BEN # 42

Adolf Ceska aceska at CUE.BC.CA
Tue Sep 29 02:44:00 EST 1992

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No. 42                            September 29, 1992

Address: aceska at         Victoria, B.C.

From: Evelyn Hamilton <ehamilton at>

                    III. GENETIC DIVERSITY

Understanding genetic diversity
Russell Lande, Dept. of Biology, OSU, Corvalis, OR

Genetic variation is only adaptive in  predictably  changing  en-
vironments.  If  there  is a gradient, adaptation will be to that
gradient. If there is global  change,  the  location  of  optimal
conditions  will  move  in  space. The ability to migrate to find
situations that the organism is adapted to will be important.  He
was  pessimistic  about  the ability of small populations to sur-

Conserving diversity in natural systems
G. Meffe, Savannah River Ecology Lab, Aiken, SC

 1. Because of genetic drift and mutations, what we have not  may
    not  be  the  most  fit.  Evolution is dynamic and we need to
    focus on allowing change and adaptation to occur, rather than
    trying to preserve things as they are now.

 2. Units of conservation should  be  evolutionarily  significant
    units - i.e. populations (Wapples 1991).

 3. We  need  to define geographic distribution of genetic diver-

 4. Small populations lose  genetic  diversity  faster  than  big

 5. One  population  may  represent  most  of  the diversity of a
    species or you may  need  to  preserve  many  populations  to
    conserve the genetic diversity of the species,

 6. We  need  to  keep subdivisions separate to retain diversity.
    Priorities should be to preserve  the  populations  resulting
    from the oldest divergences.

 7. With  salmonids in Pacific Northwest, for example, we need to
    identify conservation units and use hierarchy of structure to
    do so (e.g. stream orders).

 8. Rules of thumb can be problematic (e.g. the 50/500 rule  that
    states that 50 individuals are needed for short term survival
    and  500  are  needed for long term persistence). These rules
    may not apply to desert fish, for  example,  which  exist  in
    small populations.

 9. Scientists  have  failed  to  communicate  to  the public and
    resource managers about these issues.

Seed zones and productivity
M. Thomson Conkle, USFS PSW Lab, Berkeley, CA

He described the seed zone approach used in  California  and  its
utility  in  conserving  genetic  diversity. The basic concept is
that local sources are used  in  regeneration  and  unintentional
transfers are restrained.
His rules of thumb are:

 1. Conserve diversity by
    a)  collecting  widely  within  the  zones to capture maximum
    genetic diversity,
    b) supplement natural regeneration with local seed source and
    c) respect steep environmental gradients.

 2. Foster forest health by managing genetic resource.

Creating policy on genetic diversity
Gene Namkoong, Dept. of Genetics, N.C. State Univ., Raleigh, NC

We need to define the level of moral concern, i.e  population  or

 1. What is the overall goal?

 2. Which species are most important?

 3. Are patterns of genetic variation in 1992 important?

 4. Is the focus on threatened and endangered species a tactic or
    a  goal?  If it is a tactic other indicators of diversity may
    be substituted.

 5. Are we managing for keystone  or  flagship  species  in  par-

Our goals may be

 1. to preserve genetic material that has utility for present and
    future  humans, in which case rarity does not endow value and
    some species are more important than others,

 2. to insure that evolution is not inhibited.

He has authored a Oxford Univ. Press book on this topic and  will
be the new Chair of Forest Sciences at UBC.

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