Substrate-borne vibrations of male psyllids vary with body size and age but females are indifferent

• Male and female calls exhibit significant intraspecific variation.
• Some call parameters vary with age and correlate with body size.
• Females are polyandrous and do not choose between males of different sizes and ages.
• Mate choice possibly occurs after rather than before copulation.
• Substrate-borne vibrations are used for mate attraction but not for mate assessment.

During sexual selection members of the opposite sex utilize a variety of signal modalities to acquire information about potential mates. As a prerequisite, signal modalities must exhibit intraspecific variation and correlate with desirable traits that reflect the fitness of the signaller. Anecdotal accounts suggest that female psyllids (Hemiptera: Sternorrhyncha) utilize substrate-borne vibrations (SBVs) to choose between males. However, comprehensive studies investigating the role of SBVs in Psylloidea are lacking. We used laser vibrometry and playback experiments to study the mating and calling behaviours of a psyllid, Aacanthocnema dobsoni (Triozidae). Specifically, we quantified call parameters and asked whether they vary intraspecifically and correlate with male body size and age. We also tested whether female responsiveness is influenced by the body size and age of calling males. Calls were sex-specific: male calls were more complex and comprised long and short syllables while female calls comprised only short syllables. Temporal and spectral parameters of male calls differed significantly from those of female calls. Calls of both sexes exhibited a high level of intraspecific variation. Larger males produced calls with a lower dominant frequency and older males produced calls of higher intensity and pulse rate. We used playback to test female responsiveness to calls recorded from males of contrasting sizes and ages. Surprisingly, female responsiveness was not influenced by body size or the age of calling males. Interestingly, females are polyandrous but only virgins called or responded to male calls. Conversely, males called frequently and attempted (and often succeeded) to mate with unresponsive females. These results demonstrate that A. dobsoni utilizes SBVs for mate attraction but not for precopulatory mate selection. We suggest that polyandry in A. dobsoni potentially evolved in response to male harassment and, as a consequence of polyandry, sexual selection is probably achieved via postcopulatory sexual selection mechanisms.