It is not always about body size: evidence of Rensch's rule in a male weapon

Glauco Machado*, Bruno A. Buzatto, Diogo S.M. Samia

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    4 Citations (Scopus)


    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.

    Original languageEnglish
    Article number20210234
    Pages (from-to)1-5
    Number of pages5
    JournalBiology Letters
    Issue number6
    Publication statusPublished - Jun 2021


    • allometry
    • condition dependance
    • Opiliones
    • sexual dimorphism
    • sexual selection


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