Post on 17-Dec-2015
Announcements1. Writing assignments due Friday November 2nd by 11am
• One digital copy per group to turnitin.com• One hard copy per group to SW551• One ‘equal work-load assessment’ per person to SW551• see guidelines on Blackboard/course materials
2. Video 2 will be posted on weboption by Monday.‘Evolution: The Eternal Arms Race’
3.Office hours this week Today 11am – noon (AC254)—all questions welcome…Wednesday, 1pm – 2pm (SW551)--assignment questions ONLYFriday, 11am – noon (virtual)– all questions welcome…
For rest of term: AC254: Tues. 11am – noon; Thurs. 2pm – 3pm
Virtual: Friday 11am to noon
1. Migration
2. Genetic Drift
3. Non-random mating
4. Case studies
Lecture 13 & 14Migration, Drift & Non-random mating
Conservation genetics of the Greater Prairie Chicken (p.223 – 225; 273-275)
Example1: Migration, Drift & Inbreeding
Greater Prairie Chicken mating display
http://www.youtube.com/watch?v=s2_wdMmEupQ
Conservation genetics of greater prairie chicken
Popsize
1810-1820
2,000
76
1837Steel plow
Intensive farming
Year
Millions
25,000
500
<50
1933
1962
1990
1972
1994
Conservation genetics of greater prairie chicken
Popsize
1810-1820
2,000
76
1837Steel plow
Intensive farming
Year
Millions
25,000
500
<50
Hunting ban
1933
1962
1990
1972
1994
Jasper Sanctuary
Marion Sanctuary
Only 2 populations(Jasper & Marion)
Extirpated in its Canadian range (Alberta, Saskatchewan, Manitoba, Ontario).
Conservation genetics of greater prairie chicken
Fig. 7.3. Males displaying on leks
Despite hunting ban and increase in protected habitat, populations continued to decline
Why?
Hunting ban
Jasper Sanctuary
Marion Sanctuary
Conservation genetics of greater prairie chicken
What is the effect of habitat destruction?
1. Reduction in
population size= individuals living in disturbed habitats die without reproducing
2. Habitat
fragmentation= suitable habitat like
islands in sea of unsuitable habitat
Small populations No migration (no gene flow)
Conservation genetics of greater prairie chicken
What violations of H-W are likely in these populations?
1. Reduction in
population size
2. Habitat
fragmentation
Small populations No migration
Genetic Drift
Non-random mating (inbreeding)
Conservation genetics of greater prairie chicken
How does this affect genetics of the remaining populations?
1. Reduction in
population size
2. Habitat
fragmentation
A. Random fixation of alleles = decreased genetic diversity
Small populations No migration
Genetic Drift
Non-random mating (inbreeding)
Conservation genetics of greater prairie chicken
How does this affect genetics of the remaining populations?
2. Habitat
fragmentation
Small populations No migration
Genetic Drift
Non-random mating (inbreeding)
B. Decreased Heterozygosity/ increased homozygosity• Increased expression of deleterious recessive alleles• Loss of any heterozygote advantage
1. Reduction in
population size
Conservation genetics of greater prairie chicken
How does this affect fitness of remaining populations?
2. Habitat
fragmentation
Small populations No migration
Genetic Drift
Non-random mating (inbreeding)
Decreased fitness
1. Reduction in
population size
Conservation genetics of greater prairie chicken
What is fitness?
What is decreased fitness?
1. Direct reduction in
population size
2. Habitat
fragmentation
Small populations No migration
Genetic Drift
Non-random mating (inbreeding)
Decreased fitness
Conservation genetics of greater prairie chicken
Extinction Vortex!= Downward spiral in population size and vigour
• caused by combination of factors: •environmental
•(habitat fragmentation)•demographic
•(population size)•genetic
•(inbreeding depression, random fixation of alleles )
Conservation genetics of greater prairie chicken
Despite hunting ban and increase in protected habitat, populations continue to decline
Why?
Hunting ban
Jasper Sanctuary
Marion Sanctuary
Fig. 7.3. Males displaying on leks
Extinction Vortex explains
population decline?
Conservation genetics of greater prairie chicken
Extinction Vortex explains population decline?
Prediction 1: evidence of inbreeding depression
% eggs hatched
YES
Fig 7.31
Extinction Vortex explains population decline?Extinction Vortex a plausible hypothesis
Conservation genetics of greater prairie chicken
Prediction 2: current Illinois populations = lower genetic diversity than past populations or larger populations
From Table 7.6
YES
Mean # alleles per locus
S.E.
Conservation genetics of greater prairie chicken
According to our model, what could reverse the decline?
1. Direct reduction in
population size
2. Habitat
fragmentation
Small populations No migration
Genetic Drift
Non-random mating (inbreeding)
Decreased fitness
Conservation genetics of greater prairie chicken
Here’s what they did….
1992 onwards: (MIGRATION)Trapped chickens in Minnesota, Nebraska &
Kansas and moved them to Illinois
Conservation genetics of greater prairie chicken
Here’s the result….
% eggs hatched
Fig 7.31. Egg hatching success
Conservation genetics of greater prairie chicken
Here’s the result….
Fig. 7.3. Males displaying on leks
# males displaying
Conservation Genetics
Example 2: Migration, Drift & Inbreeding
Know this example: p. 230-232
Skeppsvik archipelago•Dozens of islands, varying ages
Red Bladder campion•Early colonizer•By: Seed dispersal, pollinators•Eventually:
• loses competition• Pollinator-borne-disease
Recap: Consider how the 4 evolutionary mechanisms affect:
•The direction of change in allele frequencies
•The rate of evolutionary change
•Equilibrium values of allele frequencies
•Adaptation to local conditions
•Levels of genetic variation in the population (potential for future change)
Next week:
Case study:Can Evolutionary biology help us understand
and fight AIDS?
1. Biology of HIV
2. Why do HIV treatments fail?
3. Why is HIV fatal?A. Natural selection within hostsB. Transmission rate hypothesisC. Evolved resistance?
Lecture 15 & 16. Case study in Evolution: HIV
Worldwide distribution of HIV infections
• HIV: Human Immunodeficiency virus• AIDS: Acquired Immune Deficiency Syndrome, caused by HIV
(Fig 1.1)
• AIDS accounts for 4.9% of deaths worldwide (>TB, >malaria, >car accidents, >homicides >wars)
1. Biology of HIV
HIV = human immunodeficiency virus = retrovirus (RNA)HIV virion
HIV = human immunodeficiency virus = retrovirus (RNA)
*
*Epitopesviral proteins, displayed on
surface of virion or infected cell
*
1. HIV virion(extracellular stage)
2. HIV gp120 binds to host cell membrane
at CD-4 protein 3. HIV’s RNA,reverse transcriptase, protease & integrase
enter host cell
4. Reverse transcription:
HIV DNA from HIV RNA
5. HIV’s integrase splices HIV DNA into host genome. Host’s
RNA polymerase transcribes HIV mRNA.6. HIV mRNA translated
by host ribosomes to HIV protein, HIV
protease modifies proteins 7. New virions
assemble in host cell
8. New virionsbud from host cell
membrane
CD-4 protein(host membrane)
Co-receptor(host membrane)
1
23
4
56
78
(Fig. 1.5)
1) infect other cells in the same host
2) are passed to new hosts via body fluidse.g., Oral, anal, or vaginal sex, intravenous drug use, childbirth, breast feeding
New virions:
Two levels of selection affect HIV evolution:
1) Selection inside the body of each host (rapid replication favoured)
2) Selection across the population of hosts (maximum spread among hosts favoured)
HIV infects cells with CD-4 surface proteins
How does HIV make you sick?
•Helper T-cells
b) Triggers antibody formation
a) Helps activate killer T-cells
Recognizes foreign proteins (e.g., epitopes)
Immune system function
How does HIV make you sick?
1. HIV kills helper T-cells directly
2. Host’s body destroys infected helperT-cells
Reduction in # of helper T-cells:
•Eventual collapse of immune system•(= AIDS, ~8 years post-infection)
•Opportunistic infections•Death (without treatment, within 2 years of developing AIDS)
How does HIV make you sick?
Host is largely asymptomatic during chronic phase, but
immune system is very active
Immune system
collapses