The European Barberry: A Plant That Makes Complex Decisions

By Giovanna Rappocciolo, Contributor

The European barberry (Berberis vulgaris) and the Oregon grape (Mahonia aquifolium) are species of shrub distributed throughout Europe. The first is native to Europe, whereas the second is native  to North America. They’re different — and not only because of their origin. The two plants are both subjected to infestation by a specialized species of fruit fly. The larvae of this fruit fly feed on the seeds of the two plants — however, there are 10 times more larvae in the affected Oregon grape than in the affected European barberry.

Could the European barberry make informed decisions to control the number of larvae that feed on its seeds? According to a new study, it appears so. “Adaptive and Selective Seed Abortion Reveals Complex Conditional Decision Making in Plants” is by scientists at the Helmholtz Center for Environmental Research and the University of Göttingen in Germany, and was published in the March 2014 issue of the journal American Naturalist.

The Barberry fruit contains usually one or two seeds — the plant is able to stop their development when resources are scarce. According to the study, this mechanism is also employed as a defense from infestation by the fruit fly. In other words, the Barberry plant is capable to abort its own seeds to prevent infestation from the parasite.

The fruit fly punctures the berries and lays its eggs inside them and, later on, the developing larva feeds on the seeds. If the plant aborts the infested seed, the parasite in that seed also dies — as result, the second seed in the berry is saved from infestation. Scientists examined 2000 berries collected from plants across Germany and found that the seeds are not always aborted when infected. By computer modeling, they concluded that when more than one seed is present, the plant aborts the infected seed. In contrast, if only one seed is in the berry, the plant does not abort it — the scientists speculate that the plant counts on the possibility that the fruit will be saved if the parasite dies.

The fascinating conclusion is that the plant could make decisions based on memory and environmental conditions and could anticipate and weight future risks. Although the Oregon grape has been living in Europe for about 200 years and is exposed to the risk of infestation by the same fruit fly, it has not yet developed any comparable defense strategy.

Dr. Hans-Hermann Thulke (Helmholtz Center for Environmental Research) said in a press release, “This anticipative behaviour, whereby anticipated losses and outer conditions are weighed up, very much surprised us. The message of our study is therefore that plant intelligence is entering the realms of ecological possibility.”