Dispersal and Non-Random Mating

Question 1

Define dispersal.

Answer 1

Dispersal is the movement of individuals from one population to another population.

Question 2

Define gene flow.

Answer 2

Gene flow is the movement of alleles from one population to another population.

Question 3

Define migration.

Answer 3

Migration – mass movement of individuals.

Question 4

Does dispersal = gene flow?

Answer 4

Yes so long as the dispersing individual survives to reproduce.

Question 5

What are the two conclusions regarding gene flow and its effects on populations?

Answer 5

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

Question 6

How does low gene flow impact evolution?

Answer 6

Can rescue inbred populations

Question 7

How does moderate gene flow impact populations?

Answer 7

A source of genetic variation, increase rate of evolution by natural selection

Question 8

How does high gene flow impact populations?

Answer 8

Swamps out existing variation, whether adaptive or not

Question 9

In what areas might gene flow be important?

Answer 9

Conservation of rare species
Invasive species
Genetically modified organisms

Question 10

How can gene flow be beneficial and harmful to rare species conservation?

Answer 10

Good: rescue endangered species
Bad: genetically pollute endemic species

Question 11

What does this equation represent? Define all variables.

Answer 11

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

Question 12

According to this equation, when will pi be at equilibrium?

Answer 12

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.

Question 13

Define negative assortative mating.

Answer 13

mating between individuals that are phenotypically or genetically dissimilar to one another.

Question 14

How does negative assortative mating affect heterozygosity?

Answer 14

Increases heterozygosity at alleles associated with the phenotype that individuals cue into when choosing mates

Question 15

How does negative assortative mating maintain genetic variation?

Answer 15

Via negative frequency-dependent selection

Question 16

Give an example of negative assortative mating.

Answer 16

white-throated sparrow
o 96% of all matings are between morph types

Question 17

Define positive assortative mating.

Answer 17

mating between individuals that are phenotypically similar to one another.

Question 18

How does positive assortative mating affect heterozygosity?

Answer 18

• decreases heterozygosity at alleles associated with phenotypes correlated with mate choice

Question 19

What mechanisms can positive assortative mating impact?

Answer 19

• Can cause divergent selection and be important in speciation

Question 20

What is the most common form of positive assortative mating?

Answer 20

Inbreeding

Question 21

When is inbreeding inevitable?

Answer 21

In small populations

Question 22

How does inbreeding impact heterozygosity?

Answer 22

Decreases heterozygosity

Question 23

By how much per generation does exclusive selfing decreasing heterozyogsity?

Answer 23

50%`

Question 24

How does inbreeding affect allele frequencies? Genotype frequencies?

Answer 24

Inbreeding causes no change in allele frequencies, but it does cause a change in genotype frequencies

Question 25

What are the fitness consequences of inbreeding? (2)

Answer 25

Increased homozygosity increases the likelihood that recessive deleterious alleles will be expressed in completely or partially inbreeding individuals
Inbred individuals have lower fitness

Question 26

Define inbreeding depression.

Answer 26

The phenomenon when progeny produced via inbreeding have lower fitness than progeny produced by outcrossing