Variation in male song and female preference within a population of Ephippiger ephippiger (Orthoptera: Tettigoniidae)

Species-specific patterns of insect calling song are commonly assumed to show low variability. In the bushcricket Ephippiger ephippiger, male song shows large geographical variation in syllable number, and females strongly prefer song typical of their own population. Here it is shown that there is also large variation in syllable number within a population of E. ephippiger. Two factors associated with this variability were identified: eclosion sequence (which was positively correlated with mean male syllable number) and male-male interactions (with chorusing males producing more variable song than those singing in isolation). Similar variability was not evident in female preference as females did not show significant heterogeneity when offered a choice of recorded songs representing the main syllable types from the population, nor did overall preference vary amongst the main song types. A variety of factors, including genetic variability, developmental plasticity, male interactions and weak female preferences, could be responsible for this phenotypic variability.