Quantitative genetic correlation between trait and preference supports a sexually selected sperm process
- *Centre for Evolutionary Biology, School of Animal Biology (M092), University of Western Australia, Crawley 6009, Australia; and
- ‡Department of Biological and Environmental Sciences, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland
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Edited by Mary Jane West-Eberhard, Smithsonian Tropical Research Institute, Ciudad Universitaria, Costa Rica, and approved August 30, 2007 (received for review May 24, 2007)
Abstract
Sperm show patterns of rapid and divergent evolution that are characteristic of sexual selection. Sperm competition has been proposed as an important selective agent in the evolution of sperm morphology. However, several comparative analyses have revealed evolutionary associations between sperm length and female reproductive tract morphology that suggest patterns of male–female coevolution. In the dung beetle Onthophagus taurus, males with short sperm have a fertilization advantage that depends on the size of the female's sperm storage organ, the spermatheca; large spermathecae select for short sperm. Sperm length is heritable and is genetically correlated with male condition. Here we report significant additive genetic variation and heritability for spermatheca size and genetic covariance between spermatheca size and sperm length predicted by both the “good-sperm” and “sexy-sperm” models of postcopulatory female preference. Our data thus provide quantitative genetic support for the role of a sexually selected sperm process in the evolutionary divergence of sperm morphology, in much the same manner as precopulatory female preferences drive the evolutionary divergence of male secondary sexual traits.
Footnotes
- †To whom correspondence should be addressed. E-mail: lsimmons{at}cyllene.uwa.edu.au
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Author contributions: L.W.S. and J.S.K. designed research; L.W.S. and J.S.K. performed research; L.W.S. analyzed data; and L.W.S. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
- © 2007 by The National Academy of Sciences of the USA
