Studies for the evolution and maintenance of worker reproduction in paper wasps

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We analyzed the social structure of the Australian swarm-founding paper wasp Ropalidia romandi. Nest initiations were artificially induced. We observed novel behaviors where workers selected certain queens among many queens by aggressive behaviors. Genetic relatedness between the queens was higher than that between workers, suggesting that cyclical oligogyny could be applied to explain this tendency. There was no clear evidence to show worker reproduction in this species: We analyzed the production of reproductives by the Japanese paper wasp Polistes snelleni, and revealed that there was significant positive relationship between colony size and female ratio. This positive relationship could be explained either by (1) larger colonies enjoy more investment resource and which causes, more female sex ratio, (2) mated workers contribute more female production and which bring more female sex ratio. We analyzed the social structure of the Japanese paper wasp Polistes chinensis antennalis by using 13 microsatellite markers that we had originally developed. The results were (1) early males that were produced along the first brood were diploid, and eventually sterile, (2) there was a significantly positive relationship between colony size and the frequency of worker oviposition, (3) there was no clear relationship between colony size and the frequency of workers' sons. We compared the genotypes of mother wasps and the hatched larvae that were offspring the putative mothers, and indicating that most eggs by workers were eaten by both queens and workers. In monogynous and monandrous colonies like P. chinensis antennalis, mutual worker policing could not theoretically expected. But, our finding contradicts the theory and it seems a very novel one.