Evolutionary Ecology of Plant Signals and Toxins: A Conceptual Framework

Abstract

Plants are capable of acquiring information from other plants, but are they able to send signals and communicate with them? Evolutionary biologists define biological communication as information transmission that is fashioned or maintained by natural selection and signals as traits whose value to the signaler is that they convey information to receivers. Plants, then, can be said to communicate if the signaling plant derives a fitness benefit from conveying information to other plants. Examples for interplant communication that fit these definitions potentially include territorial root communications, self/non-self recognition between roots and associated with self-incompatibility, volatile signals that induce defenses against herbivores, signals from ovules to mother plants, signals associated with root graft formation, and male to female signals during pollen competition. Natural selection would favor signals that are costly to the signaler and therefore are likely to convey reliable information because they cannot be easily faked. Toxins in low concentrations may commonly act as signals between plants rather than as inhibitory allelochemicals. This explains why toxic concentrations of plant allelochemicals are rarely found in natural coevolved systems.