Experimental study on kin-selection in the mating systems of subsocial spider mites.

对与长裂叶螨Sizotetranychus Longus sait-6亲缘关系密切的一种亚社会蜘蛛Sizotetranychus miscanthi Sait6的交配系统进行了研究，比较了两种近缘种的筑巢方式，发现雄性在不同巢中的分布存在差异。虽然在大巢中有时会出现一只以上的雄鸟，但大多数巢都只有一只雄鸟占据。另一方面，许多长臂猿的巢中包含了几只雄性。这两个物种在交配系统上的差异在实验上得到了证明。由于高度攻击性的雄-雄战斗，只有一只雄性米斯坎蒂鸟在一个巢中幸存下来，而两只雄性长尾蛇同居在一个巢中。前者的交配系统为后宫一夫多妻制，后者为扰乱型一夫多妻制。另一方面，雄性攻击性在不同种群间发生变化。只有一个假说来解释这一现象，那就是雄巢成员的亲缘关系不同，即亲缘选择对雄巢成员的对抗性。此外，种群间雄性对抗的这种差异无疑影响了两性间选择的强度，因为雄性武装形态随着种群间雄性对抗的强度而平行变化。这些都是在同一物种的野外种群中亲缘关系和性别选择强度变化的重要发现。

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.