Mating assortment and the strength of sexual selection in a polyandrous population of Cook Strait giant weta

• Published in: Behavioral ecology 2023-05, Vol.34 (3), p.506-513
• Main Authors: Kelly, Clint D, Gwynne, Darryl T
• Format: Article
• Language: English
• ISSN: 1045-2249; 1465-7279
• DOI: 10.1093/beheco/arad017

Abstract Polyandry can profoundly affect the strength of pre-copulatory sexual selection acting on males because each additional mate acquired by a female means that, all else being equal, a male’s paternity share declines. However, accruing additional mates could benefit male fitness if males with greater mating success also tend to have less promiscuous females as partners. If this is indeed the case, then males should experience strong sexual selection to acquire more mates. We tested these predictions by collecting detailed mating data on male and female Cook Strait giant weta (Deinacrida rugosa) in the wild via daily radio tracking. Our sexual network-based approach indeed revealed that the most polygynous male D. rugosa mated the least polyandrous females. This finding therefore suggests that the most successful males likely face lower intensities of sperm competition and so should be selected to accrue more mates. Further, our selection analysis revealed significant pre-copulatory sexual selection on males with those having relatively smaller body size, lighter body mass, and longer legs accruing more mates than otherwise. Thus, it appears that both pre- and post-copulatory episodes of sexual selection reinforce the same male phenotype. Increased mating success might not translate into more offspring for males. This can occur when females also have many mates: increased female mating success increases sperm competition and paternity-sharing by males. This should decrease male incentives to acquire more mates. In Cook Strait giant weta in New Zealand, we found that the most successful males mated with the least promiscuous females. Therefore, successful males should accrue more offspring per copulation than otherwise.