Data from: Wolbachia-induced meiotic drive and feminization is associated with an independent occurrence of selective mitochondrial sweep in a butterfly

Maternally inherited Wolbachia endosymbionts manipulate arthropod reproduction in various ways. In the butterfly Eurema mandarina, a cytoplasmic incompatibility-inducing Wolbachia strain wCI and the associated mtDNA haplotypes are known to originate from the sister species Eurema hecabe, which offered a good case study for microbe-mediated hybrid introgression. Besides wCI, some females with the Z0 karyotype harbour a distinct Wolbachia strain wFem, which causes all-female production by meiotic drive and feminization. We report that a considerable proportion of E. mandarina females (65.7%) were infected with both wCI and wFem (CF) on Tanegashima Island. While females singly infected with wCI (C) produced offspring at a 1 : 1 sex ratio, CF females produced only females. Although Z-linked sequence polymorphism showed no signs of divergence between C and CF females, mtDNA split into two discrete clades; one consisted of C females and the other CF females, both of which formed a clade with E. hecabe but not with uninfected E. mandarina. This suggests that CF matrilines also, but independently, experienced a selective sweep after hybrid introgression from E. hecabe. Distinct evolutionary forces were suggested to have caused C and CF matrilines to diverge, which would be irreversible because of the particular phenotype of wFem.

母系遗传的沃尔巴克氏体（Wolbachia）内共生体可通过多种途径操控节肢动物的生殖活动。在曼氏黄粉蝶（Eurema mandarina）中，已知一种诱导胞质不相容的沃尔巴克氏体菌株wCI及其相关的线粒体DNA单倍型（mtDNA haplotype）源自姊妹物种宽边黄粉蝶（Eurema hecabe），该体系为研究微生物介导的杂交渐渗提供了优良的案例模型。除wCI菌株外，部分携带Z0核型的雌性个体还携带有一种独特的沃尔巴克氏体菌株wFem，该菌株可通过减数分裂驱动与雌性化诱导实现全雌性后代的产出。本研究报道，在种子岛（Tanegashima Island）上，有65.7%的曼氏黄粉蝶雌性个体同时感染wCI与wFem（以下简称CF型）。单独感染wCI的雌性个体（以下简称C型）所产后代的性别比例为1:1，而CF型雌性仅能产生雌性后代。尽管Z连锁序列多态性未显示C型与CF型雌性存在分化迹象，但线粒体DNA可分为两个分立的演化支：一支仅包含C型雌性，另一支仅包含CF型雌性；两类演化支均与宽边黄粉蝶（Eurema hecabe）聚为一支，而非未感染的曼氏黄粉蝶（Eurema mandarina）。这表明CF型母系谱系同样（但独立地）经历了源自宽边黄粉蝶的杂交渐渗后的选择性清除事件。研究表明，不同的演化压力导致C型与CF型母系谱系产生分化，且由于wFem的特殊表型，这种分化是不可逆的。