Demography, Biogeography, and Drift

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This can be determined by using the binomial expansion equation for predicting the probability of an unordered combination of events:P= n!pxqn-xx! (n -x)!P= probability that an unordered outcome will occurn= total number of eventsx= number of events in one categoryp= individual probability of xq= individual probability of the other category! = factorialDemography, Biogeography, and Drift

n= 10 (total alleles moving to the island)x = 3 (the number that will be R alleles – same as in the mainland population)p = 0.3 (probability that an allele from the mainland population will be R)q = 0.7 (probability that an allele from the mainland population will be r)P= 10!0.33(0.77) = 0.26673!(7!)So, there is a 73% chance that the island population will have different allele frequencies than were found on the mainland. Demography, Biogeography, and Drift

Genetic drift (i.e., random chance) affects not only the gene frequencies of the founding population, but the long-term frequencies of alleles in the future. Demography, Biogeography, and Drift

Genetic drift (i.e., random chance) affects not only the gene frequencies of the founding population, but the long-term frequencies of alleles in the future. What does that mean?Demography, Biogeography, and Drift

In our example, the island population has initial allele frequencies of R= 0.6 and r= 0.4. Demography, Biogeography, and Drift

Therefore, the probability that the population will become fixed for Ris ???, and the probability that is will become fixed for ris ???. Demography, Biogeography, and Drift

Therefore, the probability that the population will become fixed for Ris 0.6, and the probability that is will become fixed for ris 0.4. Demography, Biogeography, and Drift

What is leading edge expansion and what does it have to do with founder effect?Demography, Biogeography, and Drift

Black spruce expanded northward when glaciers receded after the last ice age, and Gamache et al. studied founder effect in populations in the forest tundra of the eastern coast of Canada’s Hudson Bay. Demography, Biogeography, and Drift

Dispersal in plants involves both seed and pollen dispersal. What’s the importance of this figure?Demography, Biogeography, and Drift

Assumptions > Predictions•A: Plants disperse via seeds.–Few at a time•A: Local plants pollinated both by local pollen andpollen dispersed over long distances.•P: Nuclear genomes should exhibit high diversityand relative uniformity.•P: Mitochondrial genomes should exhibit foundereffect (relatively low diversity) in the newhabitats, and higher diversity in the older, originalhabitats.

They found that all of the types of nuclear DNA found in the large parent populations were represented in the northern populations.(Consistent with broad dispersal of numerous pollen grains.)Demography, Biogeography, and Drift

They found that all of the types of nuclear DNA found in the large parent populations were represented in the northern populations.