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.
With three variables, measurement of any two allows estimate of the third. For example, if observed FST = 0.2, then estimated Nem = 1.0. If population sizes of the sub-populations are measured as Ne = 100, estimated m = 0.01, meaning 1% of the individuals in each population are newly-arrived migrants. Alternatively, if m = 0.01 (as measured by a mark & recapture experiment), then estimated Ne = 100, which may be larger or much smaller than census population size.
With three variables, measurement of any two allows estimate of the third. For example, if observed FST = 0.2, then estimated Nem = 1.0. If population sizes of the sub-populations are measured as Ne = 100, estimated m = 0.01, meaning 1% of the individuals in each population are newly-arrived migrants. Alternatively, if m = 0.01 (as measured by a mark & recapture experiment), then estimated Ne = 100, which may be larger or much smaller than census population size.
Figure © 2013 by Sinauer; Text material © 2024 by Steven M. Carr