Lecture 19 Speciation 2 Flashcards

1
Q

Two ways to disrupt gene flow

A

Reproductive isolation (intrinsic) and geographic isolation (extrinsic)

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2
Q

Disrupting gene flow normally occurs in a 3 step process

A

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

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3
Q

Allopatric

A

Gap between population’s

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4
Q

Peripatric

A

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

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5
Q

Parapatric

A

Non-overlapping without gap

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6
Q

sympatric

A

overlapping

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7
Q

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

A

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

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8
Q

Two types of divergence of interest

A

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

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9
Q

Divergence is typically a

A

Slow process of accumulating differences

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10
Q

Types of divergence (3)

A

Local adaptation
Sexual Selection
Drift

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11
Q

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

A

Drift or selection while populations are isolated

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12
Q

Types of isolating mechanisms

A

Prezygotic (premating)
Postzygotic (postmating)

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13
Q

Types of prezygotic mechanisms

A

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

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14
Q

Temporal or habitat isolation

A

Mates do not meet when reproductive

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15
Q

Behavioral or sexual isolation

A

Mates meet but do not choose the mate

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16
Q

Mechanical isolation

A

Mating occurs, but gamete are not transferred

17
Q

Gametic incompatibility

A

Chemical differences between species preventing fertilization

18
Q

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

A

And more investment from parents

19
Q

Postzygotic mechanisms

A

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

20
Q

Hybrid inviability

A

F1 has reduced survival (severe survival maladaptation

21
Q

Hybrid sterility

A

F1 viable but reduced fertility (sterile)

22
Q

Hybrid breakdown

A

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

23
Q

Reinforcement

A

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)

24
Q

Prezygotic isolating mechanisms evolve much faster in

A

Sympatric species than allopatric species

25
Instantaneous isolating mechanisms
Chromosomal rearrangements Polyploidy Hybridization (More common in plants)
26
Chromosomal rearrangements
Disrupts pairing during meiosis Can be instantaneous with some translocations or inversions or gradual after several fusions/fissions