| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 2004: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2003: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2002: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
The significance of reproductive properties and two modes of seed dispersal in the prostrate annual Chamaesyce maculata with multiple overlapping generations was analyzed in the field survey and laboratory experiments. The following results were obtained. 1)Plants that emerged in June commenced sexual reproduction from late July, and thereafter both vegetative growth and sexual reproduction occurred together until early November, the plants showing o switching from vegetative growth to sexual reproduction. 2)C.maculata could repeat a maximum of three overlapping generations within a year. Multiple generations per year were attained by non-dormant seeds produced in the first and second generaions and clearly resulted in an increased reproductive output per year. 3)It would be considered that competitions between parent plants and offspring plants occur in the early season of reproductive period, and competitions among seedlings that were derived from the seeds produced in the late seaso
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n of reproductive period occur in the emergence period in the next year. 4)In order to avoid such competitions, the seeds produced in the early season of reproductive period were automatically dispersed (autochory), resulting in seed dispersion far from parent plants. 5)the seeds produced in the late season of reproductive period were not automatically, but dispersed by seed-collecting ants (myrmecochory). Although 18 ant species visited plants of C.maculata, only two species of omnivorous ants, Tetramorium tsushimae and Pheidole nodus carried the seeds into their nests. 6)P.nodus was regarded as a typical seed predator, because P.nodus workers fed on most of the seeds carried in their nests, and the efficiency of seed dispersal by P.nodus was conspicuously low, similar as harvester ants. 7)On the other hand, workers of T.tsushimae carried out again about half number of the seeds that had carried into their nests, and the injury rates of both the seeds that carried out from their nests and those that remained in their nests were conspicuously low. Therefore, It would be considered that T.tsushimae is a superior seed disperser with high efficiency of seed dispersal for C.maculata. Less
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