F13 lecture 8 v2

A migragon can occur without gene ow b gene ow can

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Unformatted text preview: subpopulaGons of a metapopulaGon http://media.wiley.com/mrw_images/els/articles/a0002963/ image_n/nfgz001.gif table 3.1 allele frequencies genotypic frequencies within subpopulaGons piqi (vary from 0 to 1) p2, 2pq, q2 (HWE) (if A is fixed: p2=1, 2pq=q2=0; sGll HWE) overall metapopulaGon p, q =p0, q0 if no selecGon excess homozygosity due to fixaGon by geneGc driU HI •  observed heterozygosity in subpopulaGons •  calculated as we have previously done •  ideally, use mulGple loci –  average over all loci –  or can calculate HI and F- staGsGcs for individual loci HS •  expected heterozygosity with random maGng in a subpopulaGon •  previously we have called this H0 •  =2piqi HT •  expected heterozygosity if there were random maGng over the enGre metapopulaGon –  i.e. if the metapopulaGon were panmic?c •  = 2p0q0 = 2pq F- staGsGcs for 3 hierarchical levels use frequencies •  FIS = (HS- HI) / HS •  measures proporGonal reducGon of heterozygosity in subpopulaGons due to inbreeding •  same as F, which we saw previously •  bars denotes averages across subpopulaGons F- staGsGcs for 3 hierarchical levels use frequencies •  FST = (HT- HS) / HT •  measures proporGonal reducGon of heterozygosity in enGre metapopulaGon due to differenGaGon among subpopulaGons –  relaGve to expectaGon if there were no populaGon subdivision •  HS is averaged across all subpopulaGons •  meaningless for one subpopulaGon •  HT is expected heterozygosity across enGre metapopulaGon •  also = V/ pq more on FST V =variance in allele frequencies among subpopulaGons if all subpopulaGons have exactly the same allele frequencies, then FST = 0 i.e. no differenGaGon among subpopulaGons •  FST is also called the “fixaGon index” •  increases as more subpopulaGon go toward p=1 or...
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