Geography of Speciation

• Allopatric– Peripatric

• Parapatric• Sympatric

Fig. 24-6

A. harrisi A. leucurus

Sister species in allopatry

Peripatric Speciation(like allopatric, but offers drift a bigger role)

Divergent natural selection &/orGenetic 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

process?– How finely should we divide the environment?

– Habitat isolation in the same geographic area = real sympatry?

Apple maggot flySympatric or Micro-allopatric?

http://evolution.berkeley.edu/evosite/evo101/VC1eSympatric.shtml

Pre-mating RIM = host fidelityPost-mating RIM = scent tracking in F1’s

Parapatric Speciation (sympatric, micro-allopatric?)

Anthoxanthum odoratum

Mine from mid-1800’sContamination prevents most plant growthStrong, disruptive selection against interbreedingDifferent flowering times

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

• Mutation• Drift• Ecological Speciation (Driven by natural selection)• Sexual Selection

Allopatric Speciation--Mutation

http://evolution.berkeley.edu/evosite/history/modsynth2.shtml

•Gene Duplication is common•LOF mutation is common•Fixation of alternate mutations can hybrid inviability