Data from: Competition and cooperation in a synchronous bushcricket chorus
Data files
Oct 09, 2014 version files 696.01 KB
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Chorus_vs_Solo Chirp period.xlsx
101.83 KB
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DeltaT vs rmsAmplitude .xlsx
80.80 KB
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Female motivation to perform phonotaxis.xlsx
11.85 KB
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Mean time lag in a chorus.xlsx
194.31 KB
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Phonotaxis and female motivation 1s vs 2s CP.xlsx
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Phonotaxis in 4male choruses.xlsx
34.74 KB
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Phonotaxis Two Choice Trials.xlsx
21.46 KB
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Signal amplitude_Chorus_vs_solo.xlsx
208.97 KB
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Simulation Active space.xlsx
24.52 KB
Abstract
Synchronous signalling within choruses of the same species either emerges from cooperation or competition. In our study on the katydid Mecopoda elongata, we aim to identify mechanisms driving evolution towards synchrony. The increase of signal amplitude owing to synchronous signalling and the preservation of a conspecific signal period may represent cooperative mechanisms, whereas chorus synchrony may also result from the preference of females for leading signals and the resulting competition for the leader role. We recorded the timing of signals and the resulting communal signal amplitudes in small choruses and performed female choice experiments to identify such mechanisms. Males frequently timed their signals either as leader or follower with an average time lag of about 70 ms. Females selected males in such choruses on the basis of signal order and signal duration. Two-choice experiments revealed a time lag of only 70 ms to bias mate choice in favour of the leader. Furthermore, a song model with a conspecific signal period of 2 s was more attractive than a song model with an irregular or longer and shorter than average signal period. Owing to a high degree of overlap and plasticity of signals produced in ‘four male choruses’, peak and root mean square amplitudes increased by about 7 dB relative to lone singers. Modelling active space of synchronous males and solo singing males revealed a strongly increased broadcast area of synchronous signallers, but a slightly reduced per capita mating possibility compared with lone singers. These results suggest a strong leader preference of females as the ultimate causation of inter-male competition for timing signals as leader. The emerging synchrony increases the amplitude of signals produced in a chorus and has the potential to compensate a reduction of mating advantage in a chorus. We discuss a possible fitness benefit of males gained through a beacon effect and the possibility that signalling as follower is stabilized via natural selection.