Causes of variability in male vibratory signals and the role of female choice in Mantophasmatodea

Abstract

Communication systems that involve substrate vibrations are increasingly a focus of research since this communication mode - recently termed biotremology - has been found to be remarkably widespread in the animal kingdom. Vibrational signals are often used during courtship and therefore underlie both natural and sexual selection. Mantophasmatodea use species- and sex-specific substrate vibrational signals during courtship. We explored whether male vibrational signals of the South African heelwalker Karoophasma biedouwense vary with temperature, body condition and age, and tested female preference towards various signal pattern combinations. We recorded male signals under varying temperatures and over 3.5 weeks after onset of signaling. Our results show that the temporal structure of male signals is modified by changes in temperature, and changes with male age. Other characteristics, especially duty cycles, are less affected, but correlate with body condition. Females responded along a broad spectrum of signaling patterns, indicating that they do not favor signals of males of a certain age or condition. They were selective towards the fine structure of vibratory signals, suggesting that pulse repetition times carry species-specific information. Mantophasmatodea thus use vibrational signals to identify and localize a mating partner, but presumably not for precopulatory mate selection.