Centre for Biological Diversity, School of Biology, University of St Andrews, St Andrews, Fife KY16 9TH, UK.
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
Biol Lett. 2018 Feb;14(2). doi: 10.1098/rsbl.2017.0654.
The evolutionary loss of sexual traits is widely predicted. Because sexual signals can arise from the coupling of specialized motor activity with morphological structures, disruption to a single component could lead to overall loss of function. Opportunities to observe this process and characterize any remaining signal components are rare, but could provide insight into the mechanisms, indirect costs and evolutionary consequences of signal loss. We investigated the recent evolutionary loss of a long-range acoustic sexual signal in the Hawaiian field cricket Flatwing males carry mutations that remove sound-producing wing structures, eliminating all acoustic signalling and affording protection against an acoustically-orientating parasitoid fly. We show that flatwing males produce wing movement patterns indistinguishable from those that generate sonorous calling song in normal-wing males. Evolutionary song loss caused by the disappearance of structural components of the sound-producing apparatus has left behind the energetically costly motor behaviour underlying normal singing. These results provide a rare example of a vestigial behaviour and raise the possibility that such traits could be co-opted for novel functions.
性特征的进化丧失是广泛预测的。由于性信号可以由专门的运动活动与形态结构的耦合产生，因此单个组件的破坏可能导致整体功能丧失。观察这个过程并描述任何剩余信号组件的机会很少，但可以深入了解信号丧失的机制、间接成本和进化后果。我们研究了夏威夷田野蟋蟀中一种长距离声学性信号的近期进化丧失，平翅雄蟋蟀携带的突变消除了产生声音的翅膀结构，从而消除了所有声学信号，并提供了对抗声学定向寄生蝇的保护。我们表明，平翅雄蟋蟀产生的翅膀运动模式与正常翅膀雄蟋蟀产生响亮叫声的模式无法区分。由发声器官结构成分消失引起的进化性歌声丧失，留下了正常歌唱所需的能量代价高昂的运动行为。这些结果提供了一个罕见的退化行为的例子，并提出了这种特征可能被用于新功能的可能性。
