Lecture 19 Speciation 2

Question 1

Two ways to disrupt gene flow

Answer 1

Reproductive isolation (intrinsic) and geographic isolation (extrinsic)

Question 2

Disrupting gene flow normally occurs in a 3 step process

Answer 2

1) Isolation of populations (reduce gene flow)
2) divergence of populations (selection/drift)
3) evolution of reproductive barriers

Question 3

Allopatric

Answer 3

Gap between population’s

Question 4

Peripatric

Answer 4

Peripheral isolate; extreme case; Isolate’s outside main range and no gene flow after

Question 5

Parapatric

Answer 5

Non-overlapping without gap

Question 6

sympatric

Answer 6

overlapping

Question 7

Some species should be in intermediate stages of formation. How often do we see them and what do they look like?

Answer 7

Many species are found in mid-process, making it difficult to decide on the number of species

Question 8

Two types of divergence of interest

Answer 8

1) Divergence that has no effect on ability to interbreed
2) Divergence that does

Question 9

Divergence is typically a

Answer 9

Slow process of accumulating differences

Question 10

Types of divergence (3)

Answer 10

Local adaptation
Sexual Selection
Drift

Question 11

Some divergence in characters affecting the ability to interbreed can occur due to

Answer 11

Drift or selection while populations are isolated

Question 12

Types of isolating mechanisms

Answer 12

Prezygotic (premating)
Postzygotic (postmating)

Question 13

Types of prezygotic mechanisms

Answer 13

Temporal or habitat isolation
Behavioral or sexual isolation
Mechanical isolation
Gametic incompatibility

Question 14

Temporal or habitat isolation

Answer 14

Mates do not meet when reproductive

Question 15

Behavioral or sexual isolation

Answer 15

Mates meet but do not choose the mate

Question 16

Mechanical isolation

Answer 16

Mating occurs, but gamete are not transferred

Question 17

Gametic incompatibility

Answer 17

Chemical differences between species preventing fertilization

Question 18

As you move along the two scales (pre-post zygotic) there is

Answer 18

And more investment from parents

Question 19

Postzygotic mechanisms

Answer 19

Zygote mortality (zygote dies)
Hybrid inviability
Hybrid sterility
Hybrid breakdown

Question 20

Hybrid inviability

Answer 20

F1 has reduced survival (severe survival maladaptation

Question 21

Hybrid sterility

Answer 21

F1 viable but reduced fertility (sterile)

Question 22

Hybrid breakdown

Answer 22

Reduced viability or fertility in F2 or backcross (selective effects isn’t perceived until generation or two later)

Question 23

Reinforcement

Answer 23

The process by which selection acts to reduce interbreeding by assortative mating so as to decrease the formation of hybrids
(Evolution of pre-zygotic elements when post-zygotic mechanisms occur)

Question 24

Prezygotic isolating mechanisms evolve much faster in

Answer 24

Sympatric species than allopatric species

Question 25

Instantaneous isolating mechanisms

Answer 25

Chromosomal rearrangements
Polyploidy
Hybridization (More common in plants)

Question 26

Chromosomal rearrangements

Answer 26

Disrupts pairing during meiosis
Can be instantaneous with some translocations or inversions or gradual after several fusions/fissions