Circadian rhythms are ubiquitous in nature and endogenous circadian clocks drive the daily expression of many fitness-related behaviors. However, little is known about whether such traits are targets of selection imposed by natural enemies. In Hawaiian populations of the nocturnally active Pacific field cricket (Teleogryllus oceanicus), males sing to attract mates, yet sexually selected singing rhythms are also subject to natural selection from the acoustically orienting and deadly parasitoid fly, Ormia ochracea. Here, we use T. oceanicus to test whether singing rhythms are endogenous and scheduled by circadian clocks, making them possible targets of selection imposed by flies. We also develop a novel audio-to-circadian analysis pipeline, capable of extracting useful parameters from which to train machine learning algorithms and process large quantities of audio data. Singing rhythms fulfilled all criteria for endogenous circadian clock control, including being driven by photoschedule, self-sustained periodicity of approximately 24 h, and being robust to variation in temperature. Furthermore, singing rhythms varied across individuals, which might suggest genetic variation on which natural and sexual selection pressures can act. Sexual signals and ornaments are well-known targets of selection by natural enemies, but our findings indicate that the circadian timing of those traits’ expression may also determine fitness.

中文翻译：

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机器学习揭示雄性太平洋蟋蟀的歌唱节奏是受时钟控制的

昼夜节律在自然界中无处不在，内源性生物钟驱动着许多与健身相关的行为的日常表现。然而，人们对这些特征是否是天敌强加的选择目标知之甚少。在夏威夷夜间活动的太平洋田蟋蟀（Teleogryllus oceanicus）种群中，雄性通过歌唱来吸引异性，但性选择的歌唱节奏也受到声学定向和致命寄生蝇 Ormia ochracea 的自然选择的影响。在这里，我们使用 T. oceanicus 来测试歌唱节奏是否是内源性的并由生物钟安排，使它们成为苍蝇选择的可能目标。我们还开发了一种新颖的音频到昼夜节律分析管道，能够提取有用的参数来训练机器学习算法并处理大量音频数据。歌唱节奏满足内源性生物钟控制的所有标准，包括由照片时间表驱动、大约 24 小时的自我维持周期性以及对温度变化的鲁棒性。此外，不同个体的歌唱节奏也不同，这可能表明自然选择和性选择压力可以影响遗传变异。性信号和装饰品是天敌选择的众所周知的目标，但我们的研究结果表明，这些特征表达的昼夜节律时间也可能决定适应性。