HWE: Gene Flow - 9

Question 1

Define gene flow

Answer 1

movement of alleles between populations

Question 2

Define migration

Answer 2

movement of individuals in response to some kind of cue, may have gene flow. unidirectional (ex. seasonal, lack of resources, predation pressure)

Question 3

Define dispersal

Answer 3

movement of individuals or gametes (ex. dispersal)

Question 4

What are the two classical models of dispersal

Answer 4

1. stepping stone model
2. island model

Question 5

What are the two asymmetrical migration models

Answer 5

1. mainland-island model
2. metapopulation model

Question 6

Define stepping-stone model

Answer 6

a chain of islands within unsuitable habitat. movement is only seen between neighbouring patches, no migration occurs between NON-neighbouring patches

Question 7

Define island dispersal model

Answer 7

assumes all populations have the same number of individuals and equal migration rates. all patches can exchange with all patches.
(rarely the case)

Question 8

Define mainland-island model

Answer 8

one large mainland and one small island. migration is high from mainland to island and little to no movement in reverse. the migration has a high allele effect on the island and not so much on the mainland

Question 9

Define metapopulation model

Answer 9

similar to island model, but do not assume equal size and exchange rate. It involves one large metapopulation made of many subpopulations

Question 10

What is the rate of change proportional to in gene flow (4)

Answer 10

1. direction of gene flow
2. genotypes of migrants
3. population differences in allele frequencies
4. migration rate

Question 11

What is the effect of gene flow

Answer 11

Homogenizing effect = it prevents differentiation/ divergence between populations

Question 12

What does variable Fst mean

Answer 12

it measures the variability between populations. varies between 0-1
0 = high gene flow (populations are the same)
1 = fixed differences/ no gene flow

Question 13

What are the predictions in relation to variation and migration that would be seen in young vs. intermediate vs. old populations

Answer 13

young populations have high variation due to chance (ex. founder effect)
intermediate populations homogenous due to migration
old populations become structured and variation occurs due to random survival
young = most variation, then old, then intermediate

Question 14

Explain how Lake Erie water snakes display migration and selection acting against one another

Answer 14

some are banded and others are unbanded. the mainland had higher banded than the islands. on the islands it was an advantage (selection) to have unbanded to avoid predation, but would still see banded due to migration from the mainland to island

Question 15

What are the 3 strategies to measure dispersal

Answer 15

mark recapture
satellite tags
genetic markers

Question 16

Pros and Cons of mark recapture method

Answer 16

time consuming and has limited returns. doesn’t tell you where they have been and if contributed to gene flow

Question 17

Pros and Cons of satellite tags

Answer 17

Only can perform on small population size, limited time, and measures movement NOT migration

Question 18

Pros and Cons of genetic markers

Answer 18

(most commonly used)
gene flow in both directions may not be equal and results in a non-linear relationship between Fst and Nm