Section of Integrative Biology, 1 University Station C0930, University of Texas at Austin, Austin, TX 78712, USA.
Curr Biol. 2010 Mar 23;20(6):502-5. doi: 10.1016/j.cub.2010.01.021. Epub 2010 Mar 4.
Females often prefer to mate with males who produce complex signals. It is not clear why they do so. Females might prefer complexity if it predicts mate quality, or signals might evolve complexity to exploit females' sensory or cognitive biases. We tested whether complexity increases active time, the period over which a signal influences a receiver's response to that signal. Mating signals are often ephemeral, yet their active time has largely been ignored. Here we demonstrate that signal complexity influences active time in túngara frogs. Male advertisement calls consist of frequency sweeps (whines) followed by 0-7 high-frequency bursts (chucks). Females preferentially approach complex (whines with chucks) over simple (whines alone) calls but do not consistently prefer greater complexity, so the function of multiple chucks has been uncertain. We found that females remember which speaker previously broadcast complex calls when choosing between simple calls broadcast after a delay. This effect occurred for calls with multiple chucks, but not with single chucks. Neither motivation nor orientation behavior differed with chuck number, suggesting that results are due to differential memory. Thus, female memory could favor the evolution of increasing signal complexity through sexual selection.
雌性通常更喜欢与能发出复杂信号的雄性交配。但不清楚它们为什么会这样做。如果复杂信号能够预测配偶的质量，那么雌性可能会偏好复杂信号，或者信号可能会进化出复杂性，以利用雌性的感官或认知偏见。我们测试了信号复杂性是否会增加信号的有效时间，即信号影响接收者对信号反应的时间段。交配信号通常是短暂的，但它们的有效时间在很大程度上被忽视了。在这里，我们证明了信号复杂性会影响 túngara 青蛙的有效时间。雄蛙的求偶叫声由频率扫频（鸣叫） followed 由 0-7 个高频脉冲（chucks）组成。雌性更倾向于接近复杂（鸣叫伴随着 chucks）而不是简单（只有鸣叫）的叫声，但并不总是更喜欢更复杂的叫声，因此多个 chucks 的功能一直不确定。我们发现，当在延迟后选择简单的叫声时，雌性会记住之前哪个扬声器播放过复杂的叫声。这种效应发生在有多个 chucks 的叫声中，但没有发生在单个 chucks 的叫声中。无论是动机还是定向行为都与 chucks 的数量无关，这表明结果是由于记忆的差异造成的。因此，雌性的记忆可能有利于通过性选择进化出信号复杂性的增加。
