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Proc Natl Acad Sci U S A. May 1979; 76(5): 2480–2484.
PMCID: PMC383626

Simultaneous hermaphroditism and sexual selection


Theory about the evolution of sexual behavior in dioecious species is based on the general assumption that egg production is limited by a female's ability to garner resources to make eggs, not by a lack of sperm to fertilize them. Reproductive success for males is thus limited by access to females (and their eggs). I suggest that egg production by simultaneous hermaphrodites also obeys this principle—that fertilized egg production by an individual is not limited by sperm availability, but by resources allocated to eggs. If true, this suggests that sperm competition (reproduction success through male function) and a form of male—female conflict have played important roles in the evolution of hermaphroditism.

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Selected References

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  • Ghiselin MT. The evolution of hermaphroditism among animals. Q Rev Biol. 1969 Jun;44(2):189–208. [PubMed]
  • Charnov EL, Bull J. When is sex environmentally determined? Nature. 1977 Apr 28;266(5605):828–830. [PubMed]
  • Heath DJ. Simultaneous hermaphroditism; cost and benefit. J Theor Biol. 1977 Jan 21;64(2):363–373. [PubMed]
  • Hamilton WD. Extraordinary sex ratios. A sex-ratio theory for sex linkage and inbreeding has new implications in cytogenetics and entomology. Science. 1967 Apr 28;156(3774):477–488. [PubMed]
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  • Leigh EG, Jr, Charnov EL, Warner RR. Sex ratio, sex change, and natural selection. Proc Natl Acad Sci U S A. 1976 Oct;73(10):3656–3660. [PMC free article] [PubMed]

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