Parker and Hay were so surprised by their findings that they re-examined data from the scientific literature on the feeding preferences of terrestrial herbivores, including three native grasshoppers and one native and four exotic slugs. The studies they looked at had never analyzed their data for the palatability of native vs. exotic plants.
"We really wanted to challenge our findings for aquatic systems," said Parker. "We wanted to know if perhaps aquatic and terrestrial systems work differently and our unusual results were the result of working in a system that nobody had looked at before."
They were even more surprised when their new results looked exactly like their findings for aquatic herbivores. In these three studies, one conducted in the mountains of the Pacific Northwest, another in the plains of Texas and another in the forests of upstate New York, all four native herbivores again preferred exotic plants over natives. Three of the four exotic consumers again had no preference.
"Now we had essentially four separate studies with 11 herbivores and over 300 plant species collected from all around the continental United States all saying essentially the same thing: native herbivores prefer to consume exotic over native plants," said Parker.
While the results of these studies run counter to the widely accepted enemy release hypothesis, they do support the 'new associa
Contact: David Terraso
Georgia Institute of Technology