Re: Hardy-Weinberg law

From: Tim Tyler (tim_at_tt1lock.org)
Date: 06/25/04 

Date: Fri, 25 Jun 2004 05:28:47 +0000 (UTC)

Guy Hoelzer <hoelzer@unr.edu> wrote or quoted:
> Tim Tyler at tim@tt1lock.org wrote on 6/23/04 9:06 AM:
> > Perplexed in Peoria <jimmenegay@sbcglobal.net> wrote or quoted:
> >> In reply to a post from Bob containing:

> >>> I don't know which textbooks you have to hand, I have Futuyma's
> >>> "Evolutionary Biology" (2nd ed. from 1986), and in Chapter 5
> >>> ("Population Structure and Genetic Drift") he has a section called
> >>> "Population Size, Inbreeding, and Genetic Drift" where he shows that
> >>> any finite population will become inbred, which means a reduction in
> >>> heterozygosity. [...]
> >>
> >>> In essence, any finite population will become inbred over time (at
> >>> least to some extent), and this increases homozygosity.
> >>
> >> Boy, are you going to feel foolish after you get a good night's sleep
> >> and review what you have written :-)
> >
> > I believe it is conventional enough.
> >
> > A finite population will be subject to drift - which will remove
> > alleles from the population - and increase homozygosity as a result.
> >
> > Ridley also refers to this effect as "inbreeding" - writing in
> > his textbook:
> >
> > "The increase in homozygosity under drift is due to inbreeding".
>
> Yeah. This is the kind of statement that led me to stop using this textbook
> in my evolution course. Inbreeding does not cause drift, or vice versa.
> The strength of drift changes inversely with effective population size (by
> definition) and inbreeding tends to vary the same way.

A "sufficiently-inbred" section of a population could well be
indistinguishable from a population consisting of a small number
of individuals.

In that sense it would be reasonable to say that a particular kind of
inbreeding could be regarded as being solely responsible for all the
effects of small population sizes.

Incidentally - I *like* the textbook - along with most of the other stuff
Matt Ridley writes - and I expect I'll continue to refer to it in glowing
terms - at least until I'm exposed to something similar - but
significantly better. 

-- 
__________
 |im |yler  http://timtyler.org/  tim@tt1lock.org  Remove lock to reply.

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