No evidence for a trade-off between sperm length and male premating weaponry.
Male ornaments and armaments that mediate success in mate acquisition and ejaculate traits influencing competitive fertilization success are under intense sexual selection. However, relative investment in these pre- and post-copulatory traits depends on the relative importance of either selection episode and on the energetic costs and fitness gains of investing in these traits. Theoretical and empirical work has improved our understanding of how precopulatory sexual traits and investments in sperm production covary in this context. It has recently also been suggested that male weapon size may trade off with sperm length as another post-copulatory sexual trait, but the theoretical framework for this suggestion remains unclear. We evaluated the relationship between precopulatory armaments and sperm length, previously reported in ungulates, in five taxa as well as meta-analytically. Within and between taxa, we found no evidence for a negative or positive relationship between sperm length and male traits that are important in male-male contest competition. It is important to consider pre- and post-copulatory sexual selection together to understand fitness, and to study investments in different reproductive traits jointly rather than separately. A trade-off between pre- and post-copulatory sexual traits may not manifest itself in sperm length but rather in sperm number or function. Particularly in large-bodied taxa such as ungulates, sperm number is more variable interspecifically and likely to be under more intense selection than sperm length. We discuss our and the previous results in this context.
Computational and Evolutionary Biology, Faculty of Life Sciences, University of Manchester, Manchester, UK.|Department of Biology, Life Sciences Complex, Syracuse University, Syracuse, NY, USA.
S
0000-0002-5069-1992
S
Lüpold
Centre for Evolutionary Biology, School of Animal Biology (M092), University of Western Australia, Crawley, WA, Australia.
L W
LW
Simmons
Centre for Evolutionary Biology, School of Animal Biology (M092), University of Western Australia, Crawley, WA, Australia.
J L
JL
Tomkins
Computational and Evolutionary Biology, Faculty of Life Sciences, University of Manchester, Manchester, UK.
J L
JL
Fitzpatrick
D000818:Animals; D006801:Humans; D008297:Male; D012726:Sexual Behavior, Animal; D013094:Spermatozoa / Q000166:cytology*
male weaponry; male-male contest competition; meta-analysis; sexual selection; sexually selected traits; sperm competition; sperm length; trade-off