Two sexes, one body: intra- and intersex covariation of gamete phenotypes in simultaneous hermaphrodites
Article first published online: 18 MAR 2014
© 2014 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
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Ecology and Evolution
Volume 4, Issue 8, pages 1340–1346, April 2014
How to Cite
Ecology and Evolution 2014; 4(8):1340–1346
- Issue published online: 22 APR 2014
- Article first published online: 18 MAR 2014
- Manuscript Revised: 20 FEB 2014
- Manuscript Accepted: 20 FEB 2014
- Manuscript Received: 4 FEB 2014
- Australian Research Council
- Broadcast spawners;
- egg traits;
- marine invertebrates;
- sexual conflict;
- sperm traits
By harboring male and female functions in the same genome and expressing them in every individual, simultaneous hermaphrodites may incur sexual conflict unless both sex functions can evolve phenotypic optima independently of each other. The first step toward understanding their capacity to do so lies in understanding whether sex functions are phenotypically correlated within individuals, but remarkably few data address this issue. We tested the potential for intra- and intersex covariation of gamete phenotypes to mediate sexual conflict in broadcast-spawning hermaphrodites (the ascidians Ciona intestinalis and Pyura praeputialis), for which sex-specific selection acts predominantly on sperm–egg interactions in the water column. In both species, gamete phenotypes covaried within and across sex functions, implying that selection may be unable to target them independently because its direct effects on male gametes translate into correlated effects on female gametes and vice versa. This alone does not preclude the evolution of a different phenotypic optimum for each sex function, but imposes the more restrictive requirement that selection – which ultimately sorts among whole individuals, not sex functions – aligns with the direction in which gamete phenotypes covary at this level.