| Budget Amount *help |
¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥700,000 (Direct Cost: ¥700,000)
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| Research Abstract |
Researches on the evolution of eusociality in insects have so far been limited to its ethological and genetical aspects, and only a few studies have been done on the ecological conditions which allowed evolution of eusociality. I have accumulated many data on population parameters of a eusocial wasp, Ropalidia fasciata, and a eusocial aphid, Pseudoregma bambucicola, partly by the grant-in-aid for scientific research (06640826). Using these data, and additional data obtained in the first year of this study, I attempted to clarify ecological and demographic conditions for production of sterile castes and establishment of multiqueen colonies. Main resutls are as follows :
1.R.fasciata
(1) Rate of nest failure was very high due to predation and typhoon, but the colonies had high ability to reconstruct their nests. Thus more than a half of colonies could produce reproductives.
(2) Although almost all foundresses marked in spring died by the end of August, reproductives of the next year were produced after this time, suggesting that this species is, at least partly, bivoltine.
(3) On Okinawa Honto, about a half of nests were established by multiple foundresses (pleometrosis). Larger the number of foundresses, higher the nest survivorship and reconstruction rate, and earlier the production of workers. This might be a reason of high rate of pleometrosis and polygyny in this species.
(4) An English paper is now preparing. To hear opinions and advices on this study, an informal research report was printed and sent to researchers working on eusociality.
2.P.bambucicola
Field surveyps were made in Okinawa and Kagoshima, and demographic analysis of the data, including those taken before, have been carried out. The next step is preparation of English manuscript.
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