... snails.¹

It may well be characteristic of many hermaphroditic animal parasites. You should also know that I just lied. The form of self-fertilization I'm going to describe actually isn't the most extreme form of selfing possible. That honor belongs to gametophytic self-fertilization in homosporous plants. The offspring of gametophytic self-fertilization are uniformly homozygous at every locus in the genome. For more information, if you're interested, see [1]

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... changing.²

This is analogous to stopping the calculation and re-calculation of allele frequencies in the EM algorithm when the allele frequency estimates stop changing.

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... course.³

Unfortunately, I'll also be using hats to denote estimates of unknown parameters, as I did when discussing maximum-likelihood estimates of allele frequencies. I apologize for using the same notation to mean different things, but I'm afraid you'll have to get used to figuring out the meaning from the context. Believe me. Things are about to get a lot worse. Wait until I tell you how many different ways population geneticists use a parameter $f$ that is commonly called the inbreeding coefficient.

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... expectations.⁴

$f$ can be negative if there are more heterozygotes than expected, as might be the case if cross-homozygote matings are more frequent than expected at random.

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... defined.⁵

See paragraphs above describing the population and equilibrium inbreeding coefficient.

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... history.⁶

Notice that we could have had each allele mutate independently to $A_2$.

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... descent.⁷

Systematists in the audience will recognize this as the problem of homoplasy.

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... descent.⁸

Notice that if we adopt this definition for $f$ it can only take on values between 0 and 1. When used in the sense of a population or equilibrium inbreeding coefficient, however, $f$ can be negative.

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