The nightshade growing near the honeysuckle had 30 percent more of its fruit eaten and seeds dispersed.
"The newly introduced plants piggybacked on the success of the honeysuckle, which is a common phenomenon because fruit-eating birds usually feed on a variety of fruit, whatever happens to be available to them," Carlo said.
"The same birds that ate the honeysuckle also ate the American nightshade, dispersing the seeds of both plants. It's a win-win-win for all three: the birds, the honeysuckle, and the nightshades," Carlo said.
After observing the benefits that non-native species can have on an ecosystem, eradicating them without considering the consequences could be a serious mistake.
"Nature is in a constant state of flux, always shifting and readjusting as new relationships form between species, and not all of these relationships are bad just because they are novel or created by humans," Carlo said.
"We need to be more careful about shooting first and asking questions later, assuming that introduced species are inherently harmful. We should be asking: Are we responding to real threats to nature or to our cultural perception and scientific bias?" Carlo said.
The research will be published in the journal Diversity and Distributions.
IMAGE 1: Anna's Hummingbird male (Calypte anna) feeding from Mexican Honeysuckle flowers (Justicia spicigera), Arizona, USA. Credit: Charles Melton/Visuals Unlimited/Corbis IMAGE 2: Waxwing eating honeysuckle fruit (Tomás Carlo, Penn State)
IMAGE 3: Waxwing eating honeysuckle fruit (Tomás Carlo, Penn State)
IMAGE 4: Phytolacca americana, also called pokeweed (H. Zell, Wikimedia Commons)