Evidence for selective sweeps by Wolbachia infections: phylogeny of Altica leaf beetles and their reproductive parasites

Infections with maternally inherited Wolbachia bacteria may have dramatic influences on reproductive traits and speciation patterns of their hosts. We here show that in the beetle genus Altica, infection has influenced phylogenetic patterns of the host’s mtDNA and different strains led to repeated selective sweeps. By comparing a COI/II based phylogeny of the hosts with a phylogeny of the bacteria based on ftsZ, we show that co-speciation is rare and restricted to few recently diverged species. While in general each species apparently harbours a single Wolbachia strain, A. lythri presents a strikingly different pattern: in the polyphyletic species three highly divergent mtDNA haplotypes (2.1 – 4.6% p-distance) are coupled with three different Wolbachia strains (wLytA1, wLytA2, wLytB). These haplotypes and Wolbachia strains are widely distributed and mostly found in sympatry. A phylogeny based on microsatellite data supports the monophyly of A. lythri. The discrepancy between mtDNA and n...母系遗传的沃尔巴克氏体（Wolbachia）细菌感染，可对宿主的生殖性状与物种形成模式产生显著影响。本研究表明，在叶甲属（Altica）类群中，沃尔巴克氏体感染已改变宿主线粒体DNA（mtDNA）的系统发育模式，且不同菌株引发了多次选择性清除事件。通过对比基于COI/II的宿主系统发育树与基于ftsZ基因的细菌系统发育树，本研究发现协同物种形成事件十分罕见，仅局限于少数近期分化的物种。尽管多数物种通常仅携带单一沃尔巴克氏体菌株，但千屈菜叶甲（A. lythri）呈现出截然不同的模式：在这一多系类群中，三种高度分化的线粒体DNA单倍型（p距离为2.1%~4.6%）分别与三种不同的沃尔巴克氏体菌株（wLytA1、wLytA2、wLytB）匹配。这些单倍型与沃尔巴克氏体菌株分布广泛，且大多同域共存。基于微卫星数据构建的系统发育树支持千屈菜叶甲为单系类群。线粒体DNA与核基因组之间的不一致性……