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EVOLUTION > Speciation (6) > Flashcards

Speciation (6) Flashcards

1
Q

Speciation?

A

= formation of a new species.

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2
Q

Eg of speciation?

A

Darwin’s finches/ Darwin’s ground finches.

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3
Q

How do finches recognize their own species? (2)

A

• Song.
• Morphology.

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4
Q

Causes of speciation in Darwin’s finches? (2)

A

• Adaptive divergence in resource exploiting traits.
• Divergence in courtship song (SMRS).

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5
Q

In the scenario, what happened for species to form/How did speciation happen? (6)

A

Separation
|
No gene flow
|
NS acting
|
Reproductive isolation (eg change in SMRS)
|
No mating if/when they meet
|
Two distinct species arise

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6
Q

Organisms used in scenario?

A

Fruit flies (Drosophila melanogaster).

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7
Q

Things to note in the co-occurring species of Geospiza? (2)

A

• Beak size & body size.
• Songs.

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8
Q

How does reproductive isolation evolve/Through what? (2)

A

• Ecological adaptation in allopatric populations.
• Ecological adaptation in sympatry (together).

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9
Q

Explain the 1st way that RI evolves?

A

Seen in beak size & some degree of differentiation in cursive for mate choice.

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10
Q

How does RI originate?

A

As a by-product of adaptive differentiation.

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11
Q

Modes of speciation? (2)

A

• Allopatric speciation.
• Non-allopatric speciation.

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12
Q

Allopatric speciation?

A

= speciation where populations are geographically separated.

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13
Q

Allopatric speciation types? (2)

A

• Vicariant speciation.
• Peripatric speciation.

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14
Q

Vicariant speciation?

A

= Geographical isolation due to a barrier forming.

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15
Q

Vicariant speciation attributes? (4)

A

• Prevents dispersal & gene flow.
• Complete geographic separation.
• Separation from a widespread ancestral population.
• Phylogeny reflects speciation patterns.

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16
Q

Egs of Geographic barriers in Vicariant speciation? (5)

A

• Uplifting of mountains.
• Continental drift.
• Environmental changes (desertification).
• Changes in river courses.
• Man-made structures.

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17
Q

Peripatric speciation?

A

= small isolated population that is usually on the periphery of larger ancestral species gives rise to a distinct species.

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18
Q

Peripatric speciation is AKA?

A

Founder effect.

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19
Q

Peripatric speciation attributes? (2)

A

• Active dispersal occurs in an area not previously occupied by the species.
• Different allele frequency in the founder population compared to original population.

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20
Q

Eg of Peripatric speciation?

A

Giant lizard Gallotia in the Canary islands.
- disperses from island to island.

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21
Q

What happens if separated populations come into contact after removal of a barrier if they were reproductively isolated? (2)

A

• No mating.
OR
• No viable offspring.

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22
Q

What happens if separated populations come into contact after removal of a barrier if they were not completely reproductively isolated? (2)

A

• Sterile/Inviable/Less fit hybrids, causing lower rates of survival.
• May form a secondary hybrid zone.

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23
Q

Non-allopatric speciation?

A

= speciation that is initiated when there’s incomplete geographic separation of two or more populations of the original population.

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24
Q

Non-allopatric speciation in general?

A

= speciation where populations are not geographically separated.

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25
Q

Non-allopatric speciation attributes? (2)

A

• Gene flow continues to occur between population, yet there is divergence.
• Limited gene flow.

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26
Q

What happens to the gene flow in Non-allopatric speciation?

A

Limited but continues to occur between populations, yet there’s divergence.

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27
Q

Non-allopatric speciation types? (2)

A

• Parapatric speciation.
• Sympatric speciation.

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28
Q

Parapatric speciation?

A

= populations occur in adjacent regions with different selective pressures (eg in an ecological cline).

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29
Q

Parapatric speciation attributes? (7)

A

• Gene flow occurs, but hybrids are less well adapted in either habitat (less fit).
• No extrinsic barrier to gene flow.
• Non-random mating occurs (positive assortative mating).
• NS > Gene flow.
• Reduced gene flow.
• Reduced heterozygote/hybrid fitness.
• Steady genetic divergence.

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30
Q

Why is NS > Gene flow in Parapatric speciation? (2)

A

• Abrupt environmental gradient.
• Disruptive selection occurs.

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31
Q

Egs of abrupt environmental gradients? (2)

A

• Altitude.
• Seasonality.

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32
Q

Sympatric speciation?

A

= occurs when one or more new species arise without geographic segregation of populations.

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33
Q

Sympatric speciation attributes? (8)

A

• Populations co-occur.
• Organisms live in the same area.
• Ecological isolation.
• Strong disruptive selection due to ecological isolation.
• Reduced gene flow.
• Difficult to prove.
• Linked to mate selection (assortative mating).
• Hybrids have lower fitness.

34
Q

What does Sympatric speciation deal with?

A

Deals with how long it will take for gene flow to decrease.

35
Q

Categories of Sympatric speciation? (3)

A

• Temporal isolation.
• Behavioural isolation.
• Polyploidy.

36
Q

Temporal isolation?

A

= isolation that prevents species from interbreeding due to differences in the timing of mating or fertility.

37
Q

Behavioural isolation?

A

= isolation that prevents species from interbreeding due to a difference in mating rituals or behaviors.

38
Q

Polyploidy?

A

= where a completely different form of species can be formed that does not bear the identity of both of the parents.

39
Q

Result of Polyploidy?

A

Increases genome size.

40
Q

Egs of Sympatric speciation? (3)

A

• Flower forms with different pollinators.
• Maggot flies on Apples & Hawthorns.
• Cichlid fish.

41
Q

Driver of speciation in plants?

A

Pollinator-mediated selection.

42
Q

Main separation by what in Pollinator-mediated selection?

A

Separation by altitude.

43
Q

Speciation patterns in Cichlid fish? (3)

A

• High levels of endemicity.
• Have radiated in endemicity.
• Visually-orientated.

44
Q

How does Cichlid being visually orientated benefit them? (2)

A

• Good for mating.
• Good for recognition of mates.

45
Q

How are Cichlid fish an eg of Sympatric speciation?

A

Via them living at different lake depths, causing them to have different diets & therefore, different mouth shapes (NS) & speciation occurring due to SS.

46
Q

Why is Sympatric speciation difficult to prove?

A

Due to the extent of sympatry.

47
Q

What do we mean by “Extent of sympatry”?

A

We mean how “far” you are from each other even though you’re in the same area.

48
Q

3 Stage Model of Speciation? (3)

A

• Ecological factors lead us to spatial separation.
• Trophic specialization.
• SS.

49
Q

Egs of spatial separation in the 1st stage of the 3 stage model of speciation? (2)

A

• Open water vs Bottom-dwelling.
• Sandy vs Rocky.

50
Q

How does gene flow decrease in Sympatric speciation?

A

Ecological isolation.

51
Q

Explain the 2nd way that RI evolves?

A

Through divergence in songs occurring rapidly.

52
Q

Attributes of Beak size & body size under Co-occurring species of Geospiza? (2)

A

• Polygenic traits.
• High heritability.

53
Q

What does “Steady genetic divergence” in Parapatric speciation result in? (3)

A

• Reproductive isolation.
• Reproductive incompatibility.
• Divergent SS of parent species.

54
Q

Altitudinal cline?

A

= a region over which environmental change occurs.

55
Q

Hybrid zone?

A

= zone where adjacent organisms are likely to meet.

56
Q

What is NOT an eg of Vicariant speciation?

A

Volcanic eruption.

57
Q

Vicariance?

A

= geographic separation of a population by a geographic barrier like a mountain.

58
Q

Eg of how less fit hybrids cause lower rates of survival?

A

Due to epistatic incompatibility.

59
Q

Epistatic incompatibility?

A

= the effect of some genes on other genes.

60
Q

Speciation event?

A

= when a lineage or population diverges & one or two new species result from that divergence.

61
Q

Egs of Parapatric speciation? (3)

A

• Grass species growing in the vicinity of mines.
• Crows.
• Monkey flowers.

62
Q

Parapatric speciation in plants?

A

= due to pollinator-specificity.

63
Q

How are Monkey flowers angry of Parapatric speciation?

A

Through one species being at high altitudes & being pollinated by bumblebees, and the other species being at low altitudes & being pollinated by hummingbirds.

64
Q

How are Grass species growing in the vicinity of mines an eg of Parapatric speciation? (3)

A

They diverged from neighbouring populations in:

• Tolerance to heavy metals.
• Flowering time.
• Self-pollinate more frequently.

65
Q

Attributes of Songs under Co-occurring species of Geospiza? (2)

A

• Culturally transmitted from father to son.
• Female chooses mate that sings the same song as father.

66
Q

Location of study to discover how speciation occurred?

A

Daphne Major Island.

67
Q

Study to discover how speciation occurred attributes? (3)

A

• By Peter & Rosemary Grant.
• Darwin’s finches.
• Adaptive radiation is observed.

68
Q

Darwin’s finches observations from island regarding similarities? (3)

A

• Nest type.
• Courtship behaviour.
• Plumage.

69
Q

Darwin’s finches observations on island regarding differences? (3)

A

• Body size.
• Beak size & shape.
• Song.

70
Q

Lines of evidence for NS from Darwin’s finches on Daphne Major island? (3)

A

• Different food resources on islands.
• Species’ beak sizes match food type.
• Environmental change resulted in NS acting on beak size & shape, and body size.

71
Q

What do we mean by “Divergence in courtship song (SMRS)”?

A

We mean differences in signals & responses resulted in reproductive isolation of two populations.

72
Q

How did the finches recognize their own species on Daphne Major island?

A

Via Field experiments.

73
Q

What field experiments led to us discovering how Darwin’s finches recognized their own species? (2)

A

• Playback of song.
• Presentation of museum specimens (no vocal cues).

74
Q

Explain the field experiment of Playback of song?

A

Where individuals discriminate between their own & other species through song.

75
Q

Explain the field experiment of Presentation of museum specimens (no vocal cues)?

A

When individuals discriminate through appearance/morphology.

76
Q

Conclusion of field experiments?

A

Both song & morphology are premating barriers to interbreeding/SMRS.

77
Q

Another driver/cause of speciation?

A

Competition.

78
Q

Eg of how Competition is a driver/cause of speciation?

A

Iguanid lizard from Chile.

79
Q

Drivers/Causes of speciation in sympatry? (3)

A

• Adaptive divergence in resource exploiting traits.
• Divergence in courtship song.
• Competition.

80
Q

What does the Medel et al. (1988) paper show us? (2)

A

• The Iguanid lizard from Chile changing its habitat preference in the presence of a competitor species in southern Chile (i.e., in sympatry).

• Competition is a strong driver of speciation in sympatry.

81
Q

How did adaptive radiation occur in Darwin’s finches?

A

Through changes in beak size, beak shape & body size.

82
Q

Why did adaptive radiation occur in Darwin’s finches occur?

A

Due to the environmental changes that occurred in the island which determined the diets of the finches & ultimately influenced their beak size, beak shape & body size.

EVOLUTION (12 decks)

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