What is Conservation Genetics? -- Application of
genetics to preserve species as dynamic entities
capable of coping with environmental change and
encompasses:
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genetic management of small populations
resolution of taxonomic uncertainties
defining management units within species
use of molecular genetic techniques in
forensics & understanding species biology.
When a population or species disappears, all the
genetic information carried by that population
or species is lost!
When a contiguous population is fragmented into
many small populations, genetic diversity within
each may decay over time
“Gene pools are becoming diminished and
fragmented into gene puddles” (Thomas Foose, 1983)
Why Genetics?
Evolution is the single most unifying organizational
concept in all of biology and should play a
prominent role in conservation as well.
Evolution is dynamic and change is expected.
ecological systems are dynamic and generally not
in equilibrium.
The best way to manage such dynamic systems
is a Conservationist rather than Preservationist
approach.
Three biological reasons to believe genetics can
make important contribution to conservation
biology.
1. Fundamental theorem of natural selection
tells us that the rate of evolutionary change
in a population is proportional to the amount
of genetic diversity available.
Darwin-Wallace Theory of Natural Selection
If supplied with sufficient nutrients and protection
the total population size will increase geometrically.
However, due to high death rates, geometric
increase is not maintained indefinitely.
All species are variable
Darwin-Wallace Theory of Natural Selection
Those individuals with variations of characters that
better enable them to survive and reproduce will
leave proportionally more offspring.
This results in the increase of the advantageous
characters in the next generation.
2. There is a consensus among population
geneticists that heterozygosity, or high genetic
variation within individuals or populations, is
positively related to fitness.
3. The global pool of genetic diversity represents
all the information for all biological processes
on the planet.
Loss of such diversity will probably decrease
the ability of organisms to respond to
environmental changes and discard information
potentially useful to humans.
Basic problem linking genetics to conservation is
that small populations, whether in the wild or
captivity, tend to lose genetic variation over time.
This loss of variation may well increase the
probability of population extinction or reduced
opportunities for future adaptation through
evolutionary change.
The basic thrust of conservation genetics and the
message to take from this course is:
We must maintain natural patterns of genetic
diversity at many levels and thus preserve
options for future evolution!!!
Limitations of Genetics in Conservation Biology:
1. Application of genetics to conservation problems
is a young science that is still developing.
2. Many genetic techniques are not cheap and
can be misused or misapplied.
3. Plant and animal tissues must be obtained and
properly handled.
“Genetic factors do not figure among the four
major causes of extinction (the Evil Quartet):
overkill, habitat destruction and fragmentation,
impact of introduced species, and secondary
cascade effects”.
Thus, although genetic factors are major
determinants of a populations long-term viability,
conservationists can do more for a threatened
population in the short-term by managing its
ecology.
Conservation Genetics deals with the genetic
factors that affect extinction risk and genetic
management regimes required to minimize these
risks.
There are 11 major genetic issues in conservation
biology.
1. The deleterious effects of inbreeding on
reproduction and survival
(inbreeding depression)
2. Loss of genetic diversity & ability to evolve in
response to environmental change.
3. Fragmentation of populations and reduced
gene flow.
4. Random processes (genetic drift) overriding
natural selection as the main evolutionary
force.
5. Accumulation and loss (purging) of deleterious
mutations.
6. Genetic adaptation to captivity & its adverse
effects on reintroduction success.
7. Resolving taxonomic uncertainties.
8. Defining management units within species.
9. Use of molecular genetic analyses in forensics.
10.Use of molecular genetic analyses to understand
aspects of species biology
11. Deleterious effects of fitness that sometimes
occur as a result of outcrossing
(outbreeding depression).
How is genetics used to minimize extinction?
1. Reducing extinction risk by minimizing
inbreeding and loss of genetic diversity.
2. Identifying populations of concern.
3. Resolving population structure
4. Resolving taxonomic uncertainties
5. Defining management units within species.
6. Detecting hybridization
7. Non-intrusive sampling for genetic analyses.
8. Defining sites for reintroduction.
9. Choosing the best populations for reintroduction.
10.Forensics.
11. Understanding species biology
Biodiversity -- the variety of ecosystems, species,
populations within species and genetic diversity
within species.
Biological diversity of planet is being rapidly
Depleted due to direct and indirect consequences
Of humans.
Scale of this problem is enormous and has been
Termed the “Sixth Extinction” as its magnitude
Is comparable with that of the other five mass
Extinctions revealed in the geologic record.
Conservation genetics is motivated by the need
to reduce current rates of extinction and to
preserve biodiversity
Why Conserve Biodiversity? Because humans
Derive many direct and indirect benefits from
The living world, we have a stake in conserving
Biodiversity for:
resources we use
ecosystem services it provides
pleasure we derive from living organisms
ethical reasons
Bioresources includes all food, many
pharmaceuticals, clothing fibers, rubber & timber
with a value in billions of dollars annually.
About 25% of all pharmaceutical prescriptions
in the US contain active ingredients derived
from plants.
The natural world contains many potentially useful
novel resources: Ants contain novel antibiotics
that are being investigated for use in human
Medicine.
Ecosystem Services -- essential biological functions
That are provided free of charge by living organisms
And which benefit mankind such as:
Oxygen production by plants
Climate control by forests
Nutrient cycling
Natural pest control
Pollination of crop plants
These services have been valued at
$33 trillion/year or almost double the $18 trillion
yearly global national product!!!!
Aesthetics -- Humans derive pleasure from
living organisms. This translates into direct
economic value.
Koalas are estimated
to contribute $70
million annually to the
Australian tourism
industry.
Ethics -- The ethical justifications for
conserving biodiversity are simply that one
species does not have the right to drive
other species to extinction!
The IUCN (the World Conservation Union)
Recognizes the need for conservation at the
Levels of:
genetic diversity
species diversity
ecosystem diversity
Based on the principles of population biology, in
1996 the IUCN defined criteria to classify
species into:
Critically Endangered
Endangered
Vulnerable
Lower Risk
Extinct
Extinct in the wild
Conservation Dependent
Near Threatened
Data deficient
Information used by IUCN to decide whether species fall into critically endangered, endangered, or
vulnerable categories. A species falling within any of categories A-E in the critically endangered column
is defined as critically endangered. Similar rules apply to endangered and vulnerable categories.
Criteria (any 1 of A-E)
Critically Endangered
Endangered
A.
Actual or projected
reduction in pop. size
80% decline over past 10
or 3 generations
B.
Extent of occurrence or
areas of occupancy
< 100 km2
5000 km2
< 10 km2 and any 2 of:
500 km2
(i) severely fragmented or
5 locations
known to exist at single locality
(ii) continuing declines, and
(iii) extreme fluctuations
20,000 km2
2,000 km2
10 locations
C.
Population numbering
< 250 mature individuals and
< 2,500
an estimated continuing decline
<10,000
D.
Population estimated
to number
< 50 mature individuals
< 250
< 1,000
E.
Quantitative analysis
showing the probability
of extinction in the
wild.
at least 50% within 10 yrs or
3 generations, whichever is
the longer
20% in 20 yrs
or 5 generations
10% in 100
yrs
50%
Vulne
20%
It is of critical importance to define
endangerment as it is the basis for legal
protection for species.
Most countries have Endangered Species Acts
that provide legal protection for threatened
species and usually require the formulation of
recovery plans.
Additionally, trade in threatened species is
banned by countries that have signed the
Convention on International Trade in Enangered
Species (CITES).
Small populations suffer from inbreeding & loss
of genetic diversity resulting in elevated
extinction risks.
Consequently, a major objective of genetic
management is to minimize inbreeding & loss of
genetic diversity.