Institut de recherche sur la biologie de l'insecte, CNRS UMR 6035, Université François Rabelais de Tours, Parc de Grandmont, 37200 Tours, France.
J Exp Biol. 2009 Dec;212(Pt 24):4091-100. doi: 10.1242/jeb.035345.
Female evaluation of male signals in the context of sexual selection is often made on the basis of signal energy. Particularly in acoustic species, females may prefer male song that is broadcast at greater amplitude or power. However, song amplitude may be represented by various parameters, and the specific one(s) that are evaluated are not clear. We addressed this problem in an acoustic moth, Achroia grisella (Lepidoptera: Pyralidae), where males attract females with trains of paired ultrasonic pulses. Previous studies showed that females prefer songs that include pulse pairs that have greater mean peak amplitude and that are delivered with greater power (= mean peak amplitude x pulse-pair rate). Here, we report that given male songs of equal acoustic power, females prefer songs in which some pulses attain peak amplitudes that exceed the mean value and that this preference depends largely on the magnitude of amplitude fluctuation. We measured significant variation among males in their degree of amplitude fluctuation, and we note that males that broadcast with lower acoustic power typically show greater relative fluctuations and attain relatively higher amplitude maxima. We discuss the potential role of multiple integration time constants in female evaluation of mean song amplitude and amplitude maxima. We then consider the possibility that the variation observed in the male population is a response to female choice, but we also indicate that mechanical factors constraining song production may be responsible for such variation.
雌性在性选择背景下对雄性信号的评估通常基于信号能量。特别是在声学物种中，雌性可能更喜欢以更大幅度或功率广播的雄性歌曲。然而，歌曲幅度可能由各种参数表示，并且不清楚评估的具体参数。我们在声学飞蛾 Achroia grisella（鳞翅目：Pyralidae）中解决了这个问题，雄性用成对的超声脉冲发出求爱信号来吸引雌性。先前的研究表明，雌性更喜欢包含具有更大平均峰值幅度的脉冲对的歌曲，并且更喜欢以更大功率（=平均峰值幅度 x 脉冲对率）传递的歌曲。在这里，我们报告说，在具有相等声功率的雄性歌曲中，雌性更喜欢一些脉冲达到超过平均值的峰值幅度的歌曲，并且这种偏好主要取决于幅度波动的幅度。我们测量了雄性之间在幅度波动程度上的显著差异，并且我们注意到，以较低声功率广播的雄性通常表现出更大的相对波动并且达到相对较高的幅度最大值。我们讨论了多个积分时间常数在雌性对平均歌曲幅度和幅度最大值的评估中的潜在作用。然后，我们考虑了在雄性群体中观察到的这种变化是对雌性选择的反应的可能性，但我们也表明，限制歌曲产生的机械因素可能是这种变化的原因。
