The next step was to determine whether the similarity between the distribution patterns of the plants and the two aphid species was more than coincidental. To do this, the researchers observed what happened when the different aphids fed on five generations of experimentally raised Arabidopsis thaliana plants.

They confirmed that the plants were genetically adapting to the aphids, with each successive plant generation showing less damage from the feeding insects. A change in the genetic makeup of the plant populations specific to each aphid accompanied this trend — and the laboratory plants evolved in a way that tracked the geographic distribution of the two aphids and the plant chemical types.

The researchers also found that when faced with feeding by aphids, the faster-growing Arabidopsis plant types fared better in the laboratory, while the slowest-growing plant types actually went experimentally extinct.

“These data make it clear that even functionally similar plant-eating pests can affect the biochemical and genetic makeup of plant populations, playing a major role in shaping and refining the plant defenses in a natural community,” Kliebenstein said.

Plant sciences have long been a strength at UC Davis, where for decades plant biologists have contributed to our understanding of how plants evolve, grow, fight infections and pests, respond to light, absorb nutrients from the soil and turn sunlight into sugars.  Their discoveries have opened new avenues for developing crops that could grow under diverse environmental conditions.

The study was led by Tobias Züst of the University of Zürich. Other collaborators were Lindsay Turnbull, Ueli Grossniklaus and Christian Heichinger, all of the University of Zürich, and Richard Harrington of Rothamsted Research in Harpenden, U.K.

Funding for the study was provided by the University of Zürich, Swiss National Science Foundation, U.S. National Science Foundation, European Research Council, and Biotechnology and Biological Sciences Research Council of the United Kingdom.