School of Life Sciences, Arizona State University, 427 E Tyler Mall, Tempe, AZ, 85287, USA.
School of Life Sciences, Arizona State University, 427 E Tyler Mall, Tempe, AZ, 85287, USA.
Zoology (Jena). 2022 Feb;150:125988. doi: 10.1016/j.zool.2021.125988. Epub 2021 Dec 23.
In many species, males possess specialized weaponry that confers benefits during male-male combat. Because male weapons are often disproportionately larger versions of preexisting body parts, females often possess reduced versions of male weaponry. Most research focuses exclusively on sexual dimorphism in the size of male and female weapons, even though other aspects such as weapon performance can also explain the evolution of weapon sexual dimorphism. In the giant mesquite bug, Thasus neocalifornicus, males wield exaggerated hindlegs that aid in locomotion and are used as weapons to generate forceful squeezes during combat. However, female T. neocalifornicus hindlegs are relatively inconspicuous and only used for locomotion. To understand the intricacies of weapon sexual dimorphism in T. neocalifornicus hindlegs, we measured the allometry of their hindlegs morphology, biomechanics, and performance. Males and females had relatively similar sized legs when concerning only linear measurements: hindleg length did not differ between the sexes (both for intercept and slope), but males do have relatively wider hindlegs (greater intercepts). Regarding performance, however, males were relatively and proportionally stronger than females. Furthermore, the output lever of male hindlegs scales hypoallometrically and the tibial spine maintains its position as the hindlegs grows, both of which maintain the hindlegs' biomechanical efficiency as they increase in size. Overall, our finding demonstrates that selection on the performance and biomechanics of sexually selected weapons can influence the expression of sexual dimorphism, by exaggerating some aspects of the weapons morphology-but constraining others.
在许多物种中，雄性拥有专门的武器，这些武器在雄性之间的战斗中带来好处。由于雄性武器通常是预先存在的身体部位的不成比例的大型版本，因此雌性通常拥有雄性武器的缩小版本。大多数研究专门关注雄性和雌性武器大小的性别二态性，即使其他方面，如武器性能，也可以解释武器性别二态性的进化。在巨型豆科臭虫 Thasus neocalifornicus 中，雄性挥舞着夸张的后腿，这些后腿有助于运动，并被用作武器，在战斗中产生强大的挤压。然而，雌性 T. neocalifornicus 的后腿相对不显眼，仅用于运动。为了理解 T. neocalifornicus 后腿武器性别二态性的复杂性，我们测量了后腿形态、生物力学和性能的异速生长。仅考虑线性测量时，雄性和雌性的后腿大小相对相似：后腿长度在性别之间没有差异（无论是截距还是斜率），但雄性的后腿相对较宽（截距较大）。然而，就性能而言，雄性相对而言比雌性更强壮。此外，雄性后腿的输出杠杆呈亚线性缩放，胫骨刺在后腿生长时保持其位置，这两者都维持了后腿随着尺寸增大的生物力学效率。总的来说，我们的发现表明，对有性选择武器的性能和生物力学的选择可以通过夸大武器形态的某些方面来影响性别二态性的表达，但也会限制其他方面。
