Variability of vibratory signals and mate choice selectivity in the southern green stink bug

The southern green stink bug, Nezara viridula, has a complex mate recognition system that implicates chemical and acoustic signals. To localise a sexual partner acoustically, a male and female alternate between the male courtship song (MCrS) and the female calling song type 1 (FCS1). Although previous research has revealed that both signals show geographical variability, until now no studies have explored the form of this variability. We analysed the temporal and spectral characteristics of MCrS and FCS1 pulse trains of males and females from a French and a Guadeloupe population. Pulse train duration of the MCrS varied within and between populations. Likewise, spectral and temporal parameters of FCS1 varied within and between the two populations. Although females did not show any behavioural responses to pre-recorded MCrS, males responded to pre-recorded FCS1 by emitting a higher number of MCrS per minute. Furthermore, males modulated the repetition rate of their MCrS pulse trains to match those of the FCS1. All males responded to FCS1 from French and Guadeloupe females despite the temporal differences in these songs; however, they responded with a shorter latency and a higher rate of MCrS/FCS1 pulse trains to the songs of females from their own population. In choice experiments with two alternatives, responses to FCS1 were inhibited when males received a simultaneous female call from another Pentatomidae sympatric species, Acrosternum hilare. We conclude that, although males prefer FCS1 from their own population, they recognise FCS1 from French and Guadeloupe N. viridula females as species-specific female calls. Variability of vibratory signals might play a role in mate choice.