Data from: Failure to reproduce period-dependent song cycles in Drosophila is due to poor automated pulse-detection and low-intensity courtship

Stern has criticized a body of work from several groups that have independently studied the so-called “Kyriacou and Hall” courtship song rhythms of male Drosophila melanogaster, claiming that these ultradian ∼60-s cycles in the interpulse interval (IPI) are statistical artifacts that are not modulated by mutations at the period (per) locus [Stern DL (2014) BMC Biol 12:38]. We have scrutinized Stern’s raw data and observe that his automated song pulse-detection method identifies only ∼50% of the IPIs found by manual (visual and acoustic) monitoring. This critical error is further compounded by Stern’s use of recordings with very little song, the large majority of which do not meet the minimal song intensity criteria which Kyriacou and Hall used in their studies. Consequently most of Stern’s recordings only contribute noise to the analyses. Of the data presented by Stern, only perL and a small fraction of wild-type males sing vigorously, so we limited our reanalyses to these genotypes. We manually reexamined Stern’s raw song recordings and analyzed IPI rhythms using several independent time-series analyses. We observe that perL songs show significantly longer song periods than wild-type songs, with values for both genotypes close to those found in previous studies. These per-dependent differences disappear when the song data are randomized. We conclude that Stern’s negative findings are artifacts of his inadequate pulse-detection methodology coupled to his use of low-intensity courtship song records.斯特恩批判了多个独立开展雄性黑腹果蝇（Drosophila melanogaster）‘基里亚库与霍尔求偶歌节律’相关研究的工作，声称这些脉冲间隔（interpulse interval, IPI）中约60秒的超日节律周期属于统计假象，且不受周期（period, per）基因座突变的调控[Stern DL (2014) BMC Biol 12:38]。我们重新核查了斯特恩的原始数据，发现其自动化求偶歌脉冲检测方法仅能识别出人工（视觉与声学）监测所发现的约50%的IPI。这一关键错误因斯特恩选用了信号极弱的求偶歌录音而进一步放大——这类录音绝大多数未达到基里亚库与霍尔在其原始研究中设定的最低信号强度标准。因此，斯特恩的绝大多数录音仅会为分析引入冗余噪声。在斯特恩展示的数据中，仅perL突变型与少量野生型雄果蝇的求偶歌信号较强，故我们仅针对这两类基因型开展重新分析。我们手动复核了斯特恩的原始求偶歌录音，并采用多种独立的时间序列分析方法对IPI节律进行了解析。结果显示，perL突变型的求偶歌周期显著长于野生型，两种基因型的周期数值均与既往研究的结果相近。当对求偶歌数据进行随机化处理后，这些依赖于per基因的周期差异便完全消失。我们最终得出结论：斯特恩的负面研究结果实为其不完善的脉冲检测方法与低强度求偶歌录音样本共同导致的假象。