Sex releases the speed limit on evolution

Nature. 2002 Dec 12;420(6916):664-6. doi: 10.1038/nature01191.


Explaining the evolutionary maintenance of sex remains a key problem in evolutionary biology. 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 mutations. 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological
  • Animals
  • Biological Evolution*
  • Chlamydomonas reinhardtii / cytology
  • Chlamydomonas reinhardtii / genetics
  • Chlamydomonas reinhardtii / physiology*
  • Clone Cells / physiology
  • Epistasis, Genetic
  • Population Density
  • Selection, Genetic
  • Sex*
  • Stochastic Processes
  • Time Factors