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Re: small and large

At 10:37 AM 5/9/98, Colette H. Adams wrote:

>1)  Small animals have faster rates of speciation due to:
>  a) higher fecundity
>  b) shorter generation times 
>  c) greater isolation between populations

>2)  Small animals have lower extinction rates due to:
>  a) higher fecundity 
>  b) more dense populations
>  c) more limited needs
>  d) greater genetic diversity

>I would like to take a little informal opinion survey.  Please rank each of
>the 7 hypotheses above on a scale from 0 to 5 (increasing importance)
>according to how much you believe they have contributed to the exponential
>decrease in species richness with decreasing body size.  

You mean *increasing* richness, no?  Also, if I remember correctly, the
original question had to do with species richness within a given genus or
lineage, not number of species in a given size range globally.  Which is
your question aimed at?

>If you prefer yet
>another hypothesis, advance it by all means and give it a similar ranking.

I wonder whether your statement #2 is true.  That is, is there an
understanding that smaller sized species have a lower rate of extinction
(within a given lineage?)?  This is not something I've heard before.

  --Toby White