Nature 462, 90-93 (5 November 2009) | doi:10.1038/nature08504; Received 7 July 2009; Accepted 15 September 2009
Experimental evolution of bet hedging
Hubertus J. E. Beaumont1,2,3, Jenna Gallie1, Christian Kost1,3, Gayle C. Ferguson1 & Paul B. Rainey1
New Zealand Institute for Advanced Study and Allan Wilson Centre for Molecular Ecology & Evolution, Massey University, Private Bag 102904, North Shore Mail Centre, North Shore City 0745, Auckland, New Zealand
Institute of Biology Leiden, Leiden University, PO Box 9505, 2300 RA Leiden, The Netherlands
Present addresses: Institute of Biology Leiden, Leiden University, PO Box 9505, 2300 RA Leiden, The Netherlands (H.J.E.B.); Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, 07745 Jena, Germany (C.K.).
Correspondence to: Hubertus J. E. Beaumont1,2,3 Correspondence and requests for materials should be addressed to H.J.E.B. (Email: h.j.e.beaumont@biology.leidenuniv.nl).
【Abstract】
Bet hedging—stochastic switching between phenotypic states1, 2, 3—is a canonical example of an evolutionary adaptation that facilitates persistence in the face of fluctuating environmental conditions. Although bet hedging is found in organisms ranging from bacteria to humans4, 5, 6, 7, 8, 9, 10, direct evidence for an adaptive origin of this behaviour is lacking11. Here we report the de novo evolution of bet hedging in experimental bacterial populations. Bacteria were subjected to an environment that continually favoured new phenotypic states. Initially, our regime drove the successive evolution of novel phenotypes by mutation and selection; however, in two (of 12) replicates this trend was broken by the evolution of bet-hedging genotypes that persisted because of rapid stochastic phenotype switching. Genome re-sequencing of one of these switching types revealed nine mutations that distinguished it from the ancestor. The final mutation was both necessary and sufficient for rapid phenotype switching; nonetheless, the evolution of bet hedging was contingent upon earlier mutations that altered the relative fitness effect of the final mutation. These findings capture the adaptive evolution of bet hedging in the simplest of organisms, and suggest that risk-spreading strategies may have been among the earliest evolutionary solutions to life in fluctuating environments.
