"Robert Karl Stonjek"  wrote in
news:cltofj$v8j$1{at}darwin.ediacara.org: 

>       Threatened species may spiral into oblivion
> 
> 
>       Katherine Unger
> 
>       19:00 27 October 04
> 
>       Exclusive from New Scientist Print Edition. Subscribe and get 4
>       free 
> issues.
> 
>       Rampant inbreeding can put panthers, cheetahs and other
>       endangered 
> species at increased risk from parasites and infections, a new study
> suggests. That could create a vicious cycle capable of driving the
> remaining population to extinction.
> 
>       Inbreeding is known to increase the prevalence of certain
>       genetic 
> diseases and is also suspected of weakening the immune system,
> rendering animals more susceptible to other kinds of illness.
> 
>       The endangered Florida panther, for example, of which fewer than
>       100 
> individuals remain, is unusually prone to infections. And in the
> 1980s, an outbreak of feline infectious peritonitis killed more than
> half of an extremely inbred cheetah population, even though it rarely
> causes illness in most cats.
> 
>       But one of the few previous experimental tests of these ideas
>       seemed 
> to contradict the hypothesis that inbred animals find it hard to fight
> off disease. In 1997, when biologist Lori Stevens and colleagues at
> the University of Vermont looked at beetles infected with a tapeworm,
> they found that inbred beetles were just as good at resisting the
> parasite as genetically diverse ones.
> 
>       Now, conservation biologist Richard Frankham of Macquarie
>       University 
> in North Ryde, Australia, has revisited the idea. His team studied
> fruit flies, which reproduce so quickly that several inbred
> populations could be created in a matter of weeks.
> 

I don't know if the article goes into this, but an important 
consideration in the susceptibility of inbred populations is the length 
of time the population has been inbred. Populations which have managed to 
survive for a considerable time with small population sizes have had most 
of the deleterious recessives already removed. Large populations which 
"crash" to small populations, on the other hand, are much more 
susceptible. 


Yours,

Bill Morse
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