There may be perturbations of Aydin's stochastic model. Trematode
parasitism in certain pulmonate snails can cause castration, and one
consequence thereof is gigantism.
Harry
At 02:55 PM 6/4/2008, you wrote:
>For a given population, if you have a large enough sample of shells, you can
>calculate the mean & the standard deviation (SD) & then assume that the
>maximum attainable size would be about (mean + 3xSD). This follows from the
>properties of a normal distribution: the probability of encountering
>variants more than 3 standard deviations on either side of the mean are
>exceedingly small (you would need thousands of specimens before you might
>find one).
>
>But, in a different population of the same species, the mean & the SD could
>be different, which would make the maximum or minimum sizes that one is
>likely to find also different.
>
>Other than that there is no method of accurately predicting the max or min
>size of a species from evolutionary considerations except that one can
>derive approximate size limits based on surface area-volume or weight
>considerations. For example, there can't be giant insects, because their
>tracheal system wouldn't be efficient to deliver enough oxygen.
>
>Hey, I should write about this on my blog.
>
>Aydin
>snailstales.blogspot.com
>
>
>On Wed, 4 Jun 2008 13:35:04 -0300, Ross Mayhew
><[log in to unmask]> wrote:
>
>...
> >
> >My questions is: is there any way to calculate what is the "probable"
> >maximum attainable size for a given species, within normal, natural
> >parameters of genetic and environmental factors (obviously you could in
> >theory do selective breeding in a protected situation, and enhance
> >growth by manipulating environmental variables, but that would be a
> >different matter entirely!)? Have any studies been done along these
> >lines?
> >
> > From an almost-warm and almost-sunny New Scotland,
> >Ross Mayhew.
> >http://www.schnr-specimen-shells.com/
> >
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