Population Genetics III: Effective Population Size, Non-random Mating, Migration

Question 1

effective population size variable

Answer 1

Ne

Question 2

effection population size Ne

Answer 2

• the size of an idealized population in which the rate of genetic drift is the same as in the actual population
• Ne is usually less than the census N

Question 3

example of variation in the number of progeny

Answer 3

• Elephant Seals
• polygynous
• males establish narems
• a single bull male may get 77% of all the matings
• 6% of males get 88% of all matings

Question 4

Ne equation

Answer 4

Ne = 4 Nm Nf / Nm + Nf

Question 5

example of unequal numbers of males and females

Answer 5

if due to heavy hunting pressure, a population of deer has 100 females and 1 male

Question 6

when is Ne the highest?

Answer 6

when Nm = Nf

Question 7

variation of population size

Answer 7

Ne is the harmonic mean of the census population size through time

Question 8

equation: variation in population size

Answer 8

Ne = t / 1/Ne1 + 1/Ne2 + …. 1/Net

Question 9

example of variation in population size

Answer 9

• elephant seals
• 1890s: the population went through a severe bottleneck due to overhunting
• Ne approx 3.6
• no variation at 24 allozyme loci

Question 10

when does non-random mating occur?

Answer 10

when individuals mate assortatively

Question 11

example of non-random mating

Answer 11

if large females are more likely to mate with large males and vice versa

Question 12

is non-random mating a violation of HW?

Answer 12

yes

Question 13

inbreeding

Answer 13

the mating among genetic relatives, which is a form of nonrandom mating

Question 14

in what kind of populations is inbreeding a problem?

Answer 14

small populations

Question 15

where is inbreeding a serious concern?

Answer 15

conservation biology

Question 16

what is the genetic problem with inbreeding?

Answer 16

inbreeding increases homozygosity

Question 17

_______ frequencies change, _____ frequencies do not

Answer 17

genotype, alleles

Question 18

the difference between inbreeding and mate choice

Answer 18

inbreeding impacts the entire genome, whereas mate choice only impacts the loci that influence mate choice

Question 19

what if two distinct populations are mixed into a single sample?

Answer 19

you get the same signature as inbreeding: a deficit of heterozygotes and an excess of homozygotes

Question 20

Wahlund Effect

Answer 20

a deficit of heterozygotes and an excess of homozygotes

Question 21

coefficient of inbreeding

Answer 21

F

Question 22

F

Answer 22

the probability that 2 alleles are Identical by Descent

Question 23

Identical by Descent

Answer 23

• IBD
• both copies descended from the same ancestral allele in an earlier generation

Question 24

another name for alleles that are IBD

Answer 24

autozygous

Question 25

inbreeding can be quantified as the reduction in heterozygosity

Answer 25

F = Hexp - Hobs / Hexp = 1 - Hobs / Hexp

Question 26

1 - F

Answer 26

• the probability that two alleles are not IBD
• these individuals are called allozygous and can be either heterozygotes or homozygotes

Question 27

is F allozygous or autozygous?

Answer 27

autozygous alleles

Question 28

what type of equation when F=0

Answer 28

you have the normal equation

Question 29

by increasing the frequencies of homozygotes…

Answer 29

inbreeding increases the probability of homozygous deleterious alleles

Question 30

is inbreeding a problem in captive populations?

Answer 30

yes

Question 31

why is inbreeding prevalent in endangered populations?

Answer 31

endangered populations are often small, which results in inbreeding

Question 32

inbreeding avoidance

Answer 32

• mate choice
• dispersal from natal site
• self incompatibility loci in plants

Question 33

management of inbreeding avoidance

Answer 33

move individuals between populations to combat the decline in heterozygosity

Question 34

example of migration

Answer 34

• water snakes
• banded snakes are most fit on the mainland. unbanded are most fit on islands where the snakes bask in the open or on rocks
• exception: islands will have only unbanded snakes

Question 35

when will migration not change allele frequencies in a population?

Answer 35

when the equation m (pc - pi) = 0

Question 36

m

Answer 36

frequency of new migrants/generation

Question 37

pc

Answer 37

frequency of A allele in the mainland population

Question 38

pi

Answer 38

frequency of A allele in the islands population

Question 39

will the migration change the allele frequencies when m = 0 and when the frequency of the A allele is the same in both populations?

Answer 39

no

Question 40

impacts of gene flow

Answer 40

• homogenizes populations genetically
• decreases genetic variation between populations
• increases genetic variance within populations

Question 41

the effect of migration is ______ genetic drift

Answer 41

opposite

Question 42

in what direction does gene flow and selection work?

Answer 42

opposite directions

Question 43

population structure

Answer 43

the presence of allele frequency differences among populations

Question 44

population structure is due to several evolutionary processes, including:

Answer 44

• natural selection
• genetic drift
• founder effects
• gene flow
• mutation

Question 45

the most important consequence of population structure

Answer 45

a reduction in the average heterozygosity relative to that expected if all the subpopulations were a single, randomly-mating population

Question 46

what does population structure lead to?

Answer 46

loss of heterozygosity

Question 47

Hs

Answer 47

observed average heterozygosity

Question 48

Ht

Answer 48

expected heterozygosity

Question 49

little Fst

Answer 49

0.00-0.05

Question 50

moderate Fst

Answer 50

0.05-0.15

Question 51

great Fst

Answer 51

0.15-0.25

Question 52

very great Fst

Answer 52

0.25-1

Question 53

genetic drift

Answer 53

increases divergence among populations over time

Question 54

consequence of genetic drift

Answer 54

increase in Fst over time among populations

Question 55

does migration make population similar or different from each other?

Answer 55

more similar

Question 56

what will gene flow do in the absence of any other evolutionary processes?

Answer 56

completely homogenize subpopulations

Question 57

what does genetic drift increase?

Answer 57

divergence among populations over time

Question 58

island model

Answer 58

subpopulations of equal Ne with equal amounts of gene flow (m) between them