Cheetah bottleneck

Marty Marty
Wed Mar 13 11:34:01 EST 1996


In article <3146F1BE.2781E494 at unity.ncsu.edu>, sjhogart at unity.ncsu.edu 
says...
>
>Hi,
>
>I've heard "somewhere" that Cheetahs were thought to have gone through 
a
>genetic "bottleneck" a long time before humans could possibly have 
been
>responsible. Now I'm involved in a dispute over whether human activity
>has had a negative impact on Cheetah populations. I was under the
>impression that they were "doomed" genetically, and were sitting ducks
>for the first infection which targeted their surviving genotype. I 
know
>that humans are working to help Cheetahs through captive breeding.
>
>My questions:
>
>How many Cheetahs are there?
>
>Are humans responsible for Cheetah population decline? Diversity
>decline?
>
>How much diversity *is* there in Cheetah populations?
>
>What is actually being done in the way of breeding?
>
>Are they doomed?
>
>References?
>
>Thanks lots.
>-- 
>
>
>Susan Jane Hogarth
>
>"Luck is the residue of design." -- Freddy the Fish 
>
>"Personally, I'm always ready to learn, although I do not always like
>being
>taught." -- Winston Churchill
>
>http://www4.ncsu.edu/~sjhogart/public/home.html
>
>       .      .-~\
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>            \  |   `-'         `.
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>           `.\-.\       .-~      \
>             `-'/~~ -.~          /
>           .-~/|`-._ /~~-.~ -- ~
>          /  |  \    ~- . _\

Susan;
You must of missed my lectures on genetic bottlenecks and effective 
population size. In a nutshell, even if the present population of 
cheetahs is acceptably high, the effects of a past bottleneck on the 
effective population size, Ne, can last for many generations.  The 
estimate of Ne over many generations is the harmonic mean of the 
population sizes in each generation; therefore the effect of only a 
single bottleneck generation (low Ne) on the overall Ne is quite high 
regardless of any increases in the breeding population in subsequent 
generations.  For example, if there were 4 generations with population 
sizes of 20, 100, 800, and 5000, then 1/Ne = 
1/4(1/20+1/100+1/800+1/5000)= .06145/4; Ne = 65.09 and delta F, the 
rate of inbreeding  (decay)= 1/2Ne.  

Getting back to your question, I suspect that most predators at the 
top of the food chain are vulnerable to some degree due to their small 
poplation size.  This would be further exacerbated if the population 
were further subdivided into genetically isolated subpopulations. As 
for being "doomed", my guess is this probably a matter of human will to 
do something about the cheetahs.  We successfully brought the buffalo 
population back from less than 500 individuals, so why not cheetahs?  
Ciao!




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