[RML] Re: [RML] D.G inbreeding

Mach Fukada (tuhoitc at aloha.net)
Wed, 5 Feb 1997 17:29:59 -1000 (HST)

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? Looking at
the development of insect resistance to B. thuringiensis (BT), most insect
populations have an cenrtain percentage of the population have the genes
that code for resistance. However under a heavy selective pressure (lab
rearing and exposure to increasing levels of BT) it has seemed that it is
not quite possible to elliminate the genes for resistance. When selection
is removed the line reverts back to more non-resistant individuals. Of
course here we are dealing with thousands of individuals, and hundreds of
generations in an artificial environment. This simple model can not quite
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. 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. 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. Many are going extinct
because there has been many changes to Hawaii's ecosystems....
MTF

>On Wed, 5 Feb 1997, Rob Wager wrote:
>> peter.unmack at ASU.Edu wrote:
>> >On Mon, 3 Feb 1997 richard.mleczko at cit.act.edu.au wrote:
>
>> What is "adapted to inbreeding"?. Is that like Tasmanians; appear normal but
>> are all related ??? :-).
>
>Sort of. :-) Basically the idea is that some species have purged their
>genomes of bad alleles (ie deleterious recessives [ie death or poor
>survival]. For instance according to some aspects of genetic theory a
>fish like Devil's Hole pupfish that probably hasn't exceeded 800
>individuals in perhaps 10,000 years or more should have gone extinct by
>now. Pupfish tend to inhabit small isolated habitats with only
>occasional mixing, thus inbreeding is common. Same thing in desert
>gobies and probably redfinned blue eyes. One would predict that within
>population variation would be low relative to between population
>variation, although there are many variables here, ie that was a broad
>generalisation that doesn't always hold. Depends on the history of the
>species. To try to make this a little easier to understand think of it
>this way. Some species don't do well if outbred (outbreeding depression)
>as it is thought that there are series of coevolved genes that when outbred
>get broken up with a resulting lower fitness. Some species can't be inbred
>as this brings deleterious recessive alleles together, thus lowering
>fitness (probably the most common). Some species can be inbred or
>outbred as they are thought to have lost most of their variation and
>deleterious alleles thus it doesn't matter what the hell you do to them.
>Variation in species is not always a good thing to have despite what we
>always get told. Lets just say there are no easy answers in biology.
>:-) Now I bet everyone is as clear as mud on the subject. If you don't
>follow please say so and I will attempt to clear things up.
>
>Hooroo
>
>Peter J Unmack peter.unmack at asu.edu
>---------------------------------------------------------------
>DESERT FISHES RULE: To boldly thrive where no other fish can make it!
>
>Australian desert fishes pages at ozdesertfish.base.org (don't forget to
>visit the Desert Fishes Council pages too)
>Native Fish Australia pages at nfa.base.org (under construction)

Mach Fukada, Computer Specialist
Information Technology and Communications

Tokai University at Honolulu

"You need it, I'll make it. You break it, I'll fix it.
And I will love every minute of it"

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