Speciation II

Question 1

What are the evolutionary forces involved in speciation?

Answer 1

Drift, gene flow, mutation, selection

Question 2

Modes of speciation:

Answer 2

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

Question 3

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

Answer 3

• palaeontology
• biogeography
• phylogenetics
• genetics

Question 4

Mutation

Answer 4

The ultimate source of genetic variation

Question 5

Random genetic drift

Answer 5

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

Question 6

Gene flow (gene migration)

Answer 6

Movement of alleles among populations

Question 7

Random genetic drift and gene flow

Answer 7

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

Question 8

Natural selection

Answer 8

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

Question 9

Vicariant allopatric selection

Answer 9

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

Question 10

Peripatric allopatric speciation

Answer 10

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

Question 11

Stepping stone parapatric speciation

Answer 11

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

Question 12

Clines parapatric speciation

Answer 12

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

Question 13

Sympatric speciation

Answer 13

• free gene flow
• requires very strong divergent selection

Question 14

For speciation to occur, you need some combination of

Answer 14

1) isolation
2) divergent selection

Question 15

Why do you need isolation for speciation to occur?

Answer 15

• reduce/stop gene flow
• drift alone can cause speciation

Question 16

Divergent selection can result in speciation even

Answer 16

In the face of gene flow

Question 17

If there is no gene flow, the speciation is

Answer 17

Allopatric

Question 18

Behavioural isolation can develop

Answer 18

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

Question 19

Describe the speciation of snapping shrimp Alpheus

Answer 19

• 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

Question 20

Describe the case of Pinaroloxias inornata

Answer 20

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

Question 21

If gene flow is low - medium, speciation is

Answer 21

Parapatric

Question 22

If divergent selection is strong, the speciation is considered

Answer 22

Ecological

Question 23

Describe M. guttatus (Wright et al. 2013)

Answer 23

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

Question 24

It’s not an allopatry event but an allopatry

Answer 24

Phase

Question 25

What speeds up speciation?

Answer 25

- selection against immigrants - selection against hybrid intermediates - reproductive isolation as a byproduct of ecological divergence - byproduct of adaptive divergence

Question 26

Give examples of adaptive divergence

Answer 26

1) different flowering times 2) different body sizes

Question 27

Give the criteria of sympatric speciation

Answer 27

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

Question 28

Describe the Lord Howe island palms (Papadopulos 2011)

Answer 28

- 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

Question 29

Why must double colonisation be ruled out

Answer 29

To ensure group is monophyletic

Question 30

Describe the speciation of the apple maggot fly Rhagoletis pomonella

Answer 30

- 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

Question 31

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

Answer 31

- 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

Question 32

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

Answer 32

Song and bill morphology

Question 33

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

Answer 33

- 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

Question 34

Polyploidy

Answer 34

- Individuals carry 3 or more complete sets of chromosomes - common in plants, rare in animals

Question 35

An increase in chromosome sets can

Answer 35

Produce nearly instantaneous reproductive isolation

Question 36

What percentage of speciation events in ferns involve polyploidy?

Answer 36

7

Question 37

What percentage of speciation events in angiosperms involve polyploidy?

Answer 37

2-4

Question 38

Evolutionary inertia

Answer 38

Co-adapted gene complexes constrain further adaptation

Question 39

What events might break evolutionary inertia

Answer 39

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

Question 40

True allopatry means

Answer 40

No gene flow

Question 41

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

Answer 41

Mutation

Question 42

At a local level, new variation can be created by

Answer 42

Migration, and mutation

Question 43

Drift shows

Answer 43

No directionality

Question 44

What changes evolutionary trajectory?

Answer 44

Interaction between different microevolutionary processes

Question 45

Drift is a divergence by

Answer 45

Chance

Question 46

Cline

Answer 46

- gradation from one population to the other - isolation by distance

Question 47

True sympatry means

Answer 47

Completely congruous

Question 48

Theoretically,

Answer 48

- drift can result in speciation alone - but reduced gene flow rlly helps

Question 49

Parapatric speciation occurs with

Answer 49

Relatively high frequency

Question 50

Ecotones

Answer 50

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

Question 51

Reconstructing speciation is

Answer 51

Tricky

Question 52

Strong selection overcomes

Answer 52

Gene flow

Question 53

To be a ring species, you can’t have

Answer 53

Any deep biogeographic/vicariant breaks or an allopatric phase

Question 54

In a ring species, rather than flowing, genes

Answer 54

‘Trickle’