How social wasps evolved

In social Vespidae, the origin of worker behavior, which constitutes the eusociality threshold, is not based on relatedness. Incipient workers and queens on the same nest need not be related. Each behaves selfishly, and both are subject to direct natural selection. Worker traits are context-dependent maternal care behaviors directed to non-descendent offspring, hence ‘allomaternal’ care. Like maternal care, allomaternal care is based on physiological and behavioral suites that have been strongly selected. Beyond the eusociality threshold, however, worker behavior in colonies of relatives enables relaxed selection via ‘soft inheritance’ that leads to divergence of worker and queen traits. Selection segues from independent actors nesting together to selection that acts on the ensemble. Early stages of this change in the focus of selection are characterized by maternal manipulation rather than by workers choosing to work in order to enhance their inclusive fitness. Transitions from solitary to facultative, facultative to primitive, and primitive to advanced eusociality occur via exaptation, phenotypic accommodation and genetic assimilation. Roles of behavioral flexibility and developmental plasticity in the evolutionary process exceed those of genotype. Regulation in the expression of existing alleles is more important than introduction of novel alleles for worker behavior.