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From: knox@whittaker.rice.edu (Robert G. Knox)
Newsgroups: sci.environment,sci.bio
Subject: Re: Condors & Otters & Cows, Oh My ! (Re: Bringing Back Extinct Species)
Summary: Cheetahs in trouble
Keywords: inbreeding, conservation
Message-ID: <6568@brazos.Rice.edu>
Date: 11 Apr 90 23:26:49 GMT
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Admittedly species can be in trouble for many reasons, but 
cheetahs are a good example of why numbers and habitat aren't 
enough.  Due to having lost nearly all their genetic diversity 
"unrelated" cheetahs might as well be clones of one another.  
Skin grafts are not rejected between unrelated animals, which 
suggests vulnerablity to disease (a bug which can kill one
can kill them all, etc.).  More importantly at present, cheetahs 
have very poor reproductive success--either in captivity or in 
the wild.  

The explanation for poor reproductive success comes from studies 
of inbreeding in animals or plants that generally outbreed.  
Most outbred individuals carry a range of rare deleterious genes 
that are receessive in their effects.  When switched to breeding
with close relatives, some of these genetic alleles are lost, by 
chance, but others end up "homozygous"--in that form the genes 
are deleterious and would be normally eliminated by natural
selection, but there's no alternative!  The cheetahs are stuck 
with whatever made it through a past population "bottleneck" 
until new mutations replenish the supply of genetic variation 
(a very slow process).

The lesson for conservation is that it's not enough to save the 
"last" CA condor, blue whale, or panda.  By then it will usually 
be too late for long-term survival without our (expensive) help.  
We need to act early to preserve viable populations--large enough 
to include and sustain genetic diversity.  Otherwise all we save 
are living museum specimens, genetically crippled descendants of 
formerly viable species.

[Hope the tone isn't too pedantic.  I'm new at this net stuff :-)
For a readable report on the situation with cheetah genetics, see   
_BioScience_ vol.36, pp. 358-362.  An overview of genetics for 
wildlife conservation appears in the March 1990 _BioScience_, 
vol.40,no.3,pp 167-171.]

Re:  bringing back extinct species, perhaps old pelts, skins, etc.
collected before loss of genetic diversity could be used to 
reconstruct the DNA sequences of the lost genetic alleles and the 
diversity engineered back in, gene by gene.  But the biotechnology 
isn't quite there yet, and even when it is . . . now you're 
talking about *really* expensive help!