Transgenes, those little bits of genetic material that give crops desirable traits, have a habit of jumping ship, wandering and finding new homes. They start off as the key players in a genetically modified (GM) crop, usually granting disease- or pest-resistance to foods like corn, potatoes or squash. But their unpredictable nature worries many ecologists, who fear that if wild plants absorb transgenes and take on their superpower resistance, they'll quickly grow out of control.

It makes sense: Adding a finely tuned GM transgene to an already hearty wild plant could equal a fitness advantage, something that might have far-ranging consequences for the ecosystem. But it doesn't always play out how ecologists might expect.

NPR's "All Things Considered" reported on an experiment performed by Andrew Stephenson of Penn State University. Stephenson created a strain of cucurbita, or Texas gourd, with the transgene used to protect commercial squash crops. He grew the modified gourd next to its unmodified kin. Spring brought aphids, which then infected the crop with a virus. As expected, the plants with the transgene were fine, while the others got sick.

But then a plague of cucumber beetles arrived, carrying with them a plant bacteria. While the beetles weren't very interested in the sickly looking, virus-infected cucurbitas, they liked the looks of the healthy transgene-backed gourds and ate away, in turn exposing the virus-resistant plants to bacteria.

Stephenson noted that no one had expected such results — so much for a fitness advantage when the advantage just attracts another pest. But while a transgene seems to cancel out its effectiveness in wild cucurbitas, the experiment just goes to show how unpredictable genetic modification really is.

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