How plant–animal interactions signal new insights in communication

Fundamental concepts about the diversity and evolution of signals have been developed mainly in the context of sexual selection. Here, we review the functional ecology of signals in a different context, that of plant–animal interactions. The visual signals of fruits and flowers are relatively constant and clear in the message that they convey. Thus, plant signals present a particularly suitable, albeit overlooked, system with which to study signal evolution. Plant signals are aimed at multiple receivers, mutualists and antagonists, and understanding how fruit and nectar consumers perceive plant signals provides the key with which to evaluate those signal components that work efficiently for a given consumer. Recent developments in the field of plant–animal communication shed new light on fundamental concepts in signal theory such as mimicry, honest signalling, private communication channels and the sensory drive hypothesis.