Speciation Flashcards

1
Q

Define speciation.

A

The process by which one species becomes two species.

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1
Q

Define the morphological species concept.

A

Species are groups of individuals that share morphological characteristics in common.

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2
Q

Describe the biological species concept.

A

Species are groups of actually or potentially interbreeding populations, which are reproductively isolated from other groups

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3
Q

Who developed the biological species concept?

A

Theodosious Dobzhansky & Ernst Mayr

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4
Q

What are the three types of reproductive isolation?

A

Premating
Post-mating, pre-zygotic
Post-zyogtic

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5
Q

What is meant by premating as a type of reproductive isolation?

A

Different breeding/flowering times;
Incompatible sex organs
Prevents copulation

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6
Q

What is post-mating, pre-zygotic reproductive isolation?

A

Mating but not fertilization

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7
Q

What is post-zygotic reproductive isolation?

A

Offspring die or are infertile.

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8
Q

Describe the phylogenetic species concept.

A

A cluster of organisms that form a monophyletic clade.

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9
Q

What are the two steps to determining a species using the phylogenetic species concept?

A

o Estimating phylogeny
o Determining “groups”

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10
Q

Describe the pros of the morphological species concept (3).

A
  • Easy, anyone can do it
  • Doesn’t require expensive genetics
  • Objective criteria
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11
Q

Describe the cons of the morphological species concept (4).

A
  • Inaccurate, in part because what traits do you measure?
  • Variation within species
  • Cryptic species
  • Convergent evolution
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12
Q

Describe the pros of the biological species concept (3).

A
  • Objective definition
  • Experimentally testable
  • Based on the biology of organisms
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13
Q

Describe the cons of the biological species concept (3).

A
  • Not always practical or ethical
  • Infertility is not absolute
  • Doesn’t work with everything (e.g., asexual species like bacteria)
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14
Q

Describe the pros of the phylogenetic species concept (3).

A
  • Applicable to any group of organisms
  • Reflects evolutionary history
  • Objective
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15
Q

Describe the cons of the phylogenetic species concept (5).

A
  • Expensive and time consuming
  • Doesn’t necessarily reflect biology of species and mating
  • Genes vary in rates of evolution
  • Which gene?
  • Might not be able to recognize different species
16
Q

What are the three general types of speciation?

A

Allopatric
Parapatric
Sympatric

17
Q

Describe allopatric speciation.

A

o Occurs when a single population of the same species is geographically separated into two or more populations by a geographical barrier
o Through time the separated populations diverge into separate species

18
Q

What two mechanisms lead to the divergence of species in allopatric speciation?

A

Genetic drift
Natural selection

19
Q

What are the two types of allopatric speciation?

A

Vicariance
Dispersal

20
Q

Describe vicariance allopatric speciation.

A

Occurs when a single population of the same species is split into two by a new geographical barrier and through time the separated populations diverge into separate species

21
Q

What are the mechanisms for vicariance?

A

 Randomly mating population
 Separated by a barrier – NO GENE FLOW
 Divergence in isolation: Natural selection and genetic drift

22
Q

Give examples of vicariance speciation discussed in class (2).

A

 Chimps -> bonobos via Congo River
 Abert squirrel -> Kaibab squirrel via Grand Canyon

23
Q

What is believed to be the most important mechanism of speciation?

A

Dispersal (allopatric speciation)

23
Q

Describe the dispersal form of allopatric speciation.

A

o Occurs when populations of the same species are geographically separated from each other because some individuals disperse away from the parent population

23
Q

Describe the mechanism of allopatric speciation via dispersal.

A

 Randomly mating population
 Some individuals migrate away – NO GENE FLOW
 Divergence in isolation: Natural selection and genetic drift

24
Q

Give an example of allopatric speciation via dispersal discussed in class.

A

Darwin’s finches

25
Q

Describe parapatric speciation.

A

o Occurs when a single population diverges into two species at its geographic extremes without a physical barrier

26
Q

Describe sympatric speciation.

A

Occurs when a single population of one species splits into two species without any geographical barrier or separation

27
Q

Describe the mechanism of sympatric speciation.

A

 Randomly mating population
 Strong potential for GENE FLOW
 Populations diverge to be reproductively isolated

28
Q

Give an example of sympatric speciation discussed in class.

A

Apple maggot fly (Hawthornes and apples, different development time)

29
Q

What did Coyne and Orr 2004 establish about sympatric speciation? (4)

A

 Largely overlapping geographic ranges
 Speciation must be complete
 Must be sister species
 “…history of the groups must make the existence of an allopatric phase very unlikely”

30
Q

Why is sympatric speciation likely to be rare?

A

The conditions for sympatric speciation are restrictive

31
Q

Within sexual populations, when is sympatric speciation only likely? (2)

A

When there is strong divergent selection for a population to adapt to two resources, AND
When there is simultaneous selection for positive assortative mating

32
Q

Explain why some species have more lineages than others and provide an example.

A

 Number of species is a function of diversification rate and age of lineage
 Some species diversify very quickly over time (e.g., birds) and thus have more lineages

33
Q

How is diversification rate calculated?

A

Diversification rate = speciation rate – extinction rate

34
Q

Provide the three explanations for why some geographic regions have more species than others.

A
  1. High rates of speciation
  2. Low rates of extinctions
  3. The area is older, and has accumulated more species through time