Taisha is the author of today's entry. She writes:
This photo of Berberis vulgaris, or barberry, was taken by Monceau@Flickr (and shared via the Botany Photo of the Day Flickr Pool). The inspiration for this entry originates from the results of a study published a few months ago. The press release associated with the study, "Are plants more intelligent than we assumed?", was forwarded to us by a UBC colleague and instructor, Dr. David Brownstein. Thank you to Monceau@Flickr and David for contributing to today's post!
The journal article published was Adaptive and selective seed abortion reveals complex conditional decision making in plants by Meyers et al.. In the study, the researchers document ecological evidence in Berberis vulgaris for "plant intelligence" and behaviour. Behaviour, they note, is the response of an organism to internal or external stimuli. In plants, behaviour is most often expressed in the form of growth and development. Only rarely has plant behaviour been documented as a result of interactions with other trophic levels (e.g., consumers or parasites of plants). In the case of plants of Berberis vulgaris, adaptive and selective seed abortion in response to predation by a species of fruit fly was documented.
Berberis vulgaris is a deciduous shrub found in dry scrub and open forests throughout Europe. This species is predated upon by the European specialist fruit fly, Rhagoletis meigenii. The fruit flies oviposit (usually) one egg per fruit, and the larva will then feed upon the seeds within the fruits. In the developed fruit of barberry, there are typically two seeds. As the larva develops and feeds it will consume most of both seeds, indicating that more than one seed is needed for optimum development of the larvae. As a defense response, the barberry plants have the ability to abort the development of the initially-infested seed, and thereby starve the larva. This both saves the remaining seed and halts resource allocation to the damaged seed.
However, the researchers also discovered that the infested seeds are not always aborted. It depends (at least in part) on the number of seeds within the fruit and the presence of environmental stressors. If there are two seeds, then barberry will abort the infested seed 75 percent of the time in order to save the intact seed. However, if only one seed is within the fruit, the infested seed is aborted only about 5 percent of the time. This selective seed abortion response provides a fitness advantage to the host plant, as there may be a small chance the larva will die and the seed will remain functional. Additionally, if there is an external stressor such as water constraints, seed mortalities are greatly increased--but only if another intact seed exists (allowing the parent plant to save resources for better conditions).
This conditional behaviour of seed abortion is what the researchers claim is the ecological evidence for simple reasoning and complex decision-making in Berberis vulgaris. This complex behaviour sheds light on behavioural abilities of plants and on coevolutionary relationships. But, it also raises questions on the evolution of these coordinating capabilities and the physiological mechanisms.