Data from: Bacterial symbiont sharing in Megalomyrmex social parasites and their fungus-growing ant hosts

Bacterial symbionts are important fitness determinants of insects. Some hosts have independently acquired taxonomically related microbes to meet similar challenges, but whether distantly related hosts that live in tight symbiosis can maintain similar microbial communities has not been investigated. Varying degrees of nest-sharing between Megalomyrmex social parasites (Solenopsidini) and their fungus-growing ant hosts (Attini) from the genera Cyphomyrmex, Trachymyrmex and Sericomyrmex allowed us to address this question, as both ant lineages rely on the same fungal diet, interact in varying intensities, and are distantly related. We used tag-encoded FLX 454 pyrosequencing and diagnostic PCR to map bacterial symbiont diversity across the Megalomyrmex phylogenetic tree, which also contains free-living generalist predators. We show that social parasites and hosts share a subset of bacterial symbionts, primarily consisting of Entomoplasmatales, Bartonellaceae, Acinetobacter, Wolbachia and Pseudonocardia and that Entomoplasmatales and Bartonellaceae can co-infect specifically associated combinations of hosts and social parasites with identical 16S rRNA genotypes. We reconstructed in more detail the population-level infection dynamics for Entomoplasmatales and Bartonellaceae in M. symmetochus guest ants and their Sericomyrmex amabilis hosts. We further assessed the stability of the bacterial communities through a diet-manipulation experiment and evaluated possible transmission modes in shared nests such as consumption of the same fungus garden food, eating of host brood by social parasites, trophallaxis and grooming interactions between the ants, or parallel acquisition from the same nest environment. Our results imply that cohabiting ant social parasites and hosts may obtain functional benefits of bacterial symbiont transfer even when they are not closely related.

细菌共生体（Bacterial symbionts）是昆虫重要的适合度决定因子。部分宿主会独立获得分类学上亲缘关系相近的微生物以应对相似的生存压力，但目前尚未有研究探讨处于紧密共生关系的亲缘关系疏远的宿主能否维持相似的微生物群落。巨首蚁属（Megalomyrmex）社会寄生蚁隶属于盗蚁族（Solenopsidini），它们与其宿主蚁（Attini切叶蚁族）——该族蚂蚁分别隶属于顶切叶蚁属（Cyphomyrmex）、毛切叶蚁属（Trachymyrmex）和丝切叶蚁属（Sericomyrmex）——之间存在不同程度的巢内共居现象，这为我们解答上述问题提供了研究契机：两类蚂蚁谱系均依赖相同的真菌食谱，相互作用强度存在差异，且亲缘关系较为疏远。我们采用标签编码FLX 454焦磷酸测序技术与诊断聚合酶链式反应（diagnostic PCR），在同样包含自由生存广食性捕食者的巨首蚁属系统发育树中绘制了细菌共生体的多样性分布图谱。研究结果表明，社会寄生蚁与宿主共享一部分细菌共生体，其类群主要包括虫原体目（Entomoplasmatales）、巴尔通体科（Bartonellaceae）、不动杆菌属（Acinetobacter）、沃尔巴克氏体属（Wolbachia）以及假诺卡氏菌属（Pseudonocardia）；且虫原体目与巴尔通体科能够以完全一致的16S rRNA基因型共感染宿主与社会寄生蚁的特异性关联组合。我们还针对对称巨首蚁（M. symmetochus）寄居蚁及其宿主美丽丝切叶蚁（Sericomyrmex amabilis），进一步重构了虫原体目与巴尔通体科的种群水平感染动态。我们还通过饮食操控实验评估了细菌群落的稳定性，并探讨了共居蚁巢内可能的共生体传播途径，包括共享真菌苗圃食物、社会寄生蚁取食宿主幼虫、蚂蚁间的交哺行为与梳理互动，或是从同一巢环境中平行获得共生体。本研究结果表明，即使亲缘关系较为疏远，共居的蚂蚁社会寄生蚁与宿主仍可通过细菌共生体的传递获得功能性收益。