DOI: 10.5061/dryad.q824f
title: Data from: Competition and cooperation in a synchronous bushcricket chorus

description: 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.
description: Mean time lag of males
 attending a chorusThe time difference of
 chirps produced in a small chorus consisting of 4 males. Relative time
 differences were calculated by taking the leader signal as reference. Data
 is shown in Figure 2.Mean time lag in a
 chorus.xlsxChorus_vs_Solo Chirp
 periodThe Chirp period (CP) of
 males either attending a small chorus consisting of four males and the
 average chirp period of the same males singing in
 isolation.Signal amplitude in a
 ChorusThe sound recording of
 the central microphone in small choruses consisting of four males was
 evaluated using a Spike2 macro. The rms and maximum amplitude values of
 either solo singing males and signals produced by four males
 simultaneously are shown in this table. Data is shown in Fig.
 4BSignal
 amplitude_Chorus_vs_solo.xlsxCorrelation between mean
 time lag, signal amplitude and signal durationA macro was used to
 evaluate the timing and signal amplitude of four males acoustically
 interacting in a chorus. Recording channel 2 - 5 contains the evaluation
 of microphone recordings of individual males. Channel 6 refers to the
 evaluation of the microphone positioned in the middle of the chorus. CP =
 chirp period. This data was used to correlate the average time difference
 between individual signals with the signal amplitude recorded by the
 central microphone (shown in figure 4C). This data was also used to
 calculate the correlation of the time lag of chirps produced by male
 individuals with the duration of their chirps (Figure
 5).DeltaT
 vs rmsAmplitude .xlsxSimulation results:
 Active space of simulated malesA Netlogo simulation was
 run to simulate the broadcast area of senders by taking the hearing
 threshold of receivers into account (active space). The extension of the
 broadcast area of simultaneously active senders with the same intensity is
 given as the percentage of active space relative to the active space of a
 lone singing male. Per capita male mating possibilities were calculated by
 assuming three different densities of equally distributed females. Data is
 shown in figure 6Simulation Active
 space.xlsxFemale phonotaxis in
 two-choice trialsFemales given the
 possibility to approach either the left or right speaker simultaneously
 broadcasting different song models. Different chirp periods (CP) were
 presented simultaneously from different directions. Furthermore, identical
 song models were presented with a time lag of 70 ms and 140 ms. Data are
 summarized in figure 7Phonotaxis Two Choice
 Trials.xlsxPhonotaxis and female
 motivation: CP 1.0s vs 2.0sMecopoda elongata
 females were given the possibility to approach one of two speakers. One is
 broadcasting a song model with a chirp period (CP) of 1.0 s and the other
 a song model with a CP of 2.0 s. Data show female choices and how often
 females were motivated to approach either speaker. A data summary of
 female motivation is shown in Fig. 7BPhonotaxis and female
 motivation 1s vs 2s CP.xlsxFemale motivation to
 perform phonotaxis in two-choice trialsMecopoda elongata
 females were given the possibility to approach either of two speakers
 broadcasting different song models differing in chirp period (CP) or
 signal timing (time lag of 70 ms or 140 ms). The motivation of females to
 approach any speaker was evaluated and is summarized in Fig.
 7BFemale
 motivation to perform
 phonotaxis.xlsxMate choice in four male
 chorusesFemales were given the
 choice to select a male among small choruses consisting of four
 simultaneously singing males. Females were released in the middle of the
 chorus and the chirps produced by males during phonotaxis were recorded
 and evaluated with the help of a Spike2 macro. Signal timing and signal
 duration was evaluated and summarized in this table. Based on this data it
 was possible to figure out signal parameters of selected males. Data are
 shown in figure 8.Phonotaxis in 4male
 choruses.xlsx