Bio 321 F13 lecture 8 v2

Expected heterozygosity if there were random

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Unformatted text preview: es, 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 q=1 (by driU in the simplest model) •  FST increases because HS decreases •  HS decreases when alleles are fixed because maximum H is when p=q=0.5 Which of the following is not true about migraGon? A.  MigraGon can occur without gene flow B.  Gene flow can occur without migraGon C.  MigraGon tends to keep allele frequencies between subpopulaGons the same D.  MigraGon is a source of new geneGc variaGon for a populaGon more on FST •  most species http://bugguide.net/node/view/455724/bgimage –  FST ~0.15 or less (modest isolaGon between subpopulaGons) –  Sewall Wright •  0.05 – 0.15 ; moderate differenGaGon •  0.15 – 0.25; great differenGaGon •  >0.25; very great differenGaGon •  e.g. willow leaf beetle Chrysomela aeneicollis –  among different river drainages, FST=0.04 –  among locaGons within a river drainage, FST=0.02 –  (Rank 1992) another example Phlox cuspidata Pgm- 2 allozyme locus 43 subpopulaGons FST = 0.38 this species has high frequencies of self- ferGlizaGon •  (Levin 1978) •  •  •  •  •  http://www.sbs.utexas.edu/bio406d/images/pics/plm/Phlox %20cuspidata%20flower.jpg F- staGsGcs for 3 hierarchical levels use frequencies •  FIT = (HT- HI) / HT •  measures reducGon in heterozygosity of an individual (HI) relaGve to total metapopulaGon (T) •  can be due to both driU between subpopulaGons and non- random maGng within subpopulaGons •  not as informaGve as other F- staGsGcs because it confounds the effects of non- random maGng and driU the three F- staGsGcs are related •  (1- FIS)(1- FST) = (1- FIT) •  this provides a handy post- analysis check •  Now, let’s see a real example, from Box 3.1 of Conner and Hartl Levin (1978), Pgm-1 locus (2 alleles) 43 Texas subpopulations of Phlox cuspidata 40 fixed for the b allele (p=1) 3 were variable subpopulation pi Hi 1-40 1 0 41 0.49 0.17 42 0.83 0.06 43 0.91 0.06 HI = [(40x0)+0.17+0.06+0.06]/43 = 0.0067 =average observed heterozygosity across all subpopulations Levin (1978), Pgm-1 locus (2 alleles) 43 Texas subpopulations of Phlox cuspidata 40 fixed for the b allele (p=1) 3 were variable subpopulation pi Hi 1-40 1 0 41 0.49 0.17 42 0.83 0.06 43 0.91 0.06 n HS = ( Σ2p q )/n i=1 ii ; where n = number of subpopulations = [(40 x 0)+2(0.49x0.51) +...
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This note was uploaded on 10/01/2013 for the course BIO 321 taught by Professor John during the Spring '12 term at SUNY Stony Brook.

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