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Post-copulatory sexual selection and sexual conflict in the evolution of male pregnancy

Nature volume 464, pages 401404 (18 March 2010) | Download Citation


Male pregnancy in seahorses, pipefishes and sea dragons (family Syngnathidae) represents a striking reproductive adaptation that has shaped the evolution of behaviour and morphology in this group of fishes1,2,3,4. In many syngnathid species, males brood their offspring in a specialized pouch, which presumably evolved to facilitate male parental care5,6. However, an unexplored possibility is that brood pouch evolution was partly shaped by parent–offspring or sexual conflict, processes that would result in trade-offs between current and future pregnancies. Here we report a controlled breeding experiment using the sexually dimorphic Gulf pipefish, Syngnathus scovelli, to test for post-copulatory sexual selection within broods and for trade-offs between successive male pregnancies as functions of female attractiveness. Offspring survivorship within a pregnancy was affected by the size of a male’s mate, the number of eggs transferred and the male’s sexual responsiveness. Significantly, we also found that embryo survivorship in a current pregnancy was negatively related to survivorship in the prior pregnancy, clearly demonstrating fitness trade-offs between broods. Overall, our data indicate that post-copulatory sexual selection and sexual conflict occur in Gulf pipefishes. The conflict seems to be mediated by a strategy of cryptic choice in which males increase rates of offspring abortion in pregnancies from unattractive mothers to retain resources for future reproductive opportunities. Hence, the male brood pouch of syngnathid fishes, which nurtures offspring7,8,9, also seems to have an important role as an arbiter of conflict between the sexes.

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  1. 1.

    , & Mate choice, fecundity and sexual dimorphism in two pipefish species (Syngnathidae). Behav. Ecol. Sociobiol. 19, 301–307 (1986)

  2. 2.

    , , & Pipefishes and seahorses–are they all sex-role reversed? Trends Ecol. Evol. 7, 237–241 (1992)

  3. 3.

    , , , & The Bateman gradient and the cause of sexual selection in a sex-role-reversed pipefish. Proc. R. Soc. Lond. B 267, 677–680 (2000)

  4. 4.

    , , & The dynamics of male brooding, mating patterns, and sex roles in pipefishes and seahorses (family Syngnathidae). Evolution 57, 1374–1386 (2003)

  5. 5.

    , & Gene co-option without duplication during the evolution of a male pregnancy gene in pipefish. Proc. Natl Acad. Sci. USA 103, 19407–19412 (2006)

  6. 6.

    & Male pregnancy in seahorses and pipefish: beyond the mammalian model. Bioessays 29, 884–896 (2007)

  7. 7.

    , & Reversed sex roles and parental energy investment in zygotes of two pipefish (Syngnathidae) species. Mar. Ecol. Prog. Ser. 29, 209–215 (1986)

  8. 8.

    & Differential parental nutrient allocation in two congeneric pipefish species (Syngnathidae: Syngnathus spp.). J. Exp. Biol. 209, 1112–1121 (2006)

  9. 9.

    & Direct evidence for embryonic uptake of paternally-derived nutrients in two pipefishes (Syngnathidae: Syngnathus spp.). J. Comp. Physiol. B 179, 325–333 (2009)

  10. 10.

    Indo-Pacific Pipefishes (Gulf Coast Research Lab, 1985)

  11. 11.

    From pipefish to seahorse–a study of phylogenetic relationships. Proc. Calif. Acad. Sci. 29, 465–473 (1959)

  12. 12.

    , & Osmoregulatory role of the brood pouch in the euryhaline Gulf pipefish, Syngnathus scovelli. Comp. Biochem. Physiol. A 147, 556–561 (2007)

  13. 13.

    Osmoregulatory role of the paternal brood pouch for two Syngnathus species. Comp. Biochem. Physiol. A 154, 98–104 (2009)

  14. 14.

    & Sex role reversal in pipefish. Adv. Stud. Behav. 32, 131–167 (2003)

  15. 15.

    , , , & Brooding fathers, not siblings, take up nutrients from embryos. Proc. R. Soc. Lond. B 10.1098/rspb.2009.1767

  16. 16.

    in Sexual Selection and the Descent of Man (ed. Campbell, B.) 136–179 (Aldine, 1972)

  17. 17.

    , & Intrafamilial conflict and parental investment: a synthesis. Phil. Trans. R. Soc. Lond. B 357, 295–307 (2002)

  18. 18.

    & Sexual Conflict (Princeton Univ. Press, 2005)

  19. 19.

    The differential allocation hypothesis–an experimental test. Am. Nat. 132, 611–628 (1988)

  20. 20.

    Differential allocation: tests, mechanisms and implications. Trends Ecol. Evol. 15, 397–402 (2000)

  21. 21.

    The gifts that keep on giving: physiological functions and evolutionary dynamics of male seminal proteins in Drosophila. Heredity 88, 85–93 (2002)

  22. 22.

    & Reproductive mode and speciation: the viviparity-driven conflict hypothesis. Bioessays 22, 938–946 (2000)

  23. 23.

    , & Genetic evidence for extreme polyandry and extraordinary sex-role reversal in a pipefish. Proc. R. Soc. Lond. B 268, 2531–2535 (2001)

  24. 24.

    & Microsatellite analysis of maternity and the mating system in the Gulf pipefish Syngnathus scovelli, a species with male pregnancy and sex-role reversal. Mol. Ecol. 6, 203–213 (1997)

  25. 25.

    Apparent resource competition among embryos in the brood pouch of a male pipefish. Behav. Ecol. Sociobiol. 38, 167–172 (1996)

  26. 26.

    et al. The effect of perceived female parasite load on post-copulatory male choice in a sex-role-reversed pipefish. Behav. Ecol. Sociobiol. 63, 345–354 (2009)

  27. 27.

    & Sexual selection and mate choice. Trends Ecol. Evol. 21, 296–302 (2006)

  28. 28.

    , , & Male-male competition, female mate choice and their interaction: determining total sexual selection. J. Evol. Biol. 22, 13–26 (2009)

  29. 29.

    , & Potential reproductive rate of a sex-role reversed pipefish over several bouts of mating. Anim. Behav. 78, 747–753 (2009)

  30. 30.

    A Comparative Life History Study of Four Species of Pipefishes (Family Syngnathidae) in Florida. PhD thesis, Univ. Florida (1972)

  31. 31.

    & Statistically based tests for the number of common factors. Proc. Ann. Spring Meeting Psychometric Soc. (1980)

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This work was supported by grant IOS-0455927 from the US National Science Foundation. We thank S. Scobell and R. Carter for help with animal husbandry. We are also grateful to S. Arnold, A. Berglund, M. Giresi, N. Ratterman, E. Rose, G. Rosenthal, C. Small and D. Zeh for comments on the manuscript.

Author Contributions K.A.P. performed the experiments. A.G.J. and K.A.P. designed the experiments, analysed the data and wrote the manuscript.

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  1. Department of Biology, 3258 TAMU, Texas A&M University, College Station, Texas 77845, USA

    • Kimberly A. Paczolt
    •  & Adam G. Jones


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The authors declare no competing financial interests.

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Correspondence to Kimberly A. Paczolt.

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    This file contains Supplementary Analysis, Supplementary References and Supplementary Figures S1-S4 with legends.

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