The Evolution of Dispersal

Organisms may either remain in the population they currently occupy or attempt to disperse to another population. In collaboration with Dr. Robert D. Holt, University of Florida, I am using simple patch models to examine how different population dynamic regimes influence the evolution of dispersal rates. Contrary to previous analyses, we find that some level of dispersal is favored by natural selection under all regimes of habitat variability. Furthermore, we find that two very different polymorphisms are favored under different conditions; in one polymorphism an infinite number of genotypes expressing patch-specific dispersal propensities in specific ratios coexist, and in the other a dimorphism of two genotypes coexist (a high dispersal and a no dispersal genotype). The dimorphism can be invaded and replaced by one phenotypically plastic genotype that expresses a particular combination of patch-specific dispersal propensities. If however population fluctuations are generated by chaotic population dynamics and not by external environmental variation, multistate polymorphisms can be maintained indefinitely under some conditions. This model makes a number of testable predictions about the amounts of phenotypic and genetic variation in dispersal characters that are expected both within and between populations, and the degree to which the expression of phenotypic characters affecting dispersal propensity should be sensitive to environmental conditions (i.e. phenotypic plasticity).

Relevant papers

McPeek, M. A., and R. D. Holt. 1992. The evolution of dispersal in spatially and temporally varying environments. American Naturalist 140:1010-1027.

Holt, R. D., and M. A. McPeek. 1996. On the evolution of dispersal in a chaotic environment. American Naturalist 148:709-718.