Evolution of castes in Polistes

A novel hypothesis for the origin of castes in Polistes has recently been proposed: the worker and gyne castes among offspring of a Polistes colony are based on the underlying ground plan of reproductive physiology that would have characterized the non-diapause and diapause generations of a bivoltine solitary vespid wasp. Here the hypothesis is reviewed in light of the dynamic nature of diapause expression in insects in general, and it is re-named the diapause ground plan hypothesis. The diapause ground plan hypothesis differs in several significant aspects from an existing hypothesis for the origin of castes — the ovarian ground plan hypothesis. Phylogenetic implications of the diapause ground plan hypothesis also are in discord with the currently accepted classification of Vespidae, and the diapause ground plan hypothesis has been challenged for its failure to address multiple levels of analysis. Each of these areas of discord is described, and key points of difference between the diapause ground plan hypothesis and competing hypotheses are identified. Strong inference — the explicit testing of a hypothesis for possible rejection — is proposed as the most efficacious route to clearer understanding of the evolution of the castes in Polistes. Specific suggestions for some strong tests of competing hypotheses are proposed.