Data from: Male clasping ability, female polymorphism and sexual conflict: fine-scale elytral morphology as a sexually antagonistic adaptation in female diving beetles

During sexual conflict, males and females are expected to evolve traits and behaviours with a sexually antagonistic function. Recently, sexually antagonistic coevolution was proposed to occur between male and female diving beetles (Dytiscidae). Male diving beetles possess numerous suction cups on their forelegs whereas females commonly have rough structures on their elytra. These rough structures have been suggested to obstruct adhesion from male suction cups during mating attempts. However, some diving beetle species are dimorphic, where one female morph has a rough elytra and the other has a smooth elytra. Here, we used biomechanics to study the adhesive performance of male suction cups on the female morphs in two diving beetle species: Dytiscus lapponicus and Graphoderus zonatus. We compared adhesion on the rough and the smooth female morphs to infer the function of the rough elytral modifications. We found that the adhesive force on the rough structures was much lower than on other surfaces. These findings support the suggestion of sexual conflict in diving beetles and a sexually antagonistic function of the rough female structures. In addition, males differed in their adhesive capacity on different female surfaces, indicating a male trade-off between adhering to smooth and rough female morphs.

在性冲突过程中，雌雄个体均会演化出具备性拮抗功能的性状与行为。近期有研究提出，雄性与雌性龙虱（Dytiscidae）之间存在性拮抗协同演化现象。雄性龙虱的前足生有大量吸盘，而雌性龙虱的鞘翅通常带有粗糙结构。此类粗糙结构被认为可在雄性发起交配尝试时，阻碍其吸盘的附着作用。不过部分龙虱物种存在雌性二态性：一类雌性个体的鞘翅带有粗糙结构，另一类则为光滑鞘翅。
本研究通过生物力学手段，针对两种龙虱——拉普龙虱（Dytiscus lapponicus）与带纹跃龙虱（Graphoderus zonatus）的雌性不同形态，探究了雄性吸盘的附着性能。我们通过对比粗糙与光滑两种雌性形态表面的附着效果，推断雌性鞘翅粗糙特化结构的功能。研究结果显示，粗糙结构表面的附着力远低于其他表面。上述发现支持了龙虱存在性冲突，以及雌性粗糙结构具有性拮抗功能的相关假说。此外，雄性在不同雌性体表的附着能力存在差异，表明雄性在适配光滑与粗糙两种雌性形态之间存在进化权衡。