The data of parasite-induced and spontaneous displays in each limb movement for calling males, silent males and males that have females nearby

Many animals rely on complex sexual signals that target multiple senses to attract mates and repel rivals. These multimodal mating displays can however also attract unintended receivers, which can be an important driver of signal complexity. Despite being taxonomically widespread, we often lack insight into how multimodal signals evolve from unimodal signals and in particular what roles unintended eavesdroppers play. Here we assess whether the physical movements of parasite defense behavior increase the complexity and attractiveness of an acoustic sexual signal in the little torrent frog (Amolops torrentis). Calling males of this species often display limb movements in order to defend against blood-sucking parasites such as frog-biting midges that eavesdrop on their acoustic signal. Through mate choice tests we show that some of these midge-evoked movements influence female preference for acoustic signals. Our data suggest that midge-induced movements may be incorporated into a sexual display, targeting both hearing and vision in the intended receiver. Females may play an important role in incorporating these multiple components because they prefer signals which combine multiple programs. Our results thus help to understand the relationship between ecological and sexual selection pressure operating on signalers and how in turn this may influence multimodal signal evolution.

诸多动物依托靶向多感官通道的复杂性信号，以达成配偶吸引与竞争者驱逐之目的。然而这类多模态求偶展示（multimodal mating display）同样会吸引非预期接收者，而这一现象或为信号复杂性演化的重要驱动因素。尽管这类信号在分类类群中分布广泛，但学界往往尚未明晰多模态信号（multimodal signal）如何从单模态信号（unimodal signal）演化而来，尤其未厘清非预期窃听生物所扮演的具体角色。本研究旨在探究：寄生生物防御行为所伴随的肢体动作，是否会提升小湍蛙（Amolops torrentis）声学性信号（acoustic sexual signal）的复杂性与吸引力。该物种的鸣叫雄性个体常展现肢体动作，以抵御诸如吸血蛙蠓这类会窃听其声学信号的吸血寄生虫。通过配偶选择实验，本研究发现部分由蛙蠓诱发的肢体动作，会影响雌性个体对声学信号的偏好。研究数据表明，由蛙蠓诱发的肢体动作或可被整合至性展示行为中，从而同时靶向预期接收者的听觉与视觉通道。雌性个体在这类多组分信号的整合演化中或扮演关键角色，因其更青睐融合多重信号模态的通讯信号。综上，本研究结果有助于阐明施加于信号发出者的生态选择压力与性选择压力间的关联，进而明晰此类压力如何影响多模态信号的演化进程。