Do pre- and post-copulatory sexually selected traits covary in large herbivores?
BACKGROUND
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.


RESULTS
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.


CONCLUSIONS
We propose several hypotheses that could explain why male ungulates may not balance their reproductive investment between pre- and post-copulatory traits.
Mariona
M
Ferrandiz-Rovira
Jean-François
JF
Lemaître
Sophie
S
Lardy
Bernat C
BC
López
Laboratoire Biométrie et Biologie Evolutive, Université de Lyon, CNRS, UMR5558, Université Lyon 1, F-69622, Villeurbanne, F-69000 Lyon, France. aurelie.cohas@univ-lyon1.fr.
Aurélie
A
Cohas
D000818:Animals; D003307:Copulation; D005260:Female; D006733:Horns / Q000502:physiology; D008297:Male; D010802:Phylogeny; D012098:Reproduction; D012418:Ruminants / Q000235:genetics / Q000502:physiology*; D012726:Sexual Behavior, Animal; D013737:Testis / Q000502:physiology