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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
Non-allopatric speciation attributes? (2)
• Gene flow continues to occur between population, yet there is divergence. • Limited gene flow.
26
What happens to the gene flow in Non-allopatric speciation?
Limited but continues to occur between populations, yet there's divergence.
27
Non-allopatric speciation types? (2)
• Parapatric speciation. • Sympatric speciation.
28
Parapatric speciation?
= populations occur in adjacent regions with different selective pressures (eg in an ecological cline).
29
Parapatric speciation attributes? (7)
• 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.
30
Why is NS > Gene flow in Parapatric speciation? (2)
• Abrupt environmental gradient. • Disruptive selection occurs.
31
Egs of abrupt environmental gradients? (2)
• Altitude. • Seasonality.
32
Sympatric speciation?
= occurs when one or more new species arise without geographic segregation of populations.
33
Sympatric speciation attributes? (8)
• 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
What does Sympatric speciation deal with?
Deals with how long it will take for gene flow to decrease.
35
Categories of Sympatric speciation? (3)
• Temporal isolation. • Behavioural isolation. • Polyploidy.
36
Temporal isolation?
= isolation that prevents species from interbreeding due to differences in the timing of mating or fertility.
37
Behavioural isolation?
= isolation that prevents species from interbreeding due to a difference in mating rituals or behaviors.
38
Polyploidy?
= where a completely different form of species can be formed that does not bear the identity of both of the parents.
39
Result of Polyploidy?
Increases genome size.
40
Egs of Sympatric speciation? (3)
• Flower forms with different pollinators. • Maggot flies on Apples & Hawthorns. • Cichlid fish.
41
Driver of speciation in plants?
Pollinator-mediated selection.
42
Main separation by what in Pollinator-mediated selection?
Separation by altitude.
43
Speciation patterns in Cichlid fish? (3)
• High levels of endemicity. • Have radiated in endemicity. • Visually-orientated.
44
How does Cichlid being visually orientated benefit them? (2)
• Good for mating. • Good for recognition of mates.
45
How are Cichlid fish an eg of Sympatric speciation?
Via them living at different lake depths, causing them to have different diets & therefore, different mouth shapes (NS) & speciation occurring due to SS.
46
Why is Sympatric speciation difficult to prove?
Due to the extent of sympatry.
47
What do we mean by "Extent of sympatry"?
We mean how "far" you are from each other even though you're in the same area.
48
3 Stage Model of Speciation? (3)
• Ecological factors lead us to spatial separation. • Trophic specialization. • SS.
49
Egs of spatial separation in the 1st stage of the 3 stage model of speciation? (2)
• Open water vs Bottom-dwelling. • Sandy vs Rocky.
50
How does gene flow decrease in Sympatric speciation?
Ecological isolation.
51
Explain the 2nd way that RI evolves?
Through divergence in songs occurring rapidly.
52
Attributes of Beak size & body size under Co-occurring species of Geospiza? (2)
• Polygenic traits. • High heritability.
53
What does "Steady genetic divergence" in Parapatric speciation result in? (3)
• Reproductive isolation. • Reproductive incompatibility. • Divergent SS of parent species.
54
Altitudinal cline?
= a region over which environmental change occurs.
55
Hybrid zone?
= zone where adjacent organisms are likely to meet.
56
What is NOT an eg of Vicariant speciation?
Volcanic eruption.
57
Vicariance?
= geographic separation of a population by a geographic barrier like a mountain.
58
Eg of how less fit hybrids cause lower rates of survival?
Due to epistatic incompatibility.
59
Epistatic incompatibility?
= the effect of some genes on other genes.
60
Speciation event?
= when a lineage or population diverges & one or two new species result from that divergence.
61
Egs of Parapatric speciation? (3)
• Grass species growing in the vicinity of mines. • Crows. • Monkey flowers.
62
Parapatric speciation in plants?
= due to pollinator-specificity.
63
How are Monkey flowers angry of Parapatric speciation?
Through one species being at high altitudes & being pollinated by bumblebees, and the other species being at low altitudes & being pollinated by hummingbirds.
64
How are Grass species growing in the vicinity of mines an eg of Parapatric speciation? (3)
They diverged from neighbouring populations in: • Tolerance to heavy metals. • Flowering time. • Self-pollinate more frequently.
65
Attributes of Songs under Co-occurring species of Geospiza? (2)
• Culturally transmitted from father to son. • Female chooses mate that sings the same song as father.
66
Location of study to discover how speciation occurred?
Daphne Major Island.
67
Study to discover how speciation occurred attributes? (3)
• By Peter & Rosemary Grant. • Darwin's finches. • Adaptive radiation is observed.
68
Darwin's finches observations from island regarding similarities? (3)
• Nest type. • Courtship behaviour. • Plumage.
69
Darwin's finches observations on island regarding differences? (3)
• Body size. • Beak size & shape. • Song.
70
Lines of evidence for NS from Darwin's finches on Daphne Major island? (3)
• 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
What do we mean by "Divergence in courtship song (SMRS)"?
We mean differences in signals & responses resulted in reproductive isolation of two populations.
72
How did the finches recognize their own species on Daphne Major island?
Via Field experiments.
73
What field experiments led to us discovering how Darwin's finches recognized their own species? (2)
• Playback of song. • Presentation of museum specimens (no vocal cues).
74
Explain the field experiment of Playback of song?
Where individuals discriminate between their own & other species through song.
75
Explain the field experiment of Presentation of museum specimens (no vocal cues)?
When individuals discriminate through appearance/morphology.
76
Conclusion of field experiments?
Both song & morphology are premating barriers to interbreeding/SMRS.
77
Another driver/cause of speciation?
Competition.
78
Eg of how Competition is a driver/cause of speciation?
Iguanid lizard from Chile.
79
Drivers/Causes of speciation in sympatry? (3)
• Adaptive divergence in resource exploiting traits. • Divergence in courtship song. • Competition.
80
What does the Medel et al. (1988) paper show us? (2)
• 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
How did adaptive radiation occur in Darwin's finches?
Through changes in beak size, beak shape & body size.
82
Why did adaptive radiation occur in Darwin's finches occur?
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.

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