Social evolution in Australian Ropalidia wasps

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Studies on social behavior and social structure of six Australian species of the genus Ropalidia were made during two years (1993 and 1994) with cooperation of Australian entomologists. Observations of marked females of Ropalidia revolutionalis and R.sp.nr.Variegata showed that their intracolony dominance relations were mild in pre-emergence stage but severe in post-emergence stage A swarm-founding, primitively eusocial species, R.mackaynsis constructed its nest in open space while the nest had no envelope. This is different from another swarm-founding, primitively eusocial species, R.socialistica, which produced nests in cavities.Contrary to other Australian primitively eusocial Ropalidia, R.gregaria spilocephala females founed their nests frequently by haplometrosis (single-female foundation).It was found that a highly eusocial species R.romandi cabeti founded their nest by swarming, and the swarm first constructed several combs and then constructed envelope. This is the first detailed record of the initial stage of nest foundation in swarm-founders.Many adult specimens were taken from many nests of a primitively eusocial, swarm founding species R.socialistica, and a highly eusocial swarm-founder, R.romandi cabeti. These were immediately frozen for future analysis with electrophoresis and DNA-finger printing technique, to estimate the intracolony relatedness.Comparative studies on social behavior, social structure and number of effective egg-layrs indicated that the genus Ropalidia, a large genus including 136 species, has three majour groups, individually-founding, primitively eusocial-species (e.g.R.revolutionalis), swarm founding, primitively eusocial species (e.g.R.mackaynsis) and swarm-founding, highly eusocial, multiqueen species, Ropalidia romandi. The second group was suggested to be a link between facultatively polygynous, primitively eusocial species as R.revolutionalis and R.gregaria and multiqueen species as R.romandi.