BEN # 42
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 cue.bc.ca Victoria, B.C.
BIODIVERSITY IN THE MANAGED LANDSCAPE: THEORY AND PRACTICE
CONFERENCE IN SACRAMENTO JULY 13-17, 1992 (PART 2 of 5)
From: Evelyn Hamilton <ehamilton at galaxy.gov.bc.ca>
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
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
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
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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