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Genetics. Dec 1999; 153(4): 1885–1898.
PMCID: PMC1460882

Inbreeding load, average dominance and the mutation rate for mildly deleterious alleles in Mimulus guttatus.


The goal of this study is to provide information on the genetics of inbreeding depression in a primarily outcrossing population of Mimulus guttatus. Previous studies of this population indicate that there is tremendous inbreeding depression for nearly every fitness component and that almost all of this inbreeding depression is due to mildly deleterious alleles rather than recessive lethals or steriles. In this article I assayed the homozygous and heterozygous fitnesses of 184 highly inbred lines extracted from a natural population. Natural selection during the five generations of selfing involved in line formation essentially eliminated major deleterious alleles but was ineffective in purging alleles with minor fitness effects and did not appreciably diminish overall levels of inbreeding depression. Estimates of the average degree of dominance of these mildly deleterious alleles, obtained from the regression of heterozygous fitness on the sum of parental homozygous fitness, indicate that the detrimental alleles are partially recessive for most fitness traits, with h approximately 0.15 for cumulative measures of fitness. The inbreeding load, B, for total fitness is approximately 1.0 in this experiment. These results are consistent with the hypothesis that spontaneous mildly deleterious mutations occur at a rate >0.1 mutation per genome per generation.

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Selected References

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  • Awadalla P, Ritland K. Microsatellite variation and evolution in the Mimulus guttatus species complex with contrasting mating systems. Mol Biol Evol. 1997 Oct;14(10):1023–1034. [PubMed]
  • Caballero A, Keightley PD, Turelli M. Average dominance for polygenes: drawbacks of regression estimates. Genetics. 1997 Nov;147(3):1487–1490. [PMC free article] [PubMed]
  • Campbell RB. The interdependence of mating structure and inbreeding depression. Theor Popul Biol. 1986 Oct;30(2):232–244. [PubMed]
  • Charlesworth B. The cost of sex in relation to mating system. J Theor Biol. 1980 Jun 21;84(4):655–671. [PubMed]
  • Charlesworth B. Mutation-selection balance and the evolutionary advantage of sex and recombination. Genet Res. 1990 Jun;55(3):199–221. [PubMed]
  • Charlesworth B, Charlesworth D. Some evolutionary consequences of deleterious mutations. Genetica. 1998;102-103(1-6):3–19. [PubMed]
  • Johnston MO, Schoen DJ. Mutation rates and dominance levels of genes affecting total fitness in two angiosperm species. Science. 1995 Jan 13;267(5195):226–229. [PubMed]
  • Keightley PD. The distribution of mutation effects on viability in Drosophila melanogaster. Genetics. 1994 Dec;138(4):1315–1322. [PMC free article] [PubMed]
  • Keightley PD. Nature of deleterious mutation load in Drosophila. Genetics. 1996 Dec;144(4):1993–1999. [PMC free article] [PubMed]
  • Keightley PD, Caballero A. Genomic mutation rates for lifetime reproductive output and lifespan in Caenorhabditis elegans. Proc Natl Acad Sci U S A. 1997 Apr 15;94(8):3823–3827. [PMC free article] [PubMed]
  • Deng HW, Fu YX. On the three methods for estimating deleterious genomic mutation parameters. Genet Res. 1998 Jun;71(3):223–236. [PubMed]
  • Moll RH, Lindsey MF, Robinson HF. Estimates of Genetic Variances and Level of Dominance in Maize. Genetics. 1964 Mar;49(3):411–423. [PMC free article] [PubMed]
  • Morton NE, Crow JF, Muller HJ. AN ESTIMATE OF THE MUTATIONAL DAMAGE IN MAN FROM DATA ON CONSANGUINEOUS MARRIAGES. Proc Natl Acad Sci U S A. 1956 Nov;42(11):855–863. [PMC free article] [PubMed]
  • Mukai T, Yamaguchi O. The genetic structure of natural populations of Drosophila melanogaster. XI. Genetic variability in a local population. Genetics. 1974 Feb;76(2):339–366. [PMC free article] [PubMed]
  • Mukai T, Chigusa SI, Mettler LE, Crow JF. Mutation rate and dominance of genes affecting viability in Drosophila melanogaster. Genetics. 1972 Oct;72(2):335–355. [PMC free article] [PubMed]
  • Hedrick PW. Purging inbreeding depression and the probability of extinction: full-sib mating. Heredity (Edinb) 1994 Oct;73(Pt 4):363–372. [PubMed]
  • Houle D. Comparing evolvability and variability of quantitative traits. Genetics. 1992 Jan;130(1):195–204. [PMC free article] [PubMed]
  • Hughes KA. The inbreeding decline and average dominance of genes affecting male life-history characters in Drosophila melanogaster. Genet Res. 1995 Feb;65(1):41–52. [PubMed]
  • Schnell FW, Cockerham CC. Multiplicative vs. arbitrary gene action in heterosis. Genetics. 1992 Jun;131(2):461–469. [PMC free article] [PubMed]
  • Schultz ST, Lynch M, Willis JH. Spontaneous deleterious mutation in Arabidopsis thaliana. Proc Natl Acad Sci U S A. 1999 Sep 28;96(20):11393–11398. [PMC free article] [PubMed]
  • Watanabe TK, Onishi S. Genes affecting productivity in natural populations of Drosophila melanogaster. Genetics. 1975 Aug;80(4):807–810. [PMC free article] [PubMed]
  • Simmons MJ, Crow JF. Mutations affecting fitness in Drosophila populations. Annu Rev Genet. 1977;11:49–78. [PubMed]
  • Sved JA. Heterosis at the level of the chromosome and at the level of the gene. Theor Popul Biol. 1972 Dec;3(4):491–506. [PubMed]
  • Willis JH. The contribution of male-sterility mutations to inbreeding depression in Mimulus guttatus. Heredity (Edinb) 1999 Sep;83(Pt 3):337–346. [PubMed]
  • Uyenoyama MK, Waller DM. Coevolution of self-fertilization and inbreeding depression. I. Mutation-selection balance at one and two loci. Theor Popul Biol. 1991 Aug;40(1):14–46. [PubMed]
  • Uyenoyama MK, Waller DM. Coevolution of self-fertilization and inbreeding depression. II. Symmetric overdominance in viability. Theor Popul Biol. 1991 Aug;40(1):47–77. [PubMed]

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