Gene flow and selection balance in haplodiploid social insects.

Understanding the joint effects of gene flow and selection is one of the more important but difficult areas of evolutionary genetics. A method is presented to describe cases of gene flow-selection balance while accounting for the life history of haplodiploid social insects (eusocial Hymenoptera). A continent-island model is used to estimate gene flow rates from allele frequency data and provide variance formulae. The occurrence of unequal yet stable allele frequencies among social insect castes is explained and the usefulness of models with discrete generations for eusocial insects is explained. Gene flow and selection balance has been demonstrated for the fire ant Solenopsis invicta at two allozyme loci. This continent-island model gives results that well describe the system. Issues fundamental to the differences between X-linked and haplodiploid genetic systems and diploid genetic systems are also discussed.