F13 lecture 8 v2

On and variaon within and between populaons g 33a two

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Unformatted text preview: essfully reproduce hIp://www.cartoonstock.com/lowres/amc0088l.jpg a simple model – island model the whole system = a metapopulaGon •  p and q subscripted for each subpopulaGon •  in each subpopulaGon: •  pt=pt- 1(1- m)+pm •  t = generaGon •  m = migraGon rate •  p = frequency of new alleles from immigrants change in p due to migraGon •  in each subpopulaGon •  dp = pt – pt- 1 •  =m(p - pt- 1) •  p is assumed to be the same across the metapopulaGon •  allele frequencies in the enGre metapopulaGon will converge to p migraGon •  keeps populaGons from diverging •  conversely, lack of migraGon leads to isolaGon and geneGc divergence of populaGons migra?on and varia?on within and between popula?ons •  fig 3.3A •  two of the populaGons start out at p=0 and p=1 respecGvely –  all of the variaGon is between populaGons –  no variaGon within these populaGons •  aUer 50 generaGons = both populaGons are at p=q=0.5 –  maximum within populaGon variatoin –  no between populaGon variaGon •  MIGRATION CONVERTS BETWEEN- POPULATION VARIATION TO WITHIN- POPULATION VARIATION inferring gene flow •  usually done by comparing within versus between populaGon variaGon •  if there is liIle variaGon between populaGons –  infer high gene flow •  if there is a lot of variaGon between populaGons –  infer liIle gene flow geneGc driU •  some terms –  metapopula?on (see above) –  popula?on structure = the degree of geneGc differenGaGon between populaGons or between subpopulaGons of a metapopulaGon –  panmic?c = no geneGc structure; no divergence between subpopulaGons •  each individual has an equal chance of maGng with any other individual in the enGre populaGon, regardless of where in the populaGon they are geneGc driU •  due to random changes in populaGon size –  also called “random driU” or “random geneGc driU” •  the smaller the populaGon size, the stronger the effect •  ulGmate result = alleles can go to 100% (fixaGon) by chance alone –  these can be neutral (no selecGve effect) –  they...
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This document was uploaded on 02/27/2014.

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