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Morph-specific investment in testes mass in a trimorphic beetle, Proagoderus watanabei

Parrett, J. M.; Slade, E. M.; Knell, R. J.


J. M. Parrett

E. M. Slade


When competition between males for mates is intense, it is common to find that some males will adopt alternative tactics for acquiring fertilizations, often involving the use of ‘sneak’ tactics whereby males avoid precopulatory contests. These alternative tactics are sometimes associated with discrete differences in male morphology, with sneak males investing less in weaponry but more in traits such as testes which may give an advantage in sperm competition. In some cases, it appears that males develop into more than two morphs, with a number of examples of tri- and even tetramorphic arthropod species being described. Here, we analyse the scaling relations of the dung beetle species Proagoderus watanabei, which expresses two distinct weapon traits: paired head horns and a pronotal horn. We find that males of this species are trimorphic, with alpha males expressing long head horns and a pronotal horn, beta males with long head horns but no pronotal horn and gamma males with short head horns only. We also find that alpha males invest relatively less in testes than do beta or gamma males, indicating that beta and gamma males in this species probably experience higher risks of sperm competition than do alphas.


Parrett, J. M., Slade, E. M., & Knell, R. J. (2022). Morph-specific investment in testes mass in a trimorphic beetle, Proagoderus watanabei. Journal of Zoology, 316(3), 169-177.

Journal Article Type Article
Acceptance Date Oct 27, 2021
Online Publication Date Nov 17, 2021
Publication Date Mar 1, 2022
Deposit Date Jul 9, 2023
Publicly Available Date Jul 24, 2023
Journal Journal of Zoology
Print ISSN 0952-8369
Electronic ISSN 1469-7998
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 316
Issue 3
Pages 169-177
Keywords Alternative tactics; Dung beetle; Horned beetle; Intrasexual competition; Polymorphism; Polyphenism; Reproductive tactics; Sperm competition
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Copyright Statement
© 2021 The Authors. Journal of Zoology published by John Wiley & Sons Ltd on behalf of Zoological Society of London
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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