Speciation Flashcards

1
Q

Allopatric speciation

A
  • split habitat prevents gene flow
  • founder/bottleneck effect: sudden drop in population causes a new allele distribution
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2
Q

Selection effects

A
  • directional: from one end to the other
  • disruptive: centralized alleles are less frequent, periphery is more frequent
  • stabilizing: already frequent allele becomes more stable
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3
Q

Sympatric speciation

A
  • same habitat, but ecological adaptations/behavior changes lead to reproductive isolation
  • e.g. blackcap birds breed in EU and migrate to Spain in the winter; NOW, some move up to UK , due to assortative mating effects
  • would mean that natural selection is directly acting on a population to encourage reproductive isolation
  • history: allopatric speciation period must be highly unlikely
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4
Q

Why are there so many species?

A
  • ecological changes might introduce new niches
  • mating isolation by time/method
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5
Q

Pre/postzygotic barriers

A
  • pre: habitat, temporal, behavioral, mechanical, gametic
  • post: reduced hybrid viability, fertility issues, hybrid breakdown in F2 or later
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6
Q

Hybrid zones (what are they; 3 types?)

A
  • regions where genetically distinct populations meet and reproduce
    1. FUSING: high gene flow and interfertility -> new species
    2. REINFORCEMENT: mating results in loss of fitness, so speciation is reinforced
    3. STABILITY: limited gene flow, negligible effects, little change
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7
Q

What reinforces inviability between carrion and hooded crows?

A

Inverted chromosome regions make it so that crossing over is prohibited. When they do occur, genetic information is likely to remain linked.

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8
Q

Phlox and cline theory

A
  • evidence of stronger reproductive isolation in sympatric conditions by difference in flower color
  • cline theory: stronger natural selection means phenotypic changes are more geographically abrupt
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