Final Week: Lec 2 Flashcards
What is the extinction vortex?
as a population is reduced, it becomes even more susceptible to extinction through:
- genetic drift
- weaker selection
- inbreeding
- loss of gene flow
Why is understanding tasmanian devil adaptive genes important for their conservation?
- measuring their resistance to transmissible cancer can inform reintroduction
How might some populations exist for thousands of years with little genetic variation?
Phenotypic plasticity!
- ex. channel island fox
What is phenotypic plasticity?
when different phenotypes are generated from the same genome through differential gene expression or epigenetic mechanisms
What can we sequence to measure phenotypic plasticity?
RNA
What does inbreeding affect?
- genotype frequencies (not allele frequencies)
F = (He-Ho)/He
What increases the odds of individuals being identical by descent?
inbreeding
(increasing homozygosity)
What factor is inversely proportional to inbreeding and genetic drift?
Ne
What equation is used to find loss of heterozygosity over time?
Ht/Ho = [1-(1/2Ne)]^t
What is an inbreeding depression?
when inbreeding leads to a reduction in fitness
What 2 factors cause inbreeding depression?
- accumulation of deleterious homozygous recessive alleles
- Loss of heterozygote advantage/overdominance
How might inbreeding depressions be expressed?
- obvious maladaptive traits (blindness, bone deformity, etc)
- subtle traits (weak immune systems, metabolic stress, etc)
What process can prevent inbreeding depression?
purging
what is purging?
when deleterious alleles become homozygous, they are exposed to selection and removed from the population
When is purging most effective?
- on lethal inbreeding depression
- purging is weak on mildly maladaptive traits
Why is purging weaker in smaller populations?
Because s < 1/4Ne
What is genetic rescue?
translocation of individuals to the isolated population to increase gene flow and decrease inbreeding depression
How can genetic rescue increase fitness?
- heterosis (hybrid vigor)
- heterozygote advantage (overdominance) increases
- deleterious alleles are masked
How did genetic rescue affect the Scandinavian arctic fox?
translocating just 3 outbred males led to:
- reduced F
- higher juvenile survival
- higher breeding success
- higher population size and allelic richness
How did genetic rescue impact the Florida panther?
introduced 8 females of texas cougars
- population increased
- reduced inbreeding depression
Why is the Florida panther still critically endangered?
- habitat is still greatly reduced and fragmented
- large mammal, needs lots of space (corridors are very important)
