to the beetle in its native European range.

"In many other invasions, scientists have argued that enemies -- like the wasp -- do not follow the invader, thus giving the invader freedom from parasitism and the opportunity to be successful," said Agrawal. "That does not appear to be the case for the viburnum leaf beetle. It seems that host quality, or lower plant defenses, is the main driver of this pest's success," he added.

The study was funded by the National Science Foundation and Cornell University Agricultural Experiment Station federal formula funds.