Greenhouse gases influence aphid wing development

“I’ll Fly Away” may be the theme song of some insect species exposed to elevated levels of ozone, according to groundbreaking research by Edward Mondor in the entomology department. Mondor is researching the effects of the greenhouse gases carbon dioxide and ozone on insect behavior and physiology.

The research, funded by a three-year National Science Foundation grant, was conducted at the Aspen Free-Air CO2 Enrichment Site, a cooperative scientific research station in Rhinelander, where national and international researchers are studying the effects of carbon dioxide and ozone on a variety of tree, plant and insect species.

Mondor says, “At Aspen FACE, we are able to assess the individual and interactive effects of (carbon dioxide) and (ozone), associated with global climate change, on insect behavioral and physiological processes.”

And those behavioral changes could alter the balance of predator-prey relationships and the health of forest plants. The study was published in the October issue of the journal Ecology Letters.

Aphids, commonly called plant lice, are insect pests that feed on phloem, or plant sap, injecting their saliva into the plant while they suck up its juices. If the infestation is heavy, aphids can severely damage plants. In addition, aphids are carriers of plant viruses, such as soybean mosaic virus, which can cause greater yield reductions than direct insect feeding, says Mondor.

Mondor studied the goldenrod aphid, Uroleucon nigrotuberculatum. Most aphids are tiny, but at 4 to 5 millimeters long, Mondor called this one “the horse of the aphid world.” Like other aphids, the study aphids display what is called phenotypic plasticity — adults can produce offspring of several different body types. In this case, the offspring are born with or without wings, depending on whether there is a heightened threat of predation or parasitism. Offspring that can fly have greater survival chances.

Aphids are eaten by many other insects, including lady beetles, and serve as the hosts for parasitic wasps that lay eggs in them. These beneficial insects help keep aphid populations in check. But aphids have a warning that these insects are in the area. Both lady beetles and parasitic wasps leave search tracks, a trail of compounds that marks their territory, which aphids can detect.

Mondor’s research showed that aphids produced more winged offspring in response to predatory lady beetle search tracks when the carbon dioxide level was elevated and more winged offspring in response to parasitic wasp search tracks when ozone levels were elevated. Although the underlying reason for this difference is currently under investigation, it is suspected that aphids are responding to differences in natural enemy search behavior under the different atmospheric conditions.

Co-authors of the new study include Michelle Tremblay and Richard Lindroth, both in the entomology department.