Lecture 9: Conservation genetics

Question 1

The 6th Extinction

Answer 1

Geological records show there have been 5 mass extinctions. Currently witnessing the 6th mass extinction. Human activities are to blame: habitat destruction/fragmentation/poaching/hunting.

Question 2

Habitat destruction -

Answer 2

biggest threat. Causes populations to become small and geographically isolated.

Question 3

Genetic drift…

Answer 3

the process of losing genetic variation by chance.

Question 4

What genetic drift governed by?

Answer 4

population size:

• loss of genetic variation by drift is faster in small populations
• Small populations tend to be less polymorphic

Question 5

Genetic drift can play an important role in..

Answer 5

Evolution

Question 6

Northern and Southern elephant seals

Answer 6

Northern elephant seal: once abundant, but heavily exploited, almost went extinction by 1900.
southern elephant seal: exploited, however always abundant.

Question 7

Genetic variation in the Northern Elephant seal

Answer 7

-Hunting ceased in 1884
-one population survived -Isla Guadalupe
-possibly 20-30 individuals. Maybe only 1 breeding male.
This severe bottleneck has led to a decline in variation.

Question 8

The Mauritius Kestrel (bird)

Answer 8

Native forest destruction and DDT insecticide usage (1940s) caused a decline in population size.

1974. Only four left; breeding from a singe pair
1975. 400-500 birds

Question 9

Small populations do have..

Answer 9

less genetic variation (northern elephant seals, Mauritius kestrel)

Question 10

Populations that are small in size or lac genetic variation are…

Answer 10

less capable of evolving in response to new challenges (high extinction risk) e.g. genetically homogenous host populations are more vulnerable to infection than genetically diverse populations

Question 11

monoculture effect means

Answer 11

genetically homogenous host populations are more vulnerable to infection than genetically diverse populations

Question 12

Inbreeding:

Answer 12

mating between close relatives. In small populations there are fewer potential mates. Therefore the probability of mating with relatives increases.

Question 13

when are two alleles IDENTICAL BY DECENT (ibd)

Answer 13

if they trace their ancestry back to the same ancestral allele

Question 14

Wrights inbreeding coefficient (f)

Answer 14

The standard measure of the degree of inbreeding of an individual. Developed by Sewall Wright (1922)

Question 15

The greater the value of f (wrights inbreeding coefficient) means

Answer 15

the more inbred

Question 16

do inbred or outcrossed progeny have higher f values?

Answer 16

INBRED progeny. If ibd the individual must be homozygous at the locus

Question 17

homo or heterozygosity frequencies higher in inbred populations?

Answer 17

HOMOZYGOSITY.

• reveal recessive deleterious alleles (e.g. cystic fibrosis)
• Less likely to benefit from heterozygote advantage (e.g. kuru)

Question 18

Inbred progeny often suffer from…

Answer 18

INBREEDING DEPRESSION (less fit than outcrossed progeny)

Question 19

Small, isolated populations are particularly vulnerable to

Answer 19

• loss of genetic variation due to genetic drift
• inbreeding depression
• these often lead to lowered evolutionary potential, compromised reproductive fitness and elevated extinction

Question 20

Captive breeding programmes and e.g.

Answer 20

For endangered species. Populations are inevitably small. Some inbreeding may be unavoidable.
-Californian condor

Question 21

California condor:

Answer 21

Largest bird in North America.
Captive breeding programme based on last 27 birds in the world.
Now 150-200, some returned to the wild. However, recessive lethal allele has reached high freq (p=0.17) Homozygous birds suffer from CHONDRODYSTROPHIC DWARFISM (die at hatching)
Breeding programs avoid hetero carriers mating or 1/4 would die.

Question 22

Florida Panther:

Answer 22

Once down to a pop of 60-70 in Southern Florida. Road kill main cause of morality. Culverts under highways have reduced the problem. REMAINING PROBLEM: persistent inbreeding means that most males suffer CRYPTORCHIDISM (undescended testes) Poor sperm quality.
SOLUTION: introduce 6-8 females from close related subspecies in Texas. 32 surviving progeny

Question 23

example of bad recovery programme:

Answer 23

KOALAS Cause: A succession of bottlenecks

Question 24

Amish people of North America

Answer 24

Isolated human populations and disease:

• small founder population from Rhineland, Germany.
• marriage outside the community is forbidden
• excellent genealogical records - pedigrees used to understand inheritance.
• high incidence of some disorders e..g Ellis-van Creveld syndrome
• Amish collaborated with geneticists & the gene was discovered in 2000

Question 25

Gene mapping in the Finnish population

Answer 25

• Geographically remote
• Small founder population and several bottlenecks
• Uralic language - barrier to immigration and admixture
• some genetic diseases are virtually absent (CF)
• others ~30 at quite high freq and well characterised
• Good genealogical records

Question 26

Genetic drift…

Answer 26

the random loss of genetic variation

Question 27

Genetic variation is lost quickest in …

Answer 27

small populations

Question 28

Loss of genetic variation appears to affect

Answer 28

extinction tisk

Question 29

inbreeding is more likely in

Answer 29

smaller populations

Question 30

inbreeding is measured by

Answer 30

the inbreeding coefficient (f)

Question 31

inbreeding depression is the

Answer 31

reduction in fitness due to inbreeding

Question 32

conservation genetics aims to

Answer 32

reduce the loss of genetic variation & avoid inbreeding

Question 33

Isolated human populations have high

Answer 33

incidence of some genetic diseases & can be used to map disease genes