>1- The overall Devils Hole population is very small. The fish >evolved in
>an
>isolated environment which is subject to very little environmental
>pressures. There aren't any predators (right?) and water quality is
>constant. So how much variation can there be between individuals, >that
>you would see differences in their morphology over such a short >period of
>time?
Hard to say without looking. Jennifer Wilcox, at University of
Colorado-Boulder (Andy Martin's lab) addressed genetic variation in desert
Cyprinodon for her PhD diss. She gave an awesome talk at ASIH last summer on
it, but I can't remember how much variation she found in diabolis. Maybe
Peter Unmack remembers, or alternatively, I guess I could email her and
ask...
At any rate, with such a small founder population (29 individuals?), a
single mutation or frequency difference in a single individual could rapidly
go to fixation in the whole population. Admittedly, without data on genetic
variation, water temps, algal density, etc., this is speculative. If water
temps are different at the refugium, then one might be tempted to suggest
possible environmental plasticity. If there had been a difference in fin ray
counts, this would have been especially likely. If algal community
structure is appreciatively different between Devil's Hole and the refugium,
then you might expect differences in jaw or pharyngeal morphology.
cheers,
Dave
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