MALE CONTEST COMPETITION AND THE COEVOLUTION OF WEAPONRY AND TESTES IN PINNIPEDS
Article first published online: 4 JUL 2012
© 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.
Volume 66, Issue 11, pages 3595–3604, November 2012
How to Cite
Fitzpatrick, J. L., Almbro, M., Gonzalez-Voyer, A., Kolm, N. and Simmons, L. W. (2012), MALE CONTEST COMPETITION AND THE COEVOLUTION OF WEAPONRY AND TESTES IN PINNIPEDS. Evolution, 66: 3595–3604. doi: 10.1111/j.1558-5646.2012.01713.x
- Issue published online: 25 OCT 2012
- Article first published online: 4 JUL 2012
- Accepted manuscript online: 18 JUN 2012 03:05PM EST
- Received December 23, 2011 Accepted May 23, 2012
- Contest competition;
- ejaculate allocation;
- genital evolution;
- sexual selection
Male reproductive success is influenced by competitive interactions during precopulatory and postcopulatory selective episodes. Consequently, males can gain reproductive advantages during precopulatory contest competition by investing in weaponry and during postcopulatory sperm competition by investing in ejaculates. However, recent theory predicts male expenditure on weaponry and ejaculates should be subject to a trade-off, and should vary under increasing risk and intensity of sperm competition. Here, we provide the first comparative analysis of the prediction that expenditure on weaponry should be negatively associated with expenditure on testes mass. Specifically, we assess how sexual selection influences the evolution of primary and secondary sexual traits among pinnipeds (seals, sea lions, and walruses). Using recently developed comparative methods, we demonstrate that sexual selection promotes rapid divergence in body mass, sexual size dimorphism (SSD), and genital morphology. We then show that genital length appears to be positively associated with the strength of postcopulatory sexual selection. However, subsequent analyses reveal that both genital length and testes mass are negatively associated with investment in precopulatory weaponry. Thus, our results are congruent with recent theoretical predictions of contest-based sperm competition models. We discuss the possible role of trade-offs and allometry in influencing patterns of reproductive trait evolution in pinnipeds.