Differential migration from high fitness demes in the shining fungus beetle, Phalacrus substriatus

Using data from three years (1994-1996), I tested whether differential migr ation occurs from demes of high mean fitness in the shining fungus beetle, Phalacrus substriatus. The results show evidence for differential migration , thus providing evidence from a natural population for a critical demograp hic assumption of many interdemic selection models. To predict the evolutio nary response to interdemic selection through differential migration, the g enetic basis of the variation among demes in mean fitness must be known bec ause the observed patterns could also be explained by some demes having an intrinsically favorable habitat. Thus, the importance of differential migra tion through interdemic selection in natural populations cannot be unequivo cally answered without experiments specifically addressing the question of what causes differences in mean fitness among demes.