Phylogenetically closely related strains of maternally inherited endosymbiotic bacteria are often found in phylogenetically divergent, and geographically distant insect host species. The interspecies transfer of the symbiont Wolbachia has been thought to have occurred repeatedly, facilitating its observed global pandemic. Few ecological interactions have been proposed as potential routes for the horizontal transfer of Wolbachia within natural insect communities. These routes are however likely to act only at the local scale, but how they may support the global distribution of some Wolbachia strains remains unclear. Here, we characterize the Wolbachia diversity in butterflies from the tropical forest regions of central Africa to discuss transfer at both local and global scales. We show that numerous species from both the Mylothris (family Pieridae) and Bicyclus (family Nymphalidae) butterfly genera are infected with similar Wolbachia strains, despite only minor interclade contacts across the life cycles of the species within their partially overlapping ecological niches. The phylogenetic distance and differences in resource use between these genera rule out the role of ancestry, hybridization, and shared host-plants in the interspecies transfer of the symbiont. Furthermore, we could not identify any shared ecological factors to explain the presence of the strains in other arthropod species from other habitats, or even ecoregions. Only the systematic surveys of the Wolbachia strains from entire species communities may offer the material currently lacking for understanding how Wolbachia may transfer between highly different and unrelated hosts, as well as across environmental scales.

中文翻译：

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解开 Wolbachia 全球交换：来自非洲热带地区的 Bicyclus 和 Mylothris 蝴蝶的贡献

系统发育上密切相关的母系遗传内共生细菌菌株经常在系统发育不同且地理上相距遥远的昆虫宿主物种中发现。共生体沃尔巴克氏体的种间转移被认为反复发生，促进了其观察到的全球大流行。很少有生态相互作用被提议作为 Wolbachia 在天然昆虫群落内水平转移的潜在途径。然而，这些途径可能仅在局部范围内起作用，但它们如何支持某些 Wolbachia 菌株的全球分布仍不清楚。在这里，我们描述了来自中非热带森林地区的蝴蝶的 Wolbachia 多样性，以讨论在本地和全球范围内的转移。我们表明，尽管在部分重叠的生态位内物种的整个生命周期中只有很小的进化枝间接触，但来自 Mylothris（粉蝶科）和 Bicyclus（蛱蝶科）蝴蝶属的许多物种都感染了类似的 Wolbachia 菌株。这些属之间的系统发育距离和资源利用差异排除了祖先、杂交和共享宿主植物在共生体种间转移中的作用。此外，我们无法确定任何共享的生态因素来解释来自其他栖息地甚至生态区的其他节肢动物物种中菌株的存在。