Dispersal and the persistence of populations in unstable habitats: A theoretical note.

It is illustrated theoretically that in a heterogeneous habitat the dispersal of individuals, even when it is random and density-independent, may have a pronounced effect of raising the average reproductive rate of the whole population, in addition to the effect of stabilization in the usual sense of reducing its variance. This implies that in such a population the habitat instability has been converted by dispersal into a condition profitable for the population. The role played by dispersal here is therefore regarded as much more positive than that which the expression 'spreading of risk' usually means.