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where s is the proportion of progeny produced by self-fertilization each generation. This is based on the expected inbreeding coefficient at equilibrium s q = 2—s (Haldane 1924). Figure 2.21 shows the decay in gametic disequilibrium predicted by equation 2.30 for four self-fertilization rates in the cases of free recombination (r = 0.5) and tight linkage (r = 0.05). Self-fertilization clearly increases the persistence of gametic disequilibrium, with marked effects at high selfing rates. In fact, the predominantly self-fertilizing plant Arabidopsis thaliana exhibits gametic disequilibrium over much longer regions of chromosome compared to outcrossing plants and animals (see review by Flint-Garcia et al. 2003).

It is possible to observe gametic disequilibrium just by chance in small populations or small samples of gametes. Recombination itself is a random process in terms of where crossing over events occur in the genome. As shown in the Appendix, estimates are more likely to approach their true values as larger samples are taken. This applies to mating patterns and the number of gametes that contribute to surviving progeny in biological populations. If only a few individuals mate (even at random) or only a few gametes found the next generation, then this is a small "sample" of possible gametes that could deviate from independent segregation just by chance. When the chance effects due to population size and recombination are in equilibrium, the effects of population size can be summarized approximately by:

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