Data from: Origin, acquisition and diversification of heritable bacterial endosymbionts in louse flies and bat flies

The γ-proteobacterium Arsenophonus and its close relatives (Arsenophonus and like organisms, ALOs) are emerging as a novel clade of endosymbionts, which are exceptionally widespread in insects. The biology of ALOs is, however, in most cases entirely unknown, and it is unclear how these endosymbionts spread across insect populations. Here, we investigate this aspect through the examination of the presence, the diversity and the evolutionary history of ALOs in 25 related species of blood-feeding flies: tsetse flies (Glossinidae), louse flies (Hippoboscidae) and bat flies (Nycteribiidae and Streblidae). While these endosymbionts were not found in tsetse flies, we identify louse flies and bat flies as harbouring the highest diversity of ALO strains reported to date, including a novel ALO clade, as well as Arsenophonus and the recently described Candidatus Aschnera chinzeii clade. We further show that the origin of ALO endosymbiosies extends deep into the evolutionary past of louse flies and bat flies, and that it likely played a major role in the ecological specialization of their hosts. The evolutionary history of ALOs is notably complex and was shaped by both vertical transmission and horizontal transfers with frequent host turnover and apparent symbiont replacement in host lineages. In particular, ALOs have evolved repeatedly and independently close relationships with diverse groups of louse flies and bat flies, as well as phylogenetically more distant insect families, suggesting that ALO endosymbioses are exceptionally dynamic systems.

γ-变形菌（γ-proteobacterium）中的嗜砷菌属（Arsenophonus）及其近缘类群（嗜砷菌属类生物体，Arsenophonus and like organisms，ALOs）作为一类新兴的内共生菌支系，在昆虫中分布极为广泛。然而目前学界对ALOs的生物学特性大多仍一无所知，尚不清楚这类内共生菌如何在昆虫种群中实现传播。本研究针对该问题展开探究，通过调查25种吸血蝇类近缘物种——舌蝇科（Glossinidae）、虱蝇科（Hippoboscidae）以及蝠蝇科（Nycteribiidae与Streblidae）——体内ALOs的存在情况、多样性及演化历史，解析相关机制。研究结果显示，此类内共生菌并未在舌蝇体内检出，但虱蝇与蝠蝇体内携带的ALOs菌株多样性达到了目前已报道的最高水平，其中包含一个全新的ALOs支系，以及嗜砷菌属和新近描述的候选属Aschnera chinzeii（Candidatus Aschnera chinzeii）支系。本研究进一步证实，ALOs与宿主的内共生关系起源可追溯至虱蝇与蝠蝇演化历史的早期阶段，且很可能在宿主的生态特化进程中发挥了关键作用。ALOs的演化历史尤为复杂，其演化过程同时受到垂直传播与水平传播的塑造，伴随频繁的宿主转换现象，以及宿主支系中显著的共生菌替代事件。值得注意的是，ALOs已多次独立演化出与多样虱蝇、蝠蝇类群，以及系统发育关系更远的昆虫科类群的紧密共生关系，这提示ALOs相关的内共生体系是一类极具动态性的研究系统。