| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1991: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1990: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
The mating system of a subsocial spider mite, Schizotetranychus miscanthi Sait6, which is closely related to Schizotetranychus longus Sait-6 was studied in comparison with that of S. longlis.
Comparisons between nesting patterns of the two related species revealed a difference in distribution of males among nests. Although more than one male sometimes occurred in the large nests of S. miscanthi, most nests were occupied only by a single male. On the other hand, many nests of S. longtis included several males.
Differences in mating systems were experimentally demonstrated in the two species. Only a single male of S. miscanthi survived in a nest, as a result of highly aggressive male-male combat, while two males of S. longus cohabited in a nest. The mating system of the former species is thus considered as harem polygyny, while that of the latter as scramble type polygyny.
On the other hand, male aggressiveness changed between the populations of S. miscanthi. Only a hypothesis to explain this phenomenon is a difference in the relatedness of male nest members, i. e. kin selection on male antagonism. Furthermore, such a difference in male antagonism among populations has undoubtedly influenced on the intensity of intrasexual selection, because the male armed morph changed in parallel manner, with the intensity of male antagonism of populations. These are the important discoveries of the changes in the intensities of kin and sexual selections among the field populations of the same animal species.
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