Do pre- and post-copulatory sexually selected traits covary in large herbivores?
1 Laboratoire Biométrie et Biologie Evolutive, Université de Lyon, CNRS, UMR5558, Université Lyon 1, F-69622, Villeurbanne, F-69000 Lyon, France
2 Groupe Ecologie et conservation des vertébrés, Université d’Angers, Faculté des Sciences, 49045 Angers, France
3 CREAF, Cerdanyola del Vallès, 08193 Catalunya, Spain
4 Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193 Catalunya, Spain
BMC Evolutionary Biology 2014, 14:79 doi:10.1186/1471-2148-14-79Published: 10 April 2014
In most species, males compete to gain both matings (via pre-copulatory competition) and fertilizations (via post-copulatory competition) to maximize their reproductive success. However, the quantity of resources devoted to sexual traits is finite, and so males are predicted to balance their investment between pre- and post-copulatory expenditure depending on the expected pay-offs that should vary according to mating tactics. In Artiodactyla species, males can invest in weapons such as horns or antlers to increase their mating gains or in testes mass/sperm dimensions to increase their fertilization efficiency. Moreover, it has been suggested that in these species, males with territory defence mating tactic might preferentially increase their investment in post-copulatory traits to increase their fertilization efficiency whereas males with female defence mating tactic might increase their investment in pre-copulatory sexually selected traits to prevent other males from copulating with females. In this study, we thus test the prediction that male’s weapon length (pre-copulatory trait) covaries negatively with relative testes size and/or sperm dimensions (post-copulatory traits) across Artiodactyla using a phylogenetically controlled framework.
Surprisingly no association between weapon length and testes mass is found but a negative association between weapon length and sperm length is evidenced. In addition, neither pre- nor post-copulatory traits were found to be affected by male mating tactics.
We propose several hypotheses that could explain why male ungulates may not balance their reproductive investment between pre- and post-copulatory traits.