Fig. 4. Migration-Selection balance. Dispersal rate (% per
generation) between two environments required to maintain the observed
average within site phenotypic variation in the absence of mutation, as
a function of selection difference (the difference in optimal phenotype
between the two environments). A. Migration-selection balance for to
maintain variation in frond area (mm2). B.
Migration-selection balance for to maintain variation in root length
(mm).