Abstract
The association of six quantitative traits related to fitness with heterozygosity at 12 allozyme loci has been examined in three populations of Scots pine, Pinus sylvestris. Because of several characteristics of this organism and of this extensive data set, it appeared that this study would show a positive association between heterozygosity and these traits if indeed heterozygotes had higher values for these quantitative traits. Using several different statistical techniques including analysis of variance, regression with the scaling recommended from the adaptive distance model, and multiple regression, no evidence of an association was found. For example, only between 7 and 8% of the regression tests were significant at the 5% level and half of these showed a positive association and half showed a negative association. Further, the multiple regression analysis explained on average only 5.8% of the variation observed in the six different traits and only 1.5% of this variation was explained by a positive association. Power analysis was carried out (for the first time on these type of data), both for the single locus heterozygous advantage and the association of individual multiple locus heterozygosity and the quantitative traits. For diameter and height, two traits often used in similar studies, the average power to detect a single locus heterozygous advantage of 0.10 was 0.737 and the average power to detect a mean heterozygote advantage of 0.05 per locus for multiple loci was 0.797. As a result of this study and an examination of the published results from other studies, it appears that what positive associations have been observed are probably not, in large part, due to the presence of intrinsic heterozygote advantage.
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Selected References
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- Brown A. H. The estimation of Wright's fixation index from genotypic frequencies. Genetica. 1970;41(3):399–406. doi: 10.1007/BF00958921. [DOI] [PubMed] [Google Scholar]
- Gaffney P. M., Scott T. M., Koehn R. K., Diehl W. J. Interrelationships of heterozygosity, growth rate and heterozygote deficiencies in the coot clam, Mulinia lateralis. Genetics. 1990 Mar;124(3):687–699. doi: 10.1093/genetics/124.3.687. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Koehn R. K., Diehl W. J., Scott T. M. The differential contribution by individual enzymes of glycolysis and protein catabolism to the relationship between heterozygosity and growth rate in the coot clam, Mulinia lateralis. Genetics. 1988 Jan;118(1):121–130. doi: 10.1093/genetics/118.1.121. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lewontin R. C. Twenty-five years ago in Genetics: electrophoresis in the development of evolutionary genetics: milestone or millstone? Genetics. 1991 Aug;128(4):657–662. doi: 10.1093/genetics/128.4.657. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ota T. Associative overdominance caused by linked detrimental mutations. Genet Res. 1971 Dec;18(3):277–286. [PubMed] [Google Scholar]
- Ota T., Cockerham C. C. Detrimental genes with partial selfing and effects on a neutral locus. Genet Res. 1974 Apr;23(2):191–200. doi: 10.1017/s0016672300014816. [DOI] [PubMed] [Google Scholar]
- Pogson G. H., Zouros E. Allozyme and RFLP heterozygosities as correlates of growth rate in the scallop Placopecten magellanicus: a test of the associative overdominance hypothesis. Genetics. 1994 May;137(1):221–231. doi: 10.1093/genetics/137.1.221. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Strauss S. H. Heterosis at Allozyme Loci under Inbreeding and Crossbreeding in PINUS ATTENUATA. Genetics. 1986 May;113(1):115–134. doi: 10.1093/genetics/113.1.115. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Watt W. B. Eggs, enzymes, and evolution: natural genetic variants change insect fecundity. Proc Natl Acad Sci U S A. 1992 Nov 15;89(22):10608–10612. doi: 10.1073/pnas.89.22.10608. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Weir B. S., Cockerham C. C. Mixed self and random mating at two loci. Genet Res. 1973 Jun;21(3):247–262. doi: 10.1017/s0016672300013446. [DOI] [PubMed] [Google Scholar]
- Zouros E., Foltz D. W. The use of allelic isozyme variation for the study of heterosis. Isozymes Curr Top Biol Med Res. 1987;13:1–59. [PubMed] [Google Scholar]