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Year 3: Adaptation > Darwin's finches > Flashcards

Darwin's finches Flashcards

1
Q

What are Darwin’s finches?

A

A group of 14 closely related passerine birds found on the Galapagos islands

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2
Q

What family do Darwin’s finches belong to?

A

Fringillidae

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3
Q

Who has extensively studied Darwin’s finches? Why?

A

Peter and Rosemary Grant of Princeton University

They are a major model for adaptive evolution

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4
Q

What is adaptive evolution?

A

Evolution that occurs in response to a changing environment

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5
Q

What is the adaptive trait in finches? What does it correlate to?

A

Beak morphology, correlates to ecological niche filled by each species

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6
Q

What kind of beaks do Ground finches have?

A

Crushing bills for eating seeds

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7
Q

What kind of beaks do Warbler and Cactus finches have?

A

Probing bills

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8
Q

What kind of beaks do Tree finches have?

A

Grasping bills for eating invertebrates

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9
Q

What kind of beak does the Vegetarian tree finch have and why?

What is its latin name?

A

P. crassirostris

A parrot-like bill for eating buds of trees

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10
Q

Why is diversity in finch beak shape important in the Galapagos?

A

All 14 species are very similar and must diversify to exploit different niches and thus avoid competitive exclusion

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11
Q

What is it about the Galapagos islands that drives such morphological diversity? Why?

A

The harsh environmental conditions.

In unforgiving conditions selection is stronger, producing more drastic and rapid patterns of change.

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12
Q

Fluctuations in environmental conditions are mirrored by…

A

fluctuations in trait value that evolve in response

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13
Q

Who described the results of a comparative 30-year study on the medium ground finch (G. fortis) and the cactus finch (G. scandens)?

A

Grant and Grant, 2002

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14
Q

Grant and Grant, 2002;

What did the authors find?

A

Both G. fortis and G. scandens underwent fluctuations in body size, beak shape and beak size over the 30-year period.

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15
Q

Grant and Grant, 2002;

What happened to body size in G. fortis and G. scandens?

A

They had become smaller

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16
Q

Grant and Grant, 2002;

What happened to the beak of G. fortis?

A

It became more pointed

17
Q

Grant and Grant, 2002;

What happened to the beak of G. scandens?

A

It became blunter

18
Q

Grant and Grant, 2002;

Over the 30 years of the study, environmental conditions were particularly difficult on the Galapagos. Why, what happened?

A

Due to ENSO effects;

Trade winds slow, causing an accumulation of warm surface water in the Eastern Pacific, resulting in extreme rainfall due to increased evaporation.

19
Q

Who documented some of the wettest years on record? Which years were these?

A

Grant and Grant (1993)

1983 and 1987

20
Q

Grant and Grant (1993):

The extreme rains of 1983 and 1987 coincided with beak changes in…

A

G. scandens, its beak became blunter during this period

21
Q

Why would beak morph change due to environmental harshness?

A

Because it is even more difficult to secure food. Specialisation can increase the chance of securing a particular food, thus saving the animal from starvation.

22
Q

There are two major genes controlling beak shape. What are they?

A

Bmp4 and CaM

23
Q

Who described Bmp4 in beak evolution? How did they find this?

A

Abzhanov et al., 2004

They injected chick embryos with viruses containing Bmp4. This upregulation of expression caused the chick to develop a deep, wide beak

24
Q

Abzhanov et al., 2004:

Injecting Bmp4 caused the chick’s beak to resemble that of…

A

G. magnirostris, or the large ground finch

25
Q

What shape does a) high and b) low Bmp4 produce?

A

a) a deep, wide beak

b) a shallow, narrow beak

26
Q

Who described CaM in beak evolution?
How did they select CaM as a candidate gene?
What did they then do?
What did they find?

A

Abzhanov et al., 2006;

Microarrays were used to study gene expression, CaM selected as a candidate.

Upregulated CaM in the frontonasal prominence

Upregulation produced a long beak

27
Q

Abzhanov et al., 2006;

Upregulating CaM produced a beak similar in morphology to…

A

cactus finches

28
Q

What shape does a) high and b) low CaM produce?

A

a) long beak

b) short

29
Q

What is Bmp4 implicated in?

A

Bone and cartilage development in birds, tooth development in non-aves

30
Q

What is CaM?

A

A Ca2+ signalling protein

31
Q

How are these two genes controlled?

A

Via a trans-regulatory mechanism

32
Q

How do trans-regulatory elements (TREs) work?

A

They encode TSFs, and so modify the expression of distant genes

33
Q

How do cis-regulatory elements (CREs) work?

A

They encode binding sites for TSFs and so modify the expression of local genes

34
Q

How found beak morphology was attributable to TREs?

What did they do?

A

Lamichhaney et al., 2015

They compared the diversity of genomic regions between species and phenotypes (ZFst) in Darwin’s finches.

35
Q

Lamichhaney et al., 2015:

What does high ZFst show?

What did ZFst show for Bmp4 and CaM? What does this mean?

A

High ZFst = organisms are under differential selection as selection favour polymorphism, producing genomic diversity
(assume this indicates cis-regulation)

There was low ZFst for Bmp4 and CaM as there was little variation around the coding sequences, meaning changes in morphology had to be attributable to trans-regulation

36
Q

Lamichhaney et al., 2015:

Trans-regulation of Bmp4 and CaM have since been attributed to which gene?
Why?
Why is this unsurprising?

A

ALX1

It was identified as divergent between pointed and blunt beaked individuals

It is known to be integral to craniofacial development in vertebrates

They are not sure, but it COULD be this

Year 3: Adaptation (10 decks)

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