Alarm pheromone induces a transgenerational wing polyphenism in the pea aphid, Acyrthosiphon pisum

In response to increased predation risk, many organisms exhibit transgenerational polyphenisms whereby offspring have behavioural and (or) morphological adaptations to avoid natural enemies. The mechanisms underlying altered phenotypic expression, however, are not well understood. Aphids commonly exhibit a transgenerational wing-induction polyphenism in response to predators and parasitoids, but the stimuli inducing winged offspring production have not yet been identified. As aphids commonly emit the alarm pheromone (E)-β-farnesene (EBF) when physically attacked, this compound is a reliable signal of increased predation risk for asexual conspecifics. Here we show that maternal detection of EBF induces a transgenerational wing polyphenism in offspring of the pea aphid, Acyrthosiphon pisum (Harris, 1776). In response to 50, 500, or 5000 ng of EBF vapor, aphids responded with 2.5-, 5.0-, and 6.0-fold increases in winged offspring production, respectively. Thus, alarm pheromone may alter aphid transgenerational phenotypic expression, thereby influencing aphid - natural enemy dynamics.