Figure 1. Food conditions influence receptivity and offspring production.

(a) Mean number of copulations over a 24-hr period per female in pairs consisting of 1 female and 1 male or groups of 6 females and 6 males of the indicated strain. Flies were assayed either in the presence of fly food “Food” or with 1% agar in water “No Food”. Number of replicates ranges from 19–46. Error bars indicate Standard Error of the Mean (SEM). (b) Cumulative percentage of pairs of virgin male and female Canton-S that copulated on substrates either containing food or no food over 20 minutes. Mating latency in the two conditions did not significantly differ (t-test with Welch’s correction: p = 0.199). Number of replicates is indicated between parentheses. (c) Effect of fly food ingredients on copulation. Number of copulations of full fly food (red bar) is indicated for comparison but not included in the analysis. Statistical analysis reveals a significant effect of food ingredients on copulations in both Canton-S (Kruskal-Wallis test; p < 0.001) and Oregon-R (Kruskal-Wallis test; p < 0.001). Differences between “No food” treatment and individual food ingredients within strain were tested using Dunn’s post-hoc test, whose resulting p values are reported above the graph: *p < 0.05; **p < 0.001; ***p < 0.0001. n.s. = non significant. (d) Dose response curve of yeast effect on copulation in Canton-S. Statistical analysis reveals a significant effect of yeast dose on copulations (Kruskal-Wallis; p < 0.0001). Differences between no yeast (0 g/L) treatment and individual yeast doses were tested using Dunn’s post-hoc test, whose resulting p values are reported above the graph as in (c). (e) Dose response curve of glucose effect on copulation in Canton-S. Statistics are as in (c). (Kruskal-Wallis; p = 0.0006). (f–h) Correlation between the number of copulations and the number of progeny produced on different food substrates. Dots represent individual females. Slopes represent linear regressions and are significantly non-zero on all three substrates (p-value on graphs). Correlation between the number of copulations and progeny is significant for all three substrates: Spearman correlation; Food, p = 0.038; Yeast, p = 0.002; Glucose, p < 0.0001. Dashed lines represent 95% confidence intervals. See Table S1 for full statistics.