title: Rate of adaptation in sexuals and asexuals: a solvable model of the Fisher-Muller effect.
abstract: The adaptation of large asexual populations is hampered by the competition between independently arising beneficial mutations in different individuals, which is known as clonal interference. In classic work, Fisher and Muller proposed that recombination provides an evolutionary advantage in large populations by alleviating this competition. Based on recent progress in quantifying the speed of adaptation in asexual populations undergoing clonal interference, we present a detailed analysis of the Fisher-Muller mechanism for a model genome consisting of two loci with an infinite number of beneficial alleles each and multiplicative (nonepistatic) fitness effects. We solve the deterministic, infinite population dynamics exactly and show that, for a particular, natural mutation scheme, the speed of adaptation in sexuals is twice as large as in asexuals. This result is argued to hold for any nonzero value of the rate of recombination. Guided by the infinite population result and by previous work on asexual adaptation, we postulate an expression for the speed of adaptation in finite sexual populations that agrees with numerical simulations over a wide range of population sizes and recombination rates. The ratio of the sexual to asexual adaptation speed is a function of population size that increases in the clonal interference regime and approaches 2 for extremely large populations. The simulations also show that the imbalance between the numbers of accumulated mutations at the two loci is strongly suppressed even by a small amount of recombination. The generalization of the model to an arbitrary number L of loci is briefly discussed. If each offspring samples the alleles at each locus from the gene pool of the whole population rather than from two parents, the ratio of the sexual to asexual adaptation speed is approximately equal to L in large populations. A possible realization of this scenario is the reassortment of genetic material in RNA viruses with L genomic segments.
authors: Department of Physics, The Catholic University of Korea, Bucheon 420-743, Republic of Korea.
authors: Su-Chan
authors: SC
authors: Park
authors: Joachim
authors: J
authors: Krug
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000818:Animals; D019143:Evolution, Molecular; D005260:Female; D005828:Genetics, Population; D008297:Male; D008957:Models, Genetic; D009154:Mutation; D012328:RNA Viruses / Q000235:genetics / Q000502:physiology; D011995:Recombination, Genetic; D012098:Reproduction / Q000235:genetics* / Q000502:physiology*; D012100:Reproduction, Asexual / Q000235:genetics* / Q000502:physiology*
keywords: advantage of recombination; clonal interference; speed of adaptation
references: J Math Biol. 2003 Nov;47(5):453-6
references: 14605858
references: Proc Natl Acad Sci U S A. 2013 Jan 8;110(2):571-6
references: 23267075
references: Theor Popul Biol. 1970 May;1(1):88-100
references: 5527627
references: Proc Natl Acad Sci U S A. 2012 Mar 27;109(13):4950-5
references: 22371564
references: Genetics. 2008 Dec;180(4):2163-73
references: 18832359
references: PLoS Genet. 2012;8(3):e1002551
references: 22412384
references: Evolution. 2011 Feb;65(2):523-36
references: 21029076
references: Mutat Res. 1964 May;106:2-9
references: 14195748
references: Theor Popul Biol. 1974 Jun;5(3):417-30
references: 4460256
references: Proc Natl Acad Sci U S A. 2010 Mar 2;107(9):4248-53
references: 20145113
references: J Math Biol. 2011 May;62(5):763-88
references: 20617437
references: Genetics. 1998 Oct;150(2):523-32
references: 9755186
references: Am Nat. 2009 Jul;174 Suppl 1:S15-30
references: 19456267
references: Nature. 1988 Dec 1;336(6198):435-40
references: 3057385
references: Theor Popul Biol. 2008 Feb;73(1):24-46
references: 18023832
references: J Hered. 1993 Sep-Oct;84(5):372-87
references: 8409359
references: Nature. 1990 Nov 29;348(6300):454-5
references: 2247152
references: Genetics. 1999 Oct;153(2):1055-69
references: 10511578
references: Am Nat. 2009 Jul;174 Suppl 1:S1-S14
references: 19441962
references: Nature. 2001 Sep 20;413(6853):299-302
references: 11565030
references: Genetics. 2007 Jul;176(3):1759-98
references: 17483432
references: Proc Biol Sci. 1999 Dec 7;266(1436):2389-97
references: 10643083
references: Genetics. 1931 Mar;16(2):97-159
references: 17246615
references: Genetics. 2008 May;179(1):603-20
references: 18493075
references: Genetics. 1969 Apr;61(4):893-903
references: 5364968
references: Proc Natl Acad Sci U S A. 2007 Nov 13;104(46):18135-40
references: 17984061
references: Nat Rev Microbiol. 2011 Jul 04;9(8):617-26
references: 21725337
references: Genetics. 2004 Aug;167(4):2045-53
references: 15342539
references: Phys Rev Lett. 1996 Jun 3;76(23):4440-4443
references: 10061290
references: Genetics. 2011 Dec;189(4):1361-75
references: 21926305
references: Genetics. 1974 Oct;78(2):737-56
references: 4448362
references: Genetica. 1998;102-103(1-6):127-44
references: 9720276
references: Science. 2006 Apr 7;312(5770):111-4
references: 16601193
references: Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):6808-14
references: 8041701
references: Evolution. 2011 Jul;65(7):1945-55
references: 21729050
references: Genetics. 2010 Feb;184(2):467-81
references: 19948891
references: Nature. 2002 Dec 12;420(6916):664-6
references: 12478292
references: Genetics. 1994 Apr;136(4):1469-73
references: 8013919
references: Genetics. 2005 Nov;171(3):1377-86
references: 16020775
references: Genetics. 2004 Jan;166(1):19-24
references: 15020402
references: PLoS Genet. 2012;8(6):e1002740
references: 22685419
references: Genetics. 2008 Aug;179(4):2125-34
references: 18689884
references: Proc Natl Acad Sci U S A. 2003 Jan 21;100(2):587-92
references: 12525686
references: Philos Trans R Soc Lond B Biol Sci. 2010 Apr 27;365(1544):1255-63
references: 20308101
references: Nat Rev Genet. 2007 Feb;8(2):139-49
references: 17230200
references: Theor Popul Biol. 2010 May;77(3):189-204
references: 20149814
references: Genetics. 1993 Jul;134(3):971-81
references: 8349119
references: Science. 1999 Sep 10;285(5434):1745-7
references: 10481012
references: PLoS Biol. 2007 Sep;5(9):e225
references: 17713986
references: J Theor Biol. 1971 Feb;30(2):319-35
references: 5548029
references: PLoS Comput Biol. 2011 Aug;7(8):e1002134
references: 21876664
references: Evolution. 2005 Jun;59(6):1165-74
references: 16050094
references: Nature. 2009 Oct 29;461(7268):1243-7
references: 19838166