Skip to main content
NCBI home page
Genetics logoLink to Genetics
. 1999 Dec;153(4):1885–1898. doi: 10.1093/genetics/153.4.1885

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

J H Willis 1
PMCID: PMC1460882  PMID: 10581293

Abstract

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.

Full Text

The Full Text of this article is available as a PDF (157.5 KB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. 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. doi: 10.1093/oxfordjournals.molbev.a025708. [DOI] [PubMed] [Google Scholar]
  2. Caballero A., Keightley P. D., Turelli M. Average dominance for polygenes: drawbacks of regression estimates. Genetics. 1997 Nov;147(3):1487–1490. doi: 10.1093/genetics/147.3.1487. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Campbell R. B. The interdependence of mating structure and inbreeding depression. Theor Popul Biol. 1986 Oct;30(2):232–244. doi: 10.1016/0040-5809(86)90035-3. [DOI] [PubMed] [Google Scholar]
  4. Charlesworth B., Charlesworth D. Some evolutionary consequences of deleterious mutations. Genetica. 1998;102-103(1-6):3–19. [PubMed] [Google Scholar]
  5. Charlesworth B. Mutation-selection balance and the evolutionary advantage of sex and recombination. Genet Res. 1990 Jun;55(3):199–221. doi: 10.1017/s0016672300025532. [DOI] [PubMed] [Google Scholar]
  6. Charlesworth B. The cost of sex in relation to mating system. J Theor Biol. 1980 Jun 21;84(4):655–671. doi: 10.1016/s0022-5193(80)80026-9. [DOI] [PubMed] [Google Scholar]
  7. Deng H. W., Fu Y. X. On the three methods for estimating deleterious genomic mutation parameters. Genet Res. 1998 Jun;71(3):223–236. doi: 10.1017/s0016672398003255. [DOI] [PubMed] [Google Scholar]
  8. Hedrick P. W. Purging inbreeding depression and the probability of extinction: full-sib mating. Heredity (Edinb) 1994 Oct;73(Pt 4):363–372. doi: 10.1038/hdy.1994.183. [DOI] [PubMed] [Google Scholar]
  9. Houle D. Comparing evolvability and variability of quantitative traits. Genetics. 1992 Jan;130(1):195–204. doi: 10.1093/genetics/130.1.195. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Hughes K. A. The inbreeding decline and average dominance of genes affecting male life-history characters in Drosophila melanogaster. Genet Res. 1995 Feb;65(1):41–52. doi: 10.1017/s0016672300032997. [DOI] [PubMed] [Google Scholar]
  11. Johnston M. O., Schoen D. J. Mutation rates and dominance levels of genes affecting total fitness in two angiosperm species. Science. 1995 Jan 13;267(5195):226–229. doi: 10.1126/science.267.5195.226. [DOI] [PubMed] [Google Scholar]
  12. Keightley P. D., 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. doi: 10.1073/pnas.94.8.3823. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Keightley P. D. Nature of deleterious mutation load in Drosophila. Genetics. 1996 Dec;144(4):1993–1999. doi: 10.1093/genetics/144.4.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Keightley P. D. The distribution of mutation effects on viability in Drosophila melanogaster. Genetics. 1994 Dec;138(4):1315–1322. doi: 10.1093/genetics/138.4.1315. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Moll R H, Lindsey M F, Robinson H F. Estimates of Genetic Variances and Level of Dominance in Maize. Genetics. 1964 Mar;49(3):411–423. doi: 10.1093/genetics/49.3.411. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Morton N. E., Crow J. F., Muller H. J. 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. doi: 10.1073/pnas.42.11.855. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Mukai T., Chigusa S. I., Mettler L. E., Crow J. F. Mutation rate and dominance of genes affecting viability in Drosophila melanogaster. Genetics. 1972 Oct;72(2):335–355. doi: 10.1093/genetics/72.2.335. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. 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. doi: 10.1093/genetics/76.2.339. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Schnell F. W., Cockerham C. C. Multiplicative vs. arbitrary gene action in heterosis. Genetics. 1992 Jun;131(2):461–469. doi: 10.1093/genetics/131.2.461. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Schultz S. T., Lynch M., Willis J. H. Spontaneous deleterious mutation in Arabidopsis thaliana. Proc Natl Acad Sci U S A. 1999 Sep 28;96(20):11393–11398. doi: 10.1073/pnas.96.20.11393. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Simmons M. J., Crow J. F. Mutations affecting fitness in Drosophila populations. Annu Rev Genet. 1977;11:49–78. doi: 10.1146/annurev.ge.11.120177.000405. [DOI] [PubMed] [Google Scholar]
  22. Sved J. A. Heterosis at the level of the chromosome and at the level of the gene. Theor Popul Biol. 1972 Dec;3(4):491–506. doi: 10.1016/0040-5809(72)90019-6. [DOI] [PubMed] [Google Scholar]
  23. Uyenoyama M. K., Waller D. M. 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. doi: 10.1016/0040-5809(91)90045-h. [DOI] [PubMed] [Google Scholar]
  24. Uyenoyama M. K., Waller D. M. Coevolution of self-fertilization and inbreeding depression. II. Symmetric overdominance in viability. Theor Popul Biol. 1991 Aug;40(1):47–77. doi: 10.1016/0040-5809(91)90046-i. [DOI] [PubMed] [Google Scholar]
  25. Watanabe T. K., Onishi S. Genes affecting productivity in natural populations of Drosophila melanogaster. Genetics. 1975 Aug;80(4):807–810. doi: 10.1093/genetics/80.4.807. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Willis J. H. The contribution of male-sterility mutations to inbreeding depression in Mimulus guttatus. Heredity (Edinb) 1999 Sep;83(Pt 3):337–346. doi: 10.1038/sj.hdy.6885790. [DOI] [PubMed] [Google Scholar]

Articles from Genetics are provided here courtesy of Oxford University Press

RESOURCES