Notes 2

Question 1

Most common mode of speciation

Answer 1

Allopatric

Question 2

Allopatric speciation

Answer 2

incipient species separated by some geographical barrier of unfavorable habitat

Question 3

How does RI evolve?

Answer 3

Neutral processes and/or natural selection

Question 4

Evidence for allopatric speciation…

Answer 4

1. The degree of isolation is positively correlated with genetic distance in dusky salamanders
2. There’s a shared geogrpahic split among many species paris associated with a barrier

Question 5

Changing environmental conditions that can cause a geographic barrier (2)

Answer 5

1. rise of isthmus of Panama

2. climate warming or cooling

Question 6

Drift

Answer 6

random accumulation of neutral differences within species leads to DMIs

Question 7

Natural selection

Answer 7

not selection for RI, but selection OF Ri as a consequence of ecological/sexual selection

Question 8

Ecological speciation

Answer 8

evolution of RI as a biproduct of divergent ecological selection

Question 9

Example of ecological speciation (2)

Answer 9

1. Sticklebacks either live in open water or bottom feeding. Hybrids between the two have low probablility of spawning.
2. Timema have different walking sticks that make each more cryptic on its own plant.

Question 10

Example of RI due to sexual selection

Answer 10

Drosophila females mate strongly on wing pattern which leads to speciation.

Question 11

What leads to higher speciation?

Answer 11

strong sexual selection and mate choice

Question 12

Reinforcement

Answer 12

selection for premating RI directly rather than selection of RI as a side effect

Question 13

Evidence for reinforcement

Answer 13

Premating RI is higher when species are sympatric than when they’re allopatric.
Females choose brown pied fly catcher instead of the black one in sympatry since the black ones look lke collared flycatchers.

Question 14

Why does reinforcement focus on premating RI?

Answer 14

1. Postyzygotic RI would mean that natural selection selects for an increase of alleles that decrease fitness, which doesn’t happen.
2. Premating only requires alleles that increase preference to increase in frequency

Question 15

Peripatric speciation

Answer 15

Part of allopatric speciation in which a very small population buds off from the ancestral one
Also called founder effect

Question 16

How does peripatric speciation go to RI?

Answer 16

Combination of natural selection and strong genetic drift in smaller populations

Question 17

Why is there little evidence for peripatric speciation?

Answer 17

It would happen so fast and be geographically localized that intermediates are unlikely to be in the fossil record.