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Speciation and Phylogenies Flashcards

1
Q

What is speciation

A

The process by which one species divides into two

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2
Q

How do you initate the speciation process

A

Restricting gene flow between isolated populations

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3
Q

Whats allopatric speciation

A

Involves physical seperation between two populations

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4
Q

Whats vicariance

A

A type of allopatric speciation, large populations become split into two via a physical barrier

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5
Q

Whats peripatric

A

A peripheral population is established outside the original range of the population and forms an independant colony

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6
Q

Whats sympatric speciation

A

A population being split into two reproductively isolated populations while staying in the same geographic location

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7
Q

Whats parapatric speciation

A

When neighbouring populations of a species are geographically connect and exchange genes but diverge into seperate species

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8
Q

How can allopatric speciation occur

A

Vicariance e.g. mountain uplifts or peripatric e.g. dispersal to oceanic islands

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9
Q

Example of vicariance (1)

A

Isthmus of Panama in central America, the isthmus closed 2.8 million years ago and now species show adapted divergence either side of the lung bridge

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10
Q

Examples of vicariance (2)

A

Speciation in birds such as the South American Andes, populations shift up and down the mountain range

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11
Q

Dispersal/ peripatric/ founder effect examples

A

Archipelago and island bird colonisations dispered from mainland to isolated islands.

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12
Q

Example of sympatric speciation

A

Rhagoletis apple maggot fly, ancestor of the r. pomenella which layed eggs in fruit Hawthorn trees

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13
Q

Whats more common than sympatric speciation

A

Parapatric

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14
Q

Examples of parapatric speciation

A

Lizards at the white sands

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15
Q

What can ecological speciation be defined as

A

The evolution of reproductive isolation between populations as a result of ecologically based divergent natural selection

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16
Q

An example of ecological divergence

A

Monkey flowers (mimulus)

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17
Q

Whats sexual selection defined as

A

Differential reproduction as a result of variation in the ability to obtain mates

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18
Q

Why does sexual selection vary across populations

A

To improve conspecific recongition
To provide optimal direct benefits to mates
As a result of pleiotrophic effects
Because of variation in good gene mechanisms
Because of runaway mechanisms when trait and preference alleles become genetically linked

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19
Q

What does higher taxa refer to

A

Any grouping above the species level for example genus or family

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20
Q

Whats another process that promotes speciation

A

Reinforcement

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21
Q

What is reinforcement defined as

A

The evolution of enhanced reproductive isolation between populations due to natural selection for greater isolation

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22
Q

What needs to be low in order to reinforcement to occur

A

Hybrid fitness

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23
Q

What can reproductive character displacement be defined as

A

the accentuation of differences between sympatric populations from two species as a result of reproductive interactions between them

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24
Q

Example of reproductive character displacement

A

Ficedula fly catchers including pied flycatcher and the collared fly catcher, they look different in the area of sympatry

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25
When does polyploidy occur
When chromosomes fail to segregate during meiosis
26
How are tetraploids formed
From two individuals in the same species
27
Whats allopolyploid
Duplication of chromosomes in hybrids between species
28
What are the consequences of having more chromosomes than normal
Increase in the number of gene copies Tetraploid individuals reproductively isolated from parental species Unable to form any viable offspring
29
How common is polyploidy in plants
15% in flowering plants and 31% in ferns
30
Whats an example of polyploidy in plants
Tragogan goatsbeards.
31
How can we prevent extinction in new polyploid species
Reduce sterile triploid offspring by self fertilisation, vegetative propogation and habitat segregation
32
How can we capatilise on the advantages of polyploidy
Heterozygote advantage, extreme phenotypic traits, chance to access new fitness opitma in the adaptive landscape
33
Whats allopolyploid a form of
Hybrid speciation
34
Whats homoploid hybrid speciation
Speciation via hybridisation without change in chromosome (ploidy) number
35
Example of homoploid hybrid speciation
Helianthus sunflowers
36
Example of adaptive radiation
Cichild fish in Lake Victoria
37
Whats random genetic drift
Random changes in frequencies of two or more alleles or genotypes within a population
38
What are phenograms
Represent similarity or distance but may not represent historical relationships
39
What are phylogenetic trees
Represent a hypothesis about historical relationships
40
What are cladograms
Y axis has no meaning, only tells the relationship between species
41
What are additive trees
Where the y axis tells us about the amount of evolutionary change, how much sequence change happens
42
What are ultra-metric trees
Y axis means time
43
What are fully bifurcated trees
Assumes all speciation events involve one ting splitting into two
44
What are multifurcated trees
A node splits into more than two species/ branches
45
How do we add a root to the tree
Add information for an outgroup
46
Whats an outgroup
A taxon that we believe, a priori to be more distantly related to the focal species than they are to one another
47
How do we estimate genetic distance
K = the proportion of nucleotide sites that are different
48
What does UPGMA stand for
Unweighted pair group method with arithmetic mean
49
What does the jukes cantor distance correlation show
The more evolutionary distance there is, the more likely theres more hits (lorgarthmic scaling)
50
Examples of when Phylogenies are useful
To see if flying mammals died once or twice
51
Limitations in phlyogenetic analysis
Trees are hypotheses: scoring characters are hard homoplasy is common Acient events are hard to infer Some lineages might be diverging too rapidly Hybridisation can be a problem Incomplete lineage sorting
52
Phylogenetic imbalance definition
A difference in the number of descendent tips either side of a focal node
53
What does the equal-rates Markov model show
The probabiltiy of speciation per unit time is constant across all lineages
54
Whats lateral gene transfer defined as
The aquisition of genetic material from another organism without sexual reproduction
55
Why is Alloterepopsis important
Because its the only known species with the C4 and non-C4 enzymes
56
Why does Zambian accession have more LGT
Has a much greater rate of gains due to diverse habitiat
57
how many genes are LGT
0.04%
58
What factors drive differentiation
Speciation and extinction
59
Why do speciation rates vary
The frequency of barriers/ factors that produce geographical isolation The rate at which these isolated populations evolve isolating mechanisms The degree of these ecological diversity offering vacant ecological niches to these newly arising species
60
Whats the cycle of speciation
1. the formation of geographical isolates 2. acquisition of reproductive isolating mechanisms 3. ecological differentation 4. cycle begins again
61
What factors might affect progress through speciation
Rate of geographic isolation, rate of reproductive isolating barriers, rate of ecological differentiation and co-existence

Biology (9 decks)

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