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Michaelmas Term 1 > Speciation II > Flashcards

Speciation II Flashcards

1
Q

What are the evolutionary forces involved in speciation?

A

Drift, gene flow, mutation, selection

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2
Q

Modes of speciation:

A

1) allopatry
2) peripatry
3) parapatry
4) sympatry

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3
Q

What types of empirical evidence do we collect to assess the speciation continuum?

A
  • palaeontology
  • biogeography
  • phylogenetics
  • genetics
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4
Q

Mutation

A

The ultimate source of genetic variation

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5
Q

Random genetic drift

A

Fluctuations in allele frequencies that occur by chance and can have particularly strong effects in small populations

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6
Q

Gene flow (gene migration)

A

Movement of alleles among populations

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7
Q

Random genetic drift and gene flow

A

Speed up or constrain development of adaptations, but cannot cause it

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8
Q

Natural selection

A
  • inherited differences in the ability of organisms to survive and reproduce
  • leads to adaptation
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9
Q

Vicariant allopatric selection

A
  • no gene flow
  • drift present
  • divergent selection in different habitats
  • different mutations fixed in similar environments
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10
Q

Peripatric allopatric speciation

A
  • no gene flow
  • strong drift in small population
  • divergent selection in novel habitat
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11
Q

Stepping stone parapatric speciation

A
  • limited gene flow among discrete populations
  • drift and selection more effective
  • selection for local environment
  • results in neighbouring sister species
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12
Q

Clines parapatric speciation

A
  • less limited gene flow along environmental cline
  • selection for local environment results in neighbouring sister species
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13
Q

Sympatric speciation

A
  • free gene flow
  • requires very strong divergent selection
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14
Q

For speciation to occur, you need some combination of

A

1) isolation
2) divergent selection

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15
Q

Why do you need isolation for speciation to occur?

A
  • reduce/stop gene flow
  • drift alone can cause speciation
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16
Q

Divergent selection can result in speciation even

A

In the face of gene flow

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17
Q

If there is no gene flow, the speciation is

A

Allopatric

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18
Q

Behavioural isolation can develop

A

quickly (e.g. 5 generations of Diptera fly)

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19
Q

Describe the speciation of snapping shrimp Alpheus

A
  • emergence of the Isthmus of Panama created barrier ~3Mya: separated marine life
  • different abiotic and biotic environments
  • créâtes sister species pairs either side of the Isthmus
  • strong reproductive isolation
  • mtDNA divergence
  • morphological divergence
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20
Q

Describe the case of Pinaroloxias inornata

A
  • sole representative of a genus on an island post-colonisation
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21
Q

If gene flow is low - medium, speciation is

A

Parapatric

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22
Q

If divergent selection is strong, the speciation is considered

A

Ecological

23
Q

Describe M. guttatus (Wright et al. 2013)

A
  • widespread
  • adjacent populations on copper line waste evolve copper tolerance
  • partial gene flow, strong selection
  • reproductive isolation: hybrid lethality
24
Q

It’s not an allopatry event but an allopatry

A

Phase

25
Q

What speeds up speciation?

A
  • selection against immigrants
  • selection against hybrid intermediates
  • reproductive isolation as a byproduct of ecological divergence
  • byproduct of adaptive divergence
26
Q

Give examples of adaptive divergence

A

1) different flowering times
2) different body sizes

27
Q

Give the criteria of sympatric speciation

A

1) species must be largely or completely sympatric
2) substantial reproductive isolation, preferably genetically based
3) sympatric taxa must be sister groups (not the result of hybridisation)
4) biogeographic and evolutionary history of the groups must make existence of an allopatric phase very unlikely

28
Q

Describe the Lord Howe island palms (Papadopulos 2011)

A
  • molecular based phylogenies differentiate between sympatric speciation and double colonisation
  • 4.5-8.2% of flora arose by sympatric speciation
  • 24.8% arose by allopatric speciation
  • the rest did not spéciate
29
Q

Why must double colonisation be ruled out

A

To ensure group is monophyletic

30
Q

Describe the speciation of the apple maggot fly Rhagoletis pomonella

A
  • sympatric speciation via host shift
  • from hawthorn to apple in New York State
  • only occurred once in last 150yrs
  • assortative mating
  • maladapted hybrids
  • genetic divergence between host races creating allozymes
31
Q

Describe the assortative mating R. Pomonella (Bush, 1969)

A
  • habitat preference: adults mate on the fruit they fed on as larvae
  • incomplete temporal isolation: apple fruits earlier than hawthorn
  • adaptation to respective hosts: which howl diapause length
32
Q

What are the cues for mate choice in Darwin’s finches?

A

Song and bill morphology

33
Q

Describe the “Big Bird” lineage (Lamichhaney, 2017)

A
  • began with G. fortis (resident) female and G. conirostris (immigrant) male
  • successful ingroup breeding occured (despite intense inbreeding)
  • reproductive isolation and ecological segregation occurs in 3 generations
34
Q

Polyploidy

A
  • Individuals carry 3 or more complete sets of chromosomes
  • common in plants, rare in animals
35
Q

An increase in chromosome sets can

A

Produce nearly instantaneous reproductive isolation

36
Q

What percentage of speciation events in ferns involve polyploidy?

A

7

37
Q

What percentage of speciation events in angiosperms involve polyploidy?

A

2-4

38
Q

Evolutionary inertia

A

Co-adapted gene complexes constrain further adaptation

39
Q

What events might break evolutionary inertia

A

Severe drift (e.g. during a founder event)

40
Q

True allopatry means

A

No gene flow

41
Q

At a global level, new variation can only be created by

A

Mutation

42
Q

At a local level, new variation can be created by

A

Migration, and mutation

43
Q

Drift shows

A

No directionality

44
Q

What changes evolutionary trajectory?

A

Interaction between different microevolutionary processes

45
Q

Drift is a divergence by

A

Chance

46
Q

Cline

A
  • gradation from one population to the other
  • isolation by distance
47
Q

True sympatry means

A

Completely congruous

48
Q

Theoretically,

A
  • drift can result in speciation alone
  • but reduced gene flow rlly helps
49
Q

Parapatric speciation occurs with

A

Relatively high frequency

50
Q

Ecotones

A

Two different vegetation forms come together and mix in a relatively narrow strip relative to the overall habitat size

51
Q

Reconstructing speciation is

A

Tricky

52
Q

Strong selection overcomes

A

Gene flow

53
Q

To be a ring species, you can’t have

A

Any deep biogeographic/vicariant breaks or an allopatric phase

54
Q

In a ring species, rather than flowing, genes

A

‘Trickle’

Michaelmas Term 1 (42 decks)

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