Data from: Speciation history of three closely related oak gall wasps, Andricus mukaigawae, A. kashiwaphilus, and A. pseudoflos (Hymenoptera: Cynipidae) inferred from nuclear and mitochondrial DNA sequences

The Andricus mukaigawae complex of oak gall wasps is composed of cyclically parthenogenetic species: A. mukaigawae and A. kashiwaphilus, and a parthenogenetic species, A. pseudoflos. The component species differ in life history, host plant, karyotype, and asexual gall shape, although little difference is found in the external morphology of asexual adults. To understand the speciation history of this species complex, DNA sequences of one mitochondrial region and nine nuclear gene regions were investigated. The genetic relationship among the species suggested that a loss of sex occurred after host shift. Unexpectedly, two or three distinct groups in the parthenogenetic species, A. pseudoflos, were revealed by both mitochondrial and nuclear DNA data. Gene flow in nuclear genes from the species not infected by Wolbachia (A. kashiwaphilus) to the species infected by it (A. mukaigawae) was suggested by a method based on coalescent simulations. On the other hand gene flow in mitochondrial genes was suggested to be in the opposite direction. These findings indicate possible involvement of Wolbachia infection in the speciation process of the A. mukaigawae complex.

栎树瘿蜂的川崎瘿蜂（Andricus mukaigawae）复合群由两类类群构成：一类为周期性孤雌生殖物种，即川崎瘿蜂（A. mukaigawae）与柏氏瘿蜂（A. kashiwaphilus）；另一类为专性孤雌生殖物种，即假花瘿蜂（A. pseudoflos）。尽管该复合群内各组分物种的孤雌生殖成虫外部形态差异极小，但它们在生活史、寄主植物、核型以及无性世代虫瘿形态上均存在显著差异。为解析该物种复合群的物种形成历史，研究人员对1个线粒体基因区域及9个核基因区域的DNA序列开展了分析。物种间的遗传关系分析显示，性生殖的丢失发生在寄主转换之后。出乎意料的是，线粒体与核DNA数据均揭示，专性孤雌生殖的假花瘿蜂（A. pseudoflos）内部可划分为2至3个独立类群。基于溯祖模拟的分析方法显示，未被沃尔巴克氏体（Wolbachia）感染的柏氏瘿蜂（A. kashiwaphilus）向受其感染的川崎瘿蜂（A. mukaigawae）存在核基因的基因流；而线粒体基因的基因流则呈现相反方向。上述研究结果表明，沃尔巴克氏体感染可能参与了川崎瘿蜂复合群的物种形成过程。