"Tim Tyler"  wrote in message
news:ccei6o$mom$1{at}darwin.ediacara.org...
> a.a{at}a.se wrote or quoted:
> > Tim Tyler  wrote:
>
> > >Ridley uses a similar definiton for group selection -
> > >on p.303 - citing Wade's Trifolium experiments as
> > >an example of group selection under laboratory conditions.
> > >
> > >This used selection for low fecundity - a fairly clear
> > >example of a trait where the property of the group
> > >is the additive result of individual properties.
> >
> > Could you elaborate on this please?
>
> Wade's experiments on flour beetles (actually Tribolium castaneum) [1]
> applied periodic selection on the basis of fecundity - by
> repeatedly dividing the beetles into groups, and then systematically
> extinguishing the groups which had the bettles of the highest fecundity -
> as demonstrated by their large population sizes.
>
> As far as I understand it, those who want to define
> group selection out of existence would claim that this
> is not /really/ an example of group selection.
>
> An alternative model fits the facts well - the result is basically
> the effect of applying frequent, low-intensity selection favouring
> high-fecundity individuals, and infrequent, high-intensity
> selection favouring low fecundity individuals.
>
> Such a model makes no reference to high level selection,
> and yet explains the observed facts pretty well.
>
> Therefore, high level selection is a redunadant theory
> in this instance - an individual-level model works just fine,
> and group selection can be eliminated using Occam's razer.
>
> Fecundity isn't a heritable trait of groups anyway - so selection
> favouring it at the group level is actually impossible.  Any
> selection favouring fecundity must be going on at the level which
> is exhibiting the fecundity - and clearly it is the *individuals*
> that are fecund in Wade's experiments. [2]
>
> [1] Wade, M.J. 1976. Group selection among laboratory populations of
> Tribolium. Proceedings of the National Academy of Sciences U.S.A. 73:
> 4604?4607.
>
> [2] Or so the story goes.
> -- 

A nice balanced presentation!  But the situation is even more
complicated than you suggest.  Triboleum turns out to be somewhat
cannibalistic - adults sometimes eat other beetle's larvae.  So
there was some question as to whether group selection for small
population size was actually selecting for low fecundity.  It
could have been selecting for more aggressive cannibalism.
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