NS 04-05

FST as a function of Nm in an island model

    FST is a function of Nm in an island model in which there are equal numbers Ne of individuals per population, and in which each population receives migrants at a rate of m per generation. In the steep portion of the curve (FST > 0.2), small differences in FST can accurately estimate relatively precise value of m.  In contrast, in the flat portion of the curve (FST < 0.2), small differences in FST make it difficult to estimate m accurately. The estimation problem is complicated by variable Ne among sub-populations.

    For example, if observed
FST  = 0.2, then estimated Nem = 1.0. If population sizes of the sub-populations are Ne = 100, estimated m = 0.01, meaning 1% of the individuals in each population are newly-arrived migrants.


Figure © 2013 by Sinauer; Text material © 2022 by Steven M. Carr