N rN

y ef em

N fN

ef em j


ef em

This leads to an expression for the inbreeding effective population size in terms of the number of males and females. This equation shows us that the effective size of a diploid population with two sexes and an equal breeding sex ratio (Nf = Nlm) is equivalent to an ideal random-mating Wright-Fisher population and also gives a means to express the effective population size when the breeding sex ratio is not equal. We also see that the coalescence model allows us to reach exactly the same result that was obtained using the identity by descent approach (equation 3.44 and section 3.4).

The probability that two randomly sampled gene copies do not coalesce, PnC, over some number of generations can be used to show the overall effective population size when the population size is not constant. As the basis of modeling coalescent times with the exponential distribution (the continuous time

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