In many species, sexual dimorphism increases with body size when males are the larger sex but decreases when females are the larger sex, a macro-evolutionary pattern known as Rensch's rule (RR). Although empirical studies usually focus exclusively on body size, Rensch's original proposal included sexual differences in other traits, such as ornaments and weapons. Here, we used a clade of harvestmen to investigate whether two traits follow RR: body size and length of the fourth pair of legs (legs IV), which are used as weapons in male–male fights. We found that males were slightly smaller than females and body size did not follow RR, whereas legs IV were much longer in males and followed RR. We propose that sexual selection might be stronger on legs IV length than on body size in males, and we discuss the potential role of condition dependence in the emergence of RR.

在许多物种中，当雄性是较大的性别时，两性二态性会随着体型的增加而增加，但当雌性是较大的性别时会减少，这是一种被称为伦施规则 (RR) 的宏观进化模式。虽然实证研究通常只关注体型，但 Rensch 最初的提议包括其他特征的性别差异，例如装饰品和武器。在这里，我们使用一群收割者来研究是否有两个特征遵循 RR：身体大小和第四对腿（腿 IV）的长度，它们被用作雄性与雄性打架的武器。我们发现男性比女性略小，体型不遵循 RR，而男性的 IV 腿要长得多，遵循 RR。我们提出，男性四肢长度的性选择可能比体型强，