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Eco and Evo > Speciation > Flashcards

Speciation Flashcards

1
Q

Species

A

an evolutionary independent population or group of populations

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2
Q

Speciation

A

a splitting event that creates two or more distinct species from a single ancestral species

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3
Q

Gene Flow

A
  • AKA migration
  • the transfer of alleles from one population to another
  • makes populations increasingly similar
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4
Q

Reproductive Isolation

A
  • behaviors or processes that prevent gene flow between populations
  • creates opportunity for divergence
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5
Q

Species Concept

A

a set of criteria used to define and differentiate species

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6
Q

Biological Species Concept

A

-species are reproductively isolated

  • do not interbreed in nature
  • or if the do, offspring are not viable/sterile
  • cannot be applied to asexual or extinct species (fossils)
  • isolating mechanisms (pre/post zygotic)
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7
Q

Morphological Species Concept

A
  • based on differences in size, shape, or other morphological features
  • can be applied to asexual or extinct species (fossils)
  • morphospecies
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8
Q

Issues with the Morphological Species Concept

A
  • species with different morphs; polymorphic species
  • cryptic species
  • the singing of birds attracts
  • which traits to use?
  • how different do traits need to be?
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9
Q

Phylogenetic Tree

A
  • representation of the evolutionary relationships among organisms
  • AKA phylogeny/evolutionary tree
  • made up of hierarchies of monophyletic groups (clades)
  • can be applied to asexual and extinct species
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10
Q

Monophyletic Group or Clade

A

-a group that consists of one ancestor and all its descendants

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11
Q

Phylogenies

A

nested hierarchies of clades

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12
Q

Phylogenetic Species Concept in practice

A
  • gather data from multiple populations
  • use data to construct a phylogeny
  • analyze for monophyletic groups
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13
Q

Difficulties with the Phylogenetic Species Concept

A
  • we do not have good phylogenies for many groups of species

- yet, this is changing with advancements in DNA sequencing

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14
Q

Isolating Mechanisms

A
  • Mechanisms that prevent the formation of a zygote

- pre zygotic (before zygote formation) or post zygotic (after zygote formation)

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15
Q

Prezygotic Mechanisms

A
  • Temporal isolation
  • Habitat isolation
  • Behavioral isolation
  • Mechanical isolation
  • Gametic isolation
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16
Q

Temporal isolation

A
  • breeding at different times

- e.g. flowers coming out at different times and corals sending out sperm at different times

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17
Q

Habitat isolation

A
  • preferences for living or mating in different habitats

- may never come into contact during mating periods

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18
Q

Behavioral isolation

A
  • individuals behave in such a way that they reject or fail to recognize potential mating partners
  • not attracted to each other

For example:

  • the frogs songs
  • the displays of birds
  • pollinators may favor different floral shapes or food (nectar)
  • behavior of pollinators may isolate plants
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19
Q

Mechanical isolation

A
  • differences in size and shape of reproductive organs make mating impossible
  • genital lock-and-key
  • most common in insects
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20
Q

Gametic isolation

A
  • eggs of one species do not have appropriate chemical signals for sperm of another species
  • or sperm is not able to attach and penetrate the egg
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21
Q

Post Zygotic Isolation

A

-mechanisms that prevent zygotes from passing on alleles

  • hybrid inviability
  • hybrid sterility
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22
Q

Hybrid Inviability

A
  • hybrids do not survive to sexual maturity

- they die during development or soon after birth

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23
Q

Hybrid Sterility

A
  • hybrids survive to maturity but do not produce gametes
  • are not fertile
  • have an intermediate phenotype that keeps them from reproducing
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24
Q

How do isolating mechanisms evolve?

A

Allopatric speciation:

the most common mode of speciation because geographic isolation is so effective at reducing gene flow

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25
Q

Allopatric Speciation

A
  • the most common mode of speciation because geographic isolation is so effective at reducing gene flow
  • opportunity to evolve isolating mechanisms
  • routes to allopatry: dispersal and vicariance
26
Q

Dispersal

A
  • movement to a new habitat
  • across unsuitable habitat or barrier
  • the likelihood that speciation is negatively correlated with connectivity between patches
27
Q

Vicariance

A
  • the physical splitting of a population into smaller, isolated populations by a physical barrier
  • e.g. rising mountains, change in river course, break up of land…

-likelihood of speciation is positively correlated with the strength of the barrier

28
Q

How do populations diverge when isolated?

A
  • Natural Selection
  • Genetic Drift
  • Mutation
29
Q

Natural Selection in relation to divergence

A
  • populations in different environments experience different selection pressures
  • thus, natural selection could favor different traits/alleles
30
Q

Genetic Drift in relation to divergence

A
  • random changes can create fixation/loss of different alleles
  • smaller populations due to dispersal or vicariance
  • greater affect of drift
  • fixation/loss of different alleles in two populations
31
Q

Mutation in relation to divergence

A
  • random
  • different alleles created
  • new alleles can then diverge due to natural selection or genetic drift
32
Q

Evolution by Natural Selection

A

-populations could have different ecologies
including:
-temperature rainfall, soil…
-different communities (species interactions)

  • thus, potentially different selection pressures in each population
  • natural selection would then favor different alleles in each population
33
Q

Evolution by Genetic Drift

A
  • Smaller population due to dispersal or vicariance
  • greater affect of drift
  • fixation/loss of different alleles in two populations
34
Q

Allopatric speciation by vicariance

A
  • speciation that begins with geographic isolation

e. g. the amazon river changes over millenniums

35
Q

Secondary Contact

A
  • when allopatric populations come back into contact with each other
  • become sympatric
36
Q

When isolated populations come into contact, speciation is complete when…

A
  • they no longer recognize each other as potential mates

- or produce inviable/infertile offspring

37
Q

When isolated populations come into contact, population fusion occurs when…

A
  • random mating among individuals

- hybrids are fit

38
Q

Reinforcement

A
  • natural selection for traits that prevent interbreeding among populations
  • selection of traits that increase reproductive isolation between populations after secondary contact
39
Q

Fitness of hybrids

A
  • some gene flow, but hybrids have lower fitness than parental forms
  • partially sterile or inviable
  • intermediate phenotypes reduces realized niche or ability to attract mates
40
Q

Collared and pied flycatchers

A
  • divergence during glacial cycles
  • expansion since last glacial cycle has caused secondary contact in central Europe
  • in sympatry, hybridization is lower than expected with random mating (2-7% of breeding adults are hybrids)
  • hybrids have reduced fitness
  • females mostly sterile
  • males have reduced fertility

-since hybrids have reduced fitness, natural selection should favor traits that favor conspecific mating (=reinforcement)

  • in sympatry, there is increased divergence in male phenotypes
  • male pied flycatchers are brown/white

-also greater differences in UV color and wing patch size

41
Q

Hybrid Zone

A
  • defined geographic area with hybridization that results in fertile offspring
  • dispersal limitation and/or natural selection maintains a defined zone
  • the two species are diverged enough to be called different species by at least one species concept
42
Q

Hybrid speciation

A
  • when hybrids are fit and become reproductively isolated from parental species
  • homoploid hybrid speciation: # of chromosomes does not change
  • intermediate phenotypes promote isolation
  • occupy different niche (sunflowers in sand)
  • not recognized as potential mates
43
Q

Sympatric Speciation

A
  • no geographic isolation: sympatric individuals live in the same geographic area
  • divergence: new population begins to diverge due to selection
  • genetic isolation: eventually the two populations become genetically isolated from one another in single populations
  • single populations experience disruptive selection for extreme phenotypes
  • trait under disruptive selection must be somehow tied to mating preferences
  • e.g. small with small; big with big

-e.g. apple maggot fly

44
Q

Disruptive selection

A
  • phenotype higher and lower than mean has high fitness
  • mean could stay the same
  • genetic variation is increased
45
Q

Disruptive Selection in Sympatric Speciation

A

-single populations experience disruptive selection for extreme phenotypes

  • trait under disruptive selection must be somehow tied to mating preferences
  • e.g. small with small; big with big
46
Q

Apple Maggot Fly

A
  • Native to the US, historically associated with hawthorn (type of crab apple)
  • they lay eggs in hawthorn fruits
  • Europeans brought apples to US
  • Some individuals switched to laying eggs in apple fruits
  • individuals flies tend to looks for mates and lay eggs around the same types of fruit they were born
  • temporal variation in host availability has led to disruptive selection
  • If intermediate phenotypes have lower fitness, reinforcement is expected
  • an example of speciation by host shift
47
Q

Speciation by host shift

A
  • e.g. apple maggot fly
  • tight species interaction with host; shift to new host creates reproductive isolation
  • could be common in insects, but also found in other groups
48
Q

Synapomorphy

A

A trait that is found in certain groups of organisms and their common ancestor but is missing in more distant ancestors

e.g. fur and milk-producing glands are synapomorphies that identify mammals as a monophyletic group

49
Q

Polymorphic species

A

differing phenotypes

50
Q

Cryptic species

A

differ in traits other than morphology

51
Q

Subspecies

A

populations that live in discrete geographic areas and have distinguishing features such as coloration or calls, but are not considered different enough to be called separate species

52
Q

Biogeography

A

the study of how species and populations are distributed geographically

53
Q

Polyploidy

A

the condition of possession more than two complete sets of chromosomes

54
Q

Autopolyploid

A

produced when mutation results in a doubling of chromosome number and the chromosomes all come from the same species

55
Q

Allopolyploid

A

created when parents of different species mate, and then an error in mitosis occurs, resulting in viable, non sterile offspring with two full sets of chromosomes

56
Q

Tree of life

A
  • the most universal of all phylogenetic tree

- depicts the evolutionary relationships among all living organisms on earth

57
Q

Branch

A

A line representing a population through time

58
Q

Root

A

the most ancestral brach in the tree

59
Q

Tip (terminal node)

A
  • the endpoint go a branch

- represents a living or extinct group of genes, species, families, phyla, or other taxa

60
Q

Outgroup

A
  • a taxon that diverged prior to the taxa that are the focus of the study
  • helps to root the tree
61
Q

Node (fork)

A
  • a point within the tree where a branch splits into two or more branches
  • the node represent the most recent common ancestor of the descendent groups

Eco and Evo (15 decks)

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