Dispersal and Non-Random Mating Flashcards
Define dispersal.
Dispersal is the movement of individuals from one population to another population.
Define gene flow.
Gene flow is the movement of alleles from one population to another population.
Define migration.
Migration – mass movement of individuals.
Does dispersal = gene flow?
Yes so long as the dispersing individual survives to reproduce.
What are the two conclusions regarding gene flow and its effects on populations?
Conclusion 1: In the absence of gene flow, two populations will remain genetically diverged
Conclusion 2: In the presence of gene flow genetic divergence between populations will decrease
In other words, gene flow homogenizes populations
How does low gene flow impact evolution?
Can rescue inbred populations
How does moderate gene flow impact populations?
A source of genetic variation, increase rate of evolution by natural selection
How does high gene flow impact populations?
Swamps out existing variation, whether adaptive or not
In what areas might gene flow be important?
Conservation of rare species
Invasive species
Genetically modified organisms
How can gene flow be beneficial and harmful to rare species conservation?
Good: rescue endangered species
Bad: genetically pollute endemic species
What does this equation represent? Define all variables.
pi1 = frequency of allele A1 on the island after one generation
m = fraction of breeding individuals on island that came from the mainland
pc0 = initial frequency of allele A1 on the mainland
(1-m) = fraction of breeding individuals on the island who were originally from the island
pi0 = initial frequency of allele A1 on the island
According to this equation, when will pi be at equilibrium?
Equilibrium by definition is the point at which an allele does not change in frequency.
Thus, at equilibrium, the above equation will = 0.
pi will reach equilibrium when m = 0 (i.e., no dispersal) or when pc0 and pi0 are equal.
Define negative assortative mating.
mating between individuals that are phenotypically or genetically dissimilar to one another.
How does negative assortative mating affect heterozygosity?
Increases heterozygosity at alleles associated with the phenotype that individuals cue into when choosing mates
How does negative assortative mating maintain genetic variation?
Via negative frequency-dependent selection
Give an example of negative assortative mating.
white-throated sparrow
o 96% of all matings are between morph types
Define positive assortative mating.
mating between individuals that are phenotypically similar to one another.
How does positive assortative mating affect heterozygosity?
- decreases heterozygosity at alleles associated with phenotypes correlated with mate choice
What mechanisms can positive assortative mating impact?
- Can cause divergent selection and be important in speciation
What is the most common form of positive assortative mating?
Inbreeding
When is inbreeding inevitable?
In small populations
How does inbreeding impact heterozygosity?
Decreases heterozygosity
By how much per generation does exclusive selfing decreasing heterozyogsity?
50%`
How does inbreeding affect allele frequencies? Genotype frequencies?
Inbreeding causes no change in allele frequencies, but it does cause a change in genotype frequencies
What are the fitness consequences of inbreeding? (2)
Increased homozygosity increases the likelihood that recessive deleterious alleles will be expressed in completely or partially inbreeding individuals
Inbred individuals have lower fitness
Define inbreeding depression.
The phenomenon when progeny produced via inbreeding have lower fitness than progeny produced by outcrossing
