re: genetic diversity
Wayne Forrester (forrestr@mendel.Berkeley.EDU)
Sat, 14 Dec 1996 07:53:15 -0800 (PST)
> It's been very interesting reading all the threads on genetic diversity as
> my state (Arizona) has just realsed California Condors back into the wild.
> They have been extict here for over 70 years. It seems that the entire world
> population a few years ago numbered 21 (all in captivity, none in the wild).
> I just wonder how much diversity was able to be maintained in such a small
> population. I haven't read anything in the media about this being a
> problem, but that certainly doesn't mean that the conservationists haven't
> thought about it.
>
> Limited genetic diversity would show up in what way? Problems with
> inbreeding? Less evolutional mutations? Just curious :-)
>
Good question. I don't think we really know the answer to this.
Certainly if the population gets small enough there can be problems with
inbreeding, presumably revealing deleterious recessive mutations. An
obvious loss would be that of morphological or color variants. There
also would be fewer variations available for evolution. This last problem
may be the most significant concern for plants (I don't really know how
much trouble with inbreeding there will be in plants. Certainly for very
small animal populations, this is a major concern. Time will tell
whether the condors can be saved although I think some animal populations
have been brought to reasonably large numbers from a very few
individuals. This is also probably the case in new species introduced
into new habitats, such as on remote islands) I don't mean to suggest
that we should be concerned with losing the potential for evolving new
species. Adapatation occurs at many levels, and many plants within a
species will have perhaps subtle differences, such as some being better
adapted to deal with slightly warmer or cooler climate. If the climate
changes slightly, those plants best suited would flourish, and others may
simply not survive.
It may be helpful to point out that I don't think all this
discussion about preserving diversity really affects our cultivation of
CP per se. I only want to point out that although we may be preserving
species by keeping them growing, if we are only left with representatives of a
species in cultivation, then we have lost a great deal even though the
species survives. And although keeping a species that's been lost in the
wild going in our greenhouses or windowsills is much better than totally
losing that species, it is still a poor alternative to saving
sites in the wild. I think given a choice between harvesting significant
numbers of plants from a stable (i.e. not about to be paved over to make
a parking lot, etc) site, and preserving that site untouched, I would favor
preserving the site. I don't have a problem with limited collection
of a couple of plants or a few seeds. After all, if nobody ever collected
any of these plants or seeds, we wouldn't have one of our favorite
hobbies, and would not be having these discussions. I would guess that
most people would more or less agree with this sentiment. However, from
some of the posts I've seen on this list over the past year or so,
I'm concerned that at least some do not. Just a few more of my long winded
and rambling thoughts on this topic.
Wayne Forrester