Abstract
An important problem in population genetics is the determination of the level of genetic organization to which fitness measures can be ascribed that yield an adequate description or prediction of the outcome of selection in populations. To study this problem, we used two strains of Drosophila merca torum (S-1-Im and O-3-Im) that are capable of both sexual and parthenogenetic reproduction, a feature that allows us to experimentally control many factors which affect genetic variability. Both S and O reproduce parthenogenetically by "pronuclear duplication," a mechanism that retains normal meiosis (and hence crossing over and assortment) but results in homozygosity for all loci in a single generation. Since an isozyme survey indicated that S and O differ at a third of their loci, we hypothesized that S and O have adapted in genetically distinct fashions to the genetic environment of total homozygosity. This is tested by breeding females that are S-O hybrids for 100%, 60% and 40% of their genetic backgrounds, and scoring their respective parthenogenetic progenies for four isozyme and two visible markers. The data collected gave evidence for a coadaptation to total homozygosity involving non-additive and non-multiplicative interactions between non-alleles. As the perturbation of the parental coadapted genotypes by meiosis increases (i.e., the greater the degree of S-O hybridity), the level of genetic material which behaves as an additive/multiplicative fitness unit becomes larger. Selective neutrality of genetic variation may be an artifact of our failure to measure the proper genetic unit of selection.
Full Text
The Full Text of this article is available as a PDF (1.7 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Hildreth P E. The Problem of Synthetic Lethals in Drosophila Melanogaster. Genetics. 1956 Sep;41(5):729–742. doi: 10.1093/genetics/41.5.729. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Richardson R. H., Kojima K. I. The kinds of genetic variability in relation to selection responses in Drosophila fecundity. Genetics. 1965 Sep;52(3):583–598. doi: 10.1093/genetics/52.3.583. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Slatkin M. On treating the chromosome as the unit of selection. Genetics. 1972 Sep;72(1):157–168. doi: 10.1093/genetics/72.1.157. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wallace B, King J C, Madden C V, Kaufmann B, McGunnigle E C. An Analysis of Variability Arising through Recombination. Genetics. 1953 May;38(3):272–307. doi: 10.1093/genetics/38.3.272. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wills C., Crenshaw J., Vitale J. A computer model allowing maintenance of large amounts of genetic variability in mendelian populations. I. Assumptions and results for large populations. Genetics. 1970 Jan;64(1):107–123. doi: 10.1093/genetics/64.1.107. [DOI] [PMC free article] [PubMed] [Google Scholar]