Mate choice involves processing signals that can reach high levels of complexity and feature multiple components, even in small animals with tiny brains. This raises the question of whether and how such organisms deal with this complexity. One solution involves combinatorial processing, whereby different signal elements are processed as single units. Combinatorial processing has been described in several mammals and birds, and recently in a vibrationally signalling insect, Enchenopa treehoppers. Here, we ask about the relationship between combinatorial rules and mate preferences for continuously varying signal features. Enchenopa male advertisement signals are composed of two elements: a ‘whine’ followed by a set of pulses. The dominant frequency of the whine and element combination both matter to females. We presented synthetic signals varying in element order (natural [whine-pulses], reverse [pulses-whine]) and in frequency to Enchenopa females and recorded their responses. The reverse combination resulted in a decrease in attractiveness of the signals, and also slightly changed the shape of the preference for frequency. We found that females could be classified into three ‘types’: females with both a strong preference and a strong combinatorial rule, females with both a weak preference and weak rule, and females with a strong preference but a weak rule. Our results suggest that in Enchenopa signal processing, the mate preference for a continuous signal feature ‘takes precedence’ over, but also interacts with, the combinatorial rule. The relationship between the preference and the rule could evolve to take different forms according to selection on mate choice decisions. We suggest that exploring the relationship between such preferences and rules in species with more complex signals will bring insight into the evolution of the multi-component communication systems.

中文翻译：

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昆虫组合加工规则与连续配偶偏好函数的关系

配偶选择涉及处理可以达到高度复杂性并具有多种成分的信号，即使是在大脑很小的小动物中也是如此。这就提出了一个问题，即这些生物是否以及如何处理这种复杂性。一种解决方案涉及组合处理，其中不同的信号元素作为单个单元进行处理。已经在几种哺乳动物和鸟类中描述了组合加工，最近在振动信号昆虫 Enchenopa 树蝉中进行了描述。在这里，我们询问组合规则与连续变化信号特征的配对偏好之间的关系。Enchenopa 男性广告信号由两个元素组成：“呜呜声”后跟一组脉冲。呜呜声的主导频率和元素组合对女性都很重要。我们向 Enchenopa 雌性提供了在元素顺序（自然 [呜呜声]、反向 [脉冲-呜呜声]）和频率上不同的合成信号，并记录了它们的反应。反向组合导致信号吸引力降低，并且也略微改变了频率偏好的形状。我们发现女性可以分为三种“类型”：具有强烈偏好和强组合规则的女性，具有弱偏好和弱规则的女性，以及具有强烈偏好但弱规则的女性。我们的结果表明，在 Enchenopa 信号处理中，对连续信号特征的配偶偏好“优先”于组合规则，但也与组合规则相互作用。根据择偶决策的选择，偏好和规则之间的关系可以演变为不同的形式。我们建议探索具有更复杂信号的物种中这种偏好和规则之间的关系，将有助于深入了解多组件通信系统的进化。