Question

For comparisons of a population, I got an FST value of -0.03972 and an Nm value of -6.5. I know that as far as FST goes, you can treat negative numbers as zeros. But, I have no idea how to interpret a negative Nm value for gene flow. What does this Nm value mean?

Answer 1

FST value is nothing but fixation index which measures variation in allele frequencies among the populations. N describes effective population size and m stands for effective proportion of immigrants. As you know, Negative FST values can be treated as zeros. Nm values stands for gene flow to nullify effect of genetic drift. Negative Nm value states that there is not enough gene flow between the populations .if Nm>1 it means there is enough flow to negate the effect of gene flow. Nm>4 means the local population is one of panmictic population.