Download Conservation Genetics

Conservation
Genetics
Class 8
Presentation 3
Forces of evolution
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Natural selection
Genetic drift
Non-random mating (inbreeding)
Sexual selection (differential
survival/reproduction due to mate selection)
Gene flow (movement of genes from one
population to another)
Mutation
Why study genetics?
One component of “biodiversity”
 It is the construction library of a
population or species
 Permits population to adapt and evolve
through natural selection
 Common features define a spp
 Variability in genes allow them to adapt
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Genes & Environment
Genotype + Environment = Phenotype
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We see the phenotype: leaf shape,
colour of hair, eyes, beak size, etc.
Value of diversity
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Differences in phenotype (e.g. blue
eyes vs. brown, vs.. pink) mean
different capabilities under different
conditions such as: night vision,
tolerance to high light or UV radiation)
Adaptive Radiation
Adaptive radiation occurs when
genotypes evolve into new spp
 Natural selection acting on genotypes
or mutations = new species
 Natural selection: due to competition,
new habitat, selective predation, etc.
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Examples of adaptive
radiation
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Hawaiian Honey-Creepers
– Finch like seed eating ancestor
– Arrived about 3.5 to 8 million yrs ago
– Adapted beaks to different foods
 Fruit,
insects, nectar (tubular with feathered
tongue), seeds
Examples of adaptive
radiation
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Darwin’s finches on Galapagos Islds
Ancestor: ground dwelling, seed eater
Today 14 spp
– Tree finches
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Adapted to feed on insects, sharper bill than ground
dwellers
– Ground Dwellers
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Beak size varies with food type
Stronger bill suited for seeds
– Warbler finch
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Insect eater in trees
Examples of adaptive
radiation
Ciscoes in Algonquin Park (11k yrs)
 Ancestor: Common Cisco
 Speciation beginning with ciscoes
developing specialized feeding
apparatus: gill rakers to filter out
different food types.
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Photo: NOAA
Mutation Rates
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Usually thought to be low in the absence of
mutagens (radiation, chemicals)
Rates under “normal conditions”
– Humans: 0.5 to 25/100,000 gametes
– Bacteria: 0.00007 to 0.41/100,000 gametes
– But bacterial generations short! So adaptations
are fast.
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Most often mutations cause no visible
change
Mutation & Adaptation
in Use
Used in agriculture, industrial
applications (pollution control, ore
extraction, fermentation, etc).
 Potato (Solanum tuberosum)
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– Now 500+ varieties
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Corn (Zea mays)
– Verities range from 0.6 to 6 m tall, 2-11
months to mature
Genetic effects on
Populations
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Random drift:
– With natural selection the most important cause
of evolution
– Only some of the variation in parents passed on
to progeny
– Imagine parents have few children, variation lost
– Does not matter much if population is large
– In small population effect is fast and significant
Random drift
Not limited to individuals that have
small populations
 Depends on chance events of flower
pollination, seed falling on suitable
site, survival of fish or amphibian off
spring (remember Nemo, only he
survived out of 100!)
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Genetic bottlenecks
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Catastrophes, other chance events,
human activity sometimes reduce
population dramatically
– E.g. cheetahs population reduced a few
thousand years ago
– Elephant seal: hunting: by 1890 20
individuals, today very limited genetic
diversity.
Founder effect
Another type of genetic drift
 Caused when small population breaks
off and is reproductively isolated
 Founders genes only
 E.g. fruit flies on Pacific islands,
Icelandic cattle vs. Norwegian cattle
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Results
Small populations can suffer from
inbreeding depression
 Depressed fitness (fertility and
survival, leading to low lifetime
reproduction output)
 Due to mating between close relatives
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Results
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Out breeding depression
– Fitness down after out crossing between
genetically differentiated populations
– Example: planting same spp trees from
different location: dilutes local genetic
adaptation
– Ontario has seed zones to limit
movement of tree seed on public lands
Results
Genetic swamping: a form of out
breeding depression
 Large amount of genetic material from
closely related spp introduced by
humans
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Cutthroat trout
Rainbow trout
50/500 /5000Rule
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Soulé (1980) suggests:
Need a population of at least 50 to avoid
short term in breeding
Need 500+ to enable long term adaptability
and prevent reduction in evolutionary
potential (prevent loss due to genetic drift)
Need 5000+ to serve as reservoir for future
losses
Genetic terms
Gene: physical entities transmitted
from parent to offspring
 Genes made up two distinct types of
alleles
 Alleles=may be same or different
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– E.g. allele for tall T or short t
Genetic terms
If alleles same: homozygous (TT or tt)
 If alleles different: heterozygous (Tt)
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Locus= location
– Position on a gene, may contain may
alleles
Important features of
genetic diversity
P = proportion of loci with more than 1
allele
 A= No. of alleles at locus
 H = % of loci that are heterozygous
 Use electrophoresis to determine
these measures
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Use of genetic
measures
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Used to determine relatedness
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E.g. found that salmon along E coast have high
allelic differences
This means we should treat each river population
as separate management zones, not part of a
metapopulation
25% of returning salmon in Norway from hatcheries
Dilutes wild stock
Keep hatchery fish from escaping
Consider genetics when stocking
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Questions