Re: genetic diversity

Andrew Boyd (andrew at pcug.org.au)
Sun, 14 Apr 1996 20:03:56 +1000

At 07:10 PM 4/11/96 -0700, Joshua wrote:
>This is a comment on an ACN-L discussion from several weeks ago, which
>I am only just now reading:
>
>At 06:08 PM 4/1/96 -0700, peter.unmack at ASU.Edu wrote:
>>My understanding of genetic theory indicates that once a species loses
>>genetic diversity it isn't re-created.
>
>I have heard this, but I have also heard the opposite: that genetic
>diversity is almost always re-created. That argument went like this:
>Genetic mutations are not random: certain mutations happen over and
>over again, because that particular DNA change is easier to trigger.
>Coversely, other DNA changes are much harder to trigger. Therefore,
>if a mutation (say: A -> A') has happened once, it will likely happen
>again. So even if all the A' fish die, more will mutate. (Obviously,
>we're talking about whole populations of fish, over a period of years or
>longer.)

see (a) below.

>I do not have the biology background to argue this point, but perhaps someone
>else does? This point is relatively important for captive breeding programs.
>If it were true, then the discussions about maintaining genetic diversity
>would be moot. If the fish survived, the genetic diversity could be largely
>regenerated.

Howdy! I can see your point, but (if I may pontificate....)

(a) The case for "if a mutation has happened once, it'll happen again" is
used in certain circles as an excuse to do nothing about threats to
biodiversity, so this is a dangerous (IMHO) statement to make, and;

(b) "If the fish survived, the genetic diversity could be largely
regenerated" is possible, If the fish survive!

The problem with the above is that it fails to recognise the importance of
all genetic material, i.e. the fishes/frogs/orchids/whatever. It's sort of
like saying "It's OK, they weren't strong enough to survive in a toxic waste
dump, they probably deserved to die out anyway!"

Regards, Andrew Boyd
___________________________________________________________________
Andrew Boyd - andrew at pcug.org.au - http://www.pcug.org.au/~andrew
"I know that I am God because whenever I pray to him I realise I am
talking to myself" (Woody Allen)