12.3.07 - Darren Rothberg Biol 105 Evolution 12.3.07 I)...

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Darren Rothberg Biol 105 – Evolution 12.3.07 I) 1) Migration a Movement of individuals between populations b Causes GENE FLOW 2) Gene Flow a Movement of alleles between populations b Caused by MIGRATION 3) Migration Rates Vary a Taxonomic/organismal differences (i) Mobility (ii) Tendency to move (iii) Vulnerability to wind (iv) Effectiveness of barriers to movement b Regions (i) Habitat uniformity (ii) Number and size of barriers to dispersal (iii) Kinds of barriers to dispersal (iv) Prevailing wings/current etc. 4) Impact of Gene Flow Depends Upon a Rate of gene flow b Degree of difference of allele frequencies among populations between which gene flow occurs c Size of receiving population One Island Model Very low rates of gene flow from the mainland may not be detectable on the island High rates of gene flow will be detectable Gene flow from the island is unlikely to be detectable The larger the recipient population, the less the effect of a given rate of gene flow
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5) Gene Flow as a Homogenizing Force a If gene flow opposes selection (i) Adds maladaptive alleles to populations (ii) Opposes effects of selection (iii) Makes populations more similar than local selection would favor (iv) Outcome: balance between strength of selection and amount of gene flow 6) Gene Flow Maintains Variation within Populations
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12.3.07 - Darren Rothberg Biol 105 Evolution 12.3.07 I)...

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