3. Effects of gene flow (“migration” = dispersal = gene flow) on allele frequencies in the Northern Water Snake ( Nerodia spp. ) Oxford Fig. 7.6
4. Frequency of banded, intermediate, and unbanded snakes A = unbanded and D = banded morphs; B and C are intermediate morphs Greater predation on (i.e., selection against) banded snakes (especially younger ones) on the islands favors the unbanded phenotype. But why are there still banded snakes on the islands (and unbanded on the (southern) peninsular mainland? Fig. 7.7
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7. Genetic drift in a small population Imagine a population of ten adults with two alleles A and a for the ‘A’ gene A = 0.6 and a = 0.4 Ten zygotes are produced and by chance: AA = 0.6 Aa = 0.2 aa = 0.2 Hence, frequency of A increases significantly (to 0.70) in next generation
8. Probability of allele frequencies as a result of genetic drift (N = 10 offspring) Fig. 7.11
9. The Founder Effect is an example of Genetic Drift Silvereyes colonized islands Fig. 7.13
13. Genetic drift in 107 experimental populations Fig. 7.16 In generation 0, freq. of bw 75 = 0.5 Each pop. started with 8 randomly chosen males and 8 females from previous pop.
14. How fast will the proportion of heterozygotes in a population decline in response to drift? H g + 1 = H g [1-(1/2N)] Fig. 7.17 Predicted declines shown for N = 16 (dashed gray line) N = 9 (solid gray line)
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18. Fig. 7.27 Calculating F for one locus with two alleles For matings between half sibs:
22. Inbreeding depression can result in lower fertility and fecundity lower survival asymmetrical development and overall lower RS and becomes more apparent as individuals grow older are subjected to selection
24. F ST - measure of genetic differentiation among populations Y chromosome loci mitochondrial loci autosomal loci Genetic distance between human populations as a function of geographic distance
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