1Medical Research Institute, Tokyo Medical and Dental University 1-5-45 Yushima, Bunkyo, Tokyo 113-0034, Japan.
2Laboratory of Ecological Information, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Recently, a phenomenon that plants respond to herbivore feeding activity by producing
volatiles that in turn attract carnivorous natural enemies of the herbivores has been reported
in several tritrophic systems. These volatiles are not the mere result of mechanical damage,
but are produced by the plant as a specific response to herbivore damage.We investigated
the population dynamics of such tritrophic interactions using a method named Abstract
Rewriting system of Multi-Sets (ARMS) [1] which is a new research method in
Complex Systems and Artificial Life. In ARMS model, we regarded a tritrophic interaction
mediated by herbivore-induced plant volatiles that attract carnivorous natural enemies of
herbivores as chemical reactions of four reagents (plants, herbivores, carnivores and volatiles).
The intensity of interactions between individuals corresponded to reaction speed in the ARMS
model. We compared the case where plants produce herbivore-induced volatiles vs the case
where they do not with the model. Further, by changing the reaction speed, we found that
there was a case where herbivore-induced volatiles that attract carnivores resulted in the
population increase of the herbivores. We will discuss several conditions in tritrophic interactions
that differently affect the population density of plants, herbivores and carnivores based on the
prediction by the ARMS model.
[1] Suzuki. Y and H. Tanaka, Symbolic Chemical System based on Abstract Rewriting System
and its behavior pattern, J. Artif. Life and Robot., 1:211-219, Springer Verlag, 1997.