The differences in the vibrational signals between male O. bicornis from three countries in Europe

Research into vibrational communication is becoming increasingly important as we discover more species using vibrational signals in different types of behavior. Males of the solitary red mason bee, Osmia bicornis, are known to use vibrations in female choice, where the females not only evaluate a male’s fitness through their vibrational signal but also use them to distinguish between males of different origins. This was shown conclusively via bioassays, in which females from Germany rejected English males unless they were imbued with an artificial German signal and vice versa. However, an investigation into which parameters of the signal might differ between species and populations has been lacking so far. We therefore recorded O. bicornis as well as O. cornuta males from Germany, England, and Denmark using a laser vibrometer and analyzed the recordings using the software Spike to measure frequency, modulation range, and average pulse duration in each signal. Our results clearly showed significant differences in the signal between O. bicornis and O. cornuta males in all three parameters measured. O. bicornis populations from Germany and Denmark surprisingly also differed significantly in frequency and modulation range, with England lying in between the two. We believe that the females probably use another signal parameter that we have not evaluated yet to make their mate choice. This leaves us with the question of why the observed signal parameters differ between Germany and Denmark. From our knowledge about the system to date, we believe that we are looking at the first steps of speciation in this system and further study could help us with new insights into evolutionary processes in the future.