Variability in migratory tendency within and among natural populations of the pea aphid, Acyrthosiphon pisum.

The migratory tendencies of pea aphids were measured by determining the numbers of winged and non-winged offspring produced by parthenogenetic wingless females after a crowding test. Sources of variability in this measure were investigated. The migratory tendency of an individual clone was found to be stable. Spatial and temporal patterns in migratory tendency were found among nine natural populations. These patterns probably reflect differences in the frequencies of a large number of genetically distinct clones. Hypotheses based on the relative fitness of immigrant and resident clones and the heritability of migratory tendency are offered to account for these results. High migration rates may be required to account for genetic differentiation within and among some parthenogenetic populations of the pea aphid.