Figure 1
Behavioral responses of two Drosophila species to artificial songs with varying IPIs. (a) Courtship songs of D. melanogaster and D. simulans. The song is comprised of sine and pulse songs. Inter-pulse intervals (IPIs) of the pulse song are ~ 35 ms in D. melanogaster and ~ 55 ms in D. simulans. Modified from Kamikouchi and Ishikawa21. (b) Female copulation assay. An artificial pulse song (Right) was played via a loudspeaker to fly pairs in a courtship chamber (Left). Pulse songs designed with a conspecific intra-pulse frequency (IPF; the principal frequency component of pulses, see Supplementary Fig. S1) were used. Modified from Yamada et al.31. (c) Cumulative copulation rates during exposure to artificial pulse songs with different IPIs. Left, D. melanogaster. Right, D. simulan. n = 38–46 pairs per stimulus. (d) Restricted mean time lost (RMTL) of cumulative copulation rate for each song. Square dots and error bars represent the average of RMTL and standard errors, respectively. Inset shows hazard ratio of the interaction between IPI (35 ms and X ms) and species (D. melanogaster and D. simulans) in cumulative copulation rate (See Supplementary methods). The hazard score for the 35-ms IPI song in D. melanogaster was used as a reference. When the Hazard ratio (HR) is greater than 1, an increase of copulation rate in D. simulans at the song carrying a given IPI (15, 55, 75, or 95-ms) from that at the 35-ms IPI song is higher than that in D. melanogaster. HR = 1.44, 2.30, 1.01, and 0.93, and p = 0.538, 0.043, 0.979, and 0.890 for 15, 55, 75, and 95-ms IPIs, respectively (Supplementary Table S1). A time window of 0–7 min after the onset of the experiment was used to maintain proportionality (Supplementary Table S6). Square dots and error bars represent the average and standard errors, respectively. n.s.: p > 0.05, *: p < 0.05; Cox proportional hazard test.
