Conservation Genetics

Class 8

Presentation 3

Forces of evolution 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

Genes & Environment

Genotype + Environment = Phenotype

We see the phenotype: leaf shape, colour of hair, eyes, beak size, etc.

Value of diversity 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.

Examples of adaptive radiation

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

Darwin’s finches on Galapagos Islds Ancestor: ground dwelling, seed eater Today 14 spp

– Tree finches Adapted to feed on insects, sharper bill than ground

dwellers– Ground Dwellers

Beak size varies with food type Stronger bill suited for seeds

– Warbler finch 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.

Photo: NOAA

Mutation Rates 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. 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)– Now 500+ varieties

Corn (Zea mays)– Verities range from 0.6 to 6 m tall, 2-11

months to mature

Genetic effects on Populations

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!)

Genetic bottlenecks 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

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

Results 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

Rainbow troutCutthroat trout

50/500 /5000Rule 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

– E.g. allele for tall T or short t

Genetic terms If alleles same: homozygous (TT or tt) If alleles different: heterozygous (Tt)

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

Use of genetic measures Used to determine relatedness 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

Questions