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Sex releases the speed limit on evolution

Abstract

Explaining the evolutionary maintenance of sex remains a key problem in evolutionary biology1,2,3. One potential benefit of sex is that it may allow a more rapid adaptive response when environmental conditions change, by increasing the efficiency with which selection can fix beneficial mutations4,5,6,7. Here I show that sex can increase the rate of adaptation in the facultatively sexual single-celled chlorophyte Chlamydomonas reinhardtii, but that the benefits of sex depend crucially on the size of the population that is adapting: sex has a marked effect in large populations but little effect in small populations. Several mechanisms have been proposed to explain the benefits of sex in a novel environment, including stochastic effects in small populations, clonal interference and epistasis between beneficial alleles. These results indicate that clonal interference is important in this system.

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References

  1. 1

    Maynard Smith, J. The Evolution of Sex (Cambridge Univ. Press, Cambridge, 1978)

  2. 2

    Bell, G. The Masterpiece of Nature (Croom Helm, London, 1982)

  3. 3

    West, S. A., Lively, C. M. & Read, A. F. A pluralist approach to sex and recombination. J. Evol. Biol. 12, 1003–1012 (1999)

  4. 4

    Fisher, R. A. The Genetical Theory of Natural Selection (Clarendon, Oxford, 1958)

  5. 5

    Muller, H. J. Some genetic aspects of sex. Am. Nat. 66, 118–138 (1932)

  6. 6

    Otto, S. P. & Barton, N. H. The evolution of recombination: removing the limits to natural selection. Genetics 147, 879–906 (1997)

  7. 7

    Burt, A. Perspective: Sex, recombination, and the efficacy of selection—was Weismann right? Evolution 54, 337–351 (2000)

  8. 8

    Gerrish, P. J. & Lenski, R. E. The fate of competing mutations in an asexual population. Genetica 102/103, 127–144 (1998)

  9. 9

    de Visser, J. A. G. M., Zeyl, C. W., Gerrish, P. J., Blanchard, J. L. & Lenski, R. E. Diminishing returns from mutation supply rates in asexual populations. Science 283, 404–406 (1999)

  10. 10

    Miralles, R., Gerrish, P. J., Moya, A. & Elena, S. F. Clonal interference and the evolution of RNA viruses. Science 285, 1745–1747 (1999)

  11. 11

    Otto, S. P. & Barton, N. H. Selection for recombination in small populations. Evolution 55, 1921–1931 (2001)

  12. 12

    Colegrave, N., Kaltz, O. & Bell, G. The ecology and genetics of fitness in Chlamydomonas. VIII. The dynamics of adaptation to novel environments after a single episode of sex. Evolution 56, 14–21 (2002)

  13. 13

    Vasi, F., Travisano, M. & Lenski, R. E. Long-term experimental evolution in Escherichia coli. 2. Changes in life-history traits during adaptation to a seasonal environment. Am. Nat. 144, 432–456 (1994)

  14. 14

    Goho, S. & Bell, G. Mild environmental stress elicits mutations affecting fitness in Chlamydomonas. Proc. R. Soc. Lond. B 267, 123–129 (2000)

  15. 15

    Lenski, R. E., Rose, M. R., Simpson, S. C. & Tadler, S. C. Long-term experimental evolution in Escherichia coli. I. Adaptation and divergence during 2,000 generations. Am. Nat. 138, 1315–1341 (1991)

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Acknowledgements

I thank N. Barton, G. Bell, T. Johnson and S. Nee for discussion of this experiment and for comments on the manuscript; A. Poon for suggestions for improvement to earlier versions; S. Otto and A. Read for advice at early stages; and D. Haydon, L. Kruuk and M. Spencer for lengthy discussions on curve fitting. This work was supported by a NERC postdoctoral fellowship.

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Competing interests

The author declares that he has no competing financial interests.

Correspondence to Nick Colegrave.

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Further reading

Figure 1: Effect of bottleneck size on adaptation in asexual populations.
Figure 2: Interaction between sex and bottleneck size.

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