Difference in calling song of three field crickets of the genus Teleogryllus: the role in premating isolation

Abstract

Cricket songs are species-specific signals that are important for species recognition. To prove the effectiveness of calling songs in premating isolation, studies need to take into account closely related species distributed sympatrically in nature. I compared the calling songs of three closely related cricket species that inhabit the Japanese archipelago: Teleogryllus yezoemma, T. emma and T. taiwanemma. Teleogryllus emma is widely distributed in the archipelago and overlaps the ranges of T. taiwanemma in the south and T. yezoemma in the north; T. yezoemma and T. taiwanemma are allopatric. I compared three temporal parameters (the long-chirp duration, the interphrase duration and the pulse cycle), a frequency parameter (the dominant frequency) and two structural parameters (the number of pulses in one long chirp and the number of short chirps following one long chirp). In addition, I conducted a two-speaker playback experiment using female T. taiwanemma to test whether they can accurately distinguish conspecific males based on their calling song. The species with partially overlapping ranges had divergent songs that females could distinguish accurately, whereas the allopatric species had similar songs that females could not accurately discriminate. These results suggest that the calling song has an important role as a premating isolation mechanism.