Uesugi Ryuji, Goka Koichi, Osakabe Masahiro
Laboratory of Conservation Biology, Department of Agricultural and Environment Biology, Graduate School of Agricultural and Life Sciences, the University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
Exp Appl Acarol. 2003;31(3-4):161-76. doi: 10.1023/b:appa.0000010388.49628.56.
We studied the development of genetic differentiation and postzygotic isolation in experimental metapopulations of the two-spotted spider mite, Tetranychus urticae Koch. A genetically diverse starter population was made by allowing six inbred sublines to interbreed. Then three migration patterns were tested: no migration, or one or three immigrants per subpopulation per generation. Variations in four traits were investigated: allozymes, acaricide resistance, diapause, and hatchability. In the allozymes, acaricide resistance, and diapause, genetic variation among subpopulations became high in metapopulations with no migration, but not in the others, which showed that one immigrant is enough to prevent genetic differentiation. Hatchability, which was decreased by interbreeding among the six sublines, gradually recovered in succeeding generations. In metapopulations with no migration, hatchability was reduced again after in-migration at the 15th generation. Different karyotypes or coadapted gene complexes can survive in different subpopulations by genetic drift, and both Wolbachia-infected and -noninfected subpopulations may be selected, which would lead to postzygotic isolation between isolated subpopulations. Our results indicate that sampling effects such as genetic drift or stochastic loss of Wolbachia produce postzygotic isolation in laboratory populations of spider mite.
我们研究了二斑叶螨（Tetranychus urticae Koch）实验性集合种群中遗传分化和合子后隔离的发展情况。通过让六个近交亚系杂交，构建了一个遗传多样的起始种群。然后测试了三种迁移模式：不迁移，或每个亚种群每代有一个或三个迁入个体。研究了四个性状的变异：等位酶、杀螨剂抗性、滞育和孵化率。在等位酶、杀螨剂抗性和滞育方面，不迁移的集合种群中亚种群间的遗传变异变得很高，而其他迁移模式下则不然，这表明一个迁入个体就足以防止遗传分化。孵化率因六个亚系间的杂交而降低，但在后续世代中逐渐恢复。在不迁移的集合种群中，第15代迁入后孵化率再次降低。不同的核型或协同适应的基因复合体可通过遗传漂变在不同亚种群中存活，感染和未感染沃尔巴克氏体的亚种群都可能被选择，这将导致隔离亚种群间的合子后隔离。我们的结果表明，遗传漂变或沃尔巴克氏体的随机丢失等抽样效应在叶螨实验室种群中产生了合子后隔离。
