R.A. Fisher developed a theory of junctions to describe the loss of heterogeneity during inbreeding. When distinct strands of continuous genetic material are brought together by recombination a junction is formed at their boundary. The junction approach simplifies analysis and simulation of multilocus processes involving populations which can initially be described in terms of a finite number of distinct haplotypes. An example from Fisher's work is a sib-sib inbreeding system which initially has four haplotypes. A secondary contact hybrid zone between two populations which have diverged at many loci can be modelled as the meeting of two distinct haplotypes. Barton used this approach to show that for a tension zone at equilibrium between two infinite demes there is a critical value of selection below which loci act independently, and above which loci act in association with each other. A simulation study is used to show that the approach to this equilibrium is slow, such that within reasonable time limits after secondary contact loci act in association even under weak selection. This result is confirmed using an exact solution by Barton. An alternative approximation can be numerically solved for arbitrary selection functions, suggesting a method of dating secondary contact hybrid zones by the progress they have made toward equilibrium. The possibility of applying such a dating method to a natural hybrid zone is explored by extending the original model to consider finite populations, exchange across a continuum, and non-uniform selective effects across the genome.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:641218 |
| Date | January 1994 |
| Creators | Baird, Stuart J. E. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/10705 |
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