Migration as a mechanisms of evolution

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Migration as a mechanisms of evolution

• Water snakes (Nerodia sipedon) in Lake Erie come
  in two color phases banded and unbanded
• This is a two allele system
• Banded dominant to unbanded
• The mainland has really only banded
• The islands may have both

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Lake Erie water snakes

• It was found that, when basking on islands, the
  unbanded snakes are more cryptic and thus remain
  hidden better.
• Why wouldnt selection cause the unbanded pattern
  to go to fixation?
• Migration. Every year, banded snakes migrate
  from the mainland and introduce fresh banded
  alleles
• Therefore, migration offsets selection

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Genetic Drift
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Founder Effect

• small founding populations have less allelic
  diversity

Silvereye (Zosterops lateralis)

• Clegg, et al, 2002

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Silvereye colonization

• Clegg, et al, 2002

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Founder Effect on Allelic Diversity of the
Silvereye
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Alleles Randomly Fixed
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Average Heterogosity Decreases
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Alleles Randomly fixed in the field
Collared Lizard (Crotaphytus collaris)

• Templeton, et al, 2002

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Multilocus Genotyping of Collared Lizards in the
Ozarks
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Randomly Fixed Alleles in Isolated Collared
Lizard Populations
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The Vertebrate Mitochondrial Genetic Code
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Alcohol Dehydrogenase (ADH) Gene Alignment in
Drosophilia
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