Current hypotheses surrounding the evolution of emission and perception of volatile organic compounds (VOCs) as a communication mechanism among plants lies in their importance as internal signals. VOCs released from damaged organs induce resistance in undamaged organs of the same individual faster than vascular signaling and independent of anatomy. Earlier work shows the reduction in efficacy of VOC induced resistance as genetic and physical distance of populations increase, although the pattern of decay is not supported at the interspecies level. As evidence supports the occurrence of interspecies VOC-mediated induction, variable responses not explainable by shared evolutionary history pose a critically missing mechanism for describing the transition of the phenomenon from communication to ‘eavesdropping’. As evolutionary theory necessitates fitness consequences for ‘true communication’, it is important to disentangle chemically mediated induction events from reciprocal self-recognition (communication) among individuals from unidirectional signal interpretation (eavesdropping). Here we present several theoretical models hypothesized to lead to communication or eavesdropping, while presenting a series of experiments to disentangle this question in a phylogenetically informed manner using the annual clade of Helianthus.
