Abstract
In many species, some individuals carry one or more B chromosomes: extra, or supernumerary chromosomes not part of the normal complement. In most well-studied cases, Bs lower the fitness of their carrier and persist in populations only because of accumulation mechanisms analogous to meiotic drive. It has been suggested that such genomic parasites are expected to persist only in outcrossed sexual species, in which uninfected lines of descent can be continuously reinfected; in inbred or asexual species, all selection is between lines of descent, and the genomic parasites are either lost or must evolve into commensals or mutualists. Here we present a simple population genetic model of the effect of outcrossing rate on the frequency of B chromosomes, and find that outcrossing facilitates the spread of parasitic Bs, but inhibits the spread of mutualists. Data compiled from the literature on breeding system and B chromosomes of British plants indicate that Bs are much more likely to be reported from obligately outcrossed species than inbred species. These results support the ideas that most B chromosomes are parasitic, and that breeding systems play a central role in the biology of selfish genes.
Full Text
The Full Text of this article is available as a PDF (240.3 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bell G., Burt A. B-chromosomes: germ-line parasites which induced changes in host recombination. Parasitology. 1990;100 (Suppl):S19–S26. doi: 10.1017/s003118200007298x. [DOI] [PubMed] [Google Scholar]
- Charlesworth B., Morgan M. T., Charlesworth D. The effect of deleterious mutations on neutral molecular variation. Genetics. 1993 Aug;134(4):1289–1303. doi: 10.1093/genetics/134.4.1289. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Charlesworth D., Charlesworth B. Transposable elements in inbreeding and outbreeding populations. Genetics. 1995 May;140(1):415–417. doi: 10.1093/genetics/140.1.415. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Futcher B., Reid E., Hickey D. A. Maintenance of the 2 micron circle plasmid of Saccharomyces cerevisiae by sexual transmission: an example of a selfish DNA. Genetics. 1988 Mar;118(3):411–415. doi: 10.1093/genetics/118.3.411. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hickey D. A. Selfish DNA: a sexually-transmitted nuclear parasite. Genetics. 1982 Jul-Aug;101(3-4):519–531. doi: 10.1093/genetics/101.3-4.519. [DOI] [PMC free article] [PubMed] [Google Scholar]
- KIMURA M., KAYANO H. The maintenance of super-numerary chromosomes in wild populations of Lilium callosum by preferential segregation. Genetics. 1961 Dec;46:1699–1712. doi: 10.1093/genetics/46.12.1699. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lyttle T. W. Segregation distorters. Annu Rev Genet. 1991;25:511–557. doi: 10.1146/annurev.ge.25.120191.002455. [DOI] [PubMed] [Google Scholar]
- Nur U. Maintenance of a "Parasitic" B Chromosome in the Grasshopper MELANOPLUS FEMUR-RUBRUM. Genetics. 1977 Nov;87(3):499–512. doi: 10.1093/genetics/87.3.499. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Zeyl C., Bell G., Green D. M. Sex and the spread of retrotransposon Ty3 in experimental populations of Saccharomyces cerevisiae. Genetics. 1996 Aug;143(4):1567–1577. doi: 10.1093/genetics/143.4.1567. [DOI] [PMC free article] [PubMed] [Google Scholar]