Geography of Speciation
• Allopatric
– Peripatric
• Parapatric
• Sympatric
Fig. 24-6
Sister species in allopatry
A. harrisi
A. leucurus
Peripatric Speciation
(like allopatric, but offers drift a bigger role)
Divergent natural selection &/or
Genetic Drift
= Speciation
Divergent natural selection &/or
Genetic Drift
= Speciation
Sympatric and Parapatric Speciation
• What do we mean by sympatry or parapatry?
– In same geographic area (or side-by-side)?
– Exchanging gene flow during the speciation
– How finely should we divide the environment?
– Habitat isolation in the same geographic area = real sympatry?
Apple maggot fly
Sympatric or Micro-allopatric?
Pre-mating RIM = host fidelity
Post-mating RIM =  scent tracking in F1’s
Parapatric Speciation
(sympatric, micro-allopatric?)
Mine from mid-1800’s
Contamination prevents most plant growth
Strong, disruptive selection against interbreeding
Different flowering times
Anthoxanthum odoratum
Mine soils (black):
Flowering is earlier (flowers more developed
in a point sample)
Antonovics, Heredity (2006) 97, 33–37. doi:10.1038/sj.hdy.6800835
• Flowering stage along a transect from mine  field
(border = dashed line)
• Common garden experiment included
• Trend persists over 40 years
• 40% less mating between forms
• Parapatry, sympatry, or micro-allopatry?
Mechanisms of Speciation
Ecological Speciation (Driven by natural selection)
Sexual Selection
Allopatric Speciation--Mutation
•Gene Duplication is common
•LOF mutation is common
•Fixation of alternate mutations can  hybrid inviability

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