Re: Genetic diversity

Wayne Forrester (forrestr@mendel.Berkeley.EDU)
Thu, 12 Dec 1996 10:23:16 -0800 (PST)

>I get the impression that an unnatural bias is tried to be created
>between sound scientists doing only the right things to properly
>study, conserve, and describe cps (and a few other less interesting
>phenomena) and evil clueless amateurs who only collect, destroy, and
>confuse the same items. However, I know enough examples each of
>scientists performing rather poorly (and not only because of short
>funds!) and amateurs who have contributed a lot to the benefit of us
>all. In the end we all depend on mutual co-operation, so please stop
>dividing mankind by these artificial criteria.

I agree with this. It seems to me the relevant distinction is between
people concerned with preserving plants, animals, etc., and unscrupulous
persons interested in making money. Scientists, like any other group,
fall into both chategories. I think, however, that the distinction
between scientists and non-scientists orginally came up in the context of
access to precise locality information.

>As to genetic diversity, the process of evolution (mutation rate,
>selective pressure) does not stop in cultivation. Population size
>does mainly influence outbreeding taxa. But we have seen that
>several cps reproduce asexually predominantly (many members of
>_Drosera_ subgen. Bryastrum) or even exclusively (e.g. _Utricularia
>bremii_ which has so far never been observed to form fruits). So
>these should not suffer under cultivation. Furthermore, genetic
>diversity is frequently even increased in cultivation by mutagenesis
>(I don't know cp examples here, however) and the creation of hybrids
>which would not normally occur in nature (OK, I don't like these
>either but they still exist). I do not agree that sexual recombination
>does not increase diversity. It may even introduce new mutations
>(e.g. during crossing over in meiosis) to the gene pool.

Sorry Jan, but I must disagree with some of the points you make in this
paragraph. although evolution may not stop in cultivation, the relavent
issue is whether we are preserving genetic diversity in cultivation. On
the one hand, of course, we are. If a species is extinct in the wild but
still exists in cultivation, then there is greater diversity in
cultivation. However, clearly there are vast numbers of variants that
occur in the wild, which would be difficult if not impossible to
duplicate in cultivation. Furthermore, to maintain diversity, one must
maintain genetic isolation between the diverse populations. If you cross
variant one with variant two, you now have a plant with half itUs genes
from either parent. Although itUs true that mutations continue to occur
in cultivation, probably at a rate similar to in nature, I donUt think
this is a significant contribution to diversity. Firstly, most mutations
are deleterious, and result in a plant inferior to its parents. Secondly,
the rate of mutations is relatively low, and therefore to increase
genetic diversity in cultivation would require eons, and a very large
population of plants, neither of which are likely in cultivation. Also,
in nature there are different factors at different sites which generate
and maintain diversity. Mutagenesis will not significantly improve on
this. Treatment with a mutagen will increase the rate of mutation, but
you still need a huge number of plants, and a very long time to generate
true diversity. Finally, I think the genetic differences between
individuals from genetically isolated populations can be huge, and I
donUt think it will be possible to maintain, let alone reproduce this, in
cultivation.

>I think it is not up to scientists to supply ammunition for people
>interested in conservation to shoot at people who aren't. It is the
>task of mankind to recognize that natural diversity is in itself a
>value worth of conservation, irrespective of possible future
>applications (i.e. commercial value) to the benefit of mankind (or at
>least the selling part of which). This is apparently a very difficult
>lesson, and human cognition may not be ready to learn it in time.
>However, I see no mission for science here if common sense is not
>sufficient. Those who just go and strip sites of rare or even *all*
>species will simply not bother if you offer them scientifically
>corroborated theories why they should not do so. We do have religions
>and laws already, and still there are atheists and criminals.

Agreed. I think education is very important. However, it only takes a
single unscrupulous individual to destroy sites in the wild. Therefore, I
still feel that one must be very careful in releasing detailed locale
data to strangers.

Wayne Forrester