> I may be putting myself out on a limb, but isn't all of this dependant upon
> the ammount of genetic diversity of the population in question?
Absolutely. 100% agree.
> not quite possible to elliminate the genes for resistance. When selection
> is removed the line reverts back to more non-resistant individuals. Of
Actually, what you are saying here is that when you remove selection for
resistance, selection for other traits takes over and inadvertadly reduces
resistance.
> explain anything really, but imagine if a population was small (40+fish)
> and 30 were bumped off. The gene pool would be greatly reduced, and
> perhaps unable to have the necessary diversity to adapt to environmental
> perturbations.
But if it did, it would be set for life so to speak if it is able to
track environments that it can live in. This appears to be what pupfish
have done. They appear to lack genetic variation (although only two
techniques have been examined) yet they can survive and reproduce in
environments that will kill 99.9% of all known extant fishes! One point
that is important here to consider, pupfish don't typically (there are
several exceptions) coexist well with other fish, they do best on their
own. Also, sympatry is very rare within that genus.
> Perhaps, a line selection may not be able to adapt to other
> environmental conditions, bercause it has become adapted to the specific
> environmental conditions and the gene pool lacks sufficient diversity for
> further adaptation.
Absolutely. But, if you have many lines you can maintain genetic
diversity (old discussion from several months ago). It comes down to
polymorphism (genetic variation which occurs between lines or
populations) and heterozygosity (genetic variation between individuals
within a line or population). Thus, you can have zero heterozygosity but
high polymorphism ie, considerable genetic variation.
> The trend that is seen in Hawaii with many of its
> native birds, insects, plants, All are thought to have evolved from a few
> initial colonists and hence a small gene pool.
Also though, they probably evolved without many of the predators
introduced to Hawaii. Is it due to genetic or behavioural factors? :-)
It may have little to do with genetics.
Hooroo
Peter Unmack